Visual Fields (Ophthalmology Monographs)

Visual Fields Ophthalmology Monographs A series published by Oxford University Press in cooperation with the American...

Author: Thomas Walsh

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Visual Fields

Ophthalmology Monographs A series published by Oxford University Press in cooperation with the American Academy of Ophthalmology Series Editor: Richard K. Parrish, II, MD, Bascom Palmer Eye Institute American Academy of Ophthalmology Clinical Education Secretariat: Louis B. Cantor, MD, Indiana University School of Medicine Gregory L. Skuta, MD, Dean A. McGee Eye Institute

1. Retinal Detachment: Principles and Practices, third edition Daniel A. Brinton, MD, and Charles P. Wilkinson, MD 2. Electrophysiologic Testing in Disorders of the Retina, Optic Nerve, and Visual Pathway, second edition Gerald Allen Fishman, MD, David G. Birch, MD, Graham E. Holder, MD, and Mitchell G. Brigell, MD 3. Visual Fields: Examination and Interpretation, third edition Edited by Thomas J. Walsh, MD 4. Glaucoma Surgery: Principles and Techniques, second edition Edited by Robert N. Weinreb, MD and Richard P. Mills, MD 5. Fluorescein and Indocyanine Green Angiography: Technique and Interpretation, second edition Joseph W. Berkow, MD, Robert W. Flower, David H. Orth, MD, and James S. Kelley, MD 6. Neuroimaging in Ophthalmology, second edition Michael C. Johnson, M.D., F.R.C.S.C, Bruno A. Policeni, M.D., Andrew G. Lee, M.D., and Wendy R. K. Smoker, M.D., F.A.C.R. [First edition published as Magnetic Resonance Imaging and Computed Tomography: Clinical Neuro-Orbital Anatomy by Jonathan D. Wirtschafter, MD, Eric L. Berman, MD, and Carolyn S. McDonald, MD] 7. Cataract Surgery and Intraocular Lenses: A 21st-Century Perspective, second edition Edited by Jerry G. Ford, MD, and Carol L. Karp, MD 8. Surgery of the Eyelid, Orbit, and Lacrimal System Edited by William B. Stewart, MD 9. Surgical Anatomy of the Ocular Adnexa: A Clinical Approach David R. Jordan, MD, and Richard R. Anderson, MD 10. Optic Nerve Disorders, second edition Edited by Lanning B. Kline, MD, and Rod Foroozan, MD 11. Laser Photocoagulation of the Retina and Choroid [with slide set] James C. Folk, MD, and José S. Pulido, MD 12. Low Vision Rehabilitation: Caring for the Whole Person Edited by Donald C. Fletcher, MD 13. Glaucoma Medical Therapy: Principles and Management, second edition Edited by Peter A. Netland, MD, PhD 14. Diabetes and Ocular Disease: Past, Present, and Future Therapies, second edition Edited by Ingrid U. Scott, MD, MPH, Harry W. Flynn, Jr., MD, and William E. Smiddy, MD 15. HIV/AIDS and the Eye: A Global Perspective Emmett T. Cunningham, Jr., MD, and Rubens Belfort, Jr. 16. Corneal Dystrophies and Degenerations: A Molecular Genetics Approach [with CD] Edited by Ming X. Wang, MD, PhD 17. Strabismus Surgery: Basic and Advanced Techniques Edited by David A. Plager, MD; written by Edward G. Buckley, MD, David A. Plager, MD, Michael X. Repka, MD, and M. Edward Wilson, MD; contributions by Marshall M. Parks, MD and Gunter K. von Noorden, MD www.oup.com/us/aao/plager/strabismus 18. A Compendium of Inherited Disorders and the Eye Elias I. Traboulsi, MD www.oup.com/us/aao/traboulsi/genetic

VISUAL FIELDS Examination and Interpretation Third Edition Edited by

Thomas J. Walsh, MD Published by Oxford University Press in cooperation with the American Academy of Ophthalmology

1 2011

1 Oxford University Press, Inc., publishes works that further Oxford University’s objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Tai pei Toronto With ofﬁces in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam

Copyright © 2011 Oxford University Press Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Visual ﬁelds : examination and interpretation / edited by Thomas J. Walsh. — 3rd ed. p. ; cm. — (Ophthalmology monographs ; 3) Includes bibliographical references and index. ISBN 978-0-19-538968-5 1. Perimetry. 2. Visual ﬁelds. I. Walsh, Thomas J. (Thomas Joseph), 1931- II. Series: Ophthalmology monographs ; 3. [DNLM: 1. Perimetry. 2. Eye Diseases—diagnosis. 3. Visual Fields. W1 OP372L v.3 2010 / WW 145 V8343 2010] RE79.P4V58 2010 617.7’15—dc22 2010000009

987654321 Printed in China.

Legal Notice

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he American Academy of Ophthalmology provides the opportunity for material to be presented for educational purposes only. The material represents the approach, ideas, statements, or opinion of the authors, not necessarily the only or best method or procedure in every case, nor the position of the Academy. Unless speciﬁcally stated otherwise, the opinions expressed and statements made by various authors in this monograph reﬂect the authors’ observations and do not imply endorsement by the Academy. The material is not intended to replace a physician’s own judgment or to give speciﬁc advice for case management. The Academy does not endorse any of the products or companies, if any, mentioned in this monograph. Some material on recent developments may include information on drug or device applications that are not considered community standard, that reﬂect indications not included in approved FDA labeling, or that are approved for use only in restricted research settings. This information is provided as education only so physicians may be aware of alternative methods of the practice of medicine, and should not be considered endorsement, promotion, or in any way encouragement to use such applications. The FDA has stated that it is the responsibility of the physician to determine the FDA status of each drug or device he or she wishes to use in clinical practice, and to use these products with appropriate patient consent and in compliance with applicable law. The Academy and Oxford University Press (OUP) do not make any warranties as to the accuracy, adequacy, or completeness of any material presented here, which is provided on an “as is” basis. The Academy and OUP are not liable to anyone for any errors, inaccuracies, or omissions obtained here. The Academy speciﬁcally disclaims any and all liability for injury or other damages of any kind for any and all claims that may arise out of the use of any practice, technique, or drug described

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in any material by any author, whether such claims are asserted by a physician or any other person.

DISCLOSURE STATEMENT Unless otherwise noted below, each author states that he or she has no signiﬁcant ﬁnancial interest or other relationship with the manufacturer of any commercial product discussed in the chapters that he or she contributed to this publication or with the manufacturer of any competing commercial product.

Preface

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he ophthalmologist has many instruments available for examining different parts of the visual system. The slit lamp examines the anterior chamber of the eye. The direct and indirect ophthalmoscopes afford a detailed inspection of the central and peripheral retina. The art of examining the visual ﬁelds is probably the only ophthalmic technique that allows investigation of each and every part of the visual system. The defects that are found must then be interpreted as being in one particular area of the area of the visual system or as being the result of other conditions, such as opacities of the lens or of the media, which point to an organic abnormality in the visual system. It is my experience that although many examinations may be delegated to the ophthalmic technician, it is the ophthalmologist who is experienced in diagnosing ocular disease and therefore the person who should select the visual ﬁeld technique and program that best serve the patient. The reﬁnement of radiographic studies, such as computer tomography (CT) and magnetic resonance imaging (MRI), has permitted the identiﬁcation of discrete lesions in the visual pathway. However, these technologies are not infallible, so that many times no lesion is visualized. It is the experienced physician who puts the clinical picture and ﬁeld abnormality together in one anatomic location: The amount of information that can be seen in a current printout does not always give the answer, so we have to use other, new tests to provide the complete picture. It is the same physician, the ophthalmologist, who has mastered the different parametric techniques to obtain the most accurate information from any ﬁeld examination. The principal impetus behind the current revision of this monograph has been the widespread popularity of computerized perimetry in recent years. The discussion of the major changes in perimetry from the ﬁrst edition of this book as a monograph,

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published in 1990, will continue in this edition. And we will not forget some of the other techniques that have been useful throughout the years and need to be learned by the well-founded perimetrist. In previous editions, we have put the tangent screen illustrations next to the computerized illustrations. In this edition, we have put the tangent screen in the ﬁrst chapter to show that it still can be a valuable technique when computerized ﬁelds cannot be used. Chapter 1 “FIELD OF Vision”, reviews the type of defects that we ﬁnd in doing visual ﬁelds. There is also a review of techniques that preceded automated perimetry and have uses even today in special situations. Chapter 2, “The Anatomic Basis and Differential Diagnosis of Field Defects”, reviews the neurologic signiﬁcance of certain types of ﬁeld defects and identiﬁes the location of the defect along the long visual pathway. Chapter 3, “Essentials of Automated Perimetry,” discusses several programs such as SITA Standard and SITA Fast as well as other programs useful for glaucoma. This is followed by Chapter 4, “Automated Perimetry in Glaucoma,” which demonstrates the usefulness of these new programs in diagnosing and in monitoring progression of the disease. In Chapter 5, “Inherited or Congenital Optic Nerve Diseases,” and Chapter 6, “Acquired Optic Nerve Diseases,” the authors comment on the use of ﬂuorescein, MRI, and OCT in making a diagnosis. Chapter 7, “Visual Field Defects in Chorioretinal Disorders”, shows examples of the use of perimetry as an important adjunct in the management of Retinal disease in this era of OCT and photography. Chapter 8, “Optic Chiasm Field Defects,” discusses the current thoughts regarding Wilbrand’s knee junction scotoma and the ﬁeld defects associated with lesions of the optic chiasm. In “Optic Tract and Lateral Geniculate Body Field Defects,” Chapter 9, radiation was looked at again in terms of the history of congruity. Some new material is also provided about the size of the calcarine cortex and how much of the area is seen in a 24-2 program. There are also new chapters on chorioretinal disease and another on the optic tract. Chapter 10,”Retrogeniculate Visual Field Defects”, is more important in this era of MRI and other radiologic modalities that allow us to identify the type of lesion and its extension. In this era of more sophisticated surgery, radiation and chemotherapy it contributes signiﬁcantly to therapy and not just as a marker.Chapter 11,”Functional Visual Loss,” is one of the most important features of doing ﬁelds. Many people produce a false ﬁeld or do it so poorly as to obscure the real diagnosis. It is important to note that people with functional ﬁelds get sick also and we must be able to perform different techniques in order to get the real answer and provide the correct information to their physician to order the correct test which may be radiologic or from the laboratory. From the laboratory. In the centennial year of 1996, celebrating the founding of the American Academy of Ophthalmology, the publication of the second edition of this book on visual ﬁelds had special signiﬁcance. It was 50 years earlier that the ﬁrst edition of what was then called a manual on this topic was published. My contributors and I are indebted to

Preface

ix

C. Wilbur Rucker, MD, the author of that manual, published in 1946, on which this monograph is based. Dr. Rucker emphasized the importance of doing visual ﬁeld examinations as well as demonstrating some of the techniques for performing them successfully. Many others have contributed to earlier editions, such as the late Thomas Hedges, Jr., who is now followed by his son in this edition. In recent editions of this monograph, we have been helped by perimetrists of this era like Joseph Caprioli and Mark Weitzman, who have given valuable help in the area of glaucoma, as well as Brian Younge: all have added their knowledge and perimetry skills so that their insights can be carried over to this edition. We have also been fortunate in our department at Yale University to have the experience of Bruce Shields and James Tsai, who have added the fruits of their own extensive experience to this complex subject. Jonathan Horton, in the last edition as well as in this one, has contributed advice and illustrative explanations concerning both Wilbrand’s knee in the chiasm and the visual cortex and how it is transcribed into the Humphrey 30-2 and 24-2. One of the sad features of compiling this third edition is the loss of Jonathan Wirtschafter, both as a skilled clinician and a dear friend. He was a giant in the ﬁeld. His chapter in this volume brings together the ﬁeld defects we see in the perimeter printout and shows us their clinical neuro-ophthalmologic application. His original chapter on blending neuroanatomy and perimetry brought increased clarity to the diagnosis of visual ﬁeld disorders and remains a classic in perimetry. Those of us who have followed in his and Traquair’s tradition have endeavored to update and further contribute to the state of the art of perimetry. The updates and techniques outlined in this third edition of the monograph will continue to be valuable to the ophthalmology resident as well as to the practicing ophthalmologist. THOMAS WALSH, MD New Haven, Connecticut

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Contents

Chapter 1.

Contributors A History of Perimetry

xvii xix

Overview of Perimetry

3

Thomas J. Walsh, MD 1-1 Overview of Perimetry 1-1-1 Peripheral Fields 1-1-2 Central Fields 1-1-3 Physiologic Blind Spot 1-1-4 Recording the Fields 1-2 Structure of the Visual Pathway 1-3 Interpretation of Defects in the Fields 1-4 Techniques of Field Testing 1-4-1 Confrontation Technique 1-4-2 Central Field Technique 1-4-3 Chamlin Step Technique 1-4-4 Peripheral Field Technique 1-4-5 Amsler Grid 1-4-6 Color Testing

3 5 6 7 7 12 16 21 21 24 31 34 36 36

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Chapter 2.

Anatomic Basis and Differential Diagnosis of Field Defects

41

Jonathan D. Wirtschafter, MD, and Thomas J. Walsh, MD 2-1 Categories of Field Defects 2-2 Overview of the Visual Pathway 2-2-1 Occipital Lobe 2-3 Monocular Field Defects 2-3-1 Localized Defects 2-3-1-1 2-3-1-2 2-3-1-3 2-3-1-4 2-3-1-5 2-3-1-6 2-3-1-7

Wedge-Shaped Temporal Field Defect Arcuate and Paracentral Field Defects Central Scotoma or Depression Enlarged Physiologic Blind Spot Centrocecal Scotoma or Depression Equatorial Annular Scotoma or Depression Altitudinal Hemianopia

2-3-2 Generalized Defects 2-3-2-1 Generalized Depression or Peripheral Contraction

2-4 Binocular Field Defects 2-4-1 Homonymous Hemianopias 2-4-1-1 Complete: Macular Splitting 2-4-1-2 Incomplete Congruous: Horizontal Sectoranopia 2-4-1-3 Incomplete Congruous: Paramidline-Sparing Vertical Hemianopia 2-4-1-4 Incomplete: Macular Sparing 2-4-1-5 Incomplete: Two Scotomas 2-4-1-6 Incomplete Incongruous 2-4-1-7 Incomplete: Unilateral Sparing of Temporal Crescent 2-4-1-8 Incomplete: Unilateral Defect of Temporal Crescent

2-4-2 Bitemporal Hemianopias 2-4-2-1 Complete 2-4-2-2 With Central Depression, Scotomatous

2-4-3 Binasal Field Defects 2-4-3-1 Complete 2-4-3-2 Incomplete

2-4-4 Altitudinal Field Defects 2-4-4-1 Noncongruous Binocular and Monocular 2-4-4-2 Congruous

2-4-5 Quadrantanopias 2-4-5-1 Superior Homonymous, Incomplete 2-4-5-2 Inferior Homonymous, Complete

2-4-6 Bilateral Central Field Defects 2-4-6-1 Scotoma or Depression

2-4-7 Bilateral Peripheral Field Defects 2-4-7-1 Generalized Depression or Peripheral Contraction

2-4-8 Bilateral Checkerboard Scotomas 2-4-9 Bilateral Homonymous Hemianopias 2-5 Junctional Field Defects 2-5-1 Complete Monocular Plus Incomplete Contralateral Ocular 2-5-2 Homonymous Hemianopia Plus 2-5-3 Bitemporal Hemianopia Plus

41 43 46 48 48 48 52 54 56 57 58 59 59 59 60 60 60 62 63 64 64 65 66 67 67 67 69 70 70 71 72 72 73 75 75 76 77 77 78 78 79 80 80 80 81 83

Contents

Chapter 3.

Essentials of Automated Perimetry

xiii 85

George Shafranov, MD 3-1 Introduction 3-2 Historical Overview 3-3 Principles of Field Testing 3-3-1 Kinetic Perimetry 3-3-2 Static Perimetry 3-3-2-1 Suprathreshold Techniques 3-3-2-2 Threshold Techniques

3-3-3 Frequency-of-Seeing Curves and Fluctuations 3-4 Test Selection and Algorithms 3-4-1 Swedish Interactive Threshold Algorithm (SITA) 3-4-2 Foveal Threshold 3-4-3 Initial Values 3-4-4 Fixation Monitoring 3-4-5 Threshold Testing 3-5 Single Test Printout 3-5-1 Test Selection (and General Information) 3-5-2 Reliability Indices 3-5-3 Numeric Results and Grayscale Results (Raw Data) 3-5-4 Total Deviation 3-5-5 Pattern Deviation 3-5-6 Glaucoma Hemiﬁeld Test 3-5-7 Global Indices 3-6 Custom Tests 3-6-1 Grid Size 3-6-4 FASTPAC 3-6-5 Programs 30-1 and 24-1 3-6-6 Program 10-2 and Macula Test 3-6-7 Peripheral 60 and 60-4 Program 3-6-8 Nasal Step Program 3-6-9 Stimulus Size Option 3-7 Follow-up Printout 3-7-1 Overview Printout 3-7-2 Change Analysis Printout 3-7-3 Glaucoma Progression Analysis Printout 3-7-4 GPA-Guided Progression Analysis 3-8 Visual Function Speciﬁc Perimetric Technologies 3-8-1 Short-Wavelength Automated Perimetry (SWAP) 3-8-2 Frequency Doubling Perimetry 3-8-3 High-Pass Resolution Perimetry 3-8-4 Tendency-Oriented Perimetry 3-9 Learning Effect and Artifacts 3-9-1 Miosis and Mydriasis 3-9-2 Media Opacities 3-9-3 Eyelid and Nose Effects 3-9-4 Refractive Errors 3-9-5 Corrective Lens/Frame Artifacts 3-10 Role of the Visual Field Technician

85 85 86 88 90 90 92 92 94 94 95 95 96 99 99 99 99 101 101 101 102 105 105 108 108 109 109 110 110 111 111 111 111 114 114 114 117 117 117 118 118 118 119 119 119 120 121

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Chapter 4.

Automated Perimetry in Glaucoma

127

Hylton R. Mayer, MD, Marc L. Weitzman, MD, and Joseph Caprioli, MD 4-1 4-2 4-3 4-4

Introduction Glaucomatous Field Loss Automated Perimetry Options Evaluation of a Single Test 4-4-1 Patient Reliability 4-4-1-1 4-4-1-2 4-4-1-3 4-4-1-4 4-4-1-5 4-4-1-6

Test Duration Fixation Losses False-Positive Responses False-Negative Responses Short-Term Fluctuation Stimuli Number

4-4-2 Criteria for Abnormality 4-4-3 Staging of Field Loss 4-4-4 Test Selection 4-4-5 Follow-up of Advanced Field Loss 4-5 Evaluation of a Series of Tests 4-5-1 Baseline Establishment 4-5-2 Nature of Progression 4-5-3 Artifacts 4-5-4 Long-Term Fluctuation 4-5-5 Criteria for Progression 4-5-6 Glaucoma Progression Analysis 4-5-7 Trend Analysis 4-5-8 Follow-up of Central Abnormalities 4-6 Future of Automated Perimetry 4-6-1 Altered Stimuli 4-6-1-1 4-6-1-2 4-6-1-3 4-6-1-4 4-6-1-5 4-6-1-6 4-6-1-7

Short-Wavelength Automated Perimetry Frequency-Doubling Technology Flicker Perimetry Ring Perimetry Motion Automated Perimetry Pattern-Discrimination Perimetry Color Perimetry

4-6-2 Altered Strategies 4-6-3 Interpretive Aids

Chapter 5.

Inherited or Congenital Optic Nerve Diseases

127 127 129 132 132 133 133 133 136 136 136 140 143 144 144 144 146 149 149 154 155 157 159 159 161 161 161 165 165 167 168 168 168 169 171 177

Peter A. Quiros, MD, Carlos Filipe Chicani, MD, PhD, and Alfredo A. Sadun, MD, PhD 5-1 Introduction 5-2 Congenital Optic Disc Anomalies 5-2-1 Aplasias and Dysplasias 5-2-2 Optic Nerve Colobomas and Pits 5-2-3 Anomalous Disc Elevations: Pseudopapilledema With or Without Hyaline Bodies (Drusen) 5-2-4 Tilted Disc and Crescents

177 177 177 179 181 181

Contents

Chapter 6.

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5-3 Heredodegenerative Optic Atrophies 5-3-1 Leber’s Hereditary Optic Neuropathy 5-3-2 Dominant Optic Atrophy 5-3-3 Recessive Optic Atrophy

182 183 185 189

Acquired Optic Nerve Diseases

193

Carlos Filipe Chicani, MD, PhD, Peter A. Quiros, MD, and Alfredo A. Sadun, MD, PhD

Chapter 7.

6-1 Introduction 6-2 Optic Neuritis 6-3 Ischemic Optic Neuropathy 6-3-1 Nonarteritic Ischemic Optic Neuropathy 6-3-2 Arteritic Ischemic Optic Neuropathy 6-4 Metabolic Optic Neuropathies 6-5 Compressive Optic Neuropathy 6-6 Papilledema

193 194 196 196 196 198 198 200

Visual Field Defects in Chorioretinal Disorders

207

Ron A. Adelman, MD, MPH, FACS, and Patricia Pahk, MD 7-1 7-2 7-3 7-4 7-5 7-6 7-7

Chapter 8.

Introduction Macular Diseases Vascular Diseases Congenital and Genetic Diseases Inﬂammatory/Infectious Diseases Toxicity Peripheral Retina

Optic Chiasm Field Defects

207 207 209 211 217 226 226 233

Christine E. Lin, and Jeffrey G. Odel, MD 8-1 History and Overview 8-2 Anatomy of the Chiasm 8-2-1 Gross Anatomy 8-2-2 Nerve Fiber Anatomy 8-3 Tests for Field Defects 8-4 Chiasmal Visual Field Defects 8-5 Chiasmal Region Lesions 8-5-1 Common Lesions Affecting the Optic Chiasm 8-5-2 Pituitary Tumors 8-5-3 Meningiomas 8-5-3-1 Suprasellar Meningiomas 8-5-3-2 Suprachiasmatic Meningiomas 8-5-3-3 Parasellar Meningiomas

8-5-4 Craniopharyngiomas 8-5-5 Aneurysms 8-5-6 Dilatation of Third Ventricle 8-5-7 Miscellaneous Lesions 8-6 Pseudo Temporal and Bitemporal Hemianopia

233 234 234 236 240 241 247 247 247 248 248 249 249 249 249 250 250 250

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Contents

Chapter 9.

Optic Tract and Lateral Geniculate Body Field Defects

253

Thomas R. Hedges III, MD 9-1 Optic Tract Field Defects 9-2 Lateral Geniculate Body Field Defects

Chapter 10. Retrogeniculate Visual Field Defects

253 258 263

Thomas R. Hedges III, MD 10-1 Testing for Reticulogeniculate Visual Field Defects 10-2 Localization and Congruity of Optic Radiation and Calcarine Cortex Visual Field Defects 10-3 Temporal Lobe Field Defects 10-4 Parietal Lobe Field Defects 10-5 Occipital Lobe Field Defects 10-5-1 Types of Occipital Cortex Field Defects 10-5-2 Field Defects Unique to the Occipital Cortex 10-5-3 Color Field Defects in the Occipital Lobe

Chapter 11. Functional Visual Loss.

263 264 267 269 272 273 282 285 293

Thomas J. Walsh, MD 11-1 Types of Patients 11-2 Types of Field Loss 11-3 Tests for Functional Field Loss

293 294 295

Index

299

Contributors

Ron A. Adelman, MD, MPH, FACS

Peter A. Quiros, MD

Yale University

Doheny Eye Institute

Joseph Caprioli, MD

Alfredo A. Sadun, MD, PhD

Jules Stein UCLA School of Medicine

Doheny Eye Institute

Carlos Filipe Chicani, MD, PhD

George Shafranov, MD

Doheny Eye Institute

Yale University

Thomas R. Hedges III, MD

Thomas J. Walsh, MD

Tufts University Medical School

Yale University

Christine E. Lin

Marc L. Weitzman, MD Assistant Clinical Professor Yale University School of Medicine

Columbia University

Hylton R. Mayer, MD Yale University

Jonathan D. Wirtschafter, MD

Jeffrey G. Odel, MD

University of Minnesota School of Medicine

Columbia University

Patricia Pahk, MD Mount Sinai Medical Center

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A History of Perimetry THOMAS J. WALSH, MD

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he history of perimetry is the history of anatomy. In the early days of perimetry, in the late 1800s, the study of anatomy involved learning the muscles, vessels, and bony structures of the body. The brain was recognized as an organ, but the special functions of its different structures were generally unknown. Before the availability of current methods to study the brain—including those based on histology, electron microscopy, and electrophysiology and magnetic resonance imaging, magnetic resonance angiography, computed tomography, computed tomography angiography, optical coherence tomography, and positron emission tomography—our predecessors used their observations of visual functions to devise a technique to examine those functions: this technique is called perimetry. Just as the ﬁeld of anatomy has been dynamic, so has the development of techniques in perimetry. With the advent of more sophisticated techniques, we have been able to diagnose diseases earlier and treat them more successfully. However, some of the older techniques can still be used when sophisticated techniques do not work, especially in neuro-ophthalmology. Perimetric techniques are as variable as are the patients and the diseases that are treated. Although most of this monograph is directed at computerized perimetry, techniques such as confrontation and the tangent screen are also discussed. Just as the range of defects varies, so, too, must the range of different techniques mark the ability of an accomplished perimetrist. As newer techniques and newer computerized programs come online, updating the sophistication of perimetry, so, too, should the perimetrist continually hone his or her skills. The contributors to this monograph are humbled by the giant steps in the development of perimetry made by the observations and ingenuity of those who have preceded us. In this chapter, we present the contributions and persons who are important to the history of our understanding of perimetry. The Imaging and Perimetry Society (formerly the International Perimetric Society)1 has added to our knowledge of those who have gone before us, including a history of perimetry by Thompson

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A History of Perimetry

and Wall (see http://www.perimetry.org/PerimetryHistory/index.htm). We are also indebted to Drs. Simpson and Crompton for their exhaustive work on those who have advanced the ﬁeld of perimetry.2 They searched in many a medical library and resurrected almost-forgotten dusty manuscripts. Among their sources is a library that I have relied on in the past and have been fortunate to have virtually at my doorstep—the Harvey Cushing/John Hay Whitney Medical Library of Yale University’s School of Medicine, which I used extensively in developing this review. This library has a long distinguished history and has played an important role in the history of perimetry. The name of the library honors Dr. Cushing,3 whose lifelong interest in surgery for pituitary disease was as keen as his observation of visual defects. In this, he was helped by Dr. Clifford Walker, who worked in his clinic and conducted perimetric examinations. Dr. Cushing and Dr. Eisenhardt, in their studies of the optic chiasm in 1926, took exception to Wilbrand’s theory of the location of the inferior nasal optic ﬁbers as the ﬁbers crossed through the chiasm. This issue was elaborated on by Jonathan Horton4 in 1997 and is discussed further in Chapter XX. Determining who was ﬁrst to make observations in diagnoses based on perimetry is difﬁcult. The technique of confrontation was probably used much earlier, but late in the 1800s, William Gowers popularized it as a ﬁeld method.5 In many cases, the phenomenon of a particular defect was observed by one and its anatomic signiﬁcance was observed by another. Hippocrates was probably the ﬁrst to describe hemianopia, in the ﬁfth century BC. It was Ptolemy, around 150 BC, who started to quantify the size of the peripheral ﬁeld.6 Leonardo da Vinci in 1510 also studied this and reported that the temporal ﬁeld was 90°. This was an important observation, as we will see, with future study changing ﬁeld testing from a ﬂat screen to an arc perimeter, which, of course, does not diminish the importance of Hippocrates’ observations. Issac Newton made the observation of a partial decussation of the chiasm in 1602,7,8 which Dr. Johann Spuryheim conﬁrmed in 1820.9 In 1664, Thomas Willis published his work on the functional anatomy of the brain and reafﬁrmed the crossing of ﬁbers in the chiasm.10 William Wollaston, in 1824, described a case of left homonymous hemianopia11: the patient was himself. The defect cleared, but it was followed by another homonymous hemianopia on the right, which was due to a tumor and which did not clear. He realized each time that the defect concerned only one half of each eye and that the ﬁbers from the eye decussated. Albrecht von Graefe’s name is prominent in many areas of ophthalmology, including perimetry, ophthalmoscopy, and surgery.12 His friend Hermann von Helmholtz had perfected the ﬁrst ophthalmoscope but was not impressed with its clinical use. It was von Graefe who introduced this instrument at the German Physical Society. He fell in love with the instrument and used it to make many observations throughout his life. He observed papilledema about 1850 and noted in his ﬁrst report of that phenomenon that it was seen in cases of increased intracranial pressure from brain tumors and declared that a way of making such a diagnosis should be quantiﬁed. Some others, such as Ulmus of Padua in 1602, illustrated a visual ﬁeld he had observed. In 1856, von Graefe then described a clinical technique to measure this phenomenon. He produced a board with a ﬁxation object and

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with peripheral distances marked off (which he called isopters) so that he could reproduce these defects in the future. This was the beginning of the current tangent screen. Although the technique was a major step forward, there were those who could see the potential for perfecting this technique and immediately improved upon it. The ﬂat screen was adequate for the central ﬁeld but not for the peripheral ﬁeld, which has been described as reaching 90° by da Vinci and again by Thomas Young in 1801 and Johannes Purkinje in 1825. In 1817, Joseph Bier in Vienna was studying the central ﬁeld concept and identiﬁed defects such as central scotoma, paracentral scotoma, and central contraction. Richard Foster in 1860 constructed an arc-type perimeter to cover the peripheral ﬁeld, but it was of no use for diagnosing a central scotoma. Schweiger then produced a patient hand-held arc-type perimeter, but it was not better and it was very cumbersome. In 1889, Jannick Bjerrum became very interested in the tangent type of technique and constructed a revised one on his ofﬁce door. He standardized it so that a defect could be reproduced. Later, others added different-sized test objects to make the more subtle defects identiﬁable. Behrens thought that the ﬂat test objects were inaccurate because the test object could move from the center of the visual ﬁeld, so he devised a set of test objects in the form of balls. The test objects would then cast the same size image on the retina regardless of where they were projected in the ﬁeld. However, these were always visible and could not be “turned off” from the patient’s perception. Perimetry was developing a following, and in 1874, a book on perimetry was written by William Schon.13 Published 1874Schon worked with Dr. Horner of Zurich, renowned for his study of the pupil. Hermann Munk in 1887 performed experiments on dogs, ﬁrst ablating one half of the occipital lobe and demonstrating hemianopia in each eye. Then he performed a similar experiment in another dog, on the other side of the lobe, demonstrating reverse hemianopia. This location of different types of defectc brings us to interest in decussation of the chiasm. Dr. Edward Schafer performed the same experiment as Horner’s in monkeys and achieved the same result. However, he added another observation to our fund of knowledge. He saw that there was a difference between an occipital hemianopia and one in the tract. Optic tract A tract hemianopia would have a hemianopic pupillary abnormality, which had been observed previously by Wernicke. There would not be a pupillary response in the blind ﬁeld of a tract hemianopia. Although this is an established fact, the defect is a difﬁcult clinical sign to elicit. By the end of the 1800s, interest in perimetry was well established. Dr. Salomon Eberhard Henschen identiﬁed the location of the visual ﬁbers on the medial surface of the occipital lobe and that occipital cortical location was the same for the retinal ﬁeld location. Adolph Meyer reported in 1907 the course of the visual ﬁbers from the lateral geniculate body. He reported that the lower visual ﬁbers did not return directly through the temporal lobe.14 They went anteriorly into the temporal lobe and fanned out before they turned posteriorly along the course of the lateral ventricle. He also noted that they did not reach into the most anterior part of the temporal lobe. This information had neurosurgical as well as perimetric implications. In the 1950s, Falconer and Wendland were performing temporal lobectomy on patients

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with epilepsy.15,16 As part of that operation, meticulous measurements were made from the tip of the temporal lobe to the area resected, and a correlation was made as to how much of a ﬁeld defect was created. Up to 5 cm from the temporal tip could be resected before any ﬁeld defect was created. Because of their work, surgery for epilepsy is done differently today, resultng in fewer ﬁeld defects and better therapeutic results in most patients. That their results were truly anatomic rather than only perimetric conﬁrmed the statement made earlier by Traquair in 1933 that hemianopias in that area are congruous. Some authors disagree with that proposition, so recently Kedar and colleagues17 raised the question again. This is discussed in the chapter on The radiations radiation. That is what it is called and that author is Thomas Hedges It is title of tracts from the temporal, parietal and occitpital lobes. Many physicians have looked at ﬁeld defects in the radiations and have noted other ﬁndings seen with different deﬁcits. Purkinje noted one of these phenomena while watching a parade in Vienna.18 He noted that the people across from him all had horizontal nystagmus as the lines of soldiers moved past. Then, later in his clinic, he noted abnormalities in one direction and not in the other in persons with hemianopia. He thought that this might be a new way to diagnose hemianopia in nonverbal patients, but this was not found to be valid in all patients with hemianopia. Ohms corrected this theory and localized the hemianopia to the deep parietal lobe. As terrible as war is in terms of human sacriﬁce and suffering, it sometimes results in new methods of treatment by caring and bright physicians. During the early twentieth century, Dr. Tatsusi Inouye examined soldiers with head wounds and eye complaints during the Russo-Japanese war.19 He used an arc perimeter for his observations and recorded the tract of the wounds and the type of ﬁeld defect that would suggest the cortical location of those wounds. During World War I, Gordon Holmes, together with Chief British Army Ophthalmologist Lister, used a hand-held perimeter to conﬁrm previous work showing that the upper calcarine cortex corresponded to the upper part of the retina and that similar correspondences held for other parts of the calcarine cortex. He also supplied evidence that acuity is spared even if an entire occipital lobe is removed. However, he did not support the theory that the macula is duplicated in both occipital lobes. Then, in World War II, the neurologist John Spalding studied 180 cases of missile wounds with defects limited to the posterior radiations and occipital cortex and conﬁrmed the work of Holmes.20 Holmes created a map of the defects occurring in the occipital cortex. He allowed about 25% of the striate surface to represent central vision. Jonathan Horton and William Hoyt enlarged the ﬁeld map, showing a much larger area for the macula.21 They also proposed that a 30–2 ﬁeld would cover 89% of the ﬁeld and would be adequate except for cases of central and peripheral defects that did not involve the monocular temporal crescent. The arc perimeter had its supporters, and when I started performing perimetry, the Aimark perimeter was very popular. However, another perimeter was to take its place. In 1945, Dr. Hans Goldmann of Bern had devised a projection perimeter that took the shape of a bowl and that provided a way to change the stimulus. This again changed the way perimetry is performed. However, it was inadequate

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for static perimetry. The value of static perimetry was pointed out in 1933 by Dr. Louise Sloan, but it did not gain ready acceptance. The next development was the Tübingen perimeter in 1959, and then in 1971 Stephen Drance and Mansour Armaly introduced suprathreshold testing.22 Dr. William Hart, Jr. developed the ﬁrst perimeter to measure color contrast. Then Lars Frisén developed a technique of high-pass resolution, leading to the Octopus and Humphrey perimeters that are so familiar today and that are now equipped with software programs that make the test even more user-friendly. In 1951, Max Chamlin pointed out the signiﬁcance of a step defect at the vertical meridian, suggesting an early sign of a ﬁeld defect such as a bitemporal defect that might otherwise not have been seriously considered. This advance was achieved with just a tangent screen, but it can be performed with a Goldmann perimeter as well. Harrington then published his text on perimetry, which represented the state of the art at that time. Wilber Rucker in 194623 also began to publish his studies on perimetry under the auspices of the American Academy of Ophthalmology (AAO). We are continuing that tradition today with this book in the Ophthalmology Monographs series published by Oxford University Press in cooperation with the AAO. Rucker also provided an in-depth review of the history of the semidecussation of the optic nerves. Rucker,C W The concept of a semidecussation at the chiasm. Arch. Ophthalmol 1958:59: 159–171. Here we sought to give the reader an idea of how many people it takes to make an idea evolve. This is true in all branches of medicine. New testing techniques will continue to be developed in the future, and those physicians who succeed us will look back at us just as we are looking back at those practitioners who were using A confrontation technique. Although we look to computerized perimetry as the technique of choice, a good perimetrist must learn other techniques, such as confrontation and the tangent screen, because they are still very useful when computer-based techniques are not appropriate. If a patient cannot be examined adequately with the use of a computer program, a well-executed tangent screen test may be the answer. The reader can see from this short historical glimpse that this is a very dynamic area and that advances are still occurring. The perimetrists mentioned in this review put us on our current path as we await the next developments in the ﬁeld.

REFERENCES 1. Imaging and Perimetry Society. 2010. webeye.ophth.uiowa.edu; http://www.perimetry. org/. 2. Simpson DA, Crompton JL. The visual ﬁeld: An interdisciplinary history, 1. The evolution of knowledge. J Clin Neurosci. 2008;Feb:579–609. 3. Cushing H. Selected Papers in Neurosurgery. New Haven, Conn: Yale University Press; 1969. 4. Horton JC. Wilbrand’s knee of the primate optic chiasm is an artefact of monocular enucleation. Trans Am Ophthalmol Soc. 1997:579–609. 5. Gower WR. A Manual and Atlas of Medical Ophthalmoscopy. 2nd ed. London, England: Churchill; 1882:57–61. 6. Heitz R. The history of contact lenses. 2003;1:50.

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7. Brester D. Memories of the Life, Writing and Discoveries of Sir Isaac Newton. Vol 2. Edinburgh, UK: 1855. 8. Newton I. Opticks: Or a Treatise of the Reﬂextions, Refraction and Colours of Light. New York: McGraw-Hill; 1931. 9. Spuryheim G. The Anatomy of the Brain, With a General View of the Nervous System. TR Willis, London, England: Highly, 1826. 10. Willis T. The anatomy of the brain and nerves. In: Feindel W, ed. Classics of Neurology and Neurosurgery. Trans. by Pordage S. Facsimile 1st English ed. 1681. Birmingham: 1983:63. 11. Wollaston WH. On semi-decussation of the optic nerves. Phil Trans R Soc Lond. 1824;114:222–231. 12. von Graefe A. Ueber die unterschung des Gesechtsfeldes bei amblyopischen affectionen. Graefes Arch Ophthalmol. 1856;2:255–298. 13. Ferrier D. Munk on localization of function of the brain. Rev Brain. 1878;1:229–231. 14. Meyer A. The connections of the occipital lobes and the present status of the cerebral visual affections. Trans Assoc Am Phys. 1907;22:7–15. 15. Falconer MA. Visual ﬁeld changes following anterior temporal lobectomy. Brain. 1958;81:1–14. 16. Windland JP. Visual ﬁeld studies after temporal lobectomy for epilepsy. Arch Ophthalmol. 1960;64:195–200. 17. Kedar S, Zhang X, et al. Congruity in homonymous hemianopia. Am J Ophthalmol. 2007;143:856–858. 18. Smith JL. Optokinetic Nystagmus. Springﬁeld, Ill: Charles C Thomas; 1963:3–4. 19. Inouye T. Visual disturbances following gunshot wounds of the cortical visual area based on observations of the wounded in the recent Japanese war. Brain. 2000;spec suppl:123. 20. Spalding J. Wounds of the visual pathway, 1. The striate cortex. J Neurol Neurosurg Psychiatr. 1952;15:169–183. 21. Horton J, Hoyt W. The representation of the visual ﬁeld in human striate cortex. Arch Ophthalmol. 1991;109:816–824. 22. Armaly M. Selective perimetry for glaucomatosis defects in ocular hypertension. Arch Ophthalmol. 1972;87:518–524. 23. Rucker W. The concept of a semidecussation of the optic nerves. Arch Ophthalmol. 1958;59:159–171.

Visual Fields

Visual Fields

1 Overview of Perimetry THOMAS J. WALSH, MD

1-1 OVERVIEW OF PERIMETRY Like a painter, the practitioner of perimetry must learn his or her profession from experience. Just as a painting does not spring from the paint and brushes alone, the perimetrist does get his or her diagnosis from just a printout of the ﬁeld test. Rather, the perimetrist’s experience in interpreting ﬁeld test results, his clinical skill in examining the validity of the patient’s performance, and his selection of the needed ﬁeld technique chosen under the appropriate clinical circumstances combine to produce a suitable test and interpretation of results. In this age of computerization, we tend to accept the infallibility of perimetry. It is true that new developments have corrected some of the errors in technique that have been troubling in earlier methods such as the tangent screen and Goldmann perimeter. However, in our rush to embrace these new techniques, we might forget that there is still a place for these older techniques in selected cases. Among other things, these older techniques may allow for a human element to be introduced when the patient is overwhelmed by technology—that is, a well-performed tangent screen is more valuable on a given occasion than a poorly performed computerized ﬁeld examination. Such circumstances occur almost always with neuro-ophthalmology patients, who are usually ill in other ways than just visually and need more help in performing the test. Most other patients, particularly those with glaucoma, are much more reliable in their responses in using the newer techniques. They frequently start testing at a younger age and do their testing frequently so they become skilled at performing the test. Many neuro-ophthalmologic patients do not have that experience.

3

4

Visual Fields

Interpreting the blind spot remains a standard part of any ﬁeld examination. Interpreting the blind spot size requires experience. The blind spot may be enlarged because the patient is a slow responder or because a large myopic crescent is present. An important use of measuring the blind spot is to show the patient what a scotoma is and to test his validity of ﬁxation by putting the target in the blind spot from time to time. A cataract causes contraction of the peripheral ﬁeld. Miosis due to the use of miotics and a small cataract can cause different defects that suggest a worsening of the patient’s glaucoma, which may be fallacious. In kinetic testing, if the examiner moves the test object too quickly, the sensitivity is altered and a defect is missed. If the kinetic test object is moved too slowly, the patient becomes distracted and loses ﬁxation. (These problems are somewhat obviated by the use of computerized testing machines.) There are many different programs from which to select depending on the defect being sought and the patient’s ﬁeld testing history and defects. The selection of the most ideal program to produce a good review of both central and peripheral ﬁelds was reviewed by Horton and Hoyt1 on an anatomic basis. They believe that a 30-2 program meets the requirements for central and peripheral ﬁeld evaluation, except for monocular temporal crescent syndrome. Another variable in testing may be which eye to test ﬁrst. If this is a patient’s ﬁrst time with ﬁeld testing, then the eye with better vision eye should be tested ﬁrst to give the patient experience. If the patient has performed the test previously, then perhaps the worse eye should be tested ﬁrst while the patient is fresh. All of these considerations are part of the performance and evaluation of ﬁeld testing. Interpretation of the ﬁelds of vision forms a key part of ophthalmic and neurologic examinations. If the visual ﬁeld is not intact, something is wrong in the retina or in the visual pathway—a bundle of nerve ﬁbers that extends from the eyes, across the entire lower portion of the brain, to the visual centers of the occipital lobes. Not only will a ﬁeld defect reveal almost any disease process occurring in the region, it can also help locate the site of the lesion. When lesions interrupt various parts of the visual pathway, they cause speciﬁc types of ﬁeld defects; the nature of the defect frequently helps pinpoint the location of the lesion. The function of perimetry is to indicate the site and the extent of involvement of the visual pathway. For purposes of clinical perimetry, the ﬁeld of vision is usually regarded as the inner surface of part of a hemisphere. On this hemisphere, the level of vision is determined from the point of ﬁxation of gaze by the use of targets of various sizes and colors. A line, or an isopter, is drawn on the chart of the visual ﬁeld to represent the limit of the area within which a speciﬁc target can be recognized. The chart of the visual ﬁeld usually contains several concentric isopters, one for each target. This is best demonstrated in the Goldman perimeter. Now with computerized printouts, grayscale and numeric readouts in decibels are used to demonstrate the location and density of the defect. The Snellen acuity charts evaluate the foveal part of the visual ﬁeld. The remainder of the ﬁeld cannot be evaluated as easily as the central vision is evaluated with the Snellen chart. However, a 20/20 Snellen report does not rule out a paracentral scotoma, which may be the cause of the patient’s complaint about their reading.

Overview of Perimetry

5

We do not have a Snellen system as such for the rest of the ﬁeld, nor does every part of the ﬁeld have the same sensitivity as other parts. The ability to just see a certain test object is called the threshold for that area of the ﬁeld. Field testing is unlike Snellen testing, which is the same from person to person. However, the lightsensitivity threshold for given degrees away from ﬁxation has been established in all four quadrants until the outside limits of the island of vision have been reached. More details on this subject are explored in Chapter 3. Moving a test object of the same size and brightness from a nonseeing to a seeing area is called kinetic perimetry. If instead a stationary test object that increases in brightness until the patient sees it is used, this method is called static perimetry. Static suprathreshold testing uses a single test object that is above the expected threshold for that part of the ﬁeld. The threshold for a kinetic test object is lower than that of a static test object. This ﬁnding is consistent with the work of Riddoch,2 who found that moving objects are seen sooner than are stationary areas in a patient recovering from an occipital lobe lesion. There are many ways to evaluate the visual system. The tangent screen is the traditional way of examining the central ﬁelds. The recording of distant and near acuities, color vision, and fusion testing, as well as the dazzle test and pupillary responses, all primarily evaluate the macular area. It is equally important to evaluate the peripheral ﬁeld, which can be regarded as an extension of macular vision. Too often, physicians make the mistake of assuming that a good central acuity obviates the need for doing a central ﬁeld. Patients with glaucoma defects, however, expose that error. Good perimetrists learn many techniques, both gross and sophisticated, for examining each area of ﬁeld. They choose the type of test for the speciﬁc areas where a defect is most likely to occur, based on the patient’s history, state of alertness, and ability to communicate. The mark of good perimetrists is not that they can conduct one type of ﬁeld test superbly but rather that they can evaluate the individual patient well and select the appropriate ﬁeld technique for that patient. Most of this monograph will deal with computerized perimetry, which is used in the overwhelming number of patients. I believe it is important in this introduction to point out the usefulness of these techniques when the occasion presents itself. Examples of these techniques are shown for comparison in different sections of this monograph.

1-1-1 Peripheral Fields. The peripheral portions of the ﬁeld are explored on a perimeter with the aid of an arc that can be turned in any desired meridian and that is marked from 0° to 90°. One technique requires that a white test object 3 mm in diameter outside an area of seeing be carried from the point of ﬁxation along the arc until it disappears from view and then is returned to the seeing ﬁeld. The point at which the test object reappears is recorded as the edge of the ﬁeld for a test object of that size. Larger targets are used if the patient is not able to see well enough to permit use of the 3-mm test object or if there is a dense defect in the ﬁeld. At least 12 radii of each ﬁeld should be investigated. It is not sufﬁcient to determine merely the peripheral limits of the ﬁeld; the interior part of the ﬁeld should also be

6

Visual Fields

evaluated, using a tangent screen or a sophisticated ﬁeld-testing instrument such as a Goldmann or computerized perimeter. The central ﬁeld itself must be searched for defective or depressed areas, known as scotomas. The temporal ﬁeld constricts with age after the sixth decade of life. This constriction may be due partly to age-related miosis but is more probably due to decreased oxygenation of the peripheral retina with age. Oxygen concentration has been reduced experimentally during ﬁeld measurements. Peripheral loss was reported by dive-bomber pilots during World War II; they noticed peripheral loss as they went into power dives and increased the G forces, reducing the oxygenation of the head.

1-1-2 Central Fields. Different sizes and intensities in test objects are necessary to evaluate the actual density in limits of any ﬁeld defect. The use of the smallest or most sensitive test objects is necessary to outline the outside limits of the defect. The largest and brightest test object outlines a ﬁeld defect that is still demonstrable. If a larger or brighter test object is used, no defect is found. This later isopter is necessary because it is least sensitive and is the ﬁrst to vary as a ﬁeld defect improves. Thus, this isopter is useful for monitoring improvement. Vascular lesions generally have steep margins to the defect. In those cases, the outside limits of the defect are almost the same as the most and the least sensitive test objects. Tumors usually have relative defects. The central portion, which is denser at the site of the disease process, is surrounded by an edematous area that represents a variable defect in the ﬁeld. These statements about vascular lesions and tumors are good general rules of thumb, but they are not absolute. Some vascular lesions can be total infarctions with absolute defects or have areas of surrounding edema and cause relative defects in the outside isopters. Some tumors can present with dense defects when the tumor encroaches on a vascular supply. It can be very difﬁcult to outline a central scotoma when the acuity is minimally decreased. Retinal sensitivity can decrease from 20/20 to 20/40 by moving the test object only 2.5° from the fovea. To explore the central area of the visual ﬁeld in detail, the perimeter offers such a short working distance that the usual test objects are too small for practical handling. The accepted solution is an instrument such as a Goldmann or computerized perimeter, which permits exploration of the ﬁeld out to 30° and allows one to perform central ﬁeld testing at 0.33 m rather than at 1 or 2 m, which is required for a tangent screen. The tangent screen, on the other hand, allows personal contact with the patient, which aids in judging the quality of responses. Black felt is generally used to cover the screen. As exploration of the ﬁeld progresses, the various isopters can be drawn directly on the felt with a dark-colored pencil and readily brushed off. This manner of recording has supplanted the use of black-headed pins and will be described later in this chapter. According to Chamlin and Davidoff,3,4 a 1-mm white test object should be visible over most of the screen at 1 m (except at the physiologic blind spot) if there is no visual ﬁeld defect present. This, however, is not always the case, particularly if it is a patient’s ﬁrst ﬁeld test or if a patient’s level of consciousness is depressed (with such patients, I frequently use a 2- or 3-mm white test object). In patients with glaucoma who are well otherwise and have their ﬁelds tested repeatedly, however,

Overview of Perimetry

7

the 1-mm white test object is more valuable for discovering the most subtle defects. After a defect is discovered and charted with a small target, it is explored with larger targets, which may be white test objects fastened to the ends of dull-black wands. The largest target made to disappear indicates the density of the defect. It should be noted that when central vision is greatly reduced, ﬁxation is frequently unsatisfactory. This difﬁculty can be alleviated by using a pair of crossing lines or a circle of adequate size as a ﬁxation target and asking the patient to look at its center, even if the patient cannot see anything in the center. Exploration of the visual ﬁeld with white targets of various sizes is known as quantitative perimetry. The use of colored targets, or qualitative perimetry, is of value in distinguishing disturbance of the percipient elements of the retina from interruption of conduction ﬁbers. Colored test objects are also of value in eliciting and mapping scotomas in the central portion of the ﬁeld. Charting the ﬁelds in a dim light exaggerates all relative defects, especially those resulting from implication of the rods and cones.5,6 (Various uses of colored test objects and their speciﬁc applications are ampliﬁed throughout this monograph, especially in Chapters 7 & 10.)7 this is for a reference.

1-1-3 Physiologic Blind Spot. Plotting the physiologic blind spot early in the course of the examination will make patients aware of the possibility of other blind areas, as well as help them understand what is expected of them. Demonstrating a physiologic scotoma to patients early in the ﬁeld examination will help their ﬁxation when a pathologic scotoma is found. The cause of enlargement of the blind spot as a sign of papilledema has been debated since the time of Knapp’s description.8 Retinal displacement and retinal elevation of percipient elements 9,10 and the Stiles-Crawford effect11 are three of the more traditional explanations. More recently, reports suggesting a relative scotoma on the basis of induced hyperopia were suggested by Dailey et al.12 and Corbett et al.13 The theory is that edematous elevations of the percipient elements away from the blood supply of the choriocapillaris result in a decrease in sensitivity.14 As pointed out by Corbett et al.,13 a purely mechanical displacement of the retinal percipient elements would produce an absolute, not a relative, scotoma. A relative scotoma is the defect produced by papilledema.15 This may not be true if the disc edema is due to another cause such as ischemic optic neuritis, in which the retinal or optic nerve tissues have some additional insult that alters their function. Corbett et al.13 found that in most cases the scotoma could be reduced by using plus lenses. There is previous experience to support their refractive theory as a cause of ﬁeld defects, as reported by Young et al.16 in their cases of patients with tilted discs. In the tilted disc, there is a bitemporal hemianopia, which can be reduced by using minus lenses. Regardless of the explanation, these authors pointed out an important basic principle in performing ﬁelds: Unless the perimetrist pays scrupulous attention to the patient’s refractive error, false-negative or false-positive responses can be produced. 1-1-4 Recording the Fields. Artiﬁcial illumination is desirable if ﬁelds plotted on one day are to be compared with those plotted on another day; daylight is too variable

8

Visual Fields

to be satisfactory. A generally accepted standard of artiﬁcial illumination is 7 footcandles. Even if the light is not exactly 7 foot-candles, an ordinary light meter will allow one to standardize the illumination. Lighting in the room should be replaced from time to time. This is not a problem for the computerized instruments. The ﬁelds are recorded on charts that represent the ﬁeld as the patient sees it. The ﬁeld for the right eye is placed to the right on the chart: the upper portion, above; the temporal portion, to the right; and the nasal portion, to the left. The test object is recorded as a fraction, with the numerator indicating the size of the test object and the denominator indicating the distance at which the object was used. For example, 3/330 indicates that a 3-mm bead was used on the arm of a perimeter that has a distance of 330 mm (Figure 1-1). This notation system gives more information than merely stating the size of the target in degrees. To transpose the notation into degrees, the following formula can be used: object 180 × = number if degrees distance p For the 3/330 example, the formula would read: 3 180 × = 0.052° 330 301416 It is important to record not only the details of the test object size, color, and distance but also the patient’s state of cooperation and alertness. If the patient is obtunded or sick, the defect may seem worse than on a subsequent visit when the patient is well or has had more experience with ﬁeld tests. The patient may appear to be improving on the second or third ﬁeld test when in reality the change is due to increased cooperation or alertness. The degree of alertness is not a problem in the computerized perimeters because there are printouts of false-positive, falsenegative, and ﬁxation losses. The boundary of the ﬁeld for a given target is usually drawn on the chart as a solid line. Heavy lines may be used for large targets, and thin or broken lines are

Figure 1-1. Visual ﬁelds charts. Additional information given at the bottom of the charts aids in the interpretation of the ﬁelds later in the course of a patient’s disease.

Overview of Perimetry

9

used for smaller targets. Color may also be used as a coding device. The system that is adopted should be indicated at the bottom of the recorded ﬁeld so that anyone reading the chart can easily interpret it. The choice of sizes of test targets depends in part on the alertness of the patient and on the nature of the defect in the ﬁeld. It is generally advisable to start with the smallest target the patient can see (often 2 mm), proceed to one or two targets of medium size, and ﬁnally determine the largest target that will disappear in any portion of the defect. With experience, one learns to judge the ability of the patient and to guess in advance the probable or possible extent of visual loss. This approach varies with different diseases. For instance, small test objects are necessary to use to discover subtle and early changes in glaucoma. In neuro-ophthalmology, small test objects are used to ﬁnd the ﬁeld defect but are followed up with the largest test object that still demonstrates some of the defect, because the largest test object will show improvement ﬁrst. The points at which the target is seen on the perimeter are recorded, in degrees, from the point of ﬁxation. The arm of the perimeter is marked in degrees, making notations easy. Because it is preferable on the tangent screen to start with an unmarked surface, a method of transferring the results from the screen to the chart is needed. This can be done by superimposing on the screen a projected slide on which the degrees are ruled or by pulling down in front of the screen a similarly marked transparent cellophane sheet. Most good perimeters, such as the Goldmann, are self-recording and speed the taking of a ﬁeld. A pantograph has been designed for transferring the results on the tangent screen to a record card fastened to the wall at the side of the screen. This device is generally not available; however, when used, it produces quite satisfactory results when performing tangent ﬁelds. The perimetrist should be aware that a vast number of methods and instruments have been designed over the years for the purpose of seeking evidence of impaired function of the visual pathway. The confusing array of available techniques, many of them offering distinct, if limited, advantages over others, stems from an uncertainty of exactly what should be measured in perimetry. The subject is still wide open for further fundamental research. The essence of doing a good ﬁeld lies not in the perimeter used but in the acumen of the perimetrist; a tangent screen used skillfully by an experienced perimetrist is every bit as effective as the Goldmann or Humphrey perimeter. The introduction of computerized perimetry has meant a signiﬁcant step forward in measuring defects in the visual ﬁeld.17 There is no doubt that subtle defects not reported by the patient or not found on routine perimetry are being reliably found with computerized perimetry (Figures 1-2 and 1-3). However, in my experience, computerized perimetry occasionally has one drawback in the routine initial examination of neuro-ophthalmic patients: It is a prolonged procedure and may unduly fatigue a patient who is already ill with a neuro-ophthalmic disease that may impair concentration and the ability to respond reliably. The use of computerized perimetry as a way to follow a ﬁeld defect or in patients who have experience in ﬁeld examinations or who are physically well, such as patients with glaucoma, is an invaluable diagnostic instrument. For some of my neuro-ophthalmology patients, I use computerized perimetry as an adjunct, because initially it is more important

A Figure 1-2. A comparison of techniques using computerized perimetry, static perimetry, and tangent screen. (A) A Humphrey ﬁeld can be read out in grayscale or a numeric scale. The latter is shown in comparison to the normal for that area of the ﬁeld. (B) A normal Goldmann and tangent screen examination with a subnormal static proﬁle across the 0° to 180° meridian of the right eye. (C) A computerized representation in grayscale with a normal ﬁeld in the left eye but a depressed central area in the right eye. (Source: A, Courtesy California Paciﬁc Medical Center. B, C, Reprinted by permission from Younge BR. Computer-assisted perimetry in visual pathway disease: neuro-ophthalmic applications. Trans Am Ophthalmol Soc. 1984;82:899–942.)

10

Overview of Perimetry

11

B

C Figure 1-2. (Continued)

to determine the anatomic focus of a defect and to establish a likely differential diagnosis. During the past few years, we have had extensive experience with the Octopus perimeter and more recently with the Humphrey. In this monograph, for the sake of brevity, the isopters of only one or two test targets are shown in cases using the Goldmann perimeter, although in actual practice several targets are usually used. The reader is also warned against assuming that the technique selected to demonstrate a particular ﬁeld defect is the only technique that can or should be used. In any examination, both peripheral and central ﬁeld examinations should be performed to establish the true limits of the defect.

12

Visual Fields

Figure 1-3. A subtle central scotoma shown on a computerized representation. (Source: Courtesy Humphrey Instruments.)

1-2 STRUCTURE OF THE VISUAL PATHWAY The visual pathway consists of bundles of nerve ﬁbers connecting the retina of each eye with the visual cortex of the occipital lobes. In the retina, there are three layers of nerve cells: the rod and cone cells with their receptors pointing outward, a middle layer of bipolar cells, and an inner layer of large ganglion cells. Each layer sends a single axon back through the optic nerve, the optic chiasm, and one of the

Overview of Perimetry

13

optic tracts. The ﬁbers of the optic tracts end in the lateral geniculate bodies. Other ﬁbers leave the tract before its termination and turn medially to end in the pretectal region. These latter ﬁbers are concerned with pupillary reﬂexes and are not shown in Figure 1-4. The cells of each lateral geniculate body send long axons backward, forming a thick band called the optic radiation. This structure ends in the visual cortex on the medial surface of the occipital lobe, in the region of the calcarine ﬁssure. The visual pathway lies near the base of the brain. The anterior half of each optic nerve lies within the orbit; the posterior half lies within the optic canal of the sphenoid bone and within the cranial cavity. The chiasm is suspended in the basal cistern 5 to 10 mm above the hypophysis and forms part of the ﬂoor of the third ventricle. The optic tracts encircle the cerebral peduncles and are laterally covered by the foreparts of the temporal lobes. These ﬁbers terminate in the lateral geniculate bodies, gray masses of cell bodies situated at the posterior lateral margin of the peduncles. The geniculocalcarine ﬁbers, comprising the optic radiation, lie in the external sagittal stratum close to the outer walls of the lateral ventricles. The geniculocalcarine ﬁbers ﬁrst extend laterally. The upper ﬁbers soon turn backward, but the lower ones loop forward a variable distance around the inferior horn of the lateral ventricle (forming Meyer’s loop) before they pass backward and join the upper ﬁbers on their way to the visual cortex. They all lie deep within the temporal and occipital lobes. (The importance of the relationship between adjacent anatomy and a speciﬁc ﬁeld defect is graphically outlined in Chapter 2.) Figure 1-4 is a diagram of the visual pathway viewed from above. The rectangle at the top represents the ﬁeld of vision; the yellow dot at its center is the point of ﬁxation. A vertical line and a horizontal line divide the ﬁeld into quarters. The color of each quadrant corresponds to that of the portion of the visual pathway along which that quadrant is projected. The left half of the visual ﬁeld (green) is projected onto the right half of each retina. From there, axons pass back through corresponding portions of the optic nerves to the chiasm, where ﬁbers from the nasal half of the left retina cross to the opposite side, while ﬁbers arising from the temporal half of the right retina remain uncrossed. Behind the chiasm, all the nerve ﬁbers concerned with the left half of the visual ﬁeld lie within the right half of the visual pathway. The macular ﬁbers (yellow) occupy temporal sector of the optic nerve at ﬁrst; as they pass backward, they dip into the nerve, lying centrally throughout its posterior portion. Axons arising in the nasal half of the macula cross the chiasm, mostly in its posterior portion; axons arising in the temporal half of the macula remain uncrossed. In the tract, the macular bundle is at ﬁrst central; as it passes backward, it rises and ends in the upper and posterior portions of the lateral geniculate body. In the optic radiation, the macular bundle occupies the central third and spreads over a large portion of the visual cortex at the occipital pole. The macular bundle can be divided into quadrants similar to those of the more peripheral ﬁbers, but for the sake of simplicity this is not shown in the ﬁgure. The left half of the visual ﬁeld (green) is projected onto the right half of each retina. From there, axons pass back through corresponding portions of the optic nerves to the chiasm, where ﬁbers from the nasal half of the left retina cross to the

Figure 1-4. The visual pathway, viewed from above. The different colors represent

the locations of the visual ﬁbers from the retina to the optic nerve, the optic chiasm, the optic radiations, and the calcarine cortex. Anatomic cutouts on the lateral edges of the diagram show the variations for temporal and nasal ﬁbers and particularly the macular.

14

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15

opposite side, while ﬁbers arising from the temporal half of the right retina remain uncrossed. Behind the chiasm, all the nerve ﬁbers concerned with the left half of the visual ﬁeld lie within the right half of the visual pathway. The macular ﬁbers (yellow) occupy the temporal sector of the optic nerve at ﬁrst; as they pass backward, they dip into the nerve, lying centrally throughout its posterior portion. Axons arising in the nasal half of the macula cross the chiasm, mostly in its posterior portion; axons arising in the temporal half of the macula remain uncrossed. In the tract, the macular bundle is at ﬁrst central; as it passes backward, it rises and ends in the upper and posterior portions of the lateral geniculate body. In the optic radiation, the macular bundle occupies the central third and spreads over a large portion of the visual cortex at the occipital pole. The macular bundle can be divided into quadrants similar to those of the more peripheral ﬁbers, but for the sake of simplicity this is not shown in the ﬁgure. The arrangement of the nerves within the pathway is best demonstrated by tracing axons arising in the various quadrants of the retina. For example, the upper left quarters of both retinas (light blue) are concerned with the lower right quadrant of the visual ﬁeld. From their ganglion cells, axons pass back through corresponding sectors of the optic nerves. Those axons arising in the nasal portion of the right retina cross in the upper portion of the chiasm; those arising in the temporal portion of the left retina remain uncrossed. The lower nasal ﬁbers of each optic nerve cross the chiasm and turn back into the chiasm and optic tract. In the optic tract, as these ﬁbers pass backward, they turn mesially, ending in the medial portion of the lateral geniculate body. From there, nerve cells send axons back through the upper third of the optic radiation to end above the calcarine ﬁssure on the cuneus. The lower left quarters of both retinas (blue) are concerned with the upper right quadrant of the visual ﬁeld. They send axons back through corresponding sectors of the optic nerves. Those axons arising in the nasal portion of the right retina cross through the lower part of the chiasm, while those arising in the temporal portion of the left retina remain uncrossed. In the optic tract, as the axons pass backward, they turn outward and end in the lateral portion of the lateral geniculate body. From there, nerve cells send axons back through the lower third of the optic radiation, ending below the calcarine ﬁssure on the lingual gyrus. The complexity of the internal arrangements of ﬁbers in the optic nerves and tracts may be attributed in part to the intrusion of the macular bundle and to the rotation of the nerves and tracts on their longitudinal axis. The optic nerves rotate mesially as they approach the chiasm, their upper sectors becoming nasal. In the anterior portions of the tracts, as in the posterior portions of the nerves, ﬁbers that arose in the upper quadrants of the retina lie dorsomedially; those that arose in the lower quadrants of the retina lie ventrolaterally. The rotation continues within the tracts to their termination, where ﬁbers that were originally superior are now medial and those that were inferior are now lateral. The horizontal raphe of the retina is vertically projected on the lateral geniculate body. At the beginning of the optic radiation, a counterrotation returns the ﬁbers to relationships that existed at the forward portions of the optic nerves.

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Visual Fields

1-3 INTERPRETATION OF DEFECTS IN THE FIELDS Each of the many types of defects has a speciﬁc anatomic location. Some are peripheral, such as general contraction, quadrantanopsia, hemianopsia, altitudinal defects, and others. Those inside the peripheral limits of a normal ﬁeld are central, paracentral, cecocentral, and arcuate scotomas. Some defects are best seen at the vertical meridian such as temporal lobe and pituitary lesions. Arcuate lesions may be seen along the horizontal meridian and are called nasal step defects. Not all defects of the central ﬁeld cause loss of acuity. Therefore, good acuity does not rule out defects near the center that do not break out to the periphery. Hence, it is important to examine the central as well as the peripheral ﬁeld. Lesions that interrupt the visual pathways behind the chiasm produce a homonymous hemianopia; that is, they impair the function of both eyes, causing defects in either the right or the left half of both visual ﬁelds without affecting the other half-ﬁelds. The term hemianopia is not restricted to its literal sense. Rather, it implies a loss in one of the half-ﬁelds, a loss that is not necessarily complete, but that may be quadrantic, partial, or even relative. Defects of the ﬁelds that are similar in the two eyes are called congruous (Figure 1-5). Exact congruity suggests that the location of the lesion causing the defects is in the posterior portion of the optic radiation. Lesions that interrupt the anterior portion of the radiation may produce defects that are slightly incongruous (in my experience, however, they are usually congruous). Lesions that interrupt the tracts cause incongruous homonymous defects that are grossly dissimilar (Figure 1-6). The reason is that while ﬁbers from the corresponding points on the two retinas are projected onto identical areas of the visual cortex, they do not pursue exactly the same course in arriving there. Near the cortex, corresponding ﬁbers lie close together. Farther forward in the optic tract, they are only roughly sorted out. Consequently, a lesion situated in the tract may interrupt ﬁbers from a segment of the retina of one eye and from a larger or smaller segment of the retina of the other eye. Lesions situated at the chiasm, by interrupting the crossing nasal ﬁbers, bring about a loss in the temporal portion of the ﬁeld of each eye. This loss is called a bitemporal hemianopia (Figure 1-7). Such lesions are commonly tumors, which may grow toward one side more than the other and appear as incongruous defects. By interrupting an optic nerve, a central scotoma may be added to the bitemporal hemianopia, or one eye may be completely blind, leaving only a nasal half-ﬁeld in the opposite eye (Figure 1-8). If the tumor grows posteriorly or there is an anteriorly placed chiasm, the tumor encroaches on the tract and causes an incongruous homonymous hemianopia (Figure 1-9). A scotoma is a ﬁeld defect surrounded by a normal ﬁeld (Figure 1-10). This differentiates it from a hemianopia or a quadrantanopia, both of which break out to the periphery and have no ﬁeld remaining beyond their peripheral limits. Lesions that affect the retina or the optic nerve induce a defect in the ﬁeld of the corresponding eye and spare the ﬁeld of the other eye. The characteristic loss is in the form of a central scotoma, but contractions also occur and complete blindness may ensue. Certain poisons and inﬂammations may affect both optic nerves and

A

B Figure 1-5. These two central ﬁelds have the same degree of ﬁeld defect to the same testing circumstances. (A) Tangent screen representation. (B) Computerized representation of left eye. The right eye is identical, as in the tangent screen representation (A).

17

A

B Figure 1-6. A grossly incongruous ﬁeld defect. The 3-mm test object demonstrates

a different-size ﬁeld defect in each eye. (A) Tangent screen representation. (B) Computerized representation of left eye. (C) Computerized representation of right eye.

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19

C Figure 1-6. (Continued)

produce defects in the ﬁelds of both eyes. In these instances, the defects may be present in both the nasal and the temporal half of the ﬁelds and are not limited by the vertical midline, as are defects caused by postchiasmal lesions. Defects vary in their densities. In some cases, large targets disappear; in others, only small targets fade out. A defect so dense that not even light is perceived within it is said to be absolute; all other defects are relative. The density of a defect indicates the degree of interruption of the nerve ﬁbers involved. The term sloping refers to the variation of the size of the ﬁeld defect according to different sizes of test objects. The smaller the test object, the larger is the defect, so the edge of the defect looks like a children’s slide rather than a cliff. This type of defect is more commonly seen with a tumor that has a central absolute defect and surrounding tissue that is variably affected (Figure 1-11). This damaged tissue produces a defect resulting from that involvement to varying sizes of test objects or different shades of gray in the Humphrey perimeter that depicts the same variations.

20

Visual Fields

Figure 1-7. A bitemporal hemianopia is incongruous, typical of chiasmal tumors. (A) Tangent screen representation. (B) Computerized representation of left eye. (C) Computerized representation of right eye.

The term sharp margin indicates that the edge of the defect can be demonstrated by large or small test objects; the site of the defect remains the same regardless of the size of the test object (Figure 1-12).This is shown as no variation of the grayscale and numeric readout. Such a demonstration indicates a sharp margin of tissue involvement, which is usually seen with vascular infarctions. For this reason, test objects of several different sizes should be used to plot any ﬁeld defect. Merely ﬁnding the defect is not sufﬁcient. This is done in computerized perimeters by using a brackening technique. The defects affecting the optic nerve and the retina differ from those affecting the chiasm, the tract, and the optic radiation. In addition to the central scotoma (see Figure 1-10), there are defects of the following types: paracentral (Figure 1-13), cecocentral (Figure 1-14), and arcuate (Figure 1-15). Quadrantic defects also arise in the retina as a result of vascular disease, but they differ in one important aspect: Unlike quadrantic defects behind the globe, a quadrantic defect caused by

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Figure 1-8. A chiasmal tumor not only involves the crossing ﬁbers from both eyes

but also encroaches on the left optic nerve. (A) Tangent screen representation. (B) Computerized representation of left eye. (C) Computerized representation of right eye.

an infarction of the retina has the central apex of the lesion pointing toward the blind spot rather than toward the ﬁxation point. A large test object that reveals a partial quadrantic defect may not demonstrate this, so smaller and smaller test objects should be used to enlarge the defect until it extends to the blind spot or to the ﬁxation point. Neurologically, the ﬁeld of vision divides at the ﬁxation point (Figure 1-16A), whereas the vascular supply to the retina divides into quadrants at the optic nerve or at the blind spot (Figure 1-16B).

1-4 TECHNIQUES OF FIELD TESTING 1-4-1 Confrontation Technique. The easiest and most rudimentary method of ﬁeld testing is the confrontation technique.18 The procedure may involve the examiner holding up ﬁngers, which are the test object, and asking the patient whether they

22

Visual Fields

Figure 1-9. A tangent screen examination demonstrating an incongruous defect. Different isopters would still show the incongruous defect to a greater or lesser degree. (A) Tangent screen representation. (B) Computerized representation of left eye. (C) Computerized representation of right eye.

are moving. Because the patient has only two choices; however, this is not the best way to perform the test. Usually, the examiner stands several feet in front of the patient.18,19 The patient’s right eye is covered and the examiner’s left eye is closed, enabling the examiner to use the right eye as a check against the patient’s left eye for ﬁeld size. The patient is to ﬁxate on the examiner’s nose. The examiner shows ﬁngers in all four quadrants of the patient’s left eye out to the limits the examiner can see them with the right eye. If the patient counts them correctly, there is presumably no gross defect. Most people can distinguish one, two, or ﬁve ﬁngers accurately, but many cannot accurately tell three and then four ﬁngers. If three and four ﬁngers are used consecutively, incorrect answers should not be counted. How the examiner holds his or her hand is important. What appears to the examiner as two ﬁngers

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Figure 1-10. This defect is found only in the left eye and is presented to several

sizes of test objects. The defect does not respect the vertical midline and has a normal ﬁeld peripheral to it in all quadrants. (A) Tangent screen representation. (B) Computerized representation of right eye.

(Figure 1-17A) may be perceived as only one ﬁnger if one ﬁnger is behind the other in the patient’s ﬁeld of vision (Figure 1-17B). For the patient who has trouble ﬁxating, ﬁnger counting offers an advantage over other methods of ﬁeld testing. In this technique, the number of ﬁngers can easily be shown only brieﬂy before the patient is forced to change ﬁxation. If the ﬁnger-movement technique is used, however, the ﬁngers will theoretically be moving almost constantly as the examiner brieﬂy projects a few ﬁngers into one of the patient’s ﬁelds. The second step in the confrontation technique is to project a series of ﬁngers into the nasal and temporal ﬁelds of one eye simultaneously. The combinations are one and one, two and two, one and two, and one and ﬁve ﬁngers. Other combinations, such as one and three or three and four ﬁngers, should not be used, because even a patient with normal ﬁelds will frequently miss an accurate numeric identiﬁcation. The patient who fails this test of simultaneous stimulation may have a more subtle ﬁeld defect than could be demonstrated by testing each quadrant separately. Failure of the test could also represent the extinction phenomenon (discussed in Chapter 10) as the radiation passes through the parietal lobe, or it could reﬂect the patient’s inability to add one ﬁnger and two ﬁngers (a condition termed dyscalculia). The last step of the confrontation technique is to compare the temporal and nasal ﬁelds for subtle differences. This requires judgment on the part of the patient;

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Visual Fields

Figure 1-11. As smaller or subtler test objects are used, the defect becomes larger and is described as having a sloping margin with a relative defect. (A) Tangent screen representation. (B) Computerized representation of the right eye, which demonstrates a variable defect, as does the left eye. The left eye has a congruous defect to the right eye.

therefore, the interpretation is not as clear-cut as are the results of the ﬁrst two steps. The examiner shows one hand to each half-ﬁeld of the patient’s left eye as the patient continues to ﬁxate on the examiner’s nose. The patient then compares the clarity of the two hands. If the patient says the hand in the temporal ﬁeld is blurred compared with the hand in the nasal ﬁeld, a ﬁeld defect may exist. When the right eye is similarly examined, the patient may give a similar response for the temporal ﬁeld, suggesting chiasmal involvement. Blurring of the nasal ﬁeld would suggest a homonymous defect, indicating a location in the optic radiation. If the patient gives no such response for the right eye, the possibility exists that the defect is not a true defect in the left eye—that it is instead in the nasal retinal portion of the left eye or in the nasal portion of the left nerve—or that there is a defect in the right eye that is much more subtle and was not picked up. The simultaneous comparison of nasal and temporal ﬁelds can further be reﬁned by using colored test objects, such as the tops of mydriatic bottles. If you use two bottle tops at a time as comparison, it is important to repeat the test and switch bottle tops, because the difference noted by the patient may be a difference in manufacture.

1-4-2 Central Field Technique. The area encompassed by the central ﬁeld is the central 30°, and in the central ﬁeld technique this is examined at a distance of 1 m with a

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Figure 1-12. The defect as shown is the same for the three test objects. If the defect

is found with all test objects, it is called absolute. (A) Tangent screen representation. (B) Computerized representation of the right eye. The left eye, which is not shown, is a mirror image of the right eye, as demonstrated (A).

1-mm white test object. Chamlin4 found that 30° was the average limit for seeing a 1-mm white test object. There are many sizes, colors, and shapes of test objects for performing central ﬁeld examinations on the tangent screen. The advantage of a spherical test object is that it projects an image of the same size on the retina regardless of how it is held or in what part of the ﬁeld it is held. The disadvantage is that the sphere cannot be turned off or turned over so that the patient cannot see it, because it is all of one color. The ability to hide a test object or to turn it on and off during the ﬁeld test is important in testing the validity of the patient’s response. The ﬂat test objects of the Bausch & Lomb type have different colors on each side. These test objects can be modiﬁed by blackening one side and turning them over so that the color is hidden and the dark side now blends into the black tangent screen. Unless the test object is held just right, however, it is seen at different angles and, therefore, presents a different size at different times. Even if the test object is held ﬂush with the tangent screen, it projects a slightly different size on the retina as it is moved farther from ﬁxation. This small problem, however, is overshadowed by the ability of the examiner to turn the test object on and off to test the validity of the patient’s response. It is important that the examiner learns to test the validity of

Figure 1-13. Paracentral defects are different in each eye. As shown, the defects have different densities. (A) Tangent screen representation. (B) Computerized representation of right eye.

Figure 1-14. A cecocentral defect differs from a central scotoma in that the

defect extends asymmetrically from the ﬁxation point toward the blind spot and usually connects with it. (A) Tangent screen representation. (B) Computerized representation of right eye.

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27

Figure 1-15. An arcuate defect follows the direction of arcuate ﬁbers coming out

of the blind spot and stopping at the horizontal raphe, as shown in the left eye. The defect is not always continuous but may be segmental along the same meridian, as shown in the ﬁeld of the right eye. (A) Tangent screen representation. (B) Computerized representation.

the patient’s response. It is also important that the examiner learns to twist the handle of the test object between the ﬁngers so the examiner knows without looking when the test object is white or black. Turning one’s hand or head may give an unwanted clue to the patient. The projection perimeter machines, such as the Goldmann or a computerized perimeter (Figure 1-18), can switch the test object on and off and can project the same-size spot of light in all quadrants. An additional advantage of projection perimeters is that the examiner can move the test object randomly from one part of the ﬁeld to another without the examiner moving or the patient being aware of the change. This feature eliminates the otherwise obvious clue to the patient that the test object will always appear from the side on which the examiner is standing. There is no absolute, standard way to conduct a central ﬁeld examination, but there are general guidelines that should always be observed: 1. Before the examination begins, the patient is told what a ﬁeld examination is, what is going to be done with the test object, and what is expected of him or her. This is especially important for the patient who is having a ﬁeld examination for the ﬁrst time: The patient will perform more accurately if he knows what is being asked of him. There is no question that the more often a patient performs a ﬁeld, the more precise he will become. However, an initial examination can be improved immeasurably if the patient thoroughly understands the process.

28

A

Visual Fields

B

Figure 1-16. (A) The apex of this defect goes to the ﬁxation point and represents

a lesion behind the lamina cribrosa in the nerve. (B) The apex of this defect goes to the blind spot and is due to a vascular lesion in the retina that divides the ﬁeld at the blind spot, not the ﬁxation point.

2. On a tangent screen examination, the patient is shown the test object and is told to give a verbal response when the white side is exposed and to give no response for the dark side. The patient is then asked to ﬁxate on a target on the screen. At this point, before mapping the patient’s blind spot, the examiner explains that there are certain areas within which the patient will not be able to see the test object and that this is normal. The examiner then proceeds to map the blind spot as an example. The advance warning relieves the patient’s anxiety or curiosity about not seeing something essentially in front of him and allows him to ﬁxate better. So when another scotoma is found, the patient should be able to ﬁxate well during exploration of its limits. 3. After the blind spot is mapped, the peripheral limits of the ﬁeld are examined. A 1-mm white test object is usually used, but a 2-mm white test object will be required if there is too much peripheral contraction. Recordings should be made about every 15°. In the usual testing format, the test object is brought from beyond the visible limits of the ﬁeld to a point at which the patient just sees it. At this point, a recording mark that will later be transferred to a permanent record is made on the screen; it is here where a cardinal mistake is often made. The perimetrist must watch the patient all the time to make sure small lapses in ﬁxation do not mislead him. Special care should be taken when using the Goldmann perimeter because the patient’s ﬁxation must be watched through a small tube. With any perimeter, a lapse in ﬁxation of which the patient is unaware may cause a more signiﬁcant error than missing putting a mark on the tangent screen by 1°. Computerized perimeters have built-in ﬁxation sensors.

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4. After the outer limits of the central ﬁeld are examined, the inner aspects are explored. Once a defect is found, the examiner tests for the defect in all directions to map its limits. This procedure again uses the principle of going from a nonseeing, or scotomatous, area to a seeing area. The density of the scotoma is also examined by using different sizes of test objects until the defect can no longer be found. During the testing of any area, the dark side is shown periodically so that the validity of the patient’s response can be evaluated. The usual tangent screen has subtle lines sewn in, marking out the degrees from ﬁxation and the blind spot. The use of pins or chalk marks on the screen is clumsy as well as difﬁcult. In addition, if the marks are too obvious, they act as a clue for the patient as to the limits of the ﬁeld. A gray, No. 966 Eagle Prismacolor pencil is

A

B

Figure 1-17. (A) The correct way is to present two ﬁngers to a patient so they

are side by side in a frontal plane. (B) The incorrect way is to show two ﬁngers, with one behind the other so they appear as one ﬁnger to the patient. (Source: Photographs courtesy of Pamela Ossono.)

A

B

C Figure 1-18. (A) Anterior view of Goldmann perimeter. (B) Posterior view of

Goldmann perimeter. (C) Humphrey perimeter. (Source: Photograph courtesy of Pamela Ossono.)

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an excellent marker. If the pencil is used lightly, the patient cannot see the marks. Different symbols can be used to outline the different sizes of test objects. When the examination is ﬁnished, all the room lights are turned on and the marks can be seen and transferred to a permanent record. The marks can easily be erased from the felt screen with a felt blackboard eraser, and the screen is ready for another examination.

1-4-3 Chamlin Step Technique. When the examiner ﬁnds a minimal peripheral ﬁeld defect, he or she needs to determine whether it is truly an early defect or merely an artifact. Chamlin3,4 developed a theory and a method for evaluating this problem. He postulated not only that the peripheral defect affects the peripheral ﬁbers but also that there is hemiretinal suppression. Therefore, all the examiner has to do is ﬁnd a method to compare one half of the ﬁeld with the other. This is done at the vertical meridian, which separates the two homonymous or bitemporal ﬁelds. In the experience of many perimetrists, a signiﬁcant defect is one that differs at least 10° from one side to the other. If the difference is less, the test is not necessarily negative, but it is questionable. If the points of reference are at 15° on either side of 90° and at 90°, the line of the ﬁeld can look like that in Figure 1-19. If, however, one measures 2° on each side of the vertical meridian, the difference between the two ﬁelds is obvious (Figure 1-20). The examiner, therefore, should always measure on each side adjacent to the vertical meridian and not exactly at the vertical or at 15° or 30° nasal and temporal to the 90° meridian. There are several ways to evaluate the problem. The examiner can simultaneously bring down on either side of the vertical meridian two small white test objects of the same size. The patient tells when and in which ﬁeld he sees one test object and when he sees both. The patient’s ﬁxation must be scrupulously watched, since recognition of the ﬁrst object will encourage him to shift ﬁxation. If the patient truly sees the two objects at the same time, there may be no difference in the two ﬁelds. The test can also be performed by comparing one side at a time using a single test object. Any difference of 10° or more is considered signiﬁcant, and the defect, although subtle, is real. If the defect is consistently present but is equivocal such as 5° or 6°, a further reﬁnement can be added—the use of color recognition. The perimetrist brings a colored test object down from the periphery and along each side of the vertical meridian until the color of the test object is recognized. The patient’s ﬁxation must again be constantly and scrupulously watched; when he sees the test object as colorless, he may lose ﬁxation and invalidate the test. The examiner should make sure the patient maintains ﬁxation until he recognizes a color. For example, the usual Bausch & Lomb colored test objects are red and blue, back to back. By repeating the test and varying the color from red to blue, the perimetrist can keep the patient from identifying red automatically regardless of whether red is present. Perhaps the previous defect to a small white test object was 7°; now when the patient is asked to recognize red, he may miss an entire quadrant (Figure 1-21). The examiner shows the patient blue as well as red but only records responses to

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A

B

C Figure 1-19. The “X” marks are the points recorded and suggest only a right homonymous defect. The minimal slope leaves the perimetrist wondering if the defect is real. (A) Tangent screen representation. (B) Computerized representation of the left eye. (C) Computerized representation of the right eye.

the red test object. The ﬁeld to a blue test object is greater than that to the same size of red test object. If the patient has a congenital color defect or even a brunescent cataract that changes his color perception, the test will not be seriously affected because the entire ﬁeld has the color defect. If there is a hemianopic defect, there will be an even more pronounced color defect in the hemiﬁeld. A mistake that many perimetrists make is to select a colored test object that is too small. They assume that if the ﬁeld defect is equivocal when a 1-mm white object is used, the smallest red test object available (usually 3 mm) must be used. This is fallacious and will produce disappointing results, because it is color, and not size, that is being evaluated. The perimetrist is measuring the decreased sensitivity of cells in the central ﬁeld that are predominantly cones and that will show defects

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A

B

C Figure 1-20. Reference points are on either side of the vertical meridian. Note that

the test object in the left homonymous ﬁeld is seen at 30°, while just 4° away it is seen at 20°. (A) Tangent screen representation. (B) Computerized representation of the left eye. (C) Computerized representation of the right eye.

to colored test objects before defects to white test objects. All too often, patients with 20/20 or 20/25 vision miss all the colored testing plates because of optic nerve disease. This is a frequent and well-known phenomenon. A 9- or 12-mm red test object is much more effective in achieving valid results. Mindel et al.20 asserted that it is not the color but the intensity of the object that identiﬁes the defect. They believed that equal intensity of red and white test objects should produce equal results. This view is supported by Safran and Glaser.21 However, it is much easier clinically to use the red test object than the white test object of equal intensity that I use the red test object in a patient with optic neuritis and 20/25 vision. The perimetrist avoids the difﬁculty of identifying the scotoma with a small white test object and demonstrates a central scotoma more easily with a red color test object.

34

Visual Fields

Figure 1-21. A Chamlin step to a 1-mm white test object is only 7°. A defect to a

larger, red test object in color recognition, however, is 90°.

A simple method of comparing the two homonymous ﬁelds is to use the red caps from two bottles of mydriatic eye drops or red test objects cut from red paper. The examiner holds one test object in the nasal ﬁeld as the patient ﬁxates centrally on the examiner’s nose. The patient is asked to comment on whether there is a difference in the color of the two test objects. If there is no defect, the patient will describe them as the same (Figure 1-22A). If there is a defect, the patient will describe one as red and the other as light red, barely pink, or colorless (Figure 1-22B). This suggests a defect on the side described as pink or colorless. If the defect is more subtle, the patient may just comment that there is a qualitative difference between the two test objects. Although subtle, this distinction is valid if it is reproducible. If the patient is then asked to compare one test object centrally and one or two peripherally at the same time, the central one may appear faded or colorless, suggesting a central scotoma (Figure 1-22C and D). If a patient’s test results suggest a particular homonymous defect but are mildly inconsistent, another technique is available. The premise on which the testing of the Chamlin step defect is based is the difference between one homonymous ﬁeld and the other. Therefore, instead of smaller and more subtle test objects being brought down on either side of the vertical meridian, the test objects should be brought across the vertical meridian. As the test object comes from the supposedly defective side to the normal side, there will be a sudden change in color or in intensity. Repetition of this test will demonstrate that for at least part of the ﬁeld there is not only a difference but also a vertical line dividing it. In exploring the characteristics of the peripheral ﬁeld, Damgaard-Jensen22 found that about 50% of normal persons have a slight step at the vertical meridian but not 10°. He also found that the ﬁeld was always larger on the temporal side of the vertical meridian. Therefore, any suggestion of a Chamlin step with the smaller ﬁeld occurring on the temporal side should be considered pathologic.

1-4-4 Peripheral Field Technique. The examination of the peripheral ﬁeld is performed in somewhat the same way as that of the central ﬁeld. The peripheral limits of the ﬁeld are examined every 15° and recorded. The area inside that peripheral limit is also examined for defects. The selection of a ﬁeld machine usually depends on one’s training. The Goldmann perimeter is self-recording. It has the additional advantage

Overview of Perimetry

35

of being able to perform both central and peripheral ﬁeld examination. The instrument has a variety of sizes, colors, and intensities of test objects available. The Riddoch phenomenon, in which the patient perceives movement before light in the peripheral ﬁeld, was originally described as a sign of a recovering ﬁeld defect in the occipital lobe. This can be demonstrated when present by the projection perimeters. In one case, the patient perceives the movement of the projected test light but does not see that same object when it is not in motion.21 They regarded its use as not as anatomically speciﬁc—that it could be demonstrated in most ﬁeld defects using kinetic red stimuli.

A

B

C

D

Figure 1-22. (A) Two colored test objects presented simultaneously to the nasal and

temporal ﬁelds appear equal when the ﬁelds are normal. (B) The same test with test objects of equal intensity do not appear the same to this patient. In this instance, the temporal ﬁeld in the right eye is defective. The temporal ﬁeld test object is colorless or less color-saturated. (C) In this instance, three identical test objects can be used to compare the nasal, temporal, and central ﬁelds simultaneously. (D) The central target in this instance is much lighter to the patient than the peripheral ﬁeld, indicating a central ﬁeld deﬁcit. (Source: Photographs courtesy of Pamela Ossono.)

36

Visual Fields

1-4-5 Amsler Grid. Although the Amsler grid is sometimes difﬁcult for a patient to learn to use properly, it is particularly useful in subtle foveal problems or in central serous retinopathy.23 I consider using the Amsler grid for a patient who complains of a blur and whose vision is perhaps 20/30. A central scotoma is difﬁcult to demonstrate by the usual ﬁeld-testing methods. If the patient can learn to ﬁxate steadily on the center of the grid (Figure 1-23), the center lines will appear either distorted or elevated in central serous retinopathy. The image will look as if someone were leaning on the center of a chain-link fence. Two problems the perimetrist may encounter with the test are (1) getting the patient to ﬁxate steadily and to just be aware of the surrounding area rather than looking all around and (2) instructing the patient as to what he may see without suggesting any defects to him. If both of these problems can be resolved, the Amsler grid is a valuable test device. 1-4-6 Color Testing. The use of color has always been controversial. Even those who subscribe to the use of color do not agree about which technique to use. Some use color as an object of decreased sensitivity, while others use it as color recognition. I prefer to use color recognition. This experience agrees with Kollner’s law even if the law is not perfect. The decreased-sensitivity technique gives varied results even in the same patient from examination to examination. There is even some argument about which color is preferable for detecting central ﬁeld defects. Red has been the most used and seems the most reliable. If color recognition is the technique, then using the smallest red object defeats the purpose. Certainly, smaller and smaller white test objects can reveal the same scotoma, but the progressive

Figure 1-23. The Amsler grid. This type of ﬁeld covers about 10° around the ﬁxation

point and is used primarily for foveal problems such as central serous retinopathy or subtle changes in macular degeneration.

Overview of Perimetry

37

decrease in the size of white test objects is governed more by the minimal visual threshold than by any other feature. If rods are affected, blue test objects seem to be more sensitive. If the optic nerve is the location of the defect, then red has traditionally been more sensitive. It is difﬁcult to determine whether this increased sensitivity is due to lower intensity than the same-size white test object or to a different wavelength. As described previously, color is a useful method for demonstrating a Chamlin step; it is also particularly useful in demonstrating a central scotoma when small white test objects are either inadequate or inconsistent. When it is difﬁcult to establish whether a decrease in acuity is the result of retinal involvement or of optic nerve involvement, colored test plates such as the HRR plates can pinpoint the location. A patient with optic nerve involvement and 20/30 acuity often misses all the HRR plates. Similarly, a patient with retinal disease and an acuity of 20/200 may see almost all the HRR plates. Even if the patient has some degree of color blindness, there will be a signiﬁcant difference between the two eyes when one has optic nerve involvement. In central scotomas, cones are particularly involved and red test objects are most useful. Because color is the basis of the test, the perimetrist should not use the smallest colored test object in the set because it is too small to see. One of the more difﬁcult ﬁeld defects to map is the cecocentral scotoma. Early in the course of the disease, the acuity may still be only moderately depressed. Since a patient with a cecocentral scotoma tends to ﬁxate unsteadily, it is difﬁcult not only to map the defect but also to identify it as a cecocentral rather than a purely central scotoma. The distinction is important because if the examiner can establish it as a cecocentral defect, the etiologic possibilities will be limited. Cecocentral scotomas are usually due to nutritional amblyopia and rarely due to Leber’s optic neuritis or pernicious anemia. Central scotomas have a long list of possible causes. To overcome the problems of mapping the cecocentral scotoma, the “big pumpkin test,” a method involving a variation on the use of color, has been used at the Yale Medical Center.24 A large piece of orange poster board, about 2 feet square, is placed over the tangent screen so that it covers at least 7° on the nasal side of the ﬁxation point and 20° on the temporal side in order to cover the blind spot (Figure 1-24). The patient is asked to look at a ﬁxation spot and say if any part of the poster board lacks color. Even slight eye movements will generally keep the central and cecocentral areas on the orange board. In essence, the entire central ﬁeld serves as a colored test object, obviating the need to explore that same area with a colored test object to observe where it is seen and where it is not. To help in this identiﬁcation, the patient is given a 3-foot dowel rod and is asked to map out the defective area. If he continues to shift ﬁxation, he will be somewhat frustrated in mapping out the scotoma. This, in turn, will encourage the patient to ﬁxate better. A color defect, or dyschromatopsia, does occur although rarely on a cerebral basis (discussed in Chapter 10).24,25,26 Such a defect requires very careful examination to ascertain that it is not congenital or some expression of aphasia or visual agnosia.

A

B Figure 1-24. (A) Orange poster board cut out to cover beyond the cecocentral area.

The ﬁxation object is large enough to ﬁxate on. It is also displaced away from the center, to leave more room temporally for the cecocentral area. A right eye test circumstance is illustrated here. (B) The patient is pointing at the area on the poster board that is color-desaturated, corresponding to the cecocentral defect.

38

Overview of Perimetry

39

REFERENCES 1. Horton J, Hoyt W. The representation of the visual ﬁeld in human striate cortex. Arch Ophthalmol. 1991;109:816–824. 2. Riddoch G. Dissociation of visual perceptions due to occipital injuries with especial reference to appreciation of movement. Brain. 1917;40:15–29. 3. Chamlin M. Minimal defects in visual ﬁeld studies. Arch Ophthalmol. 1949;42: 126–139. 4. Chamlin M, Davidoff LM. Choice of test objects in visual ﬁeld studies. Am J Ophthalmol. 1952;35:381–391. 5. Enoksson P. A study of the visual ﬁelds with white and colored objects in cases of pituitary tumors with special reference to early diagnosis. Acta Ophthalmol. 1953;31:505–511. 6. Alexander GL. Diagnostic value of colored ﬁelds in neurosurgery. Trans Ophthalmol Soc UK. 1956;76:235–240. 7. Feldman M, Todman L, Bender MB. Flight of color in lesions of the visual system. J Neurol Neurosurg Psychiatry. 1974;37:1265–1271. 8. Knapp H. The channel by which, in cases of neuroretinitis, the exudation proceeds from the brain into the eye. Trans Am Ophthalmol Soc. 1870;1:118. 9. Wilbrand H, Saenger A, eds. Die pathologie der Netzhaut. In: Neurologie des Augen. Wiesbaden: JF Bergmann; 1909;4(pt 1):568. 10. Paton L, Holmes G. The pathology of papilledema: a histological study of sixty eyes. Brain. 1911;33:389. 11. Stiles WS, Crawford BH. The luminous efﬁciency of rays entering the eye pupil at different points. Proc R Soc Lond. 1933;12:428. 12. Dailey RA, Mills RP, Stimac GK, et al. The natural history and CT appearance of acquired hyperopia with choroidal folds. Ophthalmology. 1986;93:1336. 13. Corbett JJ, Jacobson DM, Mauer RC, et al. Enlargement of the blind spot caused by papilledema. Am J Ophthalmol. 1988;105:261–265. 14. Reese A. Peripapillary detachment of the retina accompanying papilledema. Trans Am Ophthalmol Assoc. 1930;28:341. 15. Duke-Elder S, Scott GI. Neuro-ophthalmology. In: Duke-Elder S, ed. System of Ophthalmology. St. Louis: CV Mosby; 1971:12:59. 16. Young SE, Walsh FB, Knox DL. The tilted disc syndrome. Am J Ophthalmol. 1976;82:16. 17. Younge BR. Computer-assisted perimetry in visual pathway disease: neuro-ophthalmic applications. Trans Am Ophthalmol Soc. 1984;82:899–942. 18. Welsh RC. Finger counting in the four quadrants as a method of visual ﬁeld gross screening. Arch Ophthalmol. 1961;66:678–679. 19. Frisén L. A versatile color confrontation test for the central visual ﬁeld: a comparison with quantitative perimetry. Arch Ophthalmol. 1973;89:3–9. 20. Mindel JS, Saﬁr A, Schare PW. Visual ﬁeld testing with red targets. Arch Ophthalmol. 1983;101:927–929. 21. Safran BA, Glaser JS. Statokinetic dissociation in lesions of the anterior visual pathways: a reappraisal of the Riddoch phenomenon. Arch Ophthalmol. 1985;98:291–295. 22. Damgaard-Jensen L. Demonstration of peripheral hemiopic border steps by static perimetry. Acta Ophthalmol. 1977;55:815–819.

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23. Amsler M. Earliest symptoms of diseases of the macula. Br J Ophthalmol. 1953;37: 521–525. 24. Walsh T. Paracentral scotoma testing. Ophthalmic Surg. 1973;4:72–79. 25. Green GJ, Lessell S. Acquired cerebral dyschromatopsia. Arch Ophthalmol. 1977;95:121–128. 26. Zihl J, Van Cramon D. Colour anomia restricted to the left visual hemiﬁeld after splenial disconnection. J Neurol Neurosurg Psychiatry. 1980;43:719–724.

2 Anatomic Basis and Differential Diagnosis of Field Defects JONATHAN D. WIRTSCHAFTER, MD, AND THOMAS J. WALSH, MD

2-1 CATEGORIES OF FIELD DEFECTS The purpose of any medical test is to conﬁrm or rule out a diagnosis based on the clinical facts. In performing perimetry, the printout of the defect is not the end of the test. For even the most experienced reader, the test results at best tell the location of the defect. The next step is to consider the causes of such a defect in that part of the vision system. The experienced perimetrist will look at the results and suggest a differential list of causes. The primary diagnostic list is frequently aided by adding to the perimetry the medical history and other physical signs. The results of both then lead to the next step: ordering tests to conﬁrm the cause of the ﬁeld defect. It may require the ordering of a magnetic resonance (MR) image, but that may not be the proper test if the original differential diagnosis is faulty. Sedimentation rate and C-reactive protein may be more appropriate tests if the clinical facts suggest cranial arteritis. If carotid disease is suspected, a computed tomography (CT) angiogram may be more appropriate. In the following discussion of these defects, there has been a melding of a discussion explaining anatomically why these defects occur in certain areas. Because the course and relations of the primary visual sensory pathway have been frequently and well described (including in other chapters of this monograph), this chapter concentrates on the multiple anatomic substrates that may explain each particular pattern of visual ﬁeld abnormality (Table 2-1). Visual ﬁeld abnormalities are represented by three categories: monocular, binocular, and junctional. Monocular ﬁeld defects include those that can be caused by lesions of one eye or optic nerve. Binocular ﬁeld defects include those that

41

42

Visual Fields

TABLE 2-1. Visual Field Defects Monocular Field Defects Localized Defects Wedge-shaped temporal ﬁeld defect Arcuate and paracentral ﬁeld defects Central scotoma or depression Enlarged physiologic blind spot Centrocecal scotoma or depression Equatorial annular scotoma or depression Altitudinal hemianopia Generalized Defects Generalized depression or peripheral contraction Binocular Field Defects Homonymous Hemianopias Complete: macular splitting Incomplete congruous: horizontal sectoranopia Incomplete congruous: paramidline-sparing vertical hemianopia Incomplete: macular sparing Incomplete: two scotomas Incomplete incongruous Incomplete: unilateral sparing of temporal crescent Incomplete: unilateral defect of temporal crescent Bitemporal Hemianopias Complete With central depression, scotomatous Binasal Field Defects Complete Incomplete Altitudinal Field Defects Noncongrous and monocular Congruous Quadrantanopias Superior homonymous, incomplete Inferior homonymous, complete Bilateral central Field Defects Scotoma or depression Bilateral peripheral Field Defects Generalized depression or peripheral contraction Bilateral Checkerboard Scotomas Bilateral Homonymous Hemianopias Junctional Field Defects Complete Monocular Plus Bitemporal Hemianopia plus

Anatomic Basis and Differential Diagnosis of Field Defects

43

may result from single or multiple lesions at one or more points along the visual pathway. Junctional ﬁeld defects include three types of visual ﬁeld defects resulting from a lesion at the junction of the optic nerve and optic chiasm or of the optic tract and optic chiasm.

2-2 OVERVIEW OF THE VISUAL PATHWAY The layers of the retina are illustrated in Figure 2-1. A general scheme of visual ﬁeld defects related to the anatomy of the primary visual sensory pathway is depicted in Figure 2-2, and the blood supply of the visual pathway is shown in Figure 2-3. Other relevant anatomic points will be presented with the speciﬁc categories of visual ﬁeld defects. The visual sensory pathway can be divided into “territories” according to various schemes (Table 2-2). The preretinal territory consists of those anatomic barriers

Figure 2-1. Functional microanatomy of the retina. (A) Cell types: A, amacrine; C, cone; DB, diffuse bipolar; DG, diffuse ganglion; H, horizontal; M, Müller cell; MB, midget bipolar; MG, midget ganglion; R, rod; RB, rod bipolar. (B) Layers and membranes of the retina.

Figure 2-2. Visual ﬁeld defects related to the anatomy of the visual pathway. The arrow is perpendicular to the horizontal line of the retina throughout the visual pathway. Macular projections are shown as small circles; the monocular temporal crescent ﬁeld is shown with stipple. Projections from the superior retina (inferior visual ﬁeld) are shown in red; projections from the inferior retina {superior visual ﬁeld) are shown in blue. Visual ﬁeld defects and lesions: (1) Left optic nerve—blind left eye. (2) Vascular lesion of upper aspect of right optic nerve—right inferior altitudinal hemianopia. (3) Left optic nerve involving crossed inferior retinal ﬁbers—junctional scotoma with contralateral superior quadrant ﬁeld defect. (4) Optic chiasm, crossing ﬁbers—bitemporal hemianopia. (5) Optic chiasm, uncrossed ﬁbers compressed by internal carotid arteries and/or perichiasmal tumor—binasal hemianopia. (6) Optic tract—contralateral relative afferent pupillary defect and contralateral homonymous hemianopia, often incongruous. (7) Lateral geniculate body—contralateral homonymous hemianopia. (8) Optic radiation— contralateral homonymous hemianopia, less congruous anteriorly; optic radiation is external to lateral ventricle. (9) Parietal lobe (and nonstriate occipital visual cortex)— contralateral inferior quadrantanopia. (10) Temporal lobe (and nonstriate occipital visual cortex)—contralateral superior quadrantanopia, often incongruous. (11) Occipital lobe—contralateral homonymous hemianopia. (12) Occipital pole through midportion of calcarine ﬁssure—contralateral hemianopic central scotomas. (13) Anterior portion of calcarine ﬁssure and ﬁbers to it—contralateral hemianopia with macular sparing. (14) Extreme anterior lip of calcarine ﬁssure—contralateral temporal crescent ﬁeld defect.

44

Anatomic Basis and Differential Diagnosis of Field Defects

45

Figure 2-3. Arterial supply of the visual pathway. Left optic nerve and carotid arteries viewed from left; right optic tract, optic radiation, middle and posterior cerebral arteries viewed from their medial surfaces; other cerebral structures removed. Note the dual blood supplies of the optic tract and lateral geniculate body from the anterior choroidal and posterior cerebral artery branches. The temporal isthmus is supplied by the anterior choroidal artery. Inset, Blood supply of the optic nerve head from anastomotic branches of the pial arterioles and posterior ciliary artery branches. The anastomotic vascular circle of Zinn-Haller is thought to be incomplete, explaining the watershed infarctions at the vertical poles of the optic nerve head that are characteristic of anterior ischemic optic neuropathy. Note that the intraneural course of the ophthalmic artery in the optic nerve is longer than that of the central retinal artery.

to the normal focusing of light onto the retina. There are four neural elements in the primary visual sensory pathway. Three are in the retina: the photoreceptor, the bipolar cell, and the retinal ganglion cell (see Figure 2-1). Afferent sensory systems are described as having three orders of neurons excluding the neurosensory transduction cell, which in the retina is the photoreceptor. The ﬁrst-order neurons are the bipolar cells. The retinal ganglion cells and the axons in the nerve ﬁber layer of the retina and the optic nerve comprise the second-order neurons. These neurons are also called the anterior visual pathway and include the retinal ganglion cell layer, optic nerves, optic chiasm, and optic tracts. The third-order neurons extend from the lateral geniculate body to the calcarine cortex along the optic radiation. These neurons are often called the posterior visual pathway.

46

Visual Fields

TABLE 2-2. Territories of the visual pathway Structure

Neuron order

Visual Pathway

Territory

Optical media

—

—

Preretinal

Photoreceptor

—

—

Retinal

Bipolar cell

First

—

Retinal

Retinal ganglion cell body

Second

Anterior

Neural I

Retinal ganglion cell axon

Second

Anterior

Neural II

Optic nerve axon

Second

Anterior

Neural II

Optic chiasm axon

Second

Anterior

Neural III

Optic tract axon

Second

Anterior

Neural IV

Optic radiation

Third

Posterior

Neural IV

Abnormalities of the preretinal territory may produce a generalized depression of the visual ﬁeld, a ﬂattening of the hill of vision, or sometimes a localized depression but rarely a scotoma. Visual ﬁeld defects relating to a retinal region such as the macula can involve the retinal territory (with a lesion of the outer retinal layers or choroid) or neural territory I (with a lesion of the inner retinal layers). A partialthickness macular hole involving only the internal layers of the retina would be designated as occurring in neural territory I as described by Trobe and Glaser.1 Neural territory I lesions never respect the vertical meridian but reﬂect the anatomy of the abnormal retinal sensory structures. Lesions of the retinal nerve ﬁber layer and optic nerve are designated as occurring in neural territory II, perichiasmal lesions as occurring in neural territory III, and retrochiasmal lesions as occurring in neural territory IV.

2-2-1 Occipital Lobe. Occipital lobe lesions may cause visual ﬁeld defects due to involvement of any or all of these three anatomic sites: the optic radiation, the primary or striate visual cortex, the secondary visual cortex. Studies performed in the 1990s using MR imaging (MRI), functional MRI, and computer graphics have signiﬁcantly altered our understanding of the retinotopic projection within the visual cortex. These studies have: 1. Demonstrated remarkable variability in the orientation of the calcarine ﬁssure, from almost horizontal to almost vertical in different human brains. 2. Expanded the proportional area of the macular projection so that it takes up almost all but the anterior part of the striate cortex within and adjacent to the calcarine ﬁssure of the occipital lobe2; the striate cortex is designated as VI. 3. Identiﬁed the borders of the secondary visual areas, including V2, V3, and others.3,4 The V designations for the visual areas have been carried over from studies in nonhuman primates.

Anatomic Basis and Differential Diagnosis of Field Defects

47

The medial surface of the occipital lobe is bordered anteriorly by the parietooccipital sulcus, which intersects with the anterior portion of the calcarine ﬁssure that divides the occipital lobe into a superior and an inferior portion. The orientation of the calcarine ﬁssure is now routinely observable on the sagittal MRI section. The primary projection of the fovea to the striate cortex is to the most posterior portion of the occipital lobe and usually extends 1 cm onto the lateral convexity of the occipital lobe (Figure 2-4A). The eccentricity of the projection for the fovea can be measured along the calcarine ﬁssure to the junction with the parietooccipital ﬁssure, where the most peripheral visual ﬁeld is located; this distance is about 80 mm. The linear cortical magniﬁcation factor is one way of expressing the weighting given to the retinal projection within the striate cortex. Horton and Hoyt2 have estimated that the linear cortical magniﬁcation factor is 9.9 mm/degree at 1° eccentricity, 2.0 mm/degree at 5°, and 1.6 mm/degree at 10°.

A

B

Figure 2-4. Representation of the primary visual ﬁeld on the human striate cortex. Blue, binocular representation; green, monocular representation. (A) The cortical banks surrounding the calcarine ﬁssure have been slightly opened to better expose the borders of this region. The lower vertical visual ﬁeld meridian is located on or close to the medial cortical surface of the upper bank, while the upper vertical visual ﬁeld meridian is located on or close to the medial cortical surface of the lower bank. Most of the primary visual cortex is hidden within the ﬁssure. (B) The calcarine ﬁssure has been widely opened so that the horizontal meridian is indicated at the depth of the ﬁssure. The fovea is represented at the most posterior portion of the ﬁssure (the fundus), and the relative location of the physiologic blind spot of the contralateral eye is indicated by the dark ellipse. The most anterior 8-10% of the striate cortex (green area) represents the monocular temporal ﬁeld of the contralateral eye. The scale bar is calibrated in centimeters. (Source: Redrawn with permission from Horton JC, Hoyt WF. The representation of the visual ﬁeld in human striate cortex: a revision of the classic Holmes map. Arch Ophthalmol. 1991;109:816–824. Copyright 1991, American Medical Association.)

48

Visual Fields

The clinical implications of this magniﬁed projection of the macula in the primary visual cortex are many. With regard to the selection of the automated visual techniques, this information diminishes the concern that a 24° radius visual ﬁeld might miss some cortical lesion that could have been detected by a 30° radius examination. Actually, a 30° visual ﬁeld tests 83% of the cortical area, while a 24° visual ﬁeld tests 80%. Thus, only 3% of the cortical visual ﬁeld is lost from the examination by the reduction of the tested area and the test time. Conversely, only the most anterior 10% of the striate cortex is involved in the uniocular temporal crescent, a cortical area equal to that devoted to the central 1° of the visual ﬁeld. The large proportion of the striate cortex devoted to the macula also explains why the central 8° of stimulation during pattern-shift visually evoked cortical potential testing generates 60% of the voltage of the P100 wave form. The most important implication of this expanded representation of the macula is that there is a large anatomic substrate for the phenomenon of macular sparing. Survival of even a small portion of the striate cortex provides some possibility for retained macular function. Most of the striate cortex is contained within the superior and inferior banks of the calcarine ﬁssure. The unfolded size of the striate cortex is 40 × 80 mm. The horizontal meridian for V1 is thus buried along the fold line separating the superior and inferior banks, while the lower and upper visual ﬁeld vertical meridians are represented on the superior and inferior gyri of the calcarine ﬁssure (Figure 2-4B). The horizontal and vertical visual ﬁeld meridians meet at the posterior pole of the occipital lobe, where the fovea is represented, and again anteriorly at the anterior pole of the calcarine ﬁssure, where the temporal crescent is projected. The reader can conceptualize this representation by imagining the right visual hemiﬁeld as an elastic sheet in visual space attached on an opened semicircular fan with a pivot at the fovea (Figure 2-5). The extrastriate visual cortex is situated above, below, and surrounding the striate cortex on the medial and lateral surfaces of the occipital lobe. This relationship is best seen with computer graphic techniques that unfold, and then cut and ﬂatten the occipital lobe (Figure 2-6).3 These maps can now be made in normal subjects with physiologic, functional MRI and conﬁrm maps made from pathologic cases. While such studies should have many applications with regard to our comprehension of human visual performance, the most immediate application is understanding that an extrastriate lesion that crosses both a horizontal and a vertical meridian of the secondary visual cortex (V2 and/or V3) can cause an inferior homonymous quadrantanopia in the absence of lesions in the parietal lobe or calcarine ﬁssure (Figure 2-7).

2-3 MONOCULAR FIELD DEFECTS 2-3-1 Localized Defects 2-3-1-1 Wedge-Shaped Temporal Field Defect. This pattern of ﬁeld defect has its apex pointing toward the physiologic blind spot and involves ganglion cell axons from the nasal retina (Figure 2-8).

Anatomic Basis and Differential Diagnosis of Field Defects

A

B

49

C

Figure 2-5. Topologic representation of the right visual hemiﬁeld onto the left visual cortex. (A) The reader can conceptualize by imagining the right hemiﬁeld as an elastic sheet in visual space attached on an open semicircular fan with a pivot at the fovea. (B) As the fan collapses around the foveal pivot, the vertical meridians become parallel (and inverted due to the inverted image in the eye) and the elastic sheet collapses along the temporal border. The foveal region is stretched toward the periphery, thus magnifying the proportional area of the representation of the central visual ﬁeld. (C) The ﬂattened representation of the hemiﬁeld in the left visual cortex. The upper and lower vertical meridians are parallel, and the temporal borders collapse at the most anterior part of the calcarine cortex. The green areas correspond to the monocular temporal crescent. HM, horizontal meridian; LTB, lower temporal border; LVM, lower vertical meridian; UTB, upper temporal border; UVM, upper vertical meridian. (Source: Redrawn with permission from Horton JC, Hoyt WF. The representation of the visual ﬁeld in human striate cortex: a revision of the classic Holmes map. Arch Ophthalmol. 1991;109:816–824. Copyright 1991, American Medical Association.)

Retina (1). In the nasal retina, the ganglion cell layer contains the nuclei of the axons that will travel through the retinal nerve ﬁber layer to approach the optic nerve head in fan-shaped bundles: the superior (A) and inferior (B) radiating bundles. Any lesion causing complete destruction of a region of the inner retinal layers—retinal nerve ﬁber, ganglion cell, inner plexiform, or inner nuclear (bipolar cell) layer—is likely to cause a dense ﬁeld defect. Occlusion of one of the nasal branches of the central retinal artery or nasal tributaries of the central retinal vein can cause a wedge-shaped ﬁeld loss with its apex at the physiologic blind spot. Although the usual pattern of distribution of the branch retinal arteries is quadrantic, it should be noted that the central point of the quadrants is the optic nerve head, not the fovea. When analyzing a visual ﬁeld defect that involves one or more quadrants of the visual ﬁeld, one should determine if the quadrants are retinovascular and related to the physiologic blind spot or neurologic and related to the point of ﬁxation. Embolic disease involves the superotemporal branch retinal arterioles more frequently than the nasal branch retinal arteries. The initial ﬁnding may consist of a dense scotoma reﬂecting a complete loss of function of the inner retinal layers, including the nerve ﬁber layer. Unless recovery occurs within a few days, the ﬁeld loss may be permanent. The blind spot–based quadrantic ﬁeld loss may not have its apex extend to the blind spot if the occlusion occurs at a peripheral bifurcation of a retinal arteriole. The inner retinal swelling may ﬁrst manifest a white appearance (e.g., the cherry-red

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A

B

C

D

Figure 2-6. Retinotopic projection of human visual areas as derived from functional MRI studies. (A) MRI snowing original cortical surface of right cerebral hemisphere with retinal isoeccentricity indicated by a color code on the cortical surface. Red indicates the fovea, then blue, then green (for the parafovea), then yellow, then brown for the far periphery. (B) The cortical surface is unfolded by computer manipulation, thus expanding the apparent area of the brain. The local areas and local angles are preserved. The sulcal cortex is dark gray and the gyral cortex is light gray. (C) The cortical surface of the occipital lobe is ﬂattened after the occipital lobe has been cut off, and an additional cut (dashed line in B) has been made in the fundus of the calcarine sulcus. (D) The schematic functional representation of the primate (striate, V1) and the secondary visual cortex (extrastriate visual areas, V2, and to some extent V3 are shown as repetitive mirror images surrounding the primary visual cortex). V4 is present only in the lingual gyrus of the inferior occipital lobe and is associated with color recognition. The arrow shows the location of the fovea. VP, ventroposterior area. (Source: Redrawn with permission from Sereno MI, Dale AM, Reppas JB, et al. Borders of multiple visual areas in humans revealed by functional magnetic resonance imaging. Science. 1995;268:889–893.)

spot of the macula that is seen if both the inferior and the superior temporal branch retinal arterioles are occluded). Occlusion of the superior branch retinal arteriole produces an inferior altitudinal ﬁeld defect. Acute systemic hypotension can have effects similar to those of arterial occlusion. Thrombosis of the tributary retinal veins usually occurs at and distal to the arteriovenous crossings. Systemic arterial hypotension and ocular hypertension (glaucoma) are predisposing factors. The ﬁeld defects following venous occlusion are often more peripheral and less dense, giving more hope for late recovery than is

Anatomic Basis and Differential Diagnosis of Field Defects

51

B

A Figure 2-7. (A) A schematic representation showing the retinotopic organization of the left posteromedial occipital lobe and the coordinates of the right visual ﬁeld projected onto the striate (V1) and extrastriate (V2, V3) visual cortex. The hemivisual ﬁeld projection is arranged from posterior to anterior so that the horizontal meridian (HM) and the vertical meridian (VM) alternate at the extrastriate area boundaries. A lesion (gray area) that crosses these boundaries will produce a congruous inferior quadrantic visual ﬁeld defect. (B) The lesion shown is rather anterior so that the fovea 10° is spared. Occipital lobe lesions that do not involve the calcarine ﬁssure can produce a quadrantic visual ﬁeld defect mimicking a parietal lobe lesion. (Source: Redrawn with permission from Horton JC, Hoyt WF. The representation of the visual ﬁeld in human striate cortex: a revision of the classic Holmes map. Arch Ophthalmol. 1991;109:816– 824. Copyright 1991, American Medical Association.)

Figure 2-8. Wedge-shaped temporal ﬁeld defect.

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possible for the ﬁeld defects of arterial occlusion. Secondary ﬁeld changes may occur as a result of chronic macular edema or preretinal and vitreous hemorrhages. Lesions nasal to the optic nerve head will cause wedge-shaped scotomas or peripheral contraction in the ﬁeld temporal to the blind spot. Lesions of the choroid or outer retinal layers will usually cause less dense defects, because the nerve ﬁbers passing in the overlying nerve ﬁber layer and some of the input to the bipolar cells in the affected region may be spared. Complete loss of ﬁeld occurs in regions where retinoschisis has split the retina, thus disconnecting the retinal ganglion cells from the photoreceptors. In contrast, retinal detachments produce milder depressions with less steep margins, at least in their early stages. Optic Nerve Head (2). The retinal course of the axons is such that the most posterior enter the peripheral portions of the optic nerve head while the most anterior retinal axons enter the central portion. Drusen of the optic nerve head produce local injury to axons at the optic nerve head and may cause progressive (rarely sudden) contraction of the visual ﬁeld or localized depressions or scotomas. The arterial anatomy of the optic nerve head is invoked to explain various patterns of ﬁeld loss. The ophthalmic artery is the ultimate source of supply to a continuous capillary bed that extends throughout the optic nerve head. The arterial blood is delivered by three systems: (1) branches of the short posterior ciliary arteries that enter the medial and lateral peripapillary sclera within 1 mm of the peripheral margin of the optic nerve head, (2) vessels of the pial plexus and retrobulbar optic nerve, and (3) branches of the central retinal artery. The posterior ciliary artery branches were formerly described as completing the arterial circle of Zinn-Haller, but an anatomically demonstrable arterial circle is generally not complete (see Figure 2-3). The circle of Zinn-Haller may also be supplied by pial arterioles supplying the anterior aspect of the optic nerve. The lack of functional anastomotic continuity is invoked to explain the altitudinal ﬁeld defects that present in anterior ischemic optic neuropathy. Focal infarctions, usually at the vertical poles of the optic nerve head, may result from infarction in watershed zones between territories served by centripetal optic nerve head branches of the short posterior ciliary arteries (C). The posterior ciliary arteries are generally situated near the horizontal poles of the optic nerve head. They also give rise to centrifugal branches that supply the peripapillary choroid. Retrobulbar Optic Nerve (3). Monocular wedge-shaped nerve ﬁber bundle defects can occur with infarction, inﬂammation, tumors, or trauma anywhere between the optic nerve head and the optic chiasm. However, the likelihood of involving only the nasal ﬁbers decreases at 1 cm behind the globe as ﬁbers from the papillomacular bundle disperse throughout the optic nerve.

2-3-1-2 Arcuate and Paracentral Field Defects. Pericentral (within 5° of the fovea) or paracentral (within 20° of the fovea) scotomas or depressions in the Bjerrum region result from injury to retinal ganglion cell arcuate axons arising from the temporal retina (Figure 2-9). These arcuate nasal defects are often referred to as “nerve ﬁber bundle defects,” although they are just one particular pattern of nerve ﬁber bundle defect. Injury to either the superior or the inferior nerve ﬁber bundle will produce an arcuate scotoma terminating at the horizontal meridian. If the superior and inferior ﬁbers are injured asymmetrically, a nasal step ﬁeld defect will result.

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Anatomic Basis and Differential Diagnosis of Field Defects

Figure 2-9. Arcuate and paracentral ﬁeld defects.

Retina (1A and 1B). During the embryogenesis of the eye, the fovea develops at the temporal periphery. At that time, all the nerve ﬁbers have a fan-shaped radiation from the optic nerve head. Later in development, the fovea migrates toward the optic nerve head. As a result, the temporal nerve ﬁber layer arches around the fovea, causing the nerve ﬁber layer to assume an arcuate shape—the superior (1A) and inferior (1B) arcuate bundles. Peripheral axons in the arcuate bundles originate in ganglion cells on either side of the horizontal retinal raphe. The initial course of these axons is parallel to the horizontal raphe (C) where the axons are in the superior or inferior temporal retinal raphe. The arcuate portion of the retinal nerve ﬁber layer also contains the blood vessels coursing around the macular region. The arcuate portion of the retinal nerve ﬁber layer is the thickest (0.5 mm), and its bundles reﬂect bright white striations especially when viewed with red-free (green-ﬁltered) light. The thickness of the nerve ﬁber layer decreases 1 or 2 disc diameters from the optic disc margin. Loss of the retinal nerve ﬁber layer may occur in various patterns ranging from diffuse atrophy to highly localized atrophic wedge defects. The minimum ophthalmoscopically detectable wedge defect is the loss of a 50-μ thickness of nerve ﬁbers adjacent to 50 μ of intact nerve ﬁbers. This would represent a loss of 15,000, or about 1% of retinal axons.5 Optic Nerve Head (2). The retinal ganglion cell axons pass as nerve ﬁber bundles through the pores of the collagenous scleral lamina within the scleral canal.

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The upper and lower quadrants of the optic nerve head contain the least dense glial and connective tissue and the largest laminar pores. It has been suggested that the vertical quadrants through which the arcuate area ganglion cell axons pass are the most susceptible regions of the optic nerve head to the effects of elevated intraocular pressure.6 This sensitivity may explain the isolated paracentral scotomas 5° to 25° from ﬁxation that are usually the earliest ﬁeld defects of glaucoma. Conversely, the central 5° and the temporal ﬁelds are preserved until the later stages of glaucoma. Glaucoma causes nerve ﬁber bundle defects that occur ﬁrst in ﬁbers of the superior (A) or inferior (B) arcuate bundles. Glaucoma is the most common cause of arcuate ﬁeld defects. The horizontal raphe is the basis for nasal step ﬁeld defects. The changes are thought to result from localized ischemia of the ﬁbers within the optic nerve head, where they are supplied by branches of the arterioles of the peripapillary region. Optic nerve head drusen, microvascular disease, low-tension glaucoma, tumors, myopia, and congenital defects of the optic nerve head can also cause arcuate ﬁeld defects. Retrobulbar Optic Nerve (3). Discrete lesions of the retrobulbar optic nerve that are within 1 cm of the globe can spare ﬁbers of the papillomacular bundle. Occasionally, monocular arcuate ﬁeld defects may appear, with lesions as far posterior as the optic chiasm. It has been observed that any anterior visual pathway lesion can mimic any other. Thus, caution should be applied when localizing a ﬁeld defect with excessive certainty.

2-3-1-3 Central Scotoma or Depression. This pattern of ﬁeld defect usually results from a lesion in the papillomacular bundle of retinal ganglion cell axons (Figure 2-10). Retina (1). The papillomacular bundle consists of many small bundles of retinal axons entering the temporal border of the optic nerve head. Axons on the horizontal meridian (A) serve the nasal aspect of the macula and project temporally to the vertical meridian of the visual ﬁeld. The superior and inferior portions of the papillomacular bundle serve the temporal aspect of the macula. These ﬁbers arch around the fovea to meet at the horizontal meridian (B). The temporal ﬁbers of the papillomacular bundle arise at right angles to the horizontal meridian, while the arcuate ﬁbers arise parallel to the horizontal raphe (C). This may explain why nasal step defects are more marked outside the macular region of the visual ﬁeld. Some ﬁbers within 3° of the macula segregate to the “wrong” side of the optic chiasm and thus may provide some explanation for some cases demonstrating up to 3° of “macular sparing” in retrochiasmal homonymous hemianopias. However, research using the scanning laser ophthalmoscope has shown that most cases of macular sparing are accompanied by nystagnoid searching movements toward the seeing hemiretina, and thus result from a perimetric artifact rather than an anatomic anomaly.7 Occlusion of the macular branches of one or more branch retinal arterioles or of a cilioretinal artery may also explain a central scotoma or depression. Photocoagulation of outer retinal layer and choroidal lesions can often be accomplished without causing a central scotoma. Initial photocoagulation may scar the nerve ﬁber layer to the underlying (outer) layers, so that repeated

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Anatomic Basis and Differential Diagnosis of Field Defects

Figure 2-10. Central scotoma or depression ﬁeld defect.

photocoagulation is likely to cause a ﬁeld defect. The papillomacular bundle contains more than half the optic nerve axons. Signiﬁcant depressions of visual acuity, central visual ﬁelds, spatial contrast sensitivity, and color perception may follow lesions in the macular region. The differential diagnosis of anatomic lesions in the macular region is beyond the scope of this chapter. The projection of human retinal ganglion cell axons of various sizes and physiologic characteristics must be deduced from studies in monkeys and cats, and these studies have not given wholly consistent results. It is generally agreed that the largest, fastest-conducting axons, including 25% of the axons originating in the parafoveal region, terminate in the magnocellular layers of the lateral geniculate nucleus. These are designated as magnocellular (M) cells and in many respects are similar to the Y cells of cats. The larger-diameter axons are thought to be important in such functions as achromatic vision, blue-yellow vision, and high temporal frequency vision (loss of the larger-diameter axons results in lowering of the critical ﬂicker fusion frequency). Glaucoma seems to be a disorder whose initial effects are on the more peripheral M (Y-like) cells. Contrast-sensitivity testing seems to be particularly sensitive to M-cell dysfunction because M cells have large receptive ﬁelds, high contrast sensitivity, and a broad band of spectral response.

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Smaller-diameter, slower-conducting axons arise throughout the entire retina and terminate in the parvocellular regions of the lateral geniculate nucleus. These are designated as parvocellular (P) cells and are similar to the X-like cells of cats. The parvocellular cells include the midget ganglion cells with small receptive ﬁelds that account for central vision acuity and color opponent features. They have low contrast sensitivity. Optic Nerve Head (2). Lesions of the optic nerve head may involve sufﬁcient numbers of papillomacular axons to cause a central scotoma. Retrobulbar Optic Nerve (3). Axons arising from the midget ganglion cells of the macula are generally smaller than other axons in the optic nerve. Although they enter on the temporal side of the nerve initially, they mingle with all the bundles from the retinal quadrants within a short distance. The ﬁbers that will cross to the contralateral optic tract are probably segregated a few millimeters prior to the junction of the optic nerve with the optic chiasm. Within the optic chiasm, the macular ﬁbers are generally superior to those from the peripheral retina.

2-3-1-4 Enlarged Physiologic Blind Spot. This pattern of visual ﬁeld defect results at or in the immediate vicinity of the optic nerve head. It is sometimes designated as a pericecal ﬁeld defect (Figure 2-11). Peripapillary Retina (1). Papilledema causes swelling of the optic nerve head axons (A) in the retina. These axons are not free to expand at the lamina scleralis (B) but

Figure 2-11. Enlarged physiologic blind spot (a pericecal ﬁeld defect).

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Anatomic Basis and Differential Diagnosis of Field Defects

57

are free to expand at the lamina choroidalis (C) and even more free to expand at the lamina retinalis (D), resulting in displacement of the adjacent retina and choroid. Because the peripapillary receptors are displaced laterally in all directions, this could partially explain the increase in the size of the absolute scotoma that comprises the physiologic blind spot. However, the major cause may be swelling of the axons and intercellular retinal edema (E). This masks some of the light falling on the peripapillary retinal receptors and, in turn, causes a relative scotoma or depression outside the absolute scotoma. Moreover, some of the enlargement of the blind spot is refractive, due to peripapillary hyperopia.8 Increased hyperopic refractive correction usually eliminates or reduces the size of an enlarged blind spot resulting from the optic nerve head swelling of increased intracranial pressure (papilledema). Other peripapillary disorders may cause absolute and relative increases in the size of the physiologic blind spot, but these are not usually as symmetric. Often they result in a pericecal depression or scotoma. Advanced papilledema may be associated with swelling of the outer plexiform layer of the retina (F, Henle’s layer). The anatomic relationships of the nerve head to the macula are reversed in the visual ﬁeld, so the nerve head is anatomically superior to the macula on the globe but the blind spot is below the ﬁxation point in the visual ﬁeld. It is useful to know certain quantitative anatomic relationships of the optic nerve head (Table 2-3), based on the assumption that 1 mm of circumference at the retina corresponds to about 5.0° of visual ﬁeld. Optic Nerve (2). Some forms of optic neuropathy, particularly ethanol-induced toxic optic neuropathy, produce centrocecal scotomas.

2-3-1-5 Centrocecal Scotoma or Depression. This phrase describes a visual ﬁeld abnormality encompassing both the central region of ﬁxation and the physiologic blind spot (Figure 2-12). Retina (1). The papillomacular bundle can be involved by regional choroidal, outer retinal, and inner retinal layer lesions. Causes can include optic pit with serous retinal detachment, macular degeneration or inﬂammation, or cilioretinal artery (1) occlusion. Superior or inferior cilioretinal arteries are present as congenital developmental variations in about 20% of normal eyes. They are retinal branches of the ophthalmic artery via a posterior ciliary artery rather than via a central retinal artery. A cilioretinal artery may be occluded alone, sparing the retinal regions supplied by the central retinal artery, or it may be uninvolved with occlusion of the central retinal artery leaving a small island of vision with good acuity. Optic Nerve (2). Many types of optic nerve lesions including toxic and nutritional amblyopias may produce centrocecal scotomas. The monoﬁxation syndrome results

TABLE 2-3. Quantitative Anatomy of the Optic Nerve Head Diameter of Optic Nerve Head

Relation of Nerve Head to Macula

Horizontal: 1.1 mm, 5.5°

Nasal: 3.0 mm, 15.0°

Vertical: 1.5 mm, 7.5°

Inferior: 0.3 mm, 1.5°

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Figure 2-12. Centrocecal scotoma or depression.

in a central scotoma of less than 3° radius in one eye. It can be detected only with binocular perimetry (e.g., red and green targets viewed with a red-ﬁltered right eye and a green-ﬁltered left eye).

2-3-1-6 Equatorial Annular Scotoma or Depression. These visual ﬁeld defects usually begin as depressions of the ﬁeld at a 25° to 45° radius from the point of ﬁxation (Figure 2-13). Preretinal Media (1). An annular, or ring, scotoma can be produced by aphakic spectacle lenses and relieved by removing them. The scotoma is produced by light rays striking the highly convex surface from an oblique direction and their being refracted outside the pupil. Equatorial Retina (2). The term retinitis pigmentosa describes a heterogeneous group of genetically determined disorders. Although there are notable exceptions (e.g., unilateral pigmentary retinopathy and sector pigmentary retinopathy), the usual pathologic and visual ﬁeld changes occur in a circular region measuring 25-50° from ﬁxation. The earliest changes of retinitis pigmentosa may be confused with the arcuate and paracentral nerve ﬁber bundle defects of glaucoma, where the ring scotoma may originate with vertical enlargement and baring of the physiologic blind spot, giving two arcuate scotomas that complete a ring (see Figure 2-9).

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Anatomic Basis and Differential Diagnosis of Field Defects

Figure 2-13. Equatorial annular scotoma or depression.

2-3-1-7 Altitudinal Hemianopia. For a discussion of monocular altitudinal hemianopia, see Section 2-4-4-1. 2-3-2 Generalized Defects 2-3-2-1 Generalized Depression or Peripheral Contraction. Generalized depression or peripheral contraction of the visual ﬁeld results when a focal light stimulus greater than the background light produces less sensory appreciation than normal at any and all locations of the visual ﬁeld. The depression may be equal in all meridians or may be unequal. An unequal diffuse ﬁeld abnormality may be the sum of the abnormalities induced by several factors. An extreme example would be a superior altitudinal defect from a ptotic eyelid plus diffuse depression of the media from a cataract plus a central scotoma from a welding burn of the fovea plus a nasal scotoma from glaucoma. Preretinal Media. The artifact caused by a lens used for central perimetry may often affect the outer points of a central 30° visual ﬁeld examination and be particularly confusing with programs that merge central and peripheral examinations on a single chart. Body parts such as the nose and upper eyelid frequently cause localized abnormalities. Media opacities include contact lenses, corneal edema, scars, and the astigmatic aspects of keratoconus. Cataracts are the most frequent media opacity and may cause either generalized, localized, or combined depression, contraction,

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or scotomas. Cataracts cause ﬁeld defects more by scatter and defocusing of the stimulus light with regard to the background light (decreased contrast) than by absorption or backscatter of the stimulus light. Vitreous hemorrhage can also depress the visual ﬁeld. Retina. Diffuse disorders of all retinal elements (photoreceptors to ganglion cells) can cause generalized depression of the visual ﬁelds. A description of all the disorders that can cause diffuse monocular pathology is beyond the scope of this chapter. Optic Nerve. Most monocular optic nerve disease is compressive, demyelinating, traumatic, or vascular. A detailed description of these disorders is beyond the scope of this chapter. About half the patients with optic neuritis present with diffuse visual ﬁeld loss; 20% have altitudinal or other nerve ﬁber bundle-type defects, while only 8% have central or centrocecal scotomas.

2-4 BINOCULAR FIELD DEFECTS 2-4-1 Homonymous Hemianopias. Any retrochiasmal lesion may present with a congruous homonymous hemianopia. The occipital lobes and the parietal lobes are more frequent than the temporal lobes as the locations of lesions causing the visual ﬁeld defects. 2-4-1-1 Complete: Macular Splitting. A complete homonymous hemianopia with macular splitting refers to the loss of either the entire right or the entire left visual ﬁeld of both eyes. The central 5° of the visual ﬁeld is designated as the macular portion of the visual ﬁeld. It may be included in the complete hemianopic ﬁeld defect; thus, the macular region is “split.” Conversely, it may not be included, in which case it is “spared” (Figure 2-14). Optic Tract (1). Any lesion ascending the visual pathway beyond the ﬁrst few millimeters of the optic tract may cause a complete homonymous hemianopia. A lesion at the junction with the optic chiasm may cause a junctional scotoma. Optic tract lesions are associated with wedge-shaped retinal axonal degeneration and death of the retinal ganglion cell layer nasal to the fovea of the contralateral eye. Ophthalmoscopy with red-free light reveals homonymous hemiretinal atrophy at the nasal aspect of the contralateral optic nerve head and in a narrow band along the horizontal meridian at the temporal aspect of the nerve head. It should be noted that the nasal aspect of the fovea is represented by ﬁbers in the middle of the papillomacular bundle. The ipsilateral eye will reveal bow-tie atrophy of the superior and inferior arcuate bundles of the retinal nerve ﬁber layer. The optic tract syndrome consists of a homonymous hemianopia, atrophy of the nasal ﬁbers of the contralateral optic nerve, atrophy of the temporal ﬁbers of the ipsilateral optic nerve, and a contralateral monocular relative afferent pupillary defect. The presumed basis is that about 60% of afferent pupil ﬁbers decussate at the chiasm, giving rise to unequal representation of the two eyes in each optic tract. Anatomic studies in monkeys have shown that the retinal vertical midline is almost absolute. Above and below the macula, there is only a 1° overlap across the vertically oriented midline strip when the axonally transported tracer horseradish

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Anatomic Basis and Differential Diagnosis of Field Defects

Figure 2-14. Complete homonymous hemianopia with macular splitting.

peroxidase is injected into the lateral geniculate body and observed in the retinal ganglion cells. At the macula the overlap widens to 3°. Thus, there is no anatomic basis for macular sparing greater than 3° in patients with a complete retrochiasmal hemianopic lesion. Any macular sparing exceeding this amount must be ascribed to errors in ﬁxation or response. (For further discussion, see Section 2-3-1-3.) There is no evidence of any representation of ipsilateral visual ﬁeld in the calcarine cortex. Lateral Geniculate Body (2). Both the lateral geniculate body and the optic tract have dual arterial supplies. The lateral and anterior aspect of the lateral geniculate body is supplied by the anterior choroidal artery, a branch of the internal carotid artery (A), while the dorsal and medial aspect is supplied by the lateral choroidal artery (B), a branch of the posterior cerebral artery (C). If both arteries are occluded, a congruous homonymous hemianopia will result. Optic Peduncle (3). The optic peduncle is the ﬁrst portion of the optic radiation. It may be considered a part of the internal capsule. It is posterior to the lentiform nucleus (D), the posterior limb of the internal capsule (E, sensory), and the anterior limb (F, motor). Occlusion of the anterior choroidal artery (A) or of the posterior choroidal artery (G) can produce contralateral hemianopia, hemianesthesia, and, sometimes, hemiplegia. Optic Radiation (4). The optic radiation passes lateral to the inferior horn (H) and the posterior horn (I) of the lateral ventricle. Field defects are often incongruous,

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with anterior lesions becoming more congruous as the ﬁbers in the optic radiation approach the calcarine cortex, except for the portion supplied by the deep optic branch (J) of the middle cerebral artery (K). The optic radiation is supplied by branches of the posterior cerebral artery (C), especially the calcarine branch (L). Calcarine Cortex (5). Field defects are congruous, except when the lesion involves only the extreme anterior portion of the calcarine cortex (6), where the contralateral temporal crescent is represented. The blood supply to the calcarine cortex is from the posterior cerebral artery (C). Occasionally, the calcarine cortex receives an anastomotic branch (M) from the middle cerebral artery. In many cases, the macular representation on the lateral convexity of the occipital lobe may be supplied by branches of the middle cerebral artery.

2-4-1-2 Incomplete Congruous: Horizontal Sectoranopia. This phrase describes a homonymous, congruous wedge-shaped ﬁeld defect extending from the point of ﬁxation to the periphery (Figure 2-15). Lateral Geniculate Body (1). This ﬁeld defect may result from a vascular lesion (e.g., a lateral choroidal artery infarction) damaging the dorsal portion of the lateral geniculate body that serves the macular function yet causing little damage to the medial portion with the terminations of axons from the inferior retina or to the lateral portion with the terminations of ﬁbers from the superior retina. Frisén9 has presented a case of a congruous homonymous sectoranopia sparing the

Figure 2-15. Horizontal sectoranopia.

Anatomic Basis and Differential Diagnosis of Field Defects

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horizontal sector. Computed tomography (CT) scanning demonstrated changes in the lateral geniculate body that followed ligation of the distal portion of the anterior choroidal artery. Incongruity with lesions of the lateral geniculate body is rare and, if present, may result from simultaneous involvement of the optic tract. Wedge-shaped defects that do not fully extend from ﬁxation to the periphery have been reported with occipital infarction (2).

2-4-1-3 Incomplete Congruous: Paramidline-Sparing Vertical Hemianopia. This phrase describes an incomplete congruous hemianopia in which the paramidline portion of the visual ﬁeld is spared. The spared portion is bordered by a vertical line tangent to a horizontal radius (Figure 2-16). Posterior and Middle Cerebral Arteries. After recovery from coronary artery bypass surgery, cardiac arrest, or similar hypoxic events, dysfunction may be present in the watershed zones (1) at the borders of perfusion of the middle (A) and posterior (B) cerebral arteries. Thus, occlusion can give rise to a ﬁeld defect stretching from the top to the bottom of the visual ﬁeld about 5-10° from the vertical midline and may coincide with the lateral border of cortical area 17. Prenatal and infantile hypoxia in these regions may lead to a dense incomplete hemianopic ﬁeld defect associated with a porencephalic cyst (2). The injured ﬁbers of the optic radiation are the most medial ﬁbers, especially those at its upper and lower margins, while the more lateral and intermediate regions of the optic radiation are spared.

Figure 2-16. Paramidline-sparing vertical hemianopia.

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Figure 2-17. Homonymous hemianopia with macular sparing.

2-4-1-4 Incomplete: Macular Sparing. If a congruous homonymous hemianopia is complete except for the central radius of less than approximately 5°, it is said to have sparing of the macular representation of the visual ﬁeld (Figure 2-17). Immediately Postchiasmal Optic Tract (1). Lesions such as craniopharyngiomas may cause a homonymous hemianopia with macular sparing, a rare form of congruous ﬁeld defect. When it occurs, the region of sparing is likely to be less than 2°; perhaps only a few macular ﬁbers remain. Calcarine Cortex (2). The more anterior the lesion of the calcarine cortex, the more the central ﬁeld is spared. Lesions with macular sparing are usually the result of calcarine artery occlusion or tumors. The anastomotic branch of the middle cerebral artery (A) may supply the posterior lateral portion of the calcarine cortex. 2-4-1-5 Incomplete: Two Scotomas. These ﬁeld defects result from two separate lesions in one retrochiasmal visual pathway (Figure 2-18). Postchiasmal Visual Pathway (1). While any location may be involved, the most typical location would be due to occlusions of two branches of one posterior cerebral artery or to occlusion of the ipsilateral posterior and middle cerebral arteries. One or both of the hemianopic homonymous scotomas may involve or spare the macula, as illustrated.

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Anatomic Basis and Differential Diagnosis of Field Defects

Figure 2-18. Two ipsilateral homonymous hemianopic scotomas.

2-4-1-6 Incomplete Incongruous. Incongruity results when the retrochiasmal ﬁbers of the projection of one eye are differentially positioned or injured than the ﬁbers of the opposite eye (Figure 2-19). Anterior Optic Tract (1). Extreme incongruity, especially near the vertical meridian, is usually related to the difference in the projections of ﬁbers from the two eyes in the anterior portion of the optic tracts. The lesions are usually caused by tumors of adjacent structures. The ﬁeld defects may have steeply sloping isopter borders as well as incongruity. Optic Radiation (2). After the ﬁbers of the optic radiation leave the lateral geniculate body through the optic peduncle of the internal capsule (A), they enter the external sagittal striatum to form the midportion of the optic radiation, which lies in the temporal and temporoparietal lobes (B). Incongruous defects may occur in the temporal lobe, because ﬁbers serving homologous points in the visual ﬁelds of the two eyes are not adjacent. The blood supply to the temporal lobe comes mostly from branches of the middle cerebral artery. The ﬁbers of the optic radiation become more compact and the arrangement more homologous as the ﬁbers pass into the posterior portion of the optic radiation in the parietal and parieto-occipital lobes (C). Incongruity and sloping margins are less frequent here. Field defects may result from tumors or middle cerebral artery disease. Because the more medial aspects of the parietal lobe are supplied

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Figure 2-19. Incongruous homonymous hemianopia.

by branches of the anterior cerebral artery, optokinetic nystagmus (OKN), which is generated in the parietal lobe, can be normal and symmetric after occlusions of the posterior or middle cerebral artery. This gives rise to the observation (“Cogan’s rule”) that a hemianopia with asymmetric OKN suggests a tumor; a hemianopia with symmetric OKN suggests a vascular lesion. Occipital Lobe. Incongruous ﬁeld defects rarely occur in the calcarine cortex, except for visual ﬁeld defects involving or sparing the uniocular temporal crescent of the visual ﬁeld. Incongruity suggests a lesion elsewhere.

2-4-1-7 Incomplete: Unilateral Sparing of Temporal Crescent. There is a complete homonymous hemianopia sparing the most peripheral visual ﬁeld of one eye (Figure 2-20). Posterior Calcarine Cortex. The peripheral temporal visual ﬁeld of the contralateral eye is represented in the cortex above and below the most anterior portion of the calcarine sulcus anterior to the junction of the parieto-occipital ﬁssure (A) with the calcarine ﬁssure (B). The lesion responsible for a homonymous hemianopia with temporal crescent sparing would anatomically spare the anterior portions of the lingual gyrus (1C) and the precuneus (ID) while injuring the cuneus (1E) and the posterior portion of the lingual gyrus (1C).

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Figure 2-20. Homonymous hemianopia with temporal crescent sparing.

2-4-1-8 Incomplete: Unilateral Defect of Temporal Crescent. In its purest sense, this is a monocular ﬁeld defect involving the temporal visual ﬁeld of one eye and could even mimic retinoschisis of the nasal retina. However, many patients with such defects have had or will have other homonymous hemianopic ﬁeld defects that are binocular (Figure 2-21). Anterior Calcarine Cortex (1). A lesion of the anterior calcarine cortex may produce a peripheral temporal ﬁeld defect corresponding to the nasal retina of the contralateral eye. The ipsilateral eye visual ﬁeld may later become involved as the lesion extends posteriorly. At this time, the true homonymous hemianopic nature of the problem will appear. In the optic radiation, the ﬁbers that will terminate in the anterior calcarine cortex are situated at the upper and lower edges of the superior (A) and inferior (B) bundles, respectively. They terminate in the precuneus (C) superiorly and in the lingual gyrus (D) inferiorly. The arterial supply comes from the posterior cerebral arteries. 2-4-2 Bitemporal Hemianopias 2-4-2-1 Complete. A bitemporal hemianopia is a temporal ﬁeld defect of each eye (Figure 2-22). Decussating Fibers of Optic Chiasm (1). The optic chiasm is within the subarachnoid basal cistern. It is surrounded by cerebrospinal ﬂuid. At its posterior margin, the

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Figure 2-21. Homonymous hemianopia minus (a unilateral temporal crescent defect).

optic chiasm indents the third ventricle (A). Anteriorly, it is continuous with the optic nerves that dive toward the optic canals at an angle of approximately 45° from the plane of the diaphragm of the sella. If the dive angle of the optic nerve is more vertical, the optic chiasm is said to be preﬁxed with regard to the sella; if the angle is more horizontal, the optic chiasm is described as postﬁxed. One may think of the brain as rotated anteriorly in the former case, while it is rotated posteriorly toward the tentorium cerebelli in the latter case. Because the optic chiasm is usually suspended 1 cm above the posterior two thirds of the diaphragm of the sella turcica, most pituitary tumors (B) must grow about 2 cm above the sella turcica before causing a ﬁeld defect. Preﬁxed optic chiasms are associated with optic tract ﬁeld defects when there is extrasellar extension of pituitary tumors, while postﬁxed optic chiasms are associated with optic nerve ﬁeld defects. Miller10 provided a critique of nerve ﬁber schemata of the optic chiasm. Because the inferior ﬁbers serve the superior ﬁelds, a bitemporal superior quadrantanopia precedes a complete bitemporal hemianopia. The progression is clockwise in the right eye and counterclockwise in the left eye. Eventually, the defect may involve uncrossed ﬁbers at the lateral aspect of the optic chiasm. A complete bitemporal hemianopia gives no clue as to which surface of the optic chiasm was involved by extrinsic processes ﬁrst. A bitemporal hemianopia progressing from the inferior to the superior temporal quadrants suggests initial

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Figure 2-22. Complete bitemporal hemianopia. (A) Third ventricle. The arrows represent the progression of the visual ﬁeld defect associated with the suprasellar extension of a pituitary adenoma (B) from a superior bitemporal quadrantanopia to a complete bitemporal hemianopia.

compression of the superior retinal ﬁbers, as may occur with a craniopharyngioma. Chiasmal visual ﬁeld defects are caused by tumors, demyelinating disorders, trauma, and other conditions.

2-4-2-2 With Central Depression, Scotomatous. In this pattern, the ﬁeld defect is similar to a bilateral centrocecal scotoma but does not involve any aspect of the visual ﬁeld nasal to ﬁxation. The visual acuity may be normal (Figure 2-23A). Nasal Portions of Both Maculas (1). Binocular macular lesions are unlikely to have a sharp vertical border through the point of ﬁxation. Optic Chiasm Fibers from the nasal portions of both eyes cross throughout the optic chiasm (2). Incomplete, diffuse, or posterior lesions may most affect the smallerdiameter macular ﬁbers, causing incomplete central hemianopic depressions, which are best detected with minimal-stimulus contrast targets. The sharp vertical line through ﬁxation is diagnostic. Since the macular ﬁbers are especially dense in the posterior region of the optic chiasm, this ﬁeld defect is even more apt to happen when pituitary tumors occur with a preﬁxed optic chiasm or when the third ventricle is enlarged, as in hydrocephalus. When the optic chiasm is preﬁxed, the intracranial portions of the

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Figure 2-23. (A) Bitemporal hemianopia with central depression, scotomatous. (B) Relationship of the optic chiasm to the turcica, lateral view.

optic nerves are relatively short and the optic chiasm lies closer to the diaphragm of the sella turcica: The optic chiasm is said to be preﬁxed if the anterior portion of the optic chiasm covers the tuberculum sellae (A). This occurs in 5% of patients. The optic chiasm is above the center of the sella turcica (B) in 12% of patients. In 79% of patients, it is above the posterior half of the sella turcica. In 4% of patients, the intracranial portions of the optic nerves are relatively long and the optic chiasm is above the dorsum sella (C). In such patients, the optic chiasm is said to be postﬁxed, and pituitary adenomas must grow a considerable distance beyond the diaphragm of the sella turcica to involve the optic chiasm (Figure 2-23B).

2-4-3 Binasal Field Defects 2-4-3-1 Complete. In this pattern, the ﬁeld defect involves the entire area nasal to ﬁxation in each eye (Figure 2-24). Nondecussating Fibers of Optic Chiasm (1). The optic nerve ﬁbers serving the temporal retina and the nasal visual ﬁeld of each eye do not cross and are in the lateral portion of the optic chiasm. The sharp vertical division of the ﬁeld at the fovea implicates the nondecussating ﬁbers of the optic chiasm. Binasal hemianopiç visual ﬁeld defects are rare and may be the result of fusiform, dolichoectatic, sclerotic, or aneurysmal enlargement of one or both internal carotid arteries (A), which lie lateral to the optic chiasm. The optic chiasm becomes trapped between the dilated

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Figure 2-24. Complete binasal hemianopia.

internal carotid and anterior cerebral arteries lying in the anterior optic chiasmal notch. These are rarely pure nasal hemianopias. Usually, the defects blend with those of one optic nerve (B) or of one optic tract (C) (junctional scotoma).

2-4-3-2 Incomplete. These ﬁeld defects involve a portion of the nasal visual ﬁeld in each eye. It is rare for them to be completely symmetric (Figure 2-25). Bitemporal Retinas (1). The nasal ﬁelds may be depressed, often asymmetrically, in disorders of the peripheral retina. Optic Nerve Head (2). Glaucomatous visual ﬁelds involve the nasal portions of the visual ﬁelds ﬁrst. Optic Nerve (3). Compression of the superolateral surfaces of the optic nerves against the anterior communicating artery and the A-1 segments of the anterior cerebral arteries (A) may occur when there are aneurysms or rarely as a result of expanding sellar tumors. More often than not, these vessels are stretched over the optic chiasm, rather than over the optic nerves. Optic Chiasm (4). Binasal ﬁeld defects resulting from optic chiasmal lesions are much rarer than binasal defects resulting from retinal or optic nerve head disorders (see Section 2-4-3-1). Optochiasmic arachnoiditis may also cause a binasal hemianopia. Dilation of the third ventricle (B) may be accompanied by stretching of the lateral aspect of the optic chiasm. This may explain the binasal hemianopia seen occasionally in patients with hydrocephalus.

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Figure 2-25. Incomplete binasal hemianopia.

2-4-4 Altitudinal Field Defects 2-4-4-1 Noncongruous Binocular and Monocular. Because noncongruous binocular altitudinal visual ﬁeld defects can arise as a result of separate processes in each eye and in the anterior visual pathway, monocular altitudinal visual ﬁeld defects are also considered in this section. Monocular disease may lead to a symmetric or an asymmetric loss of all or part of the superior and/or inferior visual ﬁeld of each eye. Retina (1). While the most signiﬁcant retinal cause of altitudinal ﬁeld loss is an embolism to the superior or inferior branch retinal artery of one eye, there is little likelihood of almost symmetric bilateral lesions without other evidence of stroke. The most common retinal causes of noncongruous altitudinal defects are disorders of the retina such as bilateral rhegmatogenous detachments or bilateral exudative detachments as seen in Harada disease. Disorders that do not directly involve the inner retinal layers may have ﬁeld defects with sloped margins. Altitudinal visual ﬁeld defects with step margins may result from the absence of retina, as occurs in inferior colobomas (Figure 2-26). Optic Nerve Head (2). The short posterior ciliary arteries supply most of the optic nerve head. Occlusion of the short posterior ciliary arteries can cause altitudinal ﬁeld defects in each eye and may be the presenting symptom of anterior ischemic

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Figure 2-26. Noncongruous altitudinal hemianopia.

optic neuropathy. Bilateral optic nerve head colobomas cause superior altitudinal ﬁeld defects. Far-advanced glaucoma could mimic bilateral altitudinal ﬁeld defects if each eye had a large nasal step and breakthrough from the blind spot to the temporal periphery. An apparent altitudinal defect found on a central visual ﬁeld examination should be further examined with peripheral testing to be certain that it is not a nerve ﬁber bundle defect breaking through to the periphery. Automated perimetry incorporates altitudinal hemiﬁeld comparisons to test for threshold asymmetries above and below the horizontal meridian as well as losses that are symmetric around the horizontal meridian. Bilateral optic nerve head drusen may also cause altitudinal visual ﬁeld defects. Optic Nerve (3). While most adult-acquired altitudinal visual ﬁeld defects were thought to result from anterior ischemic optic neuropathy and other vascular causes, it is now known that approximately 20% of persons presenting with optic neuritis have altitudinal or other nerve ﬁber bundle defects.11 Contusions of both optic nerves of the optic chiasm produce altitudinal visual ﬁeld defects. Intracranial tumors and aneurysms of the anterior cerebral and communicating arteries may compress the upper surfaces of both optic nerves.

2-4-4-2 Congruous. Altitudinal hemianopias may symmetrically involve either the superior or the inferior visual ﬁelds, with or without macular sparing

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Figure 2-27. Congruous altitudinal hemianopia.

(Figure 2-27). Clinical observations in humans and neurophysiologic studies in monkeys have revealed distinct symptom patterns depending on whether the lesion involves the inferior portions of the occipital lobes, the adjacent temporal lobes or the superior portions of the occipital lobes, and the adjacent parietal lobes. In addition to causing bilateral superior altitudinal hemianopia, bilateral infarcts of the inferior occipital and medial temporal lobes (including the fusiform and lingual gyri) can be associated with dyschromatopsia or achromatopsia of the remaining inferior hemiﬁelds so that the patient may demonstrate impaired color vision. The color vision function corresponds to monkey cortical area V4 (see Figure 2-6). Lesions in the inferomedial temporal lobes may also produce impairment of contrast sensitivity and form vision.12,13 A unilateral lesion of one inferior occipital lobe and adjacent temporal lobe may produce a contralateral superior quadrantanopia and a contralateral inferior quadrant dyschromatopsia. Conversely, patients with inferior altitudinal visual ﬁeld defects resulting from bilateral superior occipital and adjacent parietal lobe lesions may also have simultanagnosia, manifested by problems in visual/spatial processing and attention.14 Bilateral Superior or Inferior Calcarine Cortex (1). Occlusion of the calcarine branches (A) of both posterior cerebral arteries can produce a congruous altitudinal

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hemianopia if the regions below or above both calcarine sulci (B) are infarcted. Disease of both middle cerebral arteries (C) may involve both superior lips of the calcarine cortex. Congruous inferior altitudinal ﬁeld defects may follow trauma superior to the calcarine sulcus. Posttraumatic superior altitudinal ﬁeld defects following injury to the inferior calcarine cortex may be less likely to occur because patients may not survive if the injury includes laceration of the dural sinuses, including the straight sinus. The straight sinus (D), which is within the tentorium cerebelli, joins the transverse sinuses (E) (connecting the sigmoid sinuses and the internal jugular veins) and the superior sagittal sinus (which runs with the falx cerebri) at the conﬂuence of the sinuses (F) at the internal protuberance of the occipital bone.

2-4-5 Quadrantanopias 2-4-5-1 Superior Homonymous, Incomplete. In this pattern, there is a loss of the congruous superior right or left visual ﬁeld of each eye. The example shown is of an incomplete ﬁeld defect, sparing some of the affected quadrant (Figure 2-28). Temporal Lobe (1). The optic radiation arises from the lateral geniculate body (A) as the optic peduncle and then passes anteriorly into the temporal lobe. Fibers serving the inferior peripheral hemiretina (B) go most anteriorly to the tip of the inferior horn of the lateral ventricle (C). The ﬁbers are known as Meyer’s loop (1).

Figure 2-28. Incomplete superior homonymous quadrantanopia.

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The ﬁelds shown will result if the temporal lobe is amputated more than 4 cm from the tip. The defects are usually congruous and have a sharply deﬁned vertical meridian. The horizontal meridian may be included, with larger lesions yielding a congruous superior quadrantanopia with or without macular sparing. If more than 8 cm of the temporal lobe is amputated, a homonymous hemianopia will result. Tumors usually produce greater incongruity and sloping of isopters than do vascular lesions of the anterior portion of the retrochiasmal visual pathway. Lingual Gyrus of Occipital Lobe (2). Occipital lesions that produce a pure quadrantanopia do not usually result from pure involvement of the primary visual cortex (area 17), as too long a strip of tissue along the lip of the calcarine cortex would have to be injured. It has recently been demonstrated that the visual association cortex (areas 18 and 19) maps the peripheral visual ﬁeld along the horizontal meridian in a compact region near the posterior pole of the occipital lobe. Thus, a quadrantanopia can be thought of as resulting from the loss of ﬁbers going to or from the primary visual cortex.

2-4-5-2 Inferior Homonymous, Complete. In this pattern, there is loss of the overlapping inferior right or left visual ﬁeld of each eye (Figure 2-29). Parietal Lobe (1). The optic radiation passes posterolaterally from the lateral geniculate body (A) into the parietal lobe. After initial dispersion, the ﬁbers that

Figure 2-29. Complete inferior homonymous quadrantanopia.

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project from the superior retinal quadrants (B) collect into a compact bundle sooner than the temporal lobe ﬁbers serving the inferior retinal quadrants. It is for this reason that complete quadrantic loss occurs more frequently in parietal lobe lesions than in temporal lobe lesions. Cuneate Gyrus of Occipital Lobe (2). An inferior quadrantanopia of occipital origin involves the visual association area, not just the primary cortex (see earlier section “Lingual Gyrus of Occipital Lobe”).

2-4-6 Bilateral Central Field Defects 2-4-6-1 Scotoma or Depression. The central visual ﬁelds of both eyes are abnormal in this pattern of ﬁeld defect and are usually accompanied by decreased visual acuity (Figure 2-30). Media Opacities (1). See Section 2-3-1-3. Macula Denser scotomas occur with lesions that involve the inner retinal layers (2), in contrast to lesser depressions with outer retinal and choroidal disorders in the macular regions. Nutritional and toxic amblyopias may involve ganglion cells originating in the macula.

Figure 2-30. Bilateral central scotomas or depressions.

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Optic Nerve (3). The maculopapillary bundle is in the temporal quadrant of the optic nerve, immediately posterior to the optic nerve head. Axial neuritis results in dense central or centrocecal scotomas. Optic Nerve, Diffuse (4). After passing 1 cm posterior to the optic nerve head, many of the ﬁbers of the maculopapillary bundle reach the center of the optic nerve while other macular ﬁbers distribute to the peripheral quadrants of the optic nerve. Calcarine Cortex (5). The macula is represented on the posterior portion of the calcarine sulcus (6) and may extend onto the posterolateral portion of the occipital lobes. This is important in the analysis of trauma to the occipital lobes. Contusion of the superior aspect of both occipital lobes may result in an inferior altitudinal congruous ﬁeld defect (see Figure 2-27). 2-4-7 Bilateral Peripheral Field Defects 2-4-7-1 Generalized Depression or Peripheral Contraction. In this pattern, the outer isopters of the visual ﬁeld collapse or contract (Figure 2-31). Because perimetry is a subjective examination, contraction can result from patient or examiner factors. In addition to the lesions noted below, deliberate malingering, too rapid target movement, slow response times, inappropriate contrast of stimulus-target/ background ratio, and an inadequately dilated pupil can all contract the outer isopters.

Figure 2-31. Peripheral contraction.

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Media Opacities (1). Corneal scars, cataracts, Large Vitreous Hemorrhage. Peripheral Retina (2). Quinine, salicylates, thioridazine hydrochloride, and carbon monoxide poisoning are among the causes of contraction of the visual ﬁelds. Optic Nerve Head (3). Irregular, progressive constriction may occur. Sector sparing with sector and optic nerve defects may help determine the diagnosis. Glaucoma and optic nerve head swelling may lead to peripheral depressions of the visual ﬁelds but usually in combination with other more characteristic ﬁeld defects. Optic Nerve (4). Peripheral optic neuritis may occur with tertiary syphilis. When peripheral constriction is combined with central depression, retrobulbar neuritis and optic atrophy from any cause should be considered. Anterior Calcarine Sulcus (5). To cause a binocular peripheral constriction, paired visual cortical lesions would need to injure the striate cortex or pathways related with the most anterior portions of both calcarine sulci. This portion of the striate cortex serves the visual ﬁeld of the unpaired temporal crescent visual ﬁeld of the contralateral eye. Limited extension of the lesion posterior to the junction of the calcarine with parieto-occipital sulcus would involve the nasal ﬁeld of each ipsilateral eye. 2-4-8 Bilateral Checkerboard Scotomas. This pattern of visual loss consists of two congruous hemianopic scotomas, such as a right superior and left inferior ﬁeld defect (Figure 2-32).

Figure 2-32. Bilateral checkerboard scotomas.

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Posterior Cerebral Arteries (1). Occlusions of the posterior cerebral arteries may occur simultaneously in severe systemic hypotension or in basilar-vertebral artery disease (“top-of-the-basilar-artery” syndrome); each posterior cerebral artery may be occluded at a different time. Identiﬁcation of the old or new lesion depends on the history or on other neurologic ﬁndings. These are called “checkerboard scotomas” when the hemianopic visual ﬁelds are not symmetrically affected. 2-4-9 Bilateral Homonymous Hemianopias. This pattern of ﬁeld defect consists of complete or incomplete homonymous hemianopias involving both the right and the left visual ﬁelds (Figure 2-33). Posterior Cerebral Arteries (1). The area of damage from occlusion of these arteries is usually more extensive than that described for bilateral checkerboard scotomas. 2-5 JUNCTIONAL FIELD DEFECTS 2-5-1 Complete Monocular Plus Incomplete Contralateral Ocular. This pattern of ﬁeld loss involves the entire visual ﬁeld of one eye and a portion (usually superior temporal) of the visual ﬁeld of the opposite eye (Figure 2-34).

Figure 2-33. Bilateral homonymous hemianopias.

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Figure 2-34. Complete monocular plus an incomplete contralateral ocular (a junctional defect).

Both Eyes or Optic Nerves (1). One reason to perform a complete ocular examination on each patient is to avoid missing a second lesion. However, a complete monocular loss of vision plus an incomplete superior temporal quadrantanopia in the opposite eye with a short vertical meridian passing through ﬁxation is diagnostic of the single lesion described next. One Optic Nerve at Junction of Optic Chiasm (2). Inferior nasal peripheral ﬁbers from the opposite optic nerve have crossed the optic chiasm and are involved while passing by the junction with the contralateral optic nerve into the contralateral optic tract. (This arrangement was formerly known as the anterior knee of Wilbrand, but it has now been shown that the ﬁbers do not actually enter the contralateral optic nerve.) 2-5-2 Homonymous Hemianopia Plus. This ﬁeld defect includes a (usually) complete and congruous hemianopia with an additional ﬁeld defect in one eye (Figure 2-35). Junction of Optic Tract and Optic Chiasm (1). A complete right homonymous hemianopia of a left postchiasmal lesion may also involve some of the left eye axons that decussate in the optic chiasm. This adds a left eye temporal ﬁeld defect. The left superior temporal visual ﬁeld is spared because the inferonasal ﬁbers serving this ﬁeld decussate anteriorly within the optic chiasm. The ﬁbers from the superior

Figure 2-35. Homonymous hemianopia plus (a junctional scotoma).

Figure 2-36. Bitemporal hemianopia plus (a junctional scotoma).

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nasal retina of the left eye are injured because they decussate posteriorly, giving rise to the left inferior temporal visual ﬁeld constriction. (Compare this example with Figure 2-34.)

2-5-3 Bitemporal Hemianopia Plus. In this pattern of ﬁeld defect, there is a nasal ﬁeld defect in one eye or both eyes in addition to temporal ﬁeld defects in both eyes (Figure 2-36). Junction of Optic Chiasm and Optic Nerve (1). A bitemporal hemianopia can still be recognized by the fragment of sharp vertical meridian remaining in the right visual ﬁeld, but there is also involvement of uncrossed ﬁbers in the optic nerve. This may occur in pituitary tumors if the optic nerves are very long and if the optic chiasm is postﬁxed with regard to the sella turcica. Sometimes, pituitary tumors progress asymmetrically. Aneurysms of the anterior communicating artery (A) are well situated to produce these ﬁelds.

REFERENCES 1. Trobe JD, Glaser JS. The visual ﬁelds manual. Gainesville, Fla: Triad Publishing Co; 1983. 2. Horton JC, Hoyt WF. The representation of the visual ﬁeld in human striate cortex: a revision of the classic Holmes map. Arch Ophthalmol. 1991;109:816–824. 3. Sereno MI, Dale AM, Reppas JB, et al. Borders of multiple visual areas in humans revealed by functional magnetic resonance imaging. Science. 1995;268:889–893. 4. Horton JC, Hoyt WF. Quadrantic visual ﬁeld defects: a hallmark of lesions in extrastriate (V2/V3) cortex. Brain. 1991;114:1703–1718. 5. Quigley HA, Sommer A. How to use nerve ﬁber layer examination in the management of glaucoma. Trans Am Ophthalmol Soc. 1987;85:254–268. 6. Quigley HA, Addicks EM. Regional differences in the structure of the lamina cribrosa and their relation to glaucomatous optic nerve damage. Arch Ophthalmol. 1981;99: 137–143. 7. Bischoff P, Lang J, Huber A: Macular sparing as a perimetric artifact. Am J Ophthalmol. 1995;119:72–80. 8. Corbett JJ, Jacobson DM, Mauer RC, Thompson HS: Enlargement of the blind spot caused by papilledema. Am J Ophthalmol. 1988;105:261–265. 9. Frisén L: Quadruple sectoranopia and sectoral optic atrophy: a syndrome of the distal anterior choroidal artery. J Neurol Neurosurg Psychiatry. 1979;42:590–594. 10. Miller NR: Walsh and Hoyt’s Clinical neuro-ophthalmology. 4th ed. Baltimore: Williams & Wilkins; 1982:3–173. 11. Keltner JL, Johnson CA, Spurr JO, Beck RW: Baseline visual ﬁeld proﬁle of optic neuritis: the experience of the Optic Neuritis Treatment Trial. Arch Ophthalmol. 1993;111:231–234. 12. Newman RP, Kinkel WR, Jacob L: Altitudinal hemianopia caused by occipital infarcts: clinical and computerized tomographic corrections. Arch Neurol. 1984;41:413–418. 13. Schiller P: The effects of V4 and middle temporal (MT) area lesions on visual performance in the rhesus monkey. Visual Neurosci 1993;10:717–746. 14. Rizzo M, Robin DA: Simultanagnosia: a defect of sustained attention yields insights on visual information processing. Neurology. 1990;40:447–455.

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3 Essentials of Automated Perimetry GEORGE SHAFRANOV, MD

3-1 INTRODUCTION Standard automated perimetry is a standard method of measuring peripheral visual function.1 Automated static perimetry gained wide acceptance among clinicians due to the test’s high reproducibility and standardization and ability to store, exchange, and statistically analyze digital data. Advances in the computerized visual ﬁeld assessment have contributed to our understanding of the role that ﬁeld of vision plays in clinical evaluation and management of patients. The Humphrey Visual Field Analyzer/HFA II-i is the most commonly used automated perimeter in the United States, and the examples in this chapter have been obtained with this instrument.

3-2 HISTORICAL OVERVIEW Aubert and Förster2 in the 1860s developed the arc perimeter, which led to the mapping of peripheral neurologic visual ﬁeld abnormalities and advanced glaucomatous ﬁeld defects. Analysis of the central visual ﬁeld was not seen as clinically important by most clinicians until 1889, when Bjerrum2 described a detected arcuate paracentral scotoma. Later, Traquair3 further contributed to kinetic perimetry on the tangent screen. In 1893, Groenouw proposed the term “isopter” for lines with the same sensitivity on a perimetry chart. Rønne further developed kinetic isopter perimetry in 1909 and described the nasal step in glaucoma.

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Although the ﬁrst bowl perimeter was introduced in 1872 by Scherk, due to problems with achieving even illumination on the screen, it did not become popular. The version of the bowl perimeter introduced by Goldmann in 1945 became widely accepted and is a signiﬁcant contribution to clinical perimetry. The Goldmann perimeter incorporated a projected stimulus on an illuminated bowl, with standardization of background illumination as well as size and intensity of the stimulus, and allowed effective use of both static and kinetic techniques. For these reasons, the Goldmann instrument has remained the clinical standard throughout the world until widespread acceptance of automated perimetry. Harms and Aulhorn4 later designed the Tübingen perimeter with a bowl-type screen exclusively for the measurement of static threshold ﬁelds, using stationary test objects with variable light intensity.5 While excellent threshold measurements were possible with this instrument, the time and effort involved in such measurements prevented this perimeter from becoming widely used. Automated perimetry has progressed rapidly over the past few decades, largely to the credit of Fankhauser,6,7 Heijl and Krakau,8 Flammer et al.,9 and others. Automated perimeters have substantially enhanced the clinical practice due to accurate, standardized measurements of the visual function. Most of these instruments use computerized static threshold algorithms, which have proved invaluable for clinical research and patient care, and are very familiar to all ophthalmologists. Despite the complex statistical algorithms used by visual ﬁeld analyzers, standardized quantitative results allow easy and practical application of statistical methods to measure early functional loss.8-11 The high sensitivity of the methods has required attention to the multiple psychological and physiologic variables that may affect measured thresholds. Automated perimetry has improved standardization by reducing variability in the examination technique. Of course, the test still depends on the reliability of the patient’s responses and may be affected by optic, neural, and psychological factors. Static automated threshold perimetry is one of the most important tests in the care of glaucoma patients. Detailed measurements of the visual ﬁeld can be obtained, and some uncertainties regarding diagnostic and therapeutic decision making in glaucoma can be diminished. On the other hand, the large volume of data introduces uncertainties. Differentiating long-term ﬂuctuation (LTF) from progressive loss remains one of the greatest clinical challenges in visual ﬁeld interpretation.11 This chapter is designed to help in developing skills in the selection of automated perimetric tests and to afford familiarity with the various printouts used by the Humphrey perimeter. Chapter 4 [cross-check] is dedicated to the use of automated perimetry in the care of patients with glaucoma.

3-3 PRINCIPLES OF FIELD TESTING The human visual system has a relatively poor ability to estimate absolute magnitudes of light, mostly to the exceptional adaptation of that system. The human visual system has, however, a remarkable ability to perceive contrast (relative magnitudes

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of light). Thus, it is the differential light sensitivity of a stimulus against a constantilluminated background that is measured with static perimetry. Light can be measured using various units. A point source with an output of 1 candela emits a total of 4 Π lumens. The illuminance on a surface is the number of lumens per square meter incident to that surface. Some of this energy is absorbed and transformed to another form of energy (heat), and another part is reﬂected and emitted as light, known as luminance. The apostilb (asb) is the unit of measurement for the luminance of a perfectly diffusing surface that is emitting or reﬂecting 1 lumen per square meter (m2). Most commercially available perimeters generate light of varying intensities by interposing neutral density ﬁlters, graded in decibels (dB), over a maximally emitting bulb. Retinal locations of reduced sensitivity require brighter stimuli to reach threshold, represented by lower decibel values. Similarly, higher decibel threshold values represent more sensitive retinal locations (Figure 3-1). Each decibel equals 1/10th of 1 log unit. Thus, 10 dB equals 1 log unit or a 10-fold change in intensity, and 30 dB equals 3 log units or a 1000-fold change in intensity. The maximum bulb intensities vary; Goldmann and Octopus perimeters generate a maximum stimulus luminance (0 dB) of 1000 asb, while the Humphrey perimeter uses a 10,000-asb bulb (0 dB). Background luminance also varies; Humphrey Visual Field Analyzer uses 31.5 asb. The hill of vision may be mapped by using moving kinetic or stationary static stimuli. The visual threshold at a speciﬁc location in the retina is deﬁned as the luminance at which 50% of the stimulus presentations are identiﬁed by the patient as seen. A patient undergoing a threshold examination may see only half of the presented stimuli. This can be a source of frustration to patients, who may feel they have performed poorly. Understanding the phenomenon requires knowing the bracketing strategy used to make threshold measurements at each location of

Figure 3-1. Graytone symbols used in the older version of Humphrey Visual

Field Analyzer. As retinal sensitivity decreases (measured in decibels [dB] and depicted by progressively darker graytone symbols), the luminance (in apostilbs [asb]) increases to a maximum value of 10,000. Neutral density ﬁlters (graded in dB) are used to reduce the luminance of the 10,000-asb bulb.

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the visual ﬁeld. Full threshold strategy algorithms use a double crossing of the threshold. For instance, if the initial stimulus is subthreshold (not seen), intensity is increased in steps of 4 dB until the patient responds with a “yes” (seen). The stimulus intensity is then decreased in steps of 2 dB until the patient does not respond (not seen). The visual threshold is thereby crossed twice. Suprathreshold stimuli are brighter than the expected thresholds at given locations in the retina. The Humphrey Visual Field Analyzer reports threshold values as the last seen stimulus using the 4-2 strategy (Figure 3-2). If the initial stimulus is suprathreshold, stimulus intensity is decreased by 4-dB steps until the threshold is crossed, then increased in 2-dB steps (the threshold again is doubly crossed). The choice of the initial stimulus luminance is explained below. With this strategy, accurate threshold estimates are achieved by presenting on average approximately ﬁve stimuli per test location. Stimulus presentations are not performed sequentially at a single location but are moved randomly throughout the entire visual ﬁeld. This discourages cheating, because the patient does not know where to expect the next stimulus presentation.

3-3-1 Kinetic Perimetry. Kinetic perimetry uses a stimulus of constant size and intensity that moves from nonseeing to seeing areas of the visual ﬁeld (Figure 3-3), that is, from the periphery toward ﬁxation when outlining an isopter and from the center of the blind spot or a scotoma. Kinetic techniques are not very accurate for the examination of relatively ﬂat areas of the visual ﬁeld, requiring a sloping hill of vision in the tested area. Enlargement of the blind spot and Seidel’s scotoma (an arcuate-shaped elongation of the blind spot) have been described as early defects

Figure 3-2. The bracketing strategy used by the Humphrey Visual Field Analyzer to measure the visual threshold. The threshold is initially approached by stimuli at 4-dB steps. When the stimulus is seen, the direction is reversed and the threshold is crossed in 2-dB steps. Thus, each threshold is crossed twice with a measurement resolution of ±1 dB.

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Figure 3-3. Kinetic perimetry uses a stimulus of speciﬁc size and intensity that is

moved from nonseeing to seeing areas of the visual ﬁeld. A distinct end point requires a sloping hill of vision.

in glaucoma; they may in part be artifactual because slightly suprathreshold kinetic stimuli are used to explore the relatively ﬂat area of the ﬁeld just superior to the blind spot, and the technique of kinetic perimetry is not particularly sensitive to early localized depressions (Figure 3-4). Although computerized perimetry is presently somewhat limited to static algorithms, a number of computerized perimeters can use kinetic techniques

Figure 3-4. Localized, shallow depressions of the visual ﬁeld can be missed with

kinetic techniques, particularly when they occur in a relatively ﬂat area of the visual ﬁeld.

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as well. Computerized kinetic perimetry was historically thought to be less reproducible than automated static perimetry because of the complex algorithms required. Nevertheless, recent studies suggest the opposite,12 and the reliability and reproducibility of the kinetic measurements have yet to be established. The optimal rate of movement of the target is about 4° per second,13 but a slower velocity of 2° per second may provide more reproducible results in some patients.14 A combination of central static threshold perimetry and peripheral kinetic perimetry has been used in glaucoma and neuro-ophthalmology patients.15 The optimal technique for examining the peripheral visual ﬁeld that provides the most information in the shortest period of time has not yet been determined.

3-3-2 Static Perimetry. Standard automated static perimeter typically presents a projected stationary stimulus of known size, intensity, time, and location against a standard white background, also with known brightness level (Figure 3-5). Automated techniques of stimulus presentation are particularly suited to static measurements because the computer algorithms are relatively straightforward. Suprathreshold screening techniques may be used to make qualitative estimates of the visual ﬁeld. Threshold measurements are required to obtain the quantitative data needed for the early diagnosis and careful follow-up of glaucoma patients. 3-3-2-1 Suprathreshold Techniques. Suprathreshold static perimetry is a technique in which a bright stimulus with an intensity that is above the anticipated threshold for the retinal area being tested and is expected to be seen in all parts of normal visual ﬁeld. The locations at which the patient fails to recognize the target are noted as visual ﬁeld defects. It is a quick way of detecting areas of blindness, usually within the central visual ﬁeld. Stimulus intensity for suprathreshold perimetry may be constant over the entire ﬁeld (Figure 3-6) or may correspond to the slope

Figure 3-5. Static techniques use a stationary stimulus of variable intensity to measure the visual threshold at a speciﬁc location in the visual ﬁeld.

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Figure 3-6. Constant stimulus intensity may be used with suprathreshold

techniques to obtain qualitative information.

of the visual hill (threshold-related, Figure 3-7). Suprathreshold static targets are presented for a longer time, usually 0.5 to 1 second. Some automated perimeters predict the slope of the visual hill based on several initial threshold measurements in the peripheral visual ﬁeld, a solution that is not always satisfactory. While this type of screening is rapid, it does not always detect early abnormalities with localized partial depressions or increased variability of responses in localized areas.

Figure 3-7. Suprathreshold test may use a stimulus that conforms to the slope

of the visual hill. This is sometimes called a threshold-related test and can be used to obtain qualitative information about the visual ﬁeld.

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The static suprathreshold strategy is used as a screening test, to determine if visual function falls within or outside the normal range.8

3-3-2-2 Threshold Techniques. Computerized perimetry allows the performance of static threshold measurements in a short period of time under standardized conditions. Static threshold measurements are relatively sensitive to shallow depressions of the visual ﬁeld when the locations of the stimuli are close together (Figure 3-8). This high sensitivity has led to an increased detection rate of early glaucomatous defects compared with manual techniques and has enhanced the ability to meaningfully compare successive visual ﬁeld examinations. Manual perimeters can be used for quantitative threshold measurements but only by highly trained personnel. 3-3-3 Frequency-of-Seeing Curves and Fluctuations. Perimetry is a subjective psychophysical test requiring the patient’s cooperation, effort, and communication. As in any diagnostic test, the response to a speciﬁc question has an associated error. The threshold of the differential light sensitivity represents the brightness of the stimulus so dim that is seen only on 50% of repeated presentations. The frequency-of-seeing curve is a useful to emphasize the importance of probability in estimating a location’s threshold (Figure 3-9) and may be generated by repeated testing at a single location. Figure 3-9 indicates that these probabilities can never be 0% or 100% because of the inﬂuence of false-positive and false-negative responses, respectively. The slope of the curve is correlated to threshold deviation from age-appropriate normal values at a particular location. Thus, areas of high retinal sensitivity tend to test with high reproducibility, while locations with abnormally reduced sensitivity have a shallower

Figure 3-8. Static measurements of the threshold are relatively sensitive to

localized, relative depressions of the visual ﬁeld as long as the stimuli are spaced closely enough.

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Figure 3-9. Frequency-of-seeing curve. As

the intensity of the stimulus increases (abscissa), the probability of seeing the stimulus increases (ordinate). The threshold is deﬁned as the intensity that is seen 50% of the times it is presented. This implies that thresholds can only be estimated, not measured. The probability of seeing the stimulus is never 0% and never 100% because of false-positive or false-negative answers.

slope of the frequency-of-seeing curve, which is associated with greater uncertainty (Figure 3-10).16,17 Fluctuations in measurements of a physiologic parameter produce variation of a test result. Careful measurements can reveal those ﬂuctuations in visual ﬁeld thresholds. Bebie et al.18 described several components of this ﬂuctuation: short-term ﬂuctuation (STF) and LTF. STF is the variation of responses that occurs over the performance of a single test and may be caused by a combination of the instability of the threshold being tested and the level of cooperation and attentiveness of the patient.19 STF was calculated for full threshold algorithms (not often used now) of the Humphrey Visual Field Analyzer by measuring threshold values in 10 locations twice during the course of a given test. LTF is the ﬂuctuation between tests, which occurs over days, months, or years. The causes of LTF are not well established. Possible reasons include ﬂuctuations in intraocular pressure and in age and those

Figure 3-10. Normal central regions with high threshold sensitivity tend to have steep frequency-of-seeing curves. Abnormal or peripheral regions with reduced sensitivity demonstrate a broadened curve with greater threshold uncertainty.

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Figure 3-11. Conﬁdence intervals of 95% of subsequent threshold sensitivities

for test locations with initial sensitivity on the x-axis in a group of clinically stable glaucoma patients. Note the increasing interval with decreasing initial sensitivity. The 5th percentile approaches 0 if initial sensitivity is below 10 dB because of the limitation of an absolute test stimulus.

that occur as the time interval between tests increases. In a group of clinically stable glaucoma patients, LTF was correlated with initial sensitivity and with distance from ﬁxation (Figure 3-11).20 Understanding the LTF helps in comparisons of visual ﬁelds for change over time. In the Ocular Hypertension Treatment Study, less than 20% of the initial glaucomatous visual ﬁeld defects were conﬁrmed on the subsequent testing.21

3-4 TEST SELECTION AND ALGORITHMS Computerized static visual ﬁeld tests differ for retina locations that are tested and for algorithms used to test those locations. A basic understanding of the test algorithm used by automated perimeters employing threshold strategies is essential to interpreting the results and artifacts seen on visual ﬁeld printouts. Currently, most commonly used algorithms include Swedish interactive threshold algorithm (SITA) Standard or SITA Fast 24-2 or 30-2 threshold strategies. To be able to reliably compare longitudinal results, the initial algorithm should be used for follow-up tests.

3-4-1 Swedish Interactive Threshold Algorithm (SITA). The relatively new threshold strategy, known as SITA, has become increasingly popular10,22,23 and almost completely replaced full threshold algorithms. SITA is based on the probability

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analysis of the patterns of glaucomatous damage and is more time efﬁcient than full threshold strategies, utilizing standard 24-2 or 30-2 patterns to assess the visual ﬁeld. It signiﬁcantly minimizes test time without reduction of data quality. Two versions of SITA are currently available: SITA Standard and SITA Fast. SITA Standard takes approximately half the time to complete compared with the full threshold program. SITA Fast takes about half the time of the FASTPAC algorithm and was found to be useful in pediatric population,24 although SITA Fast has somewhat increased variability compared with SITA Standard.25 SITA requires signiﬁcant computer power, and therefore it is available only on the newer Humphrey Visual Field Analyzers. SITA is based on visual ﬁeld modeling that uses frequency-of-seeing curves for glaucoma and healthy patients. During the SITA test, a computer also produces an “information index,” which discontinues testing when threshold reaches a preselected level. The SITA algorithm also makes individual adjustments to patient response time, allowing the patient to be in charge of the test. After measurements are complete, the program performs additional calculation of all thresholds measured and produces estimates of false-positive and false-negative errors, displaying results as percentages. Average time reduction by SITA Standard depended on the severity of glaucomatous stage. No signiﬁcant time difference exists for advanced glaucoma ﬁelds, whereas normal ﬁelds using SITA are performed in half of the time of full threshold strategy. The reduction of test time reduces the patient fatigue, allowing for more frequent visual ﬁeld examinations and subsequent early detection of early glaucoma or progressing visual ﬁeld damage.26

3-4-2 Foveal Threshold. Measurement of the foveal sensitivity is an option that, if selected, occurs at the very beginning of the test. This option should generally be left on, as it takes very few stimulus presentations and provides information about a very valuable portion of the visual ﬁeld. The patient is asked to maintain gaze on an illuminated diamond that is projected inferior to the standard central ﬁxation target used throughout the remainder of the test. The initial stimulus intensity is 30 dB, and the regular 4-2 bracketing strategy is used to determine foveal sensitivity. Once this portion of the test is completed, the ﬁxation diamond is removed and the patient is asked to ﬁxate on the central target. 3-4-3 Initial Values. Important time savers are used to reduce the numbers of stimuli necessary to estimate the threshold level and somewhat shorten the full threshold test. Starting points for threshold determinations usually depend on results from already tested primary locations, because a location’s threshold result is statistically correlated with its neighboring location’s threshold value. The Humphrey Visual Field Analyzer initially tests four seed locations, one per quadrant located 9° from the horizontal and vertical meridians. The initial stimulus intensity at these four seed locations is 25 dB and the full 4-2 strategy is used. Threshold in each location is measured twice, and the results from these four seed locations are used to determine the starting stimuli in adjacent areas (Figure 3-12). Threshold results from these adjacent areas are, in turn, used to determine their neighbor’s starting locations until the entire test is completed.

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Figure 3-12. Seed-point and short-term ﬂuctuation locations. The initially thresholded locations are the four primary seed-point locations (circled), one per quadrant 9° from the horizontal and vertical meridians. These four locations are tested twice and used to calculate starting values for threshold measurements in the neighboring threshold. Throughout the course of the fullthreshold test, threshold values in standard locations (circled and squared) are measured twice to calculate the short-term ﬂuctuation. Additional locations (in parentheses) may be thresholded twice if the result of the ﬁrst threshold differs substantially from age-matched expected values. These additional locations are not used to calculate STF.

Some patients are attentive during the initial four central quadrant location threshold determination process and then rapidly fatigue, with deﬁcient further responses. This results in a characteristic cloverleaf-shaped ﬁeld (Figure 3-13).

3-4-4 Fixation Monitoring. Throughout the performance of the test, periodic assessment of patient ﬁxation and level of alertness is made to ensure correspondence of projected stimuli to the correct part of the retina. To monitor ﬁxation, the Humphrey Visual Field Analyzer uses the gaze tracker and the Heijl-Krakau blind spot– monitoring technique.27,28 The latter technique assumes that if stimuli projected on the blind spot location (which has a diameter of ≈5-7°) are seen, then the ﬁxation is poor. If patient does not respond to those stimuli, ﬁxation is assumed to be central— which is not always the case. A high number of ﬁxation losses may result from wandering ﬁxation but may also result from a displaced blind spot or from many false-positive responses. High-plus lenses tend to shift the blind spot toward ﬁxation (Figure 3-14), while myopic correction moves the blind spot peripherally (Figure 3-15). These optical effects can be minimized with the use of contact lenses during the test.

Figure 3-13. Cloverleaf ﬁeld. During the four primary seed-location threshold

process, the patient responded with threshold sensitivities of 25 to 31 db. Throughout the remainder of the test, the patient quickly fatigued or fell asleep, with no additional responses seen through the rest of the test. The falsenegative errors indicate that patient was not responding to the bright light in the original four locations. No response was produced when the blind spot was tested, resulting in the deceptively low rate of ﬁxation losses.

Figure 3-14. High-plus lens artifact. A patient was tested with a +12 spectacle

correction. The high-plus lens shifted the blind spot toward ﬁxation. There also appears to be a peripheral ring scotoma. When the patient was retested with a contact lens, there were no ﬁxation losses and the peripheral scotoma disappeared.

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Figure 3-15. High-minus lens artifact. A highly myopic patient was tested with spectacle correction. The high-minus lenses shifted the blind spot away from ﬁxation.

Gaze tracking is a system that records the patient’s ﬁxation during the test. Deviations from the ﬁxation are displayed on the screen and the printout. The small downward markings on the graph indicate the system’s inability to locate a reﬂection from the eye, with large downward marking indicating that the patient blinked. The upward markings indicate deviation from the ﬁxation target, with the larger markings showing greater magnitude of the deviation. Another way to reduce the percentage of ﬁxation losses is to instruct the technician to re-plot the blind spot if high ﬁxation losses are detected early in the test.29 The computer then executes a short subprogram that presents densely packed stimuli in the region of the expected blind spot until the actual blind spot is mapped. The technician’s description of patient ﬁxation, based on the observation of the patient’s eye through the video monitor, is also extremely valuable in detecting pseudo–loss of ﬁxation. The absence of a low patient-reliability indicator should not assure the examiner that the test is error-free. Consider the patient who falls asleep at the machine. Clearly, that patient is unlikely to respond to stimuli presented in the blind spot despite poor ﬁxation. False-positive errors are tested by periodic withholding of a stimulus projection, although the faint noise of a stimulus presentation is retained. False-positive responses tend to indicate anxious, “trigger-happy” patients. The rate of falsepositive responses can often be improved if the visual ﬁeld technician coaches patients to respond only when they are certain that they have seen the stimulus. False-negative errors are tested by projecting a 9-dB suprathreshold stimulus in a region already thresholded. Failure to respond to this markedly suprathreshold stimulus indicates patient fatigue. False-negative errors are less inﬂuenced by coaching; however, the visual ﬁeld technician should ensure that the patient is awake and consider giving the patient a short break. False-negative errors are produced both by patient inattentiveness and by a diseased, easily fatigued visual system. If the threshold results are markedly reduced, the machine may not generate

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suprathreshold stimuli. This may lull the inexperienced visual ﬁeld technician into a false sense of patient responsiveness.

3-4-5 Threshold Testing. Throughout the performance of the Humphrey programs, if a threshold result differs signiﬁcantly from age-matched normal values, the location will be retested to conﬁrm this deviation. Performance of a complete full threshold program 30-2 in a patient with fairly normal vision required approximately 550 questions, taking about 15 minutes per eye. This was quite fatiguing to the patient, and current SITA algorithms could perform the same test within 4 minutes.

3-5 SINGLE TEST PRINTOUT The single ﬁeld printout from Programs 30-2 and 24-2 of the Humphrey perimeter contains a large amount of data, with various analyses presented in multiple ways (Figure 3-16). Familiarity with the overall organization and the derivation of the plots and indices greatly facilitates interpretation of the printout, which can be conveniently divided into the following sections: 1. 2. 3. 5. 4. 5. 6. 7. 8. 9.

Test Selection and General Information, located at the top Reliability Indices, located at the top and at the left Numeric Results (dB), located in the second row, at the left Grayscale Results, located in the second row, at the right Total Deviation, a plot located in the third row, at the left Pattern Deviation, a plot located in the third row, in the middle Global Indices, located in the third row, at the right Glaucoma Hemiﬁeld Test, located above the Global Indices Probability Symbols and Gaze Graph, located at the bottom of the printout Practice Information, is located on the right side at the bottom of the printout

3-5-1 Test Selection (and General Information). Located at the top of the printout, the general information section displays important data about the individual patient as well as particular test variables. Included here are program name (e.g., Central 24-2 Threshold Test), patient name and patient birth date (removed from the present illustration), stimulus size, background illumination, blind spot check size, threshold strategy (SITA Standard in this example), ﬁxation target type, test time and date, optical correction, pupil diameter (optional), and Snellen acuity (optional). Patient age is calculated from the date of birth and test date information. Many of these variables can signiﬁcantly affect the raw and calculated data and can be invaluable in interpreting results. For example, a miotic pupil or incorrect refraction can reduce threshold values, while an incorrectly entered birth date will create erroneous age-compared deviations. 3-5-2 Reliability Indices. Located below and at the left of the general information section, the reliability data display the number of ﬁxation losses to characterize stability of the patient’s gaze directed at the ﬁxation target. The false positive errors score is designed to identify the “trigger-happy” patients, who press the response

Figure 3-16. Sample single ﬁeld printout demonstrating glaucomatous ﬁeld loss. (A) The important areas of the single ﬁeld printout are labeled. This patient has a superior arcuate scotoma with a superior ﬁxation loss and a superior nasal step. (B) Because the seventh-most sensitive total deviation value is −1 dB (only slightly depressed), the pattern deviation plot is similar to the total deviation plot.

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button even when stimulus is not seen. The false-negative errors indicate patient fatigue or inattention. Questions asked can be a rough indicator of the consistency of the patient’s responses. The ﬁnal items of information displayed in the reliability indices section are test time and the optional foveal sensitivity. If ﬁxation losses reach 20% or if false-positive or false-negative errors reach 33%, a double X is placed next to the percentage to attract the reviewer’s attention. Similarly, the message low patient reliability may be displayed above the reliability indices section.

3-5-3 Numeric Results and Grayscale Results (Raw Data). The two largest images on the printout, located to the right of the reliability indices, are the raw data plots. These images are displayed in numeric and gray tone format, with the actual threshold values in decibels. The testing algorithm would repeat threshold testing in the locations where the initially obtained values signiﬁcantly deviated from the age-matched normal data. The grayscale plot is extrapolated from the numeric plot, and although it implies uniform sampling of the 30° ﬁeld, in reality less than 1% of this area is actually tested. The grayscale plot remains useful to alert the examiner to problem areas and is an effective way of demonstrating visual ﬁeld results to the patient. 3-5-4 Total Deviation. Since the introduction of the Humphrey perimeter, the manufacturer has upgraded the machine with increasingly sophisticated statistical analysis packages. The main package of these, STATPAC, allows comparison of the raw threshold data against age-matched normal values at each location; accompanying probability symbols indicate the signiﬁcance of any abnormality. These plots are displayed in the lower-left portion of the printout, both numerically and with probability symbols. The P values take into account the wider range of normal values as the distance from ﬁxation increases.30 For example, a value of 23 dB located 9° superiorly and nasally from the ﬁxation (Figure 3-16) demonstrates that this reduced sensitivity is highly signiﬁcant (P < 5% [.05]) compared with the agematched normal subjects, while the same 23 dB value located 24° superotemporally to ﬁxation may is only signiﬁcant. The examiner should keep in mind that statistical signiﬁcance does not always mean clinical signiﬁcance. 3-5-5 Pattern Deviation. Patterns of visual ﬁeld loss can be divided into generalized depression, which uniformly affects the entire ﬁeld by a similar amount, and localized (“scotomatous”) loss, which is frequently more diagnostic. STATPAC modiﬁes the total deviation plots in an attempt to display any superimposed pattern of localized loss that is hidden under generalized depression. This is done by correcting the deviation of the seventh-highest threshold location within the Program 24-2 test grid to zero deviation and “adjusting” the entire ﬁeld by that value. The threshold value of this seventh-most elevated location has been termed the general height value, although it is not routinely displayed on the printout. In the situation when the entire visual ﬁeld is diffusely reduced in sensitivity by 7 dB, with an underlying moderate superior arcuate defect of an additional 12 dB, the pattern deviation plot will be reduced by those 7 dB and displayed in the pattern deviation plot, where that relative depression will become more apparent. A probability analysis is again displayed on these adjusted deviation values.

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3-5-6 Glaucoma Hemiﬁeld Test. Another strategy to analyze the result of the visual ﬁeld test is to compare localized decreased threshold values in corresponding mirror image areas of the superior and inferior hemispheres.31 In the Humphrey Visual Field Analyzer, it is called the Glaucoma Hemiﬁeld Test (GHT). This method allows a simple but clinically useful analysis of visual ﬁeld changes in glaucoma patients. The software produces the GHT result by dividing each of the upper and lower halves of the ﬁeld into ﬁve mirror-image zones; the outer edge loci, temporal loci, and loci around the blind spot are excluded, enabling the GHT to be performed on either Program 30-2 or Program 24-2 (Figure 3-17). Each zone is subsequently scored according to its pattern deviation values, and each upper zone is then compared with the corresponding lower zone. In addition, a general height of the ﬁeld is determined by analyzing the most normal region of the ﬁeld. The GHT uses a large normal database to calculate the signiﬁcance of differences between the two hemispheres31 and has been shown to signiﬁcantly improve the ability to separate between normal and glaucoma ﬁelds.32 The results of the GHT consist of ﬁve categories, which are displayed above the global indices, using plain language message: “Outside Normal Limits,” “Borderline,” “General Reduction of Sensitivity,” “Abnormally High Sensitivity,” and “Within Normal Limits.”31 The GHT “Outside Normal Limits,” used together with the pattern deviation probability plot, has been shown to provide high sensitivity and speciﬁcity for detecting early glaucomatous visual ﬁeld changes.33 The ﬁve possible GHT messages and their derivations are as follows: 1. Outside Normal Limits This message results if either of these conditions is present: (a) any upper- versus lower-sector pair difference is greater than that found in 1% of the normal population or (b) any upper-lower pair sum differs at the 0.5% normal population level.

Figure 3-17. Glaucoma hemiﬁeld test zones.83

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2. Borderline This message is displayed if the criteria for outside normal limits are not reached, but an upper-lower difference is present that occurs in less than 3% of the normal population. 3. General Reduction of Sensitivity This message occurs if the criteria for outside normal limits are not met, but the general height calculation ﬁnds the most normal region of the ﬁeld to be below the 0.5% normal population level. Borderline and general reduction of sensitivity messages can result simultaneously (Figure 3-18). 4. Abnormally High Sensitivity This message is displayed when the general height calculation concludes that the best 15% of the ﬁeld exceeds expected values for 99.5% of the normal population. If these conditions are present, the GHT will not display any of the other four messages (Figure 3-19).

Figure 3-18. Generalized depression. In this patient with cataract, with 20/40 visual acuity, the foveal sensitivity is reduced. The abnormal mean deviation, normal pattern standard deviation, and clean pattern deviation probability plot all indicate uniform ﬁeld loss.

Figure 3-19. Abnormally high sensitivity. Both the patient and the technician did not seem to understand what was supposed to be happening during this test, resulting in a false nasal defect on the pattern deviation plot.

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5. Within Normal Limits This message is displayed if the criteria for the above four conditions are not met.

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3-5-7 Global Indices. In the lower-right corner of the single ﬁeld printout, STATPAC displays two global indices, which describe the entire visual ﬁeld using averaged numeric values: 1. MD (mean deviation) is an average value of overall deviation from the expected results within the same age group of normal visual ﬁelds. This value reﬂects the average height of the entire hill of vision. Negative values represent depression. MD is relatively insensitive to localized defects and is strongly affected by generalized decrease of sensitivity, such as cataracts. 2. PSD (pattern standard deviation) represents the unevenness of the surface of the hill of vision. It is calculated by taking a location-weighted standard deviation of all the threshold values. PSD is insensitive to the overall average height and is strongly affected by localized defects. STF and corrected pattern standard deviation (CPSD) are not used by current SITA algorithms. Of historical interest, STF is the standard deviation of repeated threshold of the 10 predeﬁned locations. STF increases in inconsistent patients. This increase may be due to poor patient cooperation or attention, but STF also tends to increase in scotomatous areas, particularly at their borders. CPSD was used as an attempt to better represent the surface of the hill of vision by accounting for the inﬂuence of STF. STATPAC provides probability values for each global index value compared with age-matched normal subjects. For example, if the MD value is accompanied by a P < 5% symbol, the MD of the ﬁeld is depressed by an amount greater than that found in 99.5% of the same-age normal population. Global indices generally correlate with visual ﬁeld shape. For example, uniform generalized depression, as seen in cataract, tends to produce an increasingly negative MD. A small localized scotoma may have only slightly decreased MD and a high PSD (Figure 3-20). A dense moderate-size scotoma typically produces an elevation in both MD and PSD (Figure 3-21).

3-6 CUSTOM TESTS Several alternative tests to Program 30-2 with the full threshold strategy exist. These aim to save test time or provide more detailed information regarding speciﬁc regions of the visual ﬁeld. Increasing the number of test locations and the precision with which they are tested does not necessarily provide a more accurate picture of the visual ﬁeld. Lengthy tests become fatiguing to the patient and may result in greater variability of responses. A number of strategies have been devised in an attempt to shorten the test and reduce the number of tested points while still providing an accurate representation of the visual ﬁeld. These strategies are described in the sections that follow. Multiple other tests are available with the Humphrey perimeter, and although they are rarely used, they are available in the Humphrey Visual Field Analyzer Main Menu.

Figure 3-20. Localized scotoma. This patient has primary open-angle glaucoma with a superior nasal step. The surrounding uninvolved ﬁeld is slightly supranormal. When these values are “normalized,” the pattern deviation plot becomes slightly more signiﬁcant than the total deviation plot. The supranormal uninvolved ﬁeld, combined with the small size of the scotoma, contributes to only slight decrease in mean deviation. The pattern standard deviation is highly abnormal (99.5%), as is the Glaucoma Hemiﬁeld Test.

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Figure 3-21. Moderate to severe glaucomatous ﬁeld loss. This patient has

primary open-angle glaucoma with a dense inferior arcuate defect ending in a nasal step. Both the mean deviation and the pattern standard deviation are highly abnormal.

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3-6-1 Grid Size. The Humphrey Visual Field Analyzer 30-2 algorithm samples 76 locations with a uniform 6° grid within 30° from ﬁxation (Figure 3-22). All Humphrey programs ending in -2 (e.g., 30-2, 24-2, 10-2) are offset from the central horizontal and vertical meridians. Programs 30-2 and 24-2, which use 6° spacing, are thus offset by 3° from the central meridians. Before invention of the SITA algorithms, approximately 550 questions would have been asked in a typical full threshold test, which may have taken about 15 minutes per eye. As the distance from ﬁxation increases, the normal threshold values decrease, with a corresponding increase in the test variability, providing diminishing quality of the test. One of the initial approaches to shortening the test was to delete the outer row of locations. Program 24-2 does that by testing only out to 21° except for preservation of the important nasal extent of the 30-2 program (see Figure 3-22). The resulting test contains 54 locations, a 29% reduction compared with the Program 30-2 grid, considerably shortening the test duration. This represents a valuable tradeoff in patients who would be tired with additional testing. 3-6-4 FASTPAC. The FASTPAC algorithm uses an entirely different testing strategy. Instead of the standard 24-2 strategy with a double crossing of threshold, FASTPAC adjusts the stimulus intensity by 3-dB increments until the threshold is crossed once. FASTPAC saves the most time in normal or near-normal ﬁelds and provides little time advantage in patients with larger amounts of ﬁeld abnormality. In comparisons to full threshold strategies, FASTPAC shortens the test time by 35% to 40%. FASTPAC may be suitable for observing ocular hypertensive patients

Figure 3-22. Comparison of the grid pattern, right eye, in Programs 24-2 and

30-2. Both programs test a uniform 6° grid offset 3° from the vertical and horizontal meridians. Program 24-2 tests (excludes outer outlined locations) 54 locations extending to 21° superiorly, inferiorly, and temporally and tests to 27° nasally. Program 30-2 tests an additional 22 locations extending the grid to 27° in all four directions.

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or early glaucoma patients, although little longitudinal data are available on its use in these populations and the effect on LTF is presently unknown. One potential advantage of FASTPAC is the ability to use size V stimulus for central 10° testing, which is not available with current SITA algorithms.

3-6-5 Programs 30-1 and 24-1. Programs 30-1 and 24-1 are not used for clinical testing, because they are not offset from the horizontal and vertical meridians. Because scotomas centered on the meridians are difﬁcult to classify (superior versus inferior, nasal versus temporal), these locations have less diagnostic localizing value. 3-6-6 Program 10-2 and Macula Test. Program 10-2 provides a high-resolution test of the central 10° with a tight 2° grid, offset 1° from the meridians. A total of 68 locations are used (Figure 3-23). Central tests are useful in carefully deﬁning central or paracentral scotomas.34 In patients with advanced damage and small remaining central islands of vision, Program 10-2 can be performed with stimulus size V if the FASTPAC algorithm is used. This strategy provides the advantage of testing more areas with measurable thresholds and seems to increase patient cooperation and reduce patient fatigue. An even more localized test is the macula test, which thresholds 16 locations within the central 5° with 2° spacing. Each location is tested three times to provide better estimates of local STF (Figure 3-24).

Figure 3-23. Program 10-2 tests 68 locations with a 2° grid extending to 9°

from ﬁxation. In this example, only a small central island of vision remains.

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Figure 3-24. The macula test thresholds the central 16 locations of the Program

10-2 grid. Each location is tested three times to better assess local short-term ﬂuctuation.

3-6-7 Peripheral 60 and 60-4 Program. These programs allow additional exploration of the peripheral visual ﬁeld (beyond 30°). Peripheral 60 points of this program extend the test out to 60° with a uniform grid testing 60 additional locations. 3-6-8 Nasal Step Program. Patients with possible nasal steps can be further explored with the nasal step program, which tests 12 locations up to 50° nasally. Two additional locations in the temporal visual ﬁeld are also included to reduce the predictability of the questions.

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3-6-9 Stimulus Size Option. Most programs are performed with stimulus size III, which subtends a diameter of 0.43° in visual space. This size is derived from the 4 mm2 size III used by the Goldmann perimeter. Testing with size III allows the application of the STATPAC statistical analysis. In ﬁelds where the majority of test locations are markedly reduced, it is often preferable to increase the stimulus size to V (1.72° in diameter). This larger size is often preferred by the patient and may reduce ﬂuctuation, although the option of using the glaucoma change analysis is not available.

3-7 FOLLOW-UP PRINTOUT When evaluating a series of automated ﬁelds performed over time, the clinician may ﬁnd the integration of the massive amount of data overwhelming. The Humphrey instrument allows the creation of several serial printouts to minimize confusion and allow the performance of change-over-time statistical analysis.

3-7-1 Overview Printout. The overview printout simply presents a sequential listing of condensed single ﬁeld printouts chronologically (Figure 3-25). For each test session, four plots are displayed (from left to right): Threshold Graytone plot, Threshold (numeric) dB plot, Total Deviation P value plot, and Pattern Deviation P value plot. Above these four plots are the GHT results, reliability data, pupil size, and Snellen acuity. Below the plots are listed foveal sensitivity and global indices. The examiner familiar with the single ﬁeld analysis printout will have no difﬁculty understanding all these terms. 3-7-2 Change Analysis Printout. The change analysis printout represents each ﬁeld as a box plot depicted graphically over time (Figure 3-26). To create this plot, deviation values at each location are ranked from least to most depressed. As can be seen from the legend at the left side of the printout, each box contains the 15th to 85th percentile deviation values from this ranking, with a central triple line representing the median value. The tails extending from the box cover the full range of deviation throughout the ﬁeld. In general, a small box with long tails suggests a clumping of values with a few outliers. If a box is small and near 0 dB, most of the ﬁeld is normal. If the box changes in location over time with a stable size, a generalized change is likely occurring. A change in box dimension usually indicates a more localized process. The change analysis printout also plots the global indices over time, including threshold levels for statistical signiﬁcance, with STF and PTSD plots being empty, if SITA algorithm was used. If the MD values plot is not demonstrating progressive change, it is likely that the ﬁeld is not worsening, although a stable MD with an increasing PSD may indicate early progression of a localized scotoma. If the MD value is declining, the other indices and actual ﬁelds should be evaluated closely to discern confounding developments such as cataract formation. When ﬁve or more ﬁelds are available, linear regression analysis of the MD slope over time will be

Figure 3-25. Overview printout. The overview printout displays chronological

series of tests. These include the Graytone, numeric dB, Total Deviation, and Pattern Deviation plots from each test session. Above the plots are the test date and the Glaucoma Hemiﬁeld Test (GHT) results. Below the plots are the global and reliability indices, along with foveal sensitivity. Three tests performed over a 15-month period are displayed. Note that the probability symbols displayed in the total deviation and pattern deviation plots compare each location’s threshold with age-matched normal values. Similarly, the probability values next to the global indices are signiﬁcance values compared with normal data.

112

Figure 3-26. Change analysis printout. The glaucoma change analysis printout

displays each ﬁeld in box plot form as well as displaying the global indices graphically over time. The legend for the box plot is located to the left. The box plot is created by ranking total deviation values from most depressed (0%) to least depressed (100%). The box itself encompasses the central 70% of the ﬁeld (between 15th and 85th percentile). The median rank value is displayed as a dark triple stripe inside the box. If the box is elongated toward the bottom of the plot, as in this example, then a large dense scotoma is present.

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calculated, which describes the slope in decibels per year and assigns a signiﬁcance level, producing one of the two messages: “MD SLOPE SIGNIFICANT” or “MD SLOPE NOT SIGNIFICANT.” The MD plot and slope calculations are also included in the Glaucoma Progression Analysis printout. Studies suggest that a PSD could be used to monitor glaucoma progression in patients with glaucoma and cataract using SITA Standard to differentiate generalized worsening (cataract) from localized progression (glaucoma).35

3-7-3 Glaucoma Progression Analysis Printout. The Glaucoma Progression Analysis is an optional module in the STATPAC intended to assist with detection of glaucoma progression. At the time this chapter was written, the analysis was available for SITA Standard and SITA Fast algorithms but not for SITA-SWAP tests. Tests using Full Threshold algorithm could be used as baseline. Two initial ﬁelds are averaged into a baseline measurement, and then a point-by-point statistical comparison of each subsequent ﬁeld is performed, indicating the presence or absence of a clinically signiﬁcant change (Figure 3-27) and demonstrating each point’s change in decibels. The printout ﬁrst displays the two baseline ﬁelds in Graytone and in Total Deviation plots. At the bottom of the page, following these two ﬁelds is a plot of Mean Deviation over time (MD Slope), identical to the one seen on Change Analysis Printout. Each follow-up ﬁeld is displayed on the following pages labeled Follow-up on the top of the page. The follow-up portion of the Glaucoma Progression Analysis printout (Figure 3-28) differs from the Overview printout by replacing the Total Deviation and Pattern Deviation plots at the right with a point-by-point analysis of Deviation From Baseline plot in decibels from the baseline plot and the Progression Analysis probability plot. This latter plot identiﬁes points that have progressively changed on consecutive ﬁelds, where crosses indicate changes outside of calculable statistical range. The analysis was found to have high speciﬁcity and sensitivity and be a useful test to assist in the detection of glaucomatous progression.36 3-7-4 GPA - Guided Progression Analysis. A new Guided Progression Analysis (GPA)37 may be a somewhat confusing term (see the previously described Glaucoma Progression Analysis). The GPA presents the results of a baseline examination, Visual Field Index Plot, Glaucoma Change Probability Map, and the GPA Alert, indicating “Possible Progression,” “Likely Progression,” or “No Progression Detected” on one page.

3-8 VISUAL FUNCTION SPECIFIC PERIMETRIC TECHNOLOGIES Visual function can also be evaluated by selectively testing speciﬁc retinal ganglion cells, potentially allowing for earlier detection of glaucoma. However, no technology has been shown to be superior due to signiﬁcant variations of visual function in early glaucoma.38

Figure 3-27. Glaucoma progression analysis printout. Baselinee: Th he ﬁrst

two ﬁelds are averaged and the results are considered a basselinee ﬁeld d. Each subsequent ﬁeld undergoes a point-by-point change from m the baseliine comparison, displayed with decibel values and accompanyying prob babiliity symbols. The mean deviation (MD) change probability comp paress the MD of each follow-up ﬁeld to the baseline MD with associated P valu ues. A lineear regression of the MD values over time is displayed next to th he baaselin ne ﬁellds and, in this case, the resulting MD slope is not signiﬁcant at a 95% % con nﬁden nce level. In this case, note the same level of signiﬁcance over timee, ind dicatiing stability, despite preexisting signiﬁcant loss of sensitivity.

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Figure 3-28. Follow-up demonstrates individual test results with Deviation

from Baseline and Progression Analysis point-by-point.

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3-8-1 Short-Wavelength Automated Perimetry (SWAP). Testing a subgroup of ganglion cells, called midget ganglion cells, that are sensitive to blue stimuli may detect loss of visual function at an earlier stage of glaucoma than with standard automated perimetry.26 Short-wavelength automated perimetry (SWAP) presents a large Goldmann size V, short-wavelength blue targets on a bright yellow background.39 SWAP defects appear to represent early glaucomatous damage and may indicate signiﬁcant change in visual function before it becomes apparent on standard white-on-white visual ﬁelds. Several longitudinal studies have demonstrated the ability of blue-on-yellow perimetry to predict the development of glaucoma in ocular hypertensive patients,40,41 as well as which patients with early glaucomatous visual ﬁeld loss are most likely to progress.42 Other studies have demonstrated a signiﬁcant relationship between structural optic nerve damage and SWAP visual ﬁeld defects.43 However, the test is inﬂuenced by age and cataracts, and stringent statistical analysis in interpreting the results is necessary.44,45 The SWAP is currently available on the newer Humphrey Visual Field Analyzers, incorporating the efﬁciency of the SITA algorithm with the 24-2 testing pattern, to decrease testing time from 12 minutes to less than 4 minutes.46,47 SITA-SWAP has been shown to demonstrate a higher prevalence of visual ﬁeld deﬁcits, suggesting earlier detection of glaucomatous changes, compared with standard automated perimetry.42,48 The printout is very similar to the standard HFA printout. 3-8-2 Frequency Doubling Perimetry. Frequency doubling illusion is the base for the frequency doubling technology (FDT) perimetry.49 Each test stimulus is a series of white-and-black bands ﬂickering at 25 Hz.50 FDT perimetry is thought to be mediated by a subset of the large-diameter ganglion cells that project to the magnocellular visual pathway.51 These cells are presumed to be sensitive to motion and contrast and more vulnerable to glaucomatous damage,52 although this view has been questioned by some.53,54 The FDT is a portable and relatively inexpensive tool1 with a short testing time, making it a very useful screening device.55 However, FDT perimetry was reported to be less sensitive to visual ﬁeld damage associated with neurologic disorders compared with standard automated perimetry.56 Sensitivity to FDT was found to be reduced in the second tested eye57—this effect is accounted for in the perimeter’s normative database.58 The original FDT perimeter tested only 17 points over the central 20° of the visual ﬁeld. The second-generation FDT, Matrix, uses 69 smaller stimuli, utilizing 24-2 and 30-2 strategies to allow for early detection of glaucoma.59 The Matrix printout is organized similarly to a printout from the Humphrey Visual Field Analyzer. 3-8-3 High-Pass Resolution Perimetry. High-pass resolution perimetry (HPRP), or ring perimetry, is presumed to selectively test the parvocellular system.60 The stimuli used in HPRP are rings of different sizes with dark borders and bright centers projected at different locations on the screen, creating average luminance of the stimulus equal to the luminance of the background. The results of the test are presumed to correspond to the density of ganglion cells.1 In glaucoma patients, HPRP is comparable to standard perimetry in sensitivity and speciﬁcity.61 Some studies suggested that HPRP is a viable test for detection of glaucomatous visual ﬁeld damage.62

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3-8-4 Tendency-Oriented Perimetry. Tendency-oriented perimetry (TOP) is a fast strategy algorithm available on Octopus perimeters.63 It also uses a computational approach to estimate threshold values by extrapolating information from surrounding test points. Compared with SITA Fast, the mean testing time for the TOP strategy was slightly over 2½ minutes, compared with approximately 4 minutes for SITA Fast.64 However, the TOP algorithm may not always accurately estimate visual ﬁeld defects.65

3-9 LEARNING EFFECT AND ARTIFACTS The results of many psychophysical tests improve as the subject gains more experience performing the test. The learning effect in automated perimetry seems to be small in most patients who have had experience with manual perimetry.66 Some patients, however, may demonstrate a dramatic improvement in the second test compared with the ﬁrst.67 Occasionally, patients continue to improve over the initial three, four, or (rarely) ﬁve automated ﬁelds. The variability of test results may decrease signiﬁcantly with experience. Whenever possible, a patient who is new to perimetry should undergo several test sessions, to establish a baseline for subsequent comparisons. The magnitude of the learning effect can be reduced by an attentive, thoughtful technician who takes the time to explain the examination thoroughly to the patient. Several factors can produce abnormal-appearing ﬁeld printouts without necessarily affecting the reliability indices. Other causes may contribute to unreliable results yet not be apparent on the printout. Test areas that are noisy, have confounding stray light, or provide uncomfortable chairs may contribute to patient fatigue or inconsistent responses. Some of the clinically important artifacts are discussed in the sections that follow.

3-9-1 Miosis and Mydriasis. Pupil size of less than 3 mm, particularly if combined with lens opacity, tends to produce a diffuse depression of the visual ﬁeld. For this reason, the pupil size should be recorded on each test, and the inﬂuence of pupil size should be considered when a ﬁeld change is detected. The technician usually enters the pupil size into the general information section, so that it is available to the clinician. Newer versions of automated perimeters can automatically record the size of the pupil. If a pupil in a patient undergoing visual ﬁeld testing is less than 3 mm, as a result of miotics, neuro-ophthalmologic disease, or age-related miosis, it should be routinely dilated for perimetry. Mydriasis has less inﬂuence on the visual ﬁeld, although pupillary dilatation may reduce peripheral threshold sensitivity with automated perimetry.68,69 Although decreased pupil size should have little effect on a patient’s perception of a stimulus, because background and stimulus are affected equally, signiﬁcant miosis may depress central and peripheral threshold sensitivities and exaggerate ﬁeld defects.70 Refractive error can change considerably after pupil dilation, particularly in younger patients, who may require a dilated refraction prior to testing. One study used neutral density ﬁlters to reduce the retinal illumination

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the equivalent of decreasing the pupillary diameter in half, which reduced the mean threshold with two automated perimeters by 1.1 to 1.7 dB.71 Another study has also shown that pilocarpine signiﬁcantly worsened the visual ﬁeld global indices, such as MD and PSD.72

3-9-2 Media Opacities. Any media opacity, such as a cataract, posterior capsular ﬁbrosis, or corneal scar, can cause a generalized depression of the ﬁeld result (see Figure 3-17). Prediction of this effect by Snellen acuity is often poor. The patient with 20/25 acuity and 3+ nuclear sclerosis may have 5 dB or more of generalized depression apparent on the MD index. Cataracts produce glare and change the intensity of the stimulus. Therefore, a cataract can cause or exaggerate central or peripheral ﬁeld defects, which could be mistaken for the development or progression of glaucomatous ﬁeld loss. Even minimal light scattering, as may be caused by an early cataract that has a relatively insigniﬁcant effect on visual acuity, may signiﬁcantly inﬂuence visual ﬁeld results. After cataract extraction, eyes with glaucoma may have improvement of foveal sensitivity and visual ﬁeld scores and sometimes even a reversal of a partial or complete scotoma.73 However, cataract surgery can also reveal mild and moderate ﬁeld defects masked by cataracts.74,75 Reduced clarity of the ocular media from other causes, such as a corneal disturbance, a cloudy posterior lens capsule, or vitreous opacities, may also affect the visual ﬁelds. Applanation tonometry prior to automated perimetry was not found to have a detrimental effect on the visual ﬁeld results.76 3-9-3 Eyelid and Nose Effects. Acquired ptosis of a mild degree is very common in older adults. While it may not affect Snellen acuity, a drooping upper eyelid can produce a superior arcuate–type defect or a superior nasal step. The visual ﬁeld technician can be instrumental in recognizing this artifact, which can often be improved by taping the eyelid up during the test. Improper head positioning by the visual ﬁeld technician can also cause the nose to produce an inferonasal defect. 3-9-4 Refractive Errors. Improper refractive correction could cause the projected stimulus to be out of focus on the retina, and the stimulus may not be detected by the patient. Refractive errors primarily inﬂuence the central ﬁeld.77 With a usual size-III stimulus, spherical refractive errors of less than 1 diopter may not need to be corrected, because error in measurement is going to be only slightly more than 1 dB of general reduction of sensitivity.78 Myopia of less than 3 diopters also may not require correction, although high myopic errors can create areas of retinal blur, called refraction scotomas, which appear as a vertical wedge–type defect and may be confused with glaucomatous ﬁeld loss. Those can usually be eliminated with an appropriate refractive correction. Hyperopia has a greater inﬂuence on perimetric results, especially for the central ﬁeld, and even small hyperopic refractive errors can signiﬁcantly alter threshold sensitivity.77-79 In general, patients over age 30 require a near correction added to the distance refraction. Spherical add depends on an accommodative amplitude, for which Humphrey Visual Field Analyzer uses age data to aid in determining the appropriate correction. A contact lens provides

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the best correction for the aphakic and highly myopic80,81 eyes. Astigmatic error of more than 1 diopter should be corrected in full.

3-9-5 Corrective Lens/Frame Artifacts. A spectacle lens placed too far from the tested eye can produce a ring-type scotoma appearance. Poor lens centering can produce an arcuate-appearing defect. Frame/corrective lens artifacts tend to be perfectly semicircular, or circular and dense (Figure 3-29). They can be minimized with proper spectacle placement or eliminated entirely with contact lens testing.

Figure 3-29. Lens holder artifact. This patient was tested without a corrective

lens, while the lens holder was moved away from the patient face toward the center of the bowl, demonstrating absolute loss in a circular pattern inferiorly. The very sharp falloff in sensitivities above the horizontal meridian with an absent nasal step strongly suggests an artifactual scotoma, which was conﬁrmed when the ﬁeld appeared normal after the lens holder was moved out of the way.

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3-10 ROLE OF THE VISUAL FIELD TECHNICIAN An attentive, knowledgeable technician is of critical importance to obtaining highquality test results.82 Patients must be instructed on what to expect during the ﬁeld test, stressing the fact that at least half of the stimuli are not supposed to be seen, and the ones that are seen will barely visible, thereby allowing the proper performance to be achieved. Patients must be given feedback throughout the test on maintaining ﬁxation and proper position, minimizing false-positive and falsenegative responses, and how long the test will last. A good visual ﬁeld technician is vigilant in providing a comfortable, quiet location for reliable results, as well as recognizing the need for pupil dilation. In addition, the visual ﬁeld technician should be able to minimize the effects of ptosis and lens artifact. It may also be helpful to let the patient know that the machine will not present an additional stimulus until the button is released, providing the patient with a break to stretch and to become more comfortable and attentive to the test.

REFERENCES 1. Delgado MF, Nguyen NT, Cox TA, et al. Automated perimetry: a report by the American Academy of Ophthalmology. Ophthalmology. 2002;109:2362–2374. 2. Förster C. Vorzeigung des Perimeter. Klin Monatsbl Augenheilk. 1869;7:411–422. 3. Traquair H. An Introduction to Clinical Perimetry. London: Kimpton; 1927. 4. Harms H, Aulhorn E. [Comparative studies on the value of quantitative perimetry, skiaskotometry and fusion frequency for the recognition of beginning visual ﬁeld disorders in glaucoma.]. Doc Ophthalmol. 1959;13:303–356. 5. Wohlrab TM, Kreinberger H, Erb C, et al. [Threshold-oriented suprathreshold perimetry and threshold value perimetry with the Tubigen CC Automated Perimeter. A comparative study]. Ophthalmologe. 1998;95:92–99. 6. Gloor BP. Franz Fankhauser: the father of the automated perimeter. Surv Ophthalmol. 2009;54:417–425. 7. Fankhauser F. Background illumination and automated perimetry. Arch Ophthalmol. 1986;104:1126. 8. Heijl A, Krakau CE. An automatic perimeter for glaucoma visual ﬁeld screening and control. Construction and clinical cases. Albrecht Von Graefes Arch Klin Exp Ophthalmol. 1975;197:13–23. 9. Flammer J, Drance SM, Augustiny L, Funkhouser A. Quantiﬁcation of glaucomatous visual ﬁeld defects with automated perimetry. Invest Ophthalmol Vis Sci. 1985;26: 176–181. 10. Bengtsson B, Heijl A, Olsson J. Evaluation of a new threshold visual ﬁeld strategy, SITA, in normal subjects. Swedish Interactive Thresholding Algorithm. Acta Ophthalmol Scand. 1998;76:165–169. 11. Chauhan BC, Garway-Heath DF, Goni FJ, et al. Practical recommendations for measuring rates of visual ﬁeld change in glaucoma. Br J Ophthalmol. 2008;92: 569–573. 12. Nevalainen J, Paetzold J, Krapp E, et al. The use of semi-automated kinetic perimetry (SKP) to monitor advanced glaucomatous visual ﬁeld loss. Graefes Arch Clin Exp Ophthalmol. 2008;246:1331–1339.

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13. Johnson CA, Keltner JL. Optimal rates of movement for kinetic perimetry. Arch Ophthalmol. 1987;105:73–75. 14. Schiefer U, Strasburger H, Becker ST, et al. Reaction time in automated kinetic perimetry: effects of stimulus luminance, eccentricity, and movement direction. Vision Res. 2001;41:2157–2164. 15. Pineles SL, Volpe NJ, Miller-Ellis E, et al. Automated combined kinetic and static perimetry: an alternative to standard perimetry in patients with neuro-ophthalmic disease and glaucoma. Arch Ophthalmol. 2006;124:363–369. 16. Chauhan BC, Tompkins JD, LeBlanc RP, McCormick TA. Characteristics of frequencyof-seeing curves in normal subjects, patients with suspected glaucoma, and patients with glaucoma. Invest Ophthalmol Vis Sci. 1993;34:3534–3540. 17. Westcott MC, Fitzke FW, Crabb DP, Hitchings RA. Characteristics of frequency-ofseeing curves for a motion stimulus in glaucoma eyes, glaucoma suspect eyes, and normal eyes. Vision Res. 1999;39:631–639. 18. Bebie H, Fankhauser F, Spahr J. Static perimetry: accuracy and ﬂuctuations. Acta Ophthalmol (Copenh). 1976;54:339–348. 19. Chauhan BC, LeBlanc RP, Drance SM, et al. Effect of the number of threshold determinations on short-term ﬂuctuation in automated perimetry. Ophthalmology. 1991;98:1420–1424. 20. Boeglin RJ, Caprioli J, Zulauf M. Long-term ﬂuctuation of the visual ﬁeld in glaucoma. Am J Ophthalmol. 1992;113:396–400. 21. Keltner JL, Johnson CA, Quigg JM, et al. Conﬁrmation of visual ﬁeld abnormalities in the Ocular Hypertension Treatment Study. Ocular Hypertension Treatment Study Group. Arch Ophthalmol. 2000;118:1187–1194. 22. Bourne RR, Jahanbakhsh K, Boden C, et al. Reproducibility of visual ﬁeld end point criteria for standard automated perimetry, full-threshold, and Swedish interactive thresholding algorithm strategies: diagnostic innovations in glaucoma study. Am J Ophthalmol. 2007;144:908–913. 23. Budenz DL, Rhee P, Feuer WJ, et al. Sensitivity and speciﬁcity of the Swedish interactive threshold algorithm for glaucomatous visual ﬁeld defects. Ophthalmology. 2002;109:1052–1058. 24. Akar Y, Yilmaz A, Yucel I. Assessment of an effective visual ﬁeld testing strategy for a normal pediatric population. Ophthalmologica. 2008;222:329–33. 25. Roggen X, Herman K, Van Malderen L, et al. Different strategies for Humphrey automated perimetry: FASTPAC, SITA standard and SITA fast in normal subjects and glaucoma patients. Bull Soc Belge Ophtalmol. 2001:23–33. 26. Johnson CA. Recent developments in automated perimetry in glaucoma diagnosis and management. Curr Opin Ophthalmol. 2002;13:77–84. 27. Heijl A, Krakau CE. An automatic static perimeter, design and pilot study. Acta Ophthalmol (Copenh). 1975;53:293–310. 28. Heijl A, Krakau CE. A note of ﬁxation during perimetry. Acta Ophthalmol (Copenh). 1977;55:854–861. 29. Sanabria O, Feuer WJ, Anderson DR. Pseudo-loss of ﬁxation in automated perimetry. Ophthalmology. 1991;98:76–78. 30. Heijl A, Lindgren G, Olsson J, Asman P. Visual ﬁeld interpretation with empiric probability maps. Arch Ophthalmol. 1989;107:204–208. 31. Asman P, Heijl A. Glaucoma Hemiﬁeld Test. Automated visual ﬁeld evaluation. Arch Ophthalmol. 1992;110:812–819. 32. Asman P, Heijl A. Evaluation of methods for automated Hemiﬁeld analysis in perimetry. Arch Ophthalmol. 1992;110:820–826.

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33. Johnson CA, Sample PA, Ciofﬁ GA, et al. Structure and function evaluation (SAFE): I. criteria for glaucomatous visual ﬁeld loss using standard automated perimetry (SAP) and short wavelength automated perimetry (SWAP). Am J Ophthalmol. 2002;134: 177–185. 34. Much JW, Liu C, Piltz-Seymour JR. Long-term survival of central visual ﬁeld in endstage glaucoma. Ophthalmology. 2008;115:1162–1166. 35. Rehman Siddiqui MA, Khairy HA, Azuara-Blanco A. Effect of cataract extraction on SITA perimetry in patients with glaucoma. J Glaucoma. 2007;16:205–208. 36. Arnalich-Montiel F, Casas-Llera P, Munoz-Negrete FJ, Rebolleda G. Performance of glaucoma progression analysis software in a glaucoma population. Graefes Arch Clin Exp Ophthalmol. 2009;247:391–397. 37. Bengtsson B, Heijl A. A visual ﬁeld index for calculation of glaucoma rate of progression. Am J Ophthalmol. 2008;145:343–353. 38. Sakata LM, DeLeon-Ortega J, Girkin CA. Selective perimetry in glaucoma diagnosis. Curr Opin Ophthalmol. 2007;18:115–121. 39. Johnson CA. Diagnostic value of short-wavelength automated perimetry. Curr Opin Ophthalmol. 1996;7:54–58. 40. Polo V, Abecia E, Pablo LE, et al. Short-wavelength automated perimetry and retinal nerve ﬁber layer evaluation in suspected cases of glaucoma. Arch Ophthalmol. 1998;116: 1295–1298. 41. Lewis RA, Johnson CA, Adams AJ. Automated perimetry and short wavelength sensitivity in patients with asymmetric intraocular pressures. Graefes Arch Clin Exp Ophthalmol. 1993;231:274–278. 42. Johnson CA, Adams AJ, Casson EJ, Brandt JD. Progression of early glaucomatous visual ﬁeld loss as detected by blue-on-yellow and standard white-on-white automated perimetry. Arch Ophthalmol. 1993;111:651–656. 43. Girkin CA, Emdadi A, Sample PA, et al. Short-wavelength automated perimetry and standard perimetry in the detection of progressive optic disc cupping. Arch Ophthalmol. 2000;118:1231–1236. 44. Tafreshi A, Sample PA, Liebmann JM, et al. Visual function-speciﬁc perimetry to identify glaucomatous visual loss using three different deﬁnitions of visual ﬁeld abnormality. Invest Ophthalmol Vis Sci. 2009;50:1234–1240. 45. Sample PA, Johnson CA, Haegerstrom-Portnoy G, Adams AJ. Optimum parameters for short-wavelength automated perimetry. J Glaucoma. 1996;5:375–383. 46. Bengtsson B. A new rapid threshold algorithm for short-wavelength automated perimetry. Invest Ophthalmol Vis Sci. 2003;44:1388–1394. 47. Bengtsson B, Heijl A. Diagnostic sensitivity of fast blue-yellow and standard automated perimetry in early glaucoma: a comparison between different test programs. Ophthalmology. 2006;113:1092–1097. 48. Demirel S, Johnson CA. Short wavelength automated perimetry (SWAP) in ophthalmic practice. J Am Optom Assoc. 1996;67:451–456. 49. Johnson CA, Samuels SJ. Screening for glaucomatous visual ﬁeld loss with frequencydoubling perimetry. Invest Ophthalmol Vis Sci. 1997;38:413–425. 50. Alward WL. Frequency doubling technology perimetry for the detection of glaucomatous visual ﬁeld loss. Am J Ophthalmol. 2000;129:376–378. 51. Maddess T. Perspectives on the use of frequency doubling and short wavelength perimetry for the diagnosis of glaucoma. Clin Exp Ophthalmol. 2000;28:245–247. 52. Quigley HA. Neuronal death in glaucoma. Prog Retin Eye Res. 1999;18:39–57. 53. Harwerth RS, Carter-Dawson L, Shen F, et al. Ganglion cell losses underlying visual ﬁeld defects from experimental glaucoma. Invest Ophthalmol Vis Sci. 1999;40:2242–2250.

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54. Morgan JE, Uchida H, Caprioli J. Retinal ganglion cell death in experimental glaucoma. Br J Ophthalmol. 2000;84:303–310. 55. Mansberger SL, Edmunds B, Johnson CA, et al. Community visual ﬁeld screening: prevalence of follow-up and factors associated with follow-up of participants with abnormal frequency doubling perimetry technology results. Ophthalmic Epidemiol. 2007;14:134–140. 56. Wall M, Neahring RK, Woodward KR. Sensitivity and speciﬁcity of frequency doubling perimetry in neuro-ophthalmic disorders: a comparison with conventional automated perimetry. Invest Ophthalmol Vis Sci. 2002;43:1277–1283. 57. Tsukamoto H, Mukai S, Iwase A, Mishima HK. Recovery of reliability by retest after a 5-minute interval in frequency doubling technology perimetry. Jpn J Ophthalmol. 2006;50:380–382. 58. Brusini P, Salvetat ML, Zeppieri M, Parisi L. Frequency doubling technology perimetry with the Humphrey Matrix 30–2 test. J Glaucoma. 2006;15:77–83. 59. Johnson CA, Ciofﬁ GA, Van Buskirk EM. Frequency doubling technology perimetry using a 24–2 stimulus presentation pattern. Optom Vis Sci. 1999;76:571–581. 60. Martinez GA, Sample PA, Weinreb RN. Comparison of high-pass resolution perimetry and standard automated perimetry in glaucoma. Am J Ophthalmol. 1995;119: 195–201. 61. Martin L, Wanger P, Vancea L, Gothlin B. Concordance of high-pass resolution perimetry and frequency-doubling technology perimetry results in glaucoma: no support for selective ganglion cell damage. J Glaucoma. 2003;12:40–44. 62. Chauhan BC. The value of high-pass resolution perimetry in glaucoma. Curr Opin Ophthalmol. 2000;11:85–89. 63. Maeda H, Nakaura M, Negi A. New perimetric threshold test algorithm with dynamic strategy and tendency oriented perimetry (TOP) in glaucomatous eyes. Eye. 2000; 14(Pt 5):747–751. 64. King AJ, Taguri A, Wadood AC, Azuara-Blanco A. Comparison of two fast strategies, SITA Fast and TOP, for the assessment of visual ﬁelds in glaucoma patients. Graefes Arch Clin Exp Ophthalmol. 2002;240:481–487. 65. Anderson AJ. Spatial resolution of the tendency-oriented perimetry algorithm. Invest Ophthalmol Vis Sci. 2003;44:1962–1968. 66. Werner EB, Krupin T, Adelson A, Feitl ME. Effect of patient experience on the results of automated perimetry in glaucoma suspect patients. Ophthalmology. 1990;97:44–48. 67. Johnson CA, Keltner JL, Cello KE, et al. Baseline visual ﬁeld characteristics in the ocular hypertension treatment study. Ophthalmology. 2002;109:432–437. 68. Lindenmuth KA, Skuta GL, Rabbani R, et al. Effects of pupillary dilation on automated perimetry in normal patients. Ophthalmology. 1990;97:367–70. 69. Mendivil A. Inﬂuence of a dilated pupil on the visual ﬁeld in glaucoma. J Glaucoma. 1997;6:217–220. 70. Lindenmuth KA, Skuta GL, Rabbani R, Musch DC. Effects of pupillary constriction on automated perimetry in normal eyes. Ophthalmology. 1989;96:1298–1301. 71. Heuer DK, Anderson DR, Feuer WJ, Gressel MG. The inﬂuence of decreased retinal illumination on automated perimetric threshold measurements. Am J Ophthalmol. 1989;108:643–650. 72. Edgar DF, Crabb DP, Rudnicka AR, et al. Effects of dipivefrin and pilocarpine on pupil diameter, automated perimetry and LogMAR acuity. Graefes Arch Clin Exp Ophthalmol. 1999;237:117–124. 73. Chen PP, Budenz DL. The effects of cataract extraction on the visual ﬁeld of eyes with chronic open-angle glaucoma. Am J Ophthalmol. 1998;125:325–333.

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74. Smith SD, Katz J, Quigley HA. Effect of cataract extraction on the results of automated perimetry in glaucoma. Arch Ophthalmol. 1997;115:1515–1519. 75. Hayashi K, Hayashi H, Nakao F, Hayashi F. Inﬂuence of cataract surgery on automated perimetry in patients with glaucoma. Am J Ophthalmol. 2001;132:41–46. 76. Ruben JB, Lewis RA, Johnson CA, Adams C. The effect of Goldmann applanation tonometry on automated static threshold perimetry. Ophthalmology. 1988;95: 267–270. 77. Weinreb RN, Perlman JP. The effect of refractive correction on automated perimetric thresholds. Am J Ophthalmol. 1986;101:706–709. 78. Heuer DK, Anderson DR, Feuer WJ, Gressel MG. The inﬂuence of refraction accuracy on automated perimetric threshold measurements. Ophthalmology. 1987;94: 1550–1553. 79. Goldstick BJ, Weinreb RN. The effect of refractive error on automated global analysis program G-1. Am J Ophthalmol. 1987;104:229–232. 80. Koller G, Haas A, Zulauf M, et al. Inﬂuence of refractive correction on peripheral visual ﬁeld in static perimetry. Graefes Arch Clin Exp Ophthalmol. 2001;239:759–762. 81. Miller BA, Gelber EC. Aphakic visual ﬁelds by automated perimetry. Ann Ophthalmol. 1990;22:419–422. 82. Kutzko KE, Brito CF, Wall M. Effect of instructions on conventional automated perimetry. Invest Ophthalmol Vis Sci. 2000;41:2006–2013. 83. Demirel S, Johnson CA. Incidence and prevalence of short wavelength automated perimetry deﬁcits in ocular hypertensive patients. Am J Ophthalmol. 2001;131: 709–715.

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4 Automated Perimetry in Glaucoma HYLTON R. MAYER, MD, MARC L. WEITZMAN, MD, AND JOSEPH CAPRIOLI, MD

4-1 INTRODUCTION Clinical experience and multiple prospective studies, such as the Collaborative Normal Tension Glaucoma Study and the Los Angeles Latino Eye Study, have demonstrated that the diagnosis of glaucoma is more complex than identifying elevated intraocular pressure.1,2 As a result, increased emphasis has been placed on measurements of the structural and functional abnormalities caused by glaucoma. The reﬁnement and adoption of imaging technologies assist the clinician in the detection of glaucomatous damage and, increasingly, in identifying the progression of structural damage. Because visual ﬁeld defects in glaucoma patients occur in patterns that correspond to the anatomy of the nerve ﬁber layer of the retina and its projections to the optic nerve, visual functional tests become a link between structural damage and functional vision loss (Figure 4-1). The identiﬁcation of glaucomatous damage and management of glaucoma require appropriate, sequential measurements and interpretation of the visual ﬁeld.

4-2 GLAUCOMATOUS FIELD LOSS Glaucomatous visual ﬁeld defects usually are of the nerve ﬁber bundle type, corresponding to the anatomic arrangement of the retinal nerve ﬁber layer. It is helpful to consider the division of the nasal and temporal retina as the fovea, not the optic nerve head, because this is the location that determines the center of the visual ﬁeld. The ganglion cell axon bundles that emanate from the nasal side of the retina generally approach the optic nerve head in a radial fashion. The majority of

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Figure 4-1. The nerve ﬁber layer anatomy of the retina. Damage to discrete bundles of nerve ﬁbers, usually at the superior and inferior poles of the disc, gives rise to typical patterns of visual ﬁeld loss in glaucoma. The classic nerve ﬁber bundle defects are the arcuate scotoma, nasal step, and temporal-sector defect. Diffuse damage to nerve ﬁbers may also cause a diffuse depression of visual ﬁeld sensitivity.

these ﬁbers enter the nasal half of the optic disc, but ﬁbers that represent the nasal half of the macula form the papillomacular bundle to enter the temporal-most aspect of the optic nerve. In contrast, the temporal retinal ﬁbers, with respect to ﬁxation, arc around the macula to enter the superotemporal and inferotemporal portions of the optic disc. The origin of these arcuate temporal retinal ﬁbers strictly respects the horizontal retinal raphe, temporal to the fovea. As a consequence of this superior-inferior segregation of the temporal retinal ﬁbers, lesions that affect the superotemporal and inferotemporal poles of the optic disc, such as glaucoma, tend to cause arcuateshaped visual ﬁeld defects extending from the blind spot toward the nasal horizontal meridian. Tremendous variability characterizes the patterns of glaucomatous cupping, with some patients having fairly diffuse, concentric loss of the neuroretinal rim, while others have extremely localized loss. Glaucomatous visual ﬁeld damage shows a similar variability, with some patients demonstrating early scattered involvement of the visual ﬁeld, while others display dense localized defects. When only a single hemiﬁeld is involved, it is the superior hemiﬁeld 60% of the time.3,4 When patients have visual ﬁeld loss in both the superior and the inferior hemiﬁelds, there is still often a detectable difference in the measured threshold on either side of the nasal horizontal meridian. For the most part, clinicians familiar with the typical glaucomatous scotomas detected by manual perimetry recognize these same defects when demonstrated by automated perimetry. Seidel scotomas emenating from the optic nerve, nasal steps, and paracentral scotomas are commonly seen. When more advanced damage occurs, these smaller scotomas may coalesce to form superior and inferior arcuate

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scotomas, which may ultimately isolate a spared central and/or temporal island of vision. Temporal wedge defects, representing glaucomatous damage to the nasal nerve ﬁbers, also respect the nerve ﬁber layer anatomy but are seen less than 5% of the time.5 Scotomas involving ﬁxation (central scotomas) typically occur after advanced cupping occurs. While paracentral scotomas may be seen, classically in normal tension glaucoma, if central scotomas are identiﬁed, one should consider alternative diagnoses, such as retinal disease or nonglaucomatous optic neuropathies.6,7 Similarly, defects that respect the vertical meridian are not retinal nerve ﬁber bundle defects and are often caused by disease at or behind the optic chiasm. One defect well described with manual kinetic perimetry, which is less often seen with static testing, is the Seidel scotoma, an arcuate-shaped elongation of the physiologic blind spot. The hill of vision at the superior and inferior poles of the blind spot tends to be relatively ﬂat. As a consequence, kinetic testing originating from the blind spot can easily mimic a Seidel scotoma if the stimulus speed is slightly too fast. The occurrence of purely generalized ﬁeld loss in glaucoma is controversial.8-10 Because many common conditions, such as cataract, miosis, refractive error, and patient fatigue, can cause an elevated mean deviation (MD) with a normal pattern standard deviation (PSD) and corrected pattern standard deviation (CPSD), these elements should be carefully considered before attributing generalized depression to glaucoma. Rarely, patients present with asymmetric intraocular pressure, asymmetric cupping, no confounding factors, and asymmetric MD values without localized scotomas (Figure 4-2). As a general rule, normal patients tend to test with MD asymmetry less than 2.0 dB 95% of the time on a single test. A 1.5-dB difference trend over two ﬁelds is equally signiﬁcant, and a difference as small as 1 dB may be meaningful if reproducible over four ﬁelds.11 Several studies have suggested that normal-tension glaucoma defects are more localized and are closer to ﬁxation compared with primary open-angle glaucoma defects.12-13 This theory has not been unequivocally proved, with critics alleging bias based on presenting factors because patients with primary open-angle glaucoma are more likely to be diagnosed on a basis of elevated intraocular pressure and may often be detected at an earlier stage of ﬁeld loss compared with patients with normal-tension glaucoma.14

4-3 AUTOMATED PERIMETRY OPTIONS For more than a decade, the full threshold testing strategy was the most widely used automated perimetry algorithm. Advantages of the full threshold test include numerous stimuli presented at each testing point in the ﬁeld, theoretically offering a more reﬁned estimation of the threshold value. The full threshold testing algorithm also offers a variety of reliability indicators, including estimations of short-term ﬂuctuation (STF) within the test itself. Finally, many landmark studies regarding glaucoma diagnosis and management used full threshold automated perimetry, establishing it as a gold standard in automated static perimetry. Disadvantages

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of the full threshold strategy include longer testing times, which can decrease patient comfort and test reliability. Patient fatigue during full threshold testing may also artiﬁcially depress sensitivities and overestimate glaucomatous damage or progression. Evolutions in testing algorithms involved adjustments in the grid size from 30-2 to 24-2, or from manipulation of the starting sensitivity or frequency of points crossing the threshold value, such as in fast threshold, FASTPAC. While FASTPAC can shorten test times 35-40% compared with full threshold strategies, it is thought to underestimate the size and density of scotomas. Humphrey ﬁeld machines now offer the Swedish interactive threshold algorithm (SITA) that has

A Figure 4-2. Generalized depression on a full threshold test. The intraocular pressure is in the high 20s in the left eye and in the high teens in the right eye, with asymmetric cupping. There is 2.45 dB of asymmetry in the mean deviation between the two eyes with otherwise normal ﬁelds. This can be taken as evidence of early glaucomatous generalized depression. (A) Field chart of left eye. (B) Field chart of right eye. (C) Fundus photograph of right eye. (D) Fundus photograph of left eye.

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B

C

D

Figure 4-2. (Continued)

largely supplanted previous testing strategies. SITA uses a proprietary software to more rapidly and accurately identify threshold values. In comparison with full threshold tests, SITA tests are 50% shorter, typically lasting about 5 minutes per eye. SITA has been extensively evaluated against full threshold strategies and is widely accepted to be equivalent to the “gold standard.”15 SITA tests have been

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applied to large multicenter prospective studies, allowing more direct comparison to clinical applications and improving longitudinal data.16,17 Advanced analytical software is available to assist in identifying glaucomatous defects, progression, and trends (see Section 4-5). SITA is also available in a more streamlined testing algorithm, SITA Fast, which decreases testing time (70% faster than full threshold) by reducing the number of times the threshold limit is checked.18 In comparison with SITA, many believe the advantages in shorter test times are offset by the reduction in the quality of the test data. Advances in testing algorithms, software, and hardware are improving efforts to increase patient comfort by decreasing test duration while maintaining or improving reliability and reproducibility.

4-4 EVALUATION OF A SINGLE TEST Regardless of the method used to obtain them, visual ﬁeld measurements should not be interpreted in a vacuum. It is almost always preferable to integrate other clinical data, such as refractive status, corneal clarity, condition of the crystalline lens, intraocular pressure, appearance of the optic nerve head, estimation of the patient’s vascular status, and assessment of the patient’s general health. An analysis of speciﬁc risk factors and potential side effects should be included in decisions about therapy. Before diagnostic and therapeutic decisions based on visual ﬁeld information are made, patient reliability, artifacts, and other confounding variables must be considered. The Advanced Glaucoma Intervention Study (AGIS) and The Collaborative Initial Glaucoma Treatment Study (CIGTS) demonstrated that visual ﬁeld defects on one test often ﬂuctuated on subsequent follow-ups, and patients often demonstrated wide STFs and long-term ﬂuctuations (LTFs).19,20

4-4-1 Patient Reliability. Determination of patient performance is an important initial step in visual ﬁeld interpretation. A number of routinely measured elements can supply an estimate of patient reliability and are generally displayed with the ﬁelds: 1. 2. 3. 4. 5.

Test duration Number of ﬁxation losses Rate of false-positive answers Rate of false-negative answers STF, or the ﬂuctuation of repeated threshold measurements within the same test. This parameter is present on full threshold programs and is not evaluated in the more recent SITA tests. 6. Number of stimuli. This parameter is present on full threshold programs and is not reported in the SITA tests. Also important is the operator’s ability to comment on or score patient cooperation and alertness during the examination. Maintaining accurate ﬁxation and alertness depends on both the patient and the technician.

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The standard limits for acceptable false-positive and false-negative answers have been set at 33%, and for ﬁxation losses, at 20%. If these limits are exceeded, the value is highlighted and a warning message is displayed. These messages should not necessarily prompt the examiner to discard the entire ﬁeld but should result in a review of possible causal factors.

4-4-1-1 Test Duration. It is not uncommon for a normal subject with prior visual ﬁeld experience to complete an SITA Standard Humphrey Program 24-2 in less than 5 minutes. Both lack of experience and localized scotomas increase test time. Nevertheless, it is unusual for reliable patients to require more than 10 minutes to complete Program 24-2. (Full threshold test times for 24-2 and 30-2 should take about 9 and 12 minutes, respectively.) 4-4-1-2 Fixation Losses. Fixation losses, as measured by blind spot checking, can occur with wandering gaze but can also result from a displaced blind spot or from a high rate of false-positive answers (see Section 3-4-4). Wandering gaze may result in peripheral threshold values as high as foveal sensitivity values. Further, an acceptable rate of ﬁxation losses does not ensure that ﬁxation was good (see Section 3-4-4 for an explanation of this apparent paradox). Evaluation of the quality of ﬁxation can be best determined by a dedicated and attentive operator, but gaze tracking software enables a graphic record of ﬁxation at the bottom of the Humphrey Visual Field printout (Figure 4-3). 4-4-1-3 False-Positive Responses. High false-positive values (Figure 4-4) tend to occur if the patient repeatedly responds when no stimulus is presented and correlate with patient response to subthreshold stimuli. If a false-positive response occurs during a blind spot check, a ﬁxation loss is recorded. False-positive responses tend to create the false impression that the ﬁeld contains high sensitivity. The graytone display may reveal regions without any gray stippling (decibel values higher than 41 dB), which are clearly nonphysiologic. These are known as white scotomas or a moth-eaten visual ﬁeld.

Figure 4-3. Humphrey visual ﬁeld analyzer software graphically displays variations in gaze for a semiquantitative record of visual ﬁxation stability; a smooth line indicates steady ﬁxation. Patients A and B both scored 3/14 ﬁxation losses, but Patient B had more and larger eye movements.

Figure 4-4. High false-positive errors. Although the testing parameters identiﬁed only 6% false-positive results, note the frequent midperipheral threshold values greater than 41 dB, which produce white scotomas. The general height correction of the total deviation by approximately 17 dB in this case produces a markedly abnormal pattern deviation plot. Because more than 15% of the test locations contain abnormally high sensitivity values, the glaucoma hemiﬁeld test (GHT) displays abnormally high sensitivity. In addition, the mean deviation is positive.

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Frequent false-positive responses are seen in the total deviation plot as scattered positive numbers. These are not ﬂagged on the total deviation probability plot, because they are not reduced below the 5th percentile. The pattern deviation values, however, are affected differently. Because the instrument adjusts the entire ﬁeld by a value that sets the seventh-highest locus on the total deviation plot to 0, loci where the patient responded appropriately may become markedly reduced. These may reach statistically signiﬁcant levels and be highlighted by probability symbols. Frequent false-positive responses tend to affect the global indices as well. MD becomes positive and the GHT alerts the interpreter that more than 15% of the test locations contain abnormally high sensitivity values (Figure 4-5).

Figure 4-5. High false-positive errors superimposed on glaucomatous defects in a full threshold test. This ﬁeld, although identiﬁed as low patient reliability, still provides evidence of nerve ﬁber bundle defects. Despite the high rate of ﬁxation losses and falsepositive errors, there is a recognizable superior arcuate defect ending in a superior nasal step. Because less than 15% of the locations in the total deviation plot are elevated above the 99.5% percentile, the GHT does not display abnormal high sensitivity and correctly identiﬁes the ﬁeld as outside normal limits. The inferior arcuate defect suggested on the pattern deviation plot may be partly an artifact based on the 6-dB correction of the total deviation plot by the general height index.

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In general, high false-positive responses are not physiologic and greatly affect the reliability of the ﬁeld. Fortunately, this problem can often be mitigated with instruction and encouragement of the patient by the perimetrist.

4-4-1-4 False-Negative Responses. In most respects, the patient with high falsenegative responses is the opposite of the patient with high false-positive responses. Instead of being “trigger-happy,” the former patients do not respond to stimuli that are much brighter than already measured thresholds. This situation correlates with technician comments such as “patient tired” or “patient falling asleep.” These patients often become increasingly fatigued during the test, with a tendency toward clusters of reduction in sensitivity toward the edge of the ﬁeld, the ﬁnal area tested. The total deviation plots become falsely abnormal, while the pattern deviation plot may be artifactually improved. MD is shifted more negatively. GHT may produce the message outside normal limits or on the borderline or with a general reduction in sensitivity. An extreme example is the cloverleaf ﬁeld, in which the patient responds to the four primary seed location determinations and then becomes progressively less responsive (Figure 4-6A and B). A major interpretation problem can occur because bona ﬁde ﬁeld loss secondary to disease tends to increase the remaining ﬁeld fatigability. High false-negative responses can thus be physiologic and the ﬁeld results reliable. Long programs can cause fatigue and reduce reliability. Critics of a fatigue-reducing program like FASTPAC or SITA Fast claim that it underestimates true defects, although perhaps it is the full threshold strategy that is overestimating defects by producing a perimetric “stress test.” Some clues may help the clinician distinguish between a normal ﬁeld that looks abnormal because of patient fatigue or frustration and a truly abnormal ﬁeld, with high false-negative responses as one of its features. True defects are more reproducible and tend to respect anatomic distributions (e.g., arcuate, paracentral), while pseudodefects tend to occur variably in the periphery. Either defect type can produce dense constriction with only a central island of vision remaining. Performance of a 10° program on a subsequent day or after the patient has had a break often disproves or conﬁrms the defect’s presence (Figure 4-7A and 7B). Similarly, the patient can be retested with a less fatiguing test such SITA Fast or with manual kinetic perimetry. Finally, correlation with the clinical examination of the optic nerve head, nerve ﬁber layer, and nerve ﬁber layer analysis cannot be overemphasized. 4-4-1-5 STF. STF on the full threshold algorithm, or intratest ﬂuctuation as measured on the full threshold algorithm, can be caused by an inconsistent patient or by true visual ﬁeld loss that causes the patient to tire easily. If the STF value in the global indices is ﬂagged with a probability symbol, a careful inspection of the actual threshold data may reveal the cause (see Figure 4-8A and B) 4-4-1-6 Stimuli Number. The number of stimuli needed to complete an examination can be used to estimate patient consistency. An abnormal ﬁeld may require an

A Figure 4-6. Apparent dense peripheral constriction, actually due to patient fatigue (A, B). The cloverleaf pattern develops in some patients because the testing algorithm begins by evaluating the center of each of the four quadrants of the ﬁeld. Patients often initially pay attention and thresholds are high in the center of each quadrant but later, as fatigue prevails, thresholds in each quadrant decline and the ﬁeld develops a nonphysiologic pattern of depression.

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B Figure 4-6. (Continued)

increased number of questions to complete the examination. If the patient is inconsistent, the testing strategy requires the presentation of more stimuli to arrive at a ﬁnal threshold value. Even with markedly abnormal ﬁelds, it is unusual for a reliable patient to complete a full threshold central 30° (24°) examination with more than a total of 550 (450) questions.

A Figure 4-7. True dense peripheral constriction. (A) The results of this patient’s Program 24-2 suggested marked constriction. (B) When the patient was retested with Program 10-2, the defect was conﬁrmed; there was only a small remaining central island of vision.

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B Figure 4-7. (Continued)

4-4-2 Criteria for Abnormality. Once armed with a solid understanding of the methods by which the automated perimeter tests and analyzes the ﬁeld, as well as familiarity with artifacts and other confounding factors, the clinician is much better equipped to interpret the results. Often, interpretation is relatively easy, as in an ocular hypertensive patient with mildly elevated intraocular pressure, a normal-appearing

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A Figure 4-8. Learning effect recognized. (A) In this series of ﬁelds, signiﬁcant learning occurs between the ﬁrst and second ﬁelds. (B) This improvement is seen as an upward shift in box location on the change analysis printout. The mean deviation also improves greatly from −10.69 dB to −5.07 dB between the ﬁrst and second tests. (C) The glaucoma change probability function of Auto STATPAC averages the second and third ﬁeld for a baseline. Because the ﬁrst ﬁeld is deleted, the mean deviation (MD) slope is reported as a modiﬁed MD slope.

optic disc, normal retinal nerve ﬁber layer analysis, and a completely unremarkable, reliably performed test. Interpreting moderately abnormal ﬁelds is also fairly simple, especially when they conform to classic patterns of loss, such as a sharply demarcated arcuate scotoma ending in a nasal step. More difﬁcult is the patient who exhibits an abnormal disc and an abnormal ﬁeld, with evidence of reduced reliability and other confounding factors (e.g., cataract,

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B

C Figure 4-8. (Continued)

retinovascular abnormality, prior retinal laser treatment). Although recognizing that a ﬁeld is not normal may be reasonably straightforward, classifying the amount of damage attributable to a speciﬁc disorder may pose considerable difﬁculty. Equally difﬁcult can be determining a subtle abnormality in a borderline clinical case. When attempting to classify precisely the degree of abnormality, clinicians should

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TABLE 4-1. Minimal Criteria for Grading Abnormality (Central 30°) Strict ≥ 4 adjacent points of ≥ 5 dB loss* each ≥ 3 adjacent points of ≥ 10 dB loss* each Difference of ≥ 10 dB across nasal horizontal meridian at ≥ 3 adjacent points Exclusions: physiologic blind spot; superior and inferior rows Moderate ≥ 3 adjacent points of ≥ 5 dB loss* each ≥ 2 adjacent points of ≥ 10 dB loss* each Difference of ≥ 10 dB across nasal horizontal meridian at ≥ 2 adjacent points Exclusions: physiologic blind spot; superior and inferior rows Liberal ≥ 2 adjacent points of ≥ 5 dB loss* each ≥ 1 adjacent points of ≥ 10 dB loss* each Difference of ≥ 5 dB across nasal horizontal meridian at ≥ 2 adjacent points Exclusions: physiologic blind spot; superior and inferior rows *Loss is relative to normal values or to values of surrounding points. For probability maps that compare measured thresholds to normal values. Substitute P <.05 for 5 dB loss, and P <.01 for 10 dB loss. Reprinted with permission from Caprioli J: Automated perimetry in glaucoma. Am J Ophthalmol 1991;111:235–239.

bear in mind that the majority of true glaucomatous ﬁeld losses are not reversible. Therefore, it is often more valuable and more possible to simply establish a baseline for the purpose of measuring stability versus change over time. Despite these caveats, several published guides exist that deﬁne diagnostic features for minimal localized abnormalities. Table 4-1 provides strict, moderate, and liberal criteria, which can be modiﬁed according to the clinician’s index of suspicion.21 Application of these criteria should take into account the learning effect in a patient new to perimetry (Figure 4-8C). In addition, the importance of conﬁrming a newly recognized defect with a second test cannot be overstated. Anderson22 published a similar scheme, which deﬁnes a minimally signiﬁcant defect as three or more non-edge points in the pattern deviation plot with sensitivities below the 5th percentile and one of these points below the 1st percentile in a reliably performed ﬁeld. In general, this cluster should conform to anatomic expectations. A CPSD value below the 5th percentile or a GHT result of abnormal may also be used to deﬁne typical minimal criteria (Table 4-2). It is critically important to consider the entire clinical picture in these determinations and not interpret the ﬁeld in a vacuum. Figures 4-9 through 4-11 demonstrate subtle scotomas that exactly correspond to nerve ﬁber layer wedge defects seen on fundus examination. Although these ﬁelds might be classiﬁed as normal by isolated criteria, the patients all have early, recognizable glaucomatous visual ﬁeld loss when clinical correlation is used.

4-4-3 Staging of Field Loss. Some staging guidelines for glaucomatous visual ﬁeld loss measured with the Humphrey perimeter have been published. It is reasonable to

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TABLE 4-2. Minimal Critreria for Diagnoising Acquired Glaucomatous Damage A glaucoma hemiﬁeld test (GHT) outside normal limits on at least 2 ﬁelds OR A cluster of 3 or more nonedge points in a location typical for glaucoma, all of which are depressed on the pattern deviation plot at a P <5% level and 1 of which is depressed at a P <1% level on 2 consecutive ﬁelds OR A corrected pattern standard deviation (CPSD) that occurs in less than 5% of normal ﬁelds on 2 consecutive ﬁelds Adapted with permission from Anderson DR: Automated Static Perimetry. St Louis: Mosby –Year Book;1992:123.

use scotoma location as well as density and size to deﬁne stage, because paracentral defects may have greater functional impact. Although, in general, advanced visual ﬁeld loss is treated more aggressively, it is important to individualize each case and not rely on a cookbook approach (Table 4-3).23

4-4-4 Test Selection. Standard practice in many ofﬁces is to evaluate most glaucoma patients and glaucoma suspects with SITA Standard 24-2 initially. Patients who test poorly often produce reliable results after a second or even third test session with close feedback from the perimetrist. If, after several sessions, the patient is still unable to perform a reliable ﬁeld, SITA Fast can be used. If automated static perimetry efforts fail, Goldmann perimetry can be performed. 4-4-5 Follow-up of Advanced Field Loss. If a dense defect is found within the central 10°, the defect may be deﬁned with Program 10-2. When widespread absolute defects occur, retesting the patient with stimulus size V is helpful. Areas of the visual ﬁeld with absolute loss determined with stimulus size III are often found to have some remaining nonabsolute loci (when tested with size V), which can be followed over time (Figure 4-12A and B). The amount of spatial summation is largely a function of the initial sensitivity. Thresholds near zero with stimulus size III can increase by 20 dB when tested with stimulus size V.24 In particular, tiny central islands of vision, with threatened or early loss of ﬁxation, are often amenable to testing with stimulus size V using Program 10-2.25 4-5 EVALUATION OF A SERIES OF TESTS The primary reason for evaluating a series of tests is to detect the progression of a disease. Because comparisons over time will be made, it is critical to establish an adequate baseline. Recognizing typical LTF and maintaining constant vigilance for evolving artifacts and other confounding factors will help ensure high speciﬁcity to detect subtle glaucoma progression.

A

B Figure 4-9. Minimal abnormality suggested by clinical correlation. (A) Both the glaucoma hemiﬁeld test and the global indices are unremarkable. Careful inspection of the pattern deviation plot reveals a cluster of three nonedge locations, each signiﬁcant at a P < 5% level. (B) When this ﬁnding is correlated with a superior nerve ﬁber layer wedge defect on fundus photography, the diagnosis of glaucoma is conﬁrmed. (C) The defect was reproduced when the patient was tested the following year.

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C Figure 4-9. (Continued)

4-5-1 Baseline Establishment. Several caveats regarding the establishment of a baseline ﬁeld are worth mentioning. A major confounding variable to establishing an accurate baseline ﬁeld is the learning effect. If the ﬁrst ﬁeld is poorly performed, the baseline may be artiﬁcially depressed and may reduce the sensitivity to detect subsequent deterioration. With a patient inexperienced in perimetry, baseline testing should be repeated up to three times over several weeks or months until an apparent plateau of ﬁeld improvement has occurred. The two or three most suitable ﬁelds can then be selected and averaged for a sensitive baseline (master) ﬁeld against which future tests can be compared. Occasionally, patients have sufﬁciently high LTF during the establishment of the baseline that particular ﬁelds may be inappropriate for inclusion. In that event, the two ﬁelds that appear to be least damaged should be included if the reliability indices demonstrate a lack of false-positive responses and ﬁxation losses. Patients who show signiﬁcant glaucoma progression should usually undergo more aggressive ocular hypotensive therapy or surgical intervention. Once the

A

B Figure 4-10. Another example of minimal abnormality correlated with fundus examination. (A) Despite low patient reliability, normal GHT, and normal global indices, there is a pattern of depression within the inferior arcuate region that corresponds to a superotemporal nerve ﬁber layer defect. (B) Fundus photograph.

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A

B Figure 4-11. Early defect conﬁrmed by disc hemorrhage. (A) Despite low patient reliability, there is a cluster of four nonedge points, each reduced to at least the P < 5% level. One of these points is reduced at P < 1%. Despite the normal GHT and global indices, (B) the presence of a disc hemorrhage on fundus photography further suggests true abnormality.

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TABLE 4-3. Staging of Glaucomatous Visual Field Loss (Program 30-2) Early Defect Mean deviation (MD) is < – 6 dB Pattern deviation plot: <25%(18) of points are depressed below 5% and <10 points are depressed below 1% No point in central 5° has sensitivity of <15 dB Moderate Defect MD is < – 12 dB Pattern deviation plot: <50% (37) of points are depressed below 5% and <20 points are depressed below 1% No point in central 5° has sensitivity of 0 dB Only one hemiﬁeld may have a point with sensitivity of <15 dB within 5° of ﬁxation Severe Defect MD is > – 12 dB Pattern deviation plot: >50% (37) of points are depressed below 5% and >20 points are depressed below 1% Any point in central 5° has sensitivity of 0 dB Both hemiﬁelds have points in central 5° with sensitivity of <15 dB Reprinted with permission from Hodapp EA, Parrish RK II, Anderson DR: Clinical Decisions in Glaucoma. St Louis: Mosby–Year Book; 1993:chap 2.

intraocular pressure is lowered, it is often helpful to reestablish new baseline ﬁelds for future comparison so that further progression is not hidden by prior statistically signiﬁcant loss. This reestablishment is usually not as time-consuming as establishing the initial baseline because the learning effect is less signiﬁcant.

4-5-2 Nature of Progression. Several different perimetric characteristics of glaucoma progression can generally be applied to other causes of ﬁeld abnormality. Most commonly, a mild to moderately dense scotoma deepens as the disease worsens. Scotomas may also enlarge and new scotomas may develop in previously uninvolved locations. Whenever a series of ﬁelds appears to indicate disease progression, the clinician must consider a possible increase in other factors, such as a shift in refractive error, an increase in ptosis, or the initiation of miotic therapy. Also, the onset or worsening of confounding non-glaucomatous disease (e.g., cataractous, corneal, retinal, or neurologic conditions) must be considered (Figures 4-13 through 4-15). 4-5-3 Artifacts. Various artifacts that can inﬂuence the performance of a single ﬁeld are described in Chapter 3. These artifacts may develop or increase over time and give a false impression of glaucomatous ﬁeld loss or progressive glaucoma (Figure 4-16). Properly trained technicians and a thorough knowledge of the inﬂuences of artifact will help provide a high speciﬁcity in detecting progressive glaucoma.

A Figure 4-12. A patient with so much advanced ﬁeld loss that stimulus size III revealed little useful information that could be used for comparison (A). When tested with stimulus size V (B), a more deﬁnable island of vision is identiﬁed.

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B Figure 4-12. (Continued)

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A

B Figure 4-13. Multiple confounding variables in a glaucoma patient. The change analysis printout (A), the glaucoma change probability printout (baseline) (B), and the glaucoma change probability printout (follow-up) (C, on following pages) demonstrate gradual learning effect over the ﬁrst four ﬁelds, followed by progressive cataract. Field 7 follows cataract extraction with improvement in foveal sensitivity and mean deviation, which is stable until a left homonymous hemianopia due to a cerebrovascular accident occurs as demonstrated on ﬁeld 10.

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C

(C continues)

Figure 4-13. (Continued) (C) The glaucoma change probability (follow-up) symbols does not suggest progression because the ﬁrst two ﬁelds were selected for baseline rather than ﬁelds 3 and 4. If the glaucoma change probability is run after discarding the ﬁrst two ﬁelds because of learning effect, the subsequent seven ﬁelds, prior to the stroke, demonstrate almost twice as many values that worsen at the P < 5% value.

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C (cont.) Figure 4-13. (Continued)

4-5-4 Long-Term Fluctuation. Although the printouts allow a convenient presentation of data with sophisticated, comparative, statistical analyses, the variability of LTF in the individual patient remains problematic. Quantiﬁcation of this ﬂuctuation is suggested by the pattern of the MD slope regression analysis, but this is a single index largely inﬂuenced by the homogeneous component of LTF. Wide ﬂuctuation in the size and shape of scotomas, which is more a function of heterogeneous LTF, remains the single most difﬁcult problem in interpreting a series of ﬁelds for subtle progression over time. In a study involving six experienced observers reviewing serial visual ﬁelds from 30 patients, only half the patients had at least ﬁve-observer agreement.26 Frequent determination of visual ﬁeld status, particularly in patients with borderline intraocular pressure control or an advanced scotoma close to ﬁxation,

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C (cont.) Figure 4-13. (Continued)

is presently the best way to detect subtle progression. Some studies have suggested that four or ﬁve ﬁelds may be necessary over a short period of time to detect extremely subtle progression.27 When progression is more dramatic, either because the disease is worsening rapidly or because the time interval between tests is long, performing such extensive conﬁrmatory studies may not be necessary.

4-5-5 Criteria for Progression. Anderson28 published guidelines for recognizing progression and stresses that they should usually be conﬁrmed with subsequent testing (Table 4-4). In a previously normal region of the ﬁeld, on two or more reliable tests, the existence of a new isolated defect could be taken as evidence for progression. Criteria for a new defect include a cluster of three points worsening by 5 dB each, one of which has worsened by 10 dB. A previously abnormal region may be concluded to have deepened if two or three points have deteriorated by 10 dB with results conﬁrmed on a second test. A defect may be deemed to have widened if two or more new contiguous points are involved. This scheme was found to be overly sensitive and nonspeciﬁc when used in the Normal-Tension Glaucoma Study.27 The speciﬁcity was greatly improved when two cycles of conﬁrmatory ﬁelds are performed 3 months apart; each cycle consists

A Figure 4-14. A 61-year-old woman with age-related macular degeneration and geographic atrophy (B) with ﬁndings on Humphrey visual ﬁeld (A) mimicking paracentral glaucomatous ﬁeld loss.

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B Figure 4-14. (Continued)

of two positive tests of a possible three performed 1 to 4 weeks apart. Although, in general, conﬁrming progression with subsequent tests is recommended, it may not be necessary if other clinical features, such as optic disc cupping or retinal nerve ﬁber layer loss, are worsening. Other published guidelines stress the concept that initially normal values are not likely to ﬂuctuate as much as moderately depressed values, which can ﬂuctuate widely without true progression occurring (Table 4-5)29 By deﬁnition, absolute defects (threshold = 0 dB) at baseline cannot worsen, as the machine is already generating a maximal stimulus. In addition, analysis of pairs or clusters of locations may help minimize heterogeneous LTF. 30

4-5-6 Glaucoma Progression Analysis. The latest versions of HVF software offer automated glaucoma progression analysis (Guided Progression Analysis [GPA]). The GPA software presents analyzed data in a user-friendly report in an attempt to more accurately compare and quantify data between visual ﬁelds. Two baseline exams are selected, either automatically or manually, and used as a comparison against changes on future tests. Disease progression is deﬁned by the Early Manifest Glaucoma Trial (EMGT) criteria as a statistically signiﬁcant loss of sensitivity at three or more test points in the same location on three consecutive visual ﬁeld evaluations. Deviations from baseline are presented numerically as well as symbolically, with an open triangle demonstrating progression on one ﬁeld, a half-dark triangle indicating progression on two ﬁelds, and a fully dark triangle signifying progression on three consecutive ﬁelds. GPA software has the additional advantage of adjusting for alterations in general sensitivity from ocular changes such as cataracts, but it is not available for 10-2 programs (Figure 4-17A, B, and C).

A Figure 4-15. A 48-year-old woman with dense superior and inferior arcuate-type defects (A). Fundus exam reveals typical retinitis pigmentosa ﬁndings (B).

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B Figure 4-15. (Continued)

4-5-7 Trend Analysis. The PROGRESSOR software analysis for HVF was created at Moorﬁelds Eye Hospital and the University College, London. The PROGRESSOR program uses trend analysis to evaluate changes at individual points in the visual ﬁeld to determine a slope or rate of change, helping clinicians assess the risk of the development of glaucomatous vision loss in the future (Figure 4-18). The schemes outlined here are only guidelines; the clinician’s index for determining progression should be inﬂuenced by multiple individual patient factors such as the patient’s subjective assessment of his or her vision, age, intraocular pressure control, optic disc appearance, and nerve ﬁber layer status. 4-5-8 Follow-up of Central Abnormalities. An additional approach to minimizing the effect of LTF is to follow up defects that are present within the central 10° with Program 10-2. This program appears to be considerably more sensitive in detecting the subtle progression of scotomas located in this region compared with programs with a larger grid size.31 This increased sensitivity may occur for two reasons. First, the relatively high sensitivity in the normal central ﬁeld is less prone to LTF than the less-sensitive midperipheral regions (see Figure 3-10). Second, the high-resolution sampling provided by a 2° grid makes any subtle enlargement of the steep edge of dense scotomas more apparent. An overview plot can be created with serial tests of Program 10-2. In addition, the overview printout demonstrates the mean sensitivity of each ﬁeld over time and can perform a mean sensitivity slope calculation with a P value interpretation. Because sensitivity is displayed as opposed to deviation, there may be a slight gradual reduction in sensitivity over many years in a clinically stable patient.

Figure 4-16. An 81-year-old aphakic woman with mild ocular hypertension, but a healthy optic nerve was diagnosed with glaucoma based on the appearance of this visual ﬁeld. The dense loss superiorly is more likely related to her involutional ptosis than glaucomatous optic neuropathy.

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TABLE 4-4. Guidelines for Recognizing Progression New defect in previously normal region: cluster of 3 points worsening by 5 dB each, 1 of which has worsened by 10 dB Previously abnormal region has deepened if: 3 or more points have deteriorated by 10 dB each Previously abnormal region has widened if: 2 or more new contiguous points are involved Note: This scheme requires reliable ﬁelds.In general, progression should be conﬁrmed on a subsequent ﬁeld or ﬁelds. See text. ,

Adapted with permission from Anderson DR: Automated Static Perimetry. St Louis: Masby–Year Book;1992:208–211.

TABLE 4-5. Guidelines for Evaluating Change From One Test to Another in Single Test Location and in Adjacent Pair of Test Locations Consider as Progression If Change (dB) Exceeds Initial Sensitivity (dB) 25–30

In Single Test Location 8

3.5

20

12

15

15*

10

10

In Pair of Test Locations 5

†

6.5 8

*Values may ﬂuctuate between 0 and normal. † A single test location drop to 9 dB may be due to ﬂuctuation. Reprinted with permission from Zulauf M, Caprioli J: What constitutes progression of glaucomatous visual ﬁeld defects? Sem Ophthalmol 1992;7:130–146.

4-6 FUTURE OF AUTOMATED PERIMETRY Automated perimetry remains an evolving ﬁeld. Recent developments can be broadly classiﬁed into those that alter the nature of the presented stimulus, those that present a standard white-on-white stimulus in an altered strategy, and those that aid in the interpretation of results. Among the altered stimulus technologies are the selective functional tests that are designed to isolate one visual receptor system, such as the parvocellular, magnocellular, or koniocellular ganglion cells. Isolating one visual processing system seems to enable earlier detection by reducing redundancy that can mask damage. In addition, some types of ganglion cells may be more susceptible to glaucomatous damage.32, 33

4-6-1 Altered Stimuli 4-6-1-1 SWAP. Short-wavelength automated perimetry (SWAP), also known as blue-on-yellow or color perimetry, alters the typical white-on-white stimulus to a size V blue stimulus on a yellow background. Several longitudinal studies have shown earlier identiﬁcation of abnormality and progressive glaucoma using SWAP.34–36 The physiologic theory behind SWAP is to isolate the koniocellular, blue cone system. The lens-density effect, speciﬁcally nuclear sclerotic cataracts, diffusely may reduce a patient’s ability to perform the test and alter the ﬁeld result.

A Figure 4-17. For the guided progression analysis (GPA), two ﬁelds are selected as a baseline (A) and deviations from baseline are presented numerically as well as symbolically (B, C). An open triangle demonstrates progression on one ﬁeld, a halfdark triangle indicates progression on two ﬁelds, and a fully dark triangle signiﬁes progression on three consecutive ﬁelds. In this example, the ﬁrst baseline ﬁeld likely represents an artiﬁcially low response and should be replaced with a more reliable test. This would likely result in greater identiﬁcation of points of changing threshold sensitivity as well as a more appropriate slope on the mean deviation point analysis.

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B Figure 4-17. (Continued)

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C Figure 4-17. (Continued)

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Figure 4-18. PROGRESSOR trend analysis evaluates changes at individual points in the visual ﬁeld to determine a rate of change (slope).

Techniques that analyze patterns within the ﬁeld such as the pattern deviation plot or GHT may provide adequate speciﬁcity without the need for time-consuming density measurements.37 SWAP is available on later models of HVF analyzers and can be performed with full threshold and SITA algorithms (Figures 4-19 and 4-20).

4-6-1-2 FDT. Frequency doubling perimetry/frequency doubling technology (FDP/FDT) uses spatial frequency grating patterns that are contrast modulated at high rates to induce an optical illusion of ﬂickering. The magnocellular ganglion cells that are selectively stimulated may be more susceptible to glaucomatous damage.38 FDT has the additional advantages of short test times, limited inﬂuence by visual acuity and refractive error, and lower need for standardized background lighting, which make it a useful screening tool outside of the controlled ofﬁce setting. FDT is available in a large grid, screening-type program that tests 17 points, as well as a 30-2 and 24-2 Matrix program that tests 69 and 56 points, respectively (Figure 4-21), Multiple studies have demonstrated reasonable sensitivity and speciﬁcity for disease detection by FDT.39–41 While FDT has been shown to be useful to detect glaucomatous defects earlier than standard white-on-white perimetry and its testing point resolution has improved, small and early defects may be missed, so standard perimetry should be used to help conﬁrm disease and monitor for progression.42–44 4-6-1-3 Flicker Perimetry. Temporal-modulation/ﬂicker discrimination is also believed to selectively stimulate magnocellular ganglion cells and ﬂicker discrimination is reduced in glaucoma.45 Perimeters that present a ﬂickering whiteon-white stimulus are available on later Octopus perimeters. While increasing numbers of studies are evaluating ﬂicker perimetry, its use is not widespread and more robust data are needed to determine its role in glaucoma detection and monitoring. (Nomoto).46–48

A Figure 4-19. Short-wavelength automated perimetry (SWAP) may conﬁrm the absence of defects seen on standard white-on-white perimetry (A, B).

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B Figure 4-19. (Continued)

4-6-1-4 Ring Perimetry. High-pass resolution perimetry uses circular targets of varying sizes that consist of a white center with a dark annular margin presented on a white background to selectively stimulate parvocellular ganglion cells (Figure 4-22). The test is rapid, has been well received by patients, and is comparable in sensitivity to conventional perimetry for glaucoma diagnosis. Longitudinal data regarding disease progression are presently lacking.49–51

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,

4-6-1-5 Motion P. Motion automated perimetry (MAP) stimulates magnocellular ganglion cells by presenting simultaneous, random movement of a circular group of dots against a background of stationary dots. The threshold is determined by progressively decreasing the size of the group of dots. While not widely used, motion perimetry has been shown to detect glaucomatous damage earlier than white-on-white perimetry and has the advantage of being less affected by refractive error.52,53 In addition, motion perimetry has been successfully incorporated into a laptop computer for glaucoma screening in developing countries.54 4-6-1-6 Pattern Perimetry. Pattern-discrimination perimetry alters the conventional uniform white background to a pattern of moving random noise. The stimulus itself is a checkerboard-pattern square presented in a quadrant of the ﬁeld. The coherence of the checkerboard is adjusted from 100% (a pure checkerboard) to 0% (random noise) using a staircase technique until the threshold is reached. As with many of the new techniques, pattern-discrimination perimetry appears to be more sensitive than conventional stimuli, although standardization of the technique and its speciﬁcity remain unestablished.55, 56 4-6-1-7 Color Perimetry. Although not commercially available, tests of peripheral color contrast attempt to exploit the reduced spectral contrast sensitivity found in arcuate regions in early glaucoma. The test presents modiﬁed Landolt Cs in each quadrant, gradually reducing the spectral contrast until the target orientation is not identiﬁed. Testing the tritan axis appears to be most efﬁcient. Studies have shown this test to be extremely sensitive and quite speciﬁc when normal patients are compared with patients who have glaucomatous loss as determined by conventional perimetry. The test may be amenable to presentation on relatively inexpensive

A Figure 4-20. Short-wavelength automated perimetry (SWAP)may also help to identify early depression in Bjerrum’s zone in a patient with early glaucomatous optic neuropathy (A-C).

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B Figure 4-20. (Continued)

color monitors if background conditions and luminance can be standardized; the test would be useful for large-scale population screening. Longitudinal data are currently lacking.57

4-6-2 Altered Strategies. Several areas of research currently under way retain the conventional white-on-white stimulus but attempt to increase the efﬁciency of stimulus presentation. One technique uses posterior probability estimation with a

C Figure 4-20. (Continued)

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A Figure 4-21. Humphrey Matrix 24-2 (A) demonstrates conﬂuent central and paracentral ﬁeld loss. Follow-up testing with SITA Standard white-on-white perimetry (B) provides greater detail of the visual ﬁeld defects.

priori knowledge about normal and abnormal ﬁelds to determine the appropriate next stimulus intensity.58 An additional advantage of this technique is the ability to determine false-positive and false-negative answers from the actual threshold process.59

4-6-3 Interpretive Aids. A ﬁnal active area of research uses conventional stimuli and presentation strategies but expands the statistical manipulation of the raw data. Examples include using neural networks that have been trained to recognize visual ﬁeld abnormality or progression.60,61 Another recent advance suggests comparing mean deviation slope over time with the general height index (currently not an available index) over time to differentiate progressive cataract formation from

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B Figure 4-21. (Continued)

progressive glaucoma.62 Pointwise regression analysis of serial ﬁelds has been described by Fitzke and colleagues (Program Progressor)63,64 and Weber and Krieglstein (Graphical Analysis of Topographical Trends).65 These techniques identify both location and statistical signiﬁcance as well as rate of change. Spatial ﬁltering technique and cluster analysis also attempt to minimize the inﬂuence of LTF and improve the sensitivity for detecting scotomas or their progression.66

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Figure 4-22. High pass resolution perimetry uses progressively smaller circular targets to rapidly and reliably identify ﬁeld defects.

REFERENCES 1. Anderson DR. Collaborative normal tension glaucoma study. Curr Opin Ophthalmol. 2003;14:86–90. 2. Varma R, et al, Los Angeles Latino Eye Study Group. Prevalence of open-angle glaucoma and ocular hypertension in Latinos: the Los Angeles Latino Eye Study. Ophthalmology. 2004;111:1439–1448. 3. Hart WM Jr, Becker B. The onset and evolution of glaucomatous visual ﬁeld defects. Ophthalmology. 1982;89:268–279. 4. Heijl A, Lundqvist L. The frequency distribution of earliest glaucomatous visual ﬁeld defects documented by automatic perimetry. Acta Ophthalmol. 1984;62:658–664. 5. Phelps CD, Hayreh SS, Montague PR. Visual ﬁelds in low-tension glaucoma, primary open angle glaucoma, and anterior ischemic optic neuropathy. In: Greve EL, Heijl A, eds. Fifth International Visual Field Symposium. Dordrecht: Dr WJ Junk; 1983: 113–124. 6. Koseki N, Araie M, Suzuki Y, et al. Visual ﬁeld damage proximal to ﬁxation in normaland high-tension glaucoma eyes. Jpn J Ophthalmol. 1995;39:274–283. 7. Araie M. Pattern of visual ﬁeld defects in normal-tension and high-tension glaucoma. Curr Opin Ophthalmol. 1995;6:36–45. 8. Drance SM, Douglas GR, Airaksinen PJ, et al. Diffuse visual ﬁeld loss in chronic openangle and low-tension glaucoma. Am J Ophthalmol. 1987;104:577–580. 9. Heijl A. Lack of diffuse loss of differential light sensitivity in early glaucoma. Acta Ophthalmol. 1989;67:353–360. 10. Langerhorst CT, van den Berg TJ, Greve EL. Is there general reduction of sensitivity in glaucoma? Int Ophthalmol, 1989;13:31–35.

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11. Feuer WJ, Anderson DR. Static threshold asymmetry in early glaucomatous visual ﬁeld loss. Ophthalmology. 1989;96:1285–1297. 12. Caprioli J, Spaeth GL. Comparison of visual ﬁeld defects in the low-tension glaucomas with those in the high-tension glaucomas. Am J Ophthalmol. 1984;97:730–737. 13. Chauhan BC, Drance SM, Douglas GR, Johnson CA. Visual ﬁeld damage in normaltension and high-tension glaucoma. Am J Ophthalmol. 1989;108:636–642. 14. Motolko M, Drance SM, Douglas GR. Visual ﬁeld defects in low-tension glaucoma: comparison of defects in low-tension glaucoma and chronic open angle glaucoma. Arch Ophthalmol. 1982;100:1074–1077. 15. Budenz DL, Rhee P, Feuer WJ, et al. Comparison of glaucomatous visual ﬁeld defects using standard full threshold and Swedish interactive threshold algorithms. Arch Ophthalmol. 2002;120:1136–1141. 16. Musch DC, Gillespie BW, Motyka BM, et al. Converting to SITA-standard from fullthreshold visual ﬁeld testing in the follow-up phase of a clinical trial. Invest Ophthalmol Vis Sci. 2005;46:2755–2759. 17. Wesselink C, Heeg GP, Jansonius NM. Glaucoma monitoring in a clinical setting: glaucoma progression analysis vs nonparametric progression analysis in the Groningen Longitudinal Glaucoma Study. Arch Ophthalmol. 2009;127:270–274. 18. Budenz DL, Rhee P, Feuer WJ, et al. Sensitivity and speciﬁcity of the Swedish interactive threshold algorithm for glaucomatous visual ﬁeld defects. Ophthalmology. 2002;109:1052–1058. 19. Kim J, Dally LG, Ederer F, et al, AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS): 14. Distinguishing progression of glaucoma from visual ﬁeld ﬂuctuations. Ophthalmology. 2004;111:2109–2116. 20. Gillespie BW, Musch DC, Guire KE, et al, The CIGTS Study Group. The Collaborative Initial Glaucoma Treatment Study: baseline visual ﬁeld and test–retest variability. Invest Ophthalmol Vis Sci. 2003;44:2613–2620. 21. Caprioli J. Automated perimetry in glaucoma. Am J Ophthalmol. 1991;111:235–239. 22. Anderson DR. Automated Static Perimetry. St. Louis: Mosby–Year Book; 1992: chap 2. 23. Hodapp EA, Parrish RK II, Anderson DR. Clinical Decisions in Glaucoma. St. Louis: Mosby–Year Book; 1993:chap 2. 24. Weber J, Bakes J. Spatial summation in glaucomatous visual ﬁelds. In: Mills RP, Wall W, eds. Perimetry Update 1994/95. Amsterdam: Kugler; 1994:63. 25. Zalta AH. Use of a central 10° ﬁeld and size V stimulus to evaluate and monitor small central islands of vision in end stage glaucoma. Br J Ophthalmol. 1991;75:151–154. 26. Werner EB, Bishop KI, Koelle J, et al. A comparison of experienced clinical observers and statistical tests in detection of progressive visual ﬁeld loss in glaucoma using automated perimetry. Arch Ophthalmol 1988;108:619–623. 27. Schulzer M. Errors in the diagnosis of visual ﬁeld progression in normal-tension glaucoma. Ophthalmology 1994;101:1589–1595. 28. Anderson DR. Automated Static Perimetry. St. Louis: Mosby–Year Book; 1992:chap 9. 29. Zulauf M, Caprioli J. What constitutes progression of glaucomatous visual ﬁeld defects? Sem Ophthalmol 1992;7:130–146. 30. Mandava S, Zulauf M, Zeyen T, Caprioli J. An evaluation of clusters in the glaucomatous visual ﬁeld. Am J Ophthalmol 1993;116:684–691. 31. Weitzman ML, Zeyen T, Caprioli J. High resolution central visual ﬁeld to detect progressive glaucomatous damage. In: Mills RP, Wall W, eds. Perimetry Update 1994/95. Amsterdam: Kugler; 1994:71–72.

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Automated Perimetry in Glaucoma

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32. Yücel YH, Zhang Q, Weinreb RN, et al. Effects of retinal ganglion cell loss on magno-, parvo-, koniocellular pathways in the lateral geniculate nucleus and visual cortex in glaucoma. Prog Retin Eye Res. 2003;22:465–481. 33. Spry PG, Johnson CA, Mansberger SL, et al. Psychophysical investigation of ganglion cell loss in early glaucoma. J Glaucoma. 2005;14:11–19. 34. Johnson CA, Adams AJ, Casson EJ, et al. Progression of early glaucomatous visual ﬁeld loss as detected by blue-on-yellow and standard white-on-white automated perimetry. Arch Ophthalmol. 1993;111:651–656. 35. Sample PA, Taylor JD, Martinez GA, et al. Short-wavelength color visual ﬁelds in glaucoma suspects at risk. Am J Ophthalmol. 1993;115:225–233. 36. Polo V, Larrosa JM, Pinilla I, et al. Predictive value of short-wavelength automated perimetry: a 3-year follow-up study. Ophthalmology. 2002;109:761–765. 37. Sample PA, Martinez GA, Weinreb RN. Short-wavelength automated perimetry without lens density testing. Am J Ophthalmol. 1994;118:632–641. 38. Maddess T, Henry GH. Performance of nonlinear visual units in ocular hypertension and glaucoma. Clin Vis Sci. 1992;7:371–383. 39. Bowd C, Zangwill LM, Berry CC, et al. Detecting early glaucoma by assessment of retinal nerve ﬁber layer thickness and visual function. Invest Ophthalmol Vis Sci. 2001;42:1993–2003. 40. Mansberger SL, Johnson C, Ciofﬁ G, et al. Predictive value of frequency doubling technology perimetry for detecting glaucoma in a developing country. J Glaucoma. 2005;14:128–134. 41. Nomoto H, Matsumoto C, Takada S, et al. Detectability of glaucomatous changes using SAP, FDT, ﬂicker perimetry, and OCT. Glaucoma. 2009;18:165–171. 42. Anderson AJ, Johnson CA. Frequency-doubling technology perimetry. Ophthalmol Clin North Am. 2003;16:213–225. 43. Leeprechanon N, Giaconi JA, Manassakorn A, et al. Frequency doubling perimetry and short-wavelength automated perimetry to detect early glaucoma. Ophthalmology. 2007;114:931–937. 44. Clement CI, GoldBerg I, Graham S, et al. Humphrey matrix frequency doubling perimetry for detection of visual ﬁeld defects in open-angle glaucoma. Br J Ophthalmol. 2008, Nov 27 [Epub]. 45. Tyler C. The value of temporal contrast sensitivity testing in glaucoma and the optic neuropathies. J Glaucoma. 1994;3:S65-S72. 46. Lachenmayr BJ, Drance SM. Diffuse ﬁeld loss and central visual function in glaucoma. German J Ophthalmol. 1992;1:67–73. 47. Casson EJ, Johnson CA, Shapiro LR. Longitudinal comparison of temporal-modulation perimetry with white-on-white and blue-on-yellow perimetry in ocular hypertension and early glaucoma. J Optom Soc Am. 1993;10:1792–1806. 48. Bernardi L, Costa VP, Shiroma LO. Flicker perimetry in healthy subjects: inﬂuence of age and gender, learning effect and short-term ﬂuctuation. Arq Bras Oftalmol. 2007;70:91–99. 49. Frisén L. High-pass resolution perimetry: a clinical review. Doc Ophthalmol. 1993;83: 1–25. 50. Sample PA, Ahn DS, Lee PC, et al. High-pass resolution perimetry in eyes with ocular hypertension and primary open-angle glaucoma. Am J Ophthalmol. 1992;113: 309–316. 51. Kono Y, Maeda M, Yamamoto T, Kitazawa Y. A comparative study of high-pass resolution perimetry and differential light sense perimetry in glaucoma patients. In: Mills R, ed. Perimetry Update 1988/89. Amsterdam: Kugler; 1989:383–392.

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176

Visual Fields

52. Wall M. Motion perimetry in optic neuropathies. Perimetry Update 1994/1995. Amsterdam: Kugler; 1995:111–118. 53. Wall M, Jennisch CJ, Munden PM. Motion perimetry identiﬁes nerve ﬁber bundlelike defects in ocular hypertension. Arch Ophthalmol. 1997;115:26–33. 54. De Bruyn B, Orban GA. Human velocity and direction discrimination measured with random dot patterns. Vision Res. 1988;28:1323–1335. 55. Drum B, Severns M, O’Leary D, et al. Selective loss of pattern discrimination in early glaucoma. Appl Optics. 1989;28:1135–1144. 56. Nautaitis NJ, Stewart WC, Kelly DM, et al. Pattern discrimination perimetry in patients with glaucoma and ocular hypertension. Am J Ophthalmol. 1992;114:297–301. 57. Yu TC, Falcao-Reis F, Spileers W, Arden GB. Peripheral color contrast: a new screening test for preglaucomatous visual loss. Invest Ophthalmol Vis Sci. 1991;32:2779–2789. 58. Heijl A. Improved test algorithms for automated perimetry. In: Krieglstein GK, ed. Glaucoma Update V. Amsterdam: Kaden Verlag; 1995:168–173. 59. Zulauf M, Fehlmann P, Flammer J. Efﬁciency of the standard Octopus bracketing procedure compared to that of the “dynamic strategy” of Weber. In: Mills RP, Wall W, eds. Perimetry Update 1994/95. Amsterdam: Kugler; 1994:263–264. 60. Kelman SE, Perell HE, Autrechy LD, Scott RJ. A neural network can differentiate glaucoma and optic neuropathy visual ﬁelds through pattern recognition. In: Mills RP, Heijl A, eds. Perimetry Update 1990/91. Amsterdam: Kugler; 1991:287–290. 61. Giangiacomo A, Garway-Heath D, Caprioli J. Diagnosing glaucoma progression: current practice and promising technologies. Curr Opin Ophthalmol. 2006;17: 153–162. 62. Heijl A. Improving visual ﬁeld interpretation in glaucoma management: the importance of and the tools to separate between diffuse, homogenous, and localized visual ﬁeld loss. Invest Ophthalmol Vis Sci. 1995;36:S389. 63. McNaught AI, Crabb DP, Fitzke FW, Hitchings RA. Modelling sensitivity loss in low tension glaucoma. Invest Ophthalmol Vis Sci. 1994;35:2183. 64. Poinoosawmy D, McNaught AI, Fitzke FW, Hitchings RA. Location of early ﬁeld deterioration in glaucoma suspects. In: Mills RP, Wall W, eds. Perimetry Update 1994/95. Amsterdam: Kugler; 1994:289–297. 65. Weber J, Krieglstein GK. Graphical analysis of topographical trends (GATT) in automated perimetry. Int Ophthalmol. 1989;13:351–356. 66. Fitzke FW, Crabb DP, McNaught AI, et al. Image processing of computerised visual ﬁeld data. Br J Ophthalmol. 1995;79:207–212.

5 Inherited or Congenital Optic Nerve Diseases PETER A. QUIROS, MD, CARLOS FILIPE CHICANI, MD, PHD, AND ALFREDO A. SADUN, MD, PHD

5-1 INTRODUCTION In this chapter, we discuss inherited/congenital optic nerve diseases and their related visual ﬁelds defects. It is important for the ophthalmologist to establish, on the basis of the visual ﬁelds defect whether the optic nerve is involved and, if so, whether this is at the level of the optic disc or further back. In addition, the visual ﬁelds defect can help establish whether the etiology is acquired or congenital. If the former is the case, then the visual ﬁelds defect may reveal an insult that is rapidly progressive and hence requires immediate and aggressive management. The diseases are divided into the categories of congenital optic disc anomalies and heredodegenerative optic atrophies.

5-2 CONGENITAL OPTIC DISC ANOMALIES Congenital optic disc anomalies include aplasias, dysplasias (hyperplasia and hypoplasia), optic nerve colobomas and pits, anomalous disc elevations: pseudopapilledema with or without hyaline bodies (drusen), and tilted disc and crescents.

5-2-1 Aplasias and Dysplasias. Absence of the optic disc (aplasia) is extremely rare and only a few case reports have been published in the literature. Optic disc size varies and may be larger (hyperplasia) or smaller (hypoplasia) than normal. Hyperplasia is much less common than hypoplasia and is usually related to ametropias. 177

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Optic nerve hypoplasia (ONH) may be unilateral or bilateral and isolated or associated with different syndromes. It may be associated with good or poor visual prognosis. It is the most common congenital optic disc anomaly encountered in pediatric ophthalmic practice.1,2 When the nerve head is slightly or segmentally reduced, especially in the presence of normal visual acuity, the diagnosis is based on comparison of disc photographs or calculation of the ratio of the disc center-to-fovea distance to disc diameter. Usually this ratio is increased in hypoplasia and, if higher than 3.0, is almost diagnostic.3 Sometimes the hypoplastic disc is surrounded by a ring of sclera and a ring of hyperpigmentation, described as “double-ring sign”1,2 (Figure 5-1). Maternal diabetes and use of teratogenic agents such as phenytoin, alcohol, quinine, and cocaine may be associated with ONH. In particular, maternal diabetes is most often associated with segmental ONH of the superior portion of the nerve head.4 Septo-optic dysplasia (de Morsier syndrome) may be recognized by the triad of short stature, nystagmus, and optic disc hypoplasia. It may be also associated with neonatal hypotonia, seizures, prolonged hyperbilirubinemia, hormone deﬁciencies (antidiuretic, corticotrophin, and growth), and mental retardation. Neuroimaging demonstrates a single anterior ventricle without a midline partition, and the septum pelucidum is absent.5,6 Field defects with ONH are variable and may include the following: 1. Central depression. This corresponds to decreased visual sensitivity in the area near ﬁxation subserved by the papillomacular ﬁbers that may be selectively involved. 2. Nasal wedges. This pattern of ﬁeld defect has its apex pointing toward the physiologic blind spot and involves ganglion cell axons from the temporal retina.

Figure 5-1. Optic nerve hypoplasia (note the double-ring sign).

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3. Temporal wedges. This pattern of ﬁeld defect has its apex pointing toward the physiologic blind spot and involves ganglion cell axons from the nasal retina. 4. Hemianopias. This visual ﬁeld defect involves the ﬁeld to either the left or right of the point of ﬁxation but does not cross and hence respects the vertical midline. 5. “Altitudinal” defects. These defects involve the ﬁeld above or below the point of ﬁxation but do not cross the horizontal midline, at least not initially. Altitudinal defects may involve or spare ﬁxation, depending on the underlying pathology. 6. Generalized constriction. This usually represents an end point of arcuate scotomas that connect, top and bottom, and then expand such that only the central ﬁeld is spared.1,2,7-9 Figure 5-2 shows a central scotoma in a patient with ONH. Pediatric patients with unilateral or segmental ONH and with normal growth and development should undergo regular ophthalmic and pediatric examinations. Those with bilateral ONH should undergo neuroimaging (magnetic resonance imaging [MRI]) and endocrine evaluation. ONH discovered in neurologically intact adults requires no further workup.8

Figure 5-2. Central scotoma in a patient with optic nerve hypoplasia.

5-2-2 Optic Nerve Colobomas and Pits. Colobomas or pits are congenital malformations that enlarge or distort the nerve head circumference and shape. In most cases, the enlarged peripapillary area is irregularly pigmented with the presence of anomalous vessels. Colobomas are usually unilateral and sporadic.10 The morning glory anomaly is an enlarged, relatively round disc ﬁlled with retained embriogenic glial and vascular remnants (Figure 5-3). It often projects forward as a funnel and can be surrounded by an elevated annulus of chorioretinal pigment. When associated with congenital forebrain anomalies, including basal

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Figure 5-3. Morning glory syndrome.

Figure 5-4. Optic disc pit.

encephaloceles (spheno-orbital, transsphenoidal, or frontoethmoidal), it is termed “morning glory syndrome.” The majority of patients with this syndrome have marked visual loss and amblyopia.11 Patients with congenital disc malformations may complain of transient obscurations of vision, lasting seconds to minutes, but the mechanism of the disturbance is not known.10 Pits of the optic disc are intrapapillary pearly gray slits containing pale glial material (Figure 5-4). They are usually located within the scleral rim of the disc margin and can extend for up to one third of a disc diameter. The disc border is usually distorted, and mild pigment epithelial

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changes may be present. Pits are usually unilateral and temporally located. There is a positive association with serous detachment of the macula in up to 50% of the cases.12,13 Visual ﬁeld changes include the following: 1. Arcuate bundle scotoma. This is actually a mild form of an altitudinal defect. It does not involve ﬁxation but rather the areas just peripheral to it. 2. Fuchs colobomata. These are usually stable and in the form of dense nerve ﬁber bundle defects that extend from the blind spot, toward ﬁxation in the papillomacular area (cecocentral scotoma).14

5-2-3 Anomalous Disc Elevations: Pseudopapilledema With or Without Hyaline Bodies (Drusen). Pseudopapilledema are congenitally elevated discs that may present with or without hyaline bodies. Disc hyaline bodies are acellular laminated concretions of unknown origin, often partially calciﬁed. They are possibly related to the accumulation of axoplasmic derivatives from degenerating retinal nerve ﬁbers, in which orthograde axoplasmic ﬂow has been obliterated due to an abnormally narrow scleral canal. These hyaline bodies slowly become visible, as they enlarge toward the disc surface and margin; the overlying retinal nerve ﬁbers also become progressively thinner. Usually they become visible in the early teens. They are usually inherited as autosomal dominant trait. They present in two thirds of cases bilaterally and are not necessarily symmetric. When there is uncertainty between true edema and pseudopapilledema, examination of family members may be helpful.15-17 Hyaline bodies may become symptomatic by insidious visual ﬁeld loss or spontaneous hemorrhage.18 Visual ﬁeld defects are usually in the form of: 1. Blind spot enlargement, reﬂecting absence of functioning photoreceptors mechanically disrupted by the expanding adjacent ONH. 2. Arcuate, which is actually a mild form of an altitudinal defect. It does not involve ﬁxation but rather the areas just peripheral to it. 3. Other nerve ﬁber bundle patterns, such as altitudinal or nasal step. 4. Other less commonly irregular peripheral constriction that may occur. Normally, these defects progress slowly, with a predilection for involvement of the inferior nasal quadrant.19 Drusen are not an uncommon condition and may be seen in up to 2% of patients.15 Figure 5-5 shows optic disc drusen, and Figure 5-6 shows a central visual ﬁeld defect (blind spot enlargement) in optic disc drusen.

5-2-4 Tilted Disc and Crescents. Tilted discs usually present with depigmented peripapillary crescents. The most common variety of crescent is that located inferiorly (Fuchs colobomata), usually with inferonasal retinal quadrant involvement and superior temporal ﬁeld defect without respect for either vertical or horizontal.20, 21 In bilateral cases, visual ﬁeld shows bitemporal hemianopia, which does not respect the vertical meridian.22

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Figure 5-5. Optic disc drusen.

Figure 5-6. Central visual ﬁeld defect (blind spot enlargement) in optic disc drusen.

5-3 HEREDODEGENERATIVE OPTIC ATROPHIES Heredodegenerative inherited optic neuropathies fall under the rubric of metabolic optic neuropathies. Metabolic optic neuropathies share many common pathophysiologic and clinical characteristics. Most metabolic optic neuropathies involve derangements that affect mitochondria and oxidative phosphorylation. Common hereditary optic neuropathies include Leber’s hereditary optic neuropathy (LHON), dominant optic atrophy (DOA), and congenital recessive optic atrophy (ROA). Like most acquired metabolic optic neuropathies, inherited optic neuropathies all involve mitochondria function. In all cases, mitochondria are impaired either by mutations of their own DNA (mtDNA) or by mutations of nuclear DNA involved in the transcription of mitochondrial proteins or substrates. The presentation is usually symmetric visual loss with dyschromatopsia and central or cecocentral visual ﬁeld defects, which involve the optic disc and

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papillomacular ﬁbers. This archetypical set of clinical signs reﬂects the fact that in metabolic optic neuropathies, there is a strong predilection for the papillomacular bundle (PMB). Prompt recognition of the characteristic elements from history and physical examinations often precludes unnecessary patient laboratory evaluation.

5-3-1 Leber’s Hereditary Optic Neuropathy. LHON is a maternally inherited disease associated with point mutations in mtDNA, and it is now considered the most prevalent mitochondrial disorder. LHON typically manifests as a subacute central loss of vision that affects predominantly young adult males. The age of onset is usually between 15 and 35 years. Almost invariably, the second eye is affected, within weeks to months. LHON is usually due to one of three pathogenic mtDNA point mutations. These mutations affect nucleotide positions 11778, 3460, and 14484, respectively, in the ND4, ND1, and ND6 subunit genes of complex I, which is integral for oxidative phosphorylation in mitochondria. It is hypothesized that the respiratory chain dysfunction leads to energy depletion and reactive oxygen species (ROS) accumulation, which in turn produce axoplasmic stasis and swelling, thereby blocking ganglion cell function and causing loss of vision. In LHON, the pathologic mutation may either be homoplasmic (involving all the mitochondria) or heteroplasmic (involving only a fraction of the mitochondria). Most heteroplasmic pedigrees have much lower penetrance but, surprisingly, the disease is not milder in form. Even with homoplasmic families, penetrance is highly variable. The rate of penetrance varies with the mutation and pedigree, although it is always greater in males. Hence, in a typical family with the 11778 mtDNA mutation, 8-10% of the women and 40-50% of the men may experience devastating and sudden visual loss in young adulthood.23-28 In LHON, fundus changes, such as microangiopathy and nerve ﬁber layer swelling, have been described to immediately precede or accompany the onset of visual loss. This process, although usually bilateral, occurs asynchronously over the course of several weeks to months and eventually evolves to severe optic atrophy and irreversible impairments of vision. The acute stage of LHON usually lasts a few weeks. The affected eye characteristically demonstrates an early dropout of the PMB; an edematous appearance of the rest of the nerve ﬁber layer, especially in the arcuate bundles; and enlarged or telangiectatic and tortuous peripapillary vessels (microangiopathy). There is absence of leakage from the optic disc or peripapillary region on ﬂuorescein angiography.29-34 Figure 5-7 shows classical funduscopic ﬁndings seen in the acute phase of LHON. Clinical examination reveals decreased visual acuity and dyschromatopsia. Visual ﬁeld examination usually shows cecocentral scotoma. This defect extends from the physiologic “blind spot” to involve ﬁxation. Although a central scotoma may also encompass the blind spot, a cecocentral scotoma is smaller and typically dumbbell shaped. Later, with progression of the disease, the central scotoma becomes much larger and absolute.29-33 Figure 5-8 shows a dense central visual ﬁeld defect in a patient with LHON.

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A

B Figure 5-7. Right and left eyes of a patient with Leber’s hereditary optic neuropathy. Fundus photographs of both eyes demonstrate hyperemic optic nerve heads, with dilated tortuous vessels, and swollen retinal nerve ﬁber layer (pseudoedema of the optic disc). Note also the telangectatic vessels.

There are a few reports of spontaneous recovery, especially with the 14484/ND6 mutation (up to 60% of cases) and in younger patients. Most often, the visual loss progressing to total optic atrophy over time stabilizes within 1 year, with the early development of temporal optic atrophy. There is currently no clinical evidence for an efﬁcacious treatment to reverse vision loss in LHON. Theoretical considerations have led to the use of several agents involved with mitochondrial energy production and with antioxidant capabilities, such as coenzyme Q10 (or its analogues), succinate, L-carnitine, vitamins K1, K3, C, and B12, folate, and thiamine. It remains unlikely that any of these agents alone or in combination will prove consistently useful in the treatment of acute visual loss in LHON or in the prophylactic therapy in asymptomatic family members at risk.23,27,28,31 However, it is prudent to recommend the avoidance of agents that might induce oxidative stress or impair mitochondrial energy production. Most speciﬁcally, it is imperative to avoid exposure to smoke and alcohol because these environmental factors can trigger the loss of vision in susceptible individuals.34

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Figure 5-8. Dense central visual ﬁeld defect in patient with Leber’s hereditary optic neuropathy.

5-3-2 Dominant Optic Atrophy. DOA, or Kjer’s optic neuropathy, is one of the most common forms of hereditary optic atrophies. Presentation usually occurs at latency age (7-10 years old). It often presents with an imperceptible onset and a slowly progressive course and results in mild to moderate visual impairment (20/40 to 20/400). The inheritance of DOA is autosomal dominant. Despite the variability in expression, the penetrance is actually very high. DOA presents as mild, bilateral, sometimes asymmetric loss of visual acuity. On examination, there is temporal

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optic disc pallor, often with a wedge-shaped area of temporal excavation. There is mild generalized dyschromatopsia.35-40 Figure 5-9 shows wedge shaped optic atrophy commonly seen in patients with DOA. Visual ﬁeld ﬁndings include:

,

1. Central scotoma. This involves the central 5° to 20° surrounding ﬁxation. Central scotoma usually indicates damage to the macular retinal ganglion cells RGCs or to the papillomacular nerve ﬁbers at or within the optic nerve. If the scotoma incorporates the blind spot, the optic nerve is certainly involved. 2. Paracentral scotoma. This involves defects within 20° of the fovea. 3. Cecocentral scotoma. This defect extends from the physiologic blind spot through and into the point of ﬁxation. Although a central scotoma may also

A

B Figure 5-9. Right and left eyes in a patient with dominant optic atrophy. Fundus photographs show the characteristic wedge-shaped optic atrophy seen on the temporal side of both optic discs. 5-9 A – Right eye, 5-9-B- Left eye.

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encompass the blind spot, a cecocentral scotoma is smaller and typically dumbbell shaped.36,39,40

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Bilateral visual ﬁeld central depression in a patient with DOA is shown in Figure 5-10. In general, visual prognosis is good. The nuclear gene OPA1 located on chromosome 3 was identiﬁed in 2000 as the cause of DOA. In addition to OPA1, there are OPA4 and other OPA mutations,

A Figure 5-10. Bilateral central depression, in patient with dominant optic atrophy. (Right eye)

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B Figure 5-10. (Continued) (Left eye)

which have been mapped to the 3q and 18q regions, respectively. All these genes are responsible for mitochondrial structural proteins.42-45 In DOA, there is also an increased occurrence of associated sensorineural hearing loss such that these patients should be advised to undergo audiology testing. As in LHON, many agents have been tried as possible treatment options, and none were found to be effective. It remains unclear as to the role of environmental factors. These patients should be offered genetic counseling.36,39,46

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5-3-3 Recessive Optic Atrophy. This autosomal recessive somatic condition is the most uncommon form of inherited optic nerve disease. Unlike LHON and DOA, ROA is usually discovered in the ﬁrst 3 to 4 years of life. It often presents as severe visual impairment, frequently associated with searching nystagmus. Visual acuity ranges between no light perception (NLP) to 20/400. There is diffuse optic disc atrophy, sometimes with attenuation of the retinal arterioles, similar to that seen in tapetoretinal degenerations. Hence, the differential diagnosis of ROA is more akin to that of retinal dystrophies than to other hereditary optic neuropathies. Electroretinography plays an important role in differentiating ROA from tapetoretinal degeneration, retinitis pigmentosa, or Leber’s congenital amaurosis, in that it is normal in ROA and severely impaired in the retinal degenerations. The gene/chromosome for ROA remains to be identiﬁed. Not surprisingly there are several reports of consanguinity associated with this autosomal recessive condition.47-50

REFERENCES 1. Lambert SR, Hoyt CS, Narahara MH. Optic nerve hypoplasia. Surv Ophthalmol. 1987;32:1–9. 2. Brodsky MC. Congenital optic disc anomalies. Surv Ophthalmol. 1994;39:89–112. 3. Alvarez E, Wakakura M, Khan Z, et al. The disc-macula distance to disc diameter ratio: a new test for conﬁrming optic nerve hypoplasia in young children J Pediatr Ophthalmol Strab. 1988;25:151–154. 4. Petersen RA, Walton DS. Optic nerve hypoplasia with good visual acuity and visual ﬁeld defects: a study of children of diabetic mothers. Arch Ophthalmol. 1977;97: 254–258. 5. Williams J, Brodsky MC, Griebel M, et al. Septo-optic dysplasia: the clinical insigniﬁcance of an absent septum pellucidum. Dev Med Child Neurol. 1993;35:490–501. 6. Garcia-Filion P, Epport K, Nelson M, et al. Neuroradiographic, endocrinologic, and ophthalmic correlates of adverse developmental outcomes in children with optic nerve hypoplasia: a prospective study. Pediatrics. 2008;121:653–659. 7. Buchanan TA, Hoyt WF. Temporal visual ﬁeld defects associated with nasal hypoplasia of the optic disc. Br J Ophthalmol. 1981;65:636–640. 8. Brodsky MC, Schroeder GT, Ford R. Superior segmental optic nerve hypoplasia in identical twins. J Clin Neuroophthalmol. 1993;13:152–154. 9. Borchert M, Garcia-Filion P. The syndrome of optic nerve hypoplasia. Curr Neurol Neurosci Rep. 2008;8:395–403. 10. Maumenee IH, Mitchell TN. Colobomatous malformations of the eye. Trans Am Ophthalmol Soc. 1990;88:123–135. 11. Irvine AR, Crawford JB, Sullivan JH. The pathogenesis of retinal detachment with morning glory disc and optic pit. Trans Am Ophthalmol Soc. 1986;84:280–292. 12. Brown GC, Shields JA, Goldberg RE. Congenital pits of the optic nerve head, II: clinical studies in humans. Ophthalmology. 1980;87:51–65. 13. Postel EA, Pulido JS, McNamara JA, et al. The etiology and treatment of macular detachment associated with optic nerve pits and related anomalies. Trans Am Ophthalmol Soc. 1998;96:73–93. 14. Graham MV and Wakeﬁeld GJ. Bitemporal visual ﬁeld defects associated with anomalies of the optic discs. Br J Ophthalmol. 1973;57:307–314.

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15. Rosenberg MA, Savino PJ, Glaser JS. A clinical analysis of pseudopapilledema, I: population, laterality, acuity, refractive error, ophthtalmoscopy characteristics, and coincident disease. Arch Ophthalmol. 1979;97:65–70. 16. Friedman AH, Gartner S, Modi SS. Drusen of the optic disc. A retrospective study in cadaver eyes. Br J Ophthalmol. 1975;59:413–421. 17. Kurz-Levin MM, Landau K. A comparison of imaging techniques for diagnosing drusen of the optic nerve head. Arch Ophthalmol. 1999;117:1045–1049. 18. Sanders TE, Gay AJ, Newman M. Drüsen of the optic disc-hemorrhagic complications. Trans Am Ophthalmol Soc. 1970;68:186–218. 19. Savino PJ, Glaser JS, Rosenberg MA. A clinical analysis of pseudopapilledema. II. Visual ﬁeld defects. Arch Ophthalmol. 1979;97:71–75. 20. Apple DJ, Rabb MF, Walsh PM. Congenital anomalies of the optic disc. Surv Ophthalmol 1982;27:3–41. 21. Sanders M. Congenital abnormalities of the optic nerve and related forebrain. Br J Ophthalmol. 1984;68:511–512. 22. Dorrell D. The tilted disc. Br J Ophthalmol. 1978;62:16–20. 23. Berry H. Bitemporal depression of the visual ﬁeld due to an ocular cause. Br J Ophthalmol. 1963;47:441–444. 24. Carelli V. Leber’s hereditary optic neuropathy. In: Schapira AHV, Di Mauro S, eds. Mitochondrial Disorders in Neurology. 2nd ed. Boston: Butterworth-Heinemann; 2002;115–142. 25. Sadun AA. Metabolic optic neuropathies. Semin Ophthalmol. 2002;17:29–32. 26. Wallace DC, Singh G, Lott MT, et al. Mitochondrial DNA mutation associated with Leber’s hereditary optic neuropathy. Science. 1988;242:1427–1430. 27. Chalmers RM, Schapira AHV. Clinical, biochemical and molecular genetic features of Leber’s hereditary optic neuropathy. Biochem Biophys Acta. 1999;1410:147–158. 28. Carelli V, Ross-Cisneros FN, Sadun AA. Optic nerve degeneration and mitochondrial dysfunction: genetic and acquired optic neuropathies. Neurochem Int. 2002;40: 573–584. 29. Carelli V, Ross-Cisneros F, Sadun A. Mitochondrial dysfunction as a cause of optic neuropathies. Prog Retinal Eye Res. 2004;23:53–89. 30. Sadun AA, Carelli V, Salomao SR, et al. Extensive investigation of large Brazilian pedigree of Italian ancestry (SOA-BR) with 117788/haplogroup J Leber’s hereditary optic neuropathy (LHON). Am J Ophthalmol. 2003;136:231–238. 31. Smith JL, Hoyt WF, Susac JO. Ocular fundus in acute Leber optic neuropathy. Arch Ophthalmol. 1973;90:349–354. 32. Nikoskelainen EK. Clinical picture of LHON. Clin Neurosci. 1994;2:115–120. 33. Riordan-Eva P, Sanders MD, Govan GG, et al. The clinical features of Leber’s hereditary optic neuropathy deﬁned by the presence of pathogenic mitochondrial DNA mutation. Brain. 1995;118:319–337. 34. Barboni P, Savini G, Valentino ML, et al. Retinal nerve ﬁber layer evaluation by optical coherence tomography in Leber’s hereditary optic neuropathy. Ophthalmology. 2005;112:120–126. 35. Sadun A, Salomao SR, Berezovsky A, et al. Subclinical carriers and conversions in Leber’s hereditary optic neuropathy: a prospective psychophysical study. Trans Am Ophthalmol Soc. 2006;104:51–61. 36. Kjer P. Infantile optic atrophy with dominant mode of inheritance: a clinical and genetic study of 19 Danish families. Acta Ophthalmol. 1959;(Suppl 54):1–147. 37. Kerrison JB. Hereditary optic neuropathies. Ophthalmol Clin North Am. 2001;14: 99–107.

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Inherited or Congenital Optic Nerve Diseases

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38. Kline LB, Glaser JS. Dominant optic atrophy: the clinical proﬁle. Arch Ophthalmol. 1979;97:1680–1686. 39. Votruba M, Aijaz S, Moore AT. A review of primary hereditary optic neuropathies. J Inherit Metab Disord. 2003;26:209–227. 40. Kline LB, Siatkovsky RM. Developmental and hereditary optic nerve diseases. In: Kline LB, Foroozan R, eds. Optic Nerve Disorders (Ophthalmology Monograms). New York: Oxford University Press; 2007:151–170. 41. Newman NJ. Hereditary optic neuropathies: from the mitochondria to the optic nerve. Am J Ophthalmol. 2005;140:517–523. 42. Hoyt CS. Autosomal dominant optic atrophy: a spectrum of disability. Ophthalmology. 1980;87:245–251. 43. Delettre C, Lenaers G, Griffoin JM, et al. Nuclear gene OPA1, encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy. Nat Genet. 2000;26: 207–210. 44. Eiberg H, Kjer B, Kjer P, et al. Dominant optic atrophy (OPA1) mapped to chromosome 3q region, I: linkage analysis. Hum Mol Genet. 1994;3:977–980. 45. Delettre C, Lenaers G, Pelloquin L, et al. OPA 1 dominant optic atrophy: a novel mitochondrial disease. Mol Genet Metab. 2002;75:97–107. 46. Pesch UE, Fries JE, Bette S, et al. OPA1, the disease gene for autosomal dominant optic atrophy, is specially expressed in ganglion cells and intrinsic neurons of the retina. Invest Ophthalmol Vis Sci. 2004;45:4217–4221. 47. Johnston PB, Gaster RN, Smith VC, et al. A clinic pathologic study of autosomal dominant optic atrophy. Am J Ophthalmol. 1979;88:868–875. 48. Waardenburg PJ. Different types of hereditary optic atrophy. Acta Genet. 1957;7: 287–290. 49. Newman NJ. Hereditary optic neuropathies. In: Miller NR, Newman NJ, eds. Walsh and Hoyt’s Clinical Neuro-Ophthalmology. Baltimore: Williams & Wilkins; 1998: 742–756. 50. Newman NJ, Biousse V. Hereditary optic neuropathies. Eye. 2004;11:1144–1160.

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6 Acquired Optic Nerve Diseases CARLOS FILIPE CHICANI, MD, PHD, PETER A. QUIROS, MD, AND ALFREDO A. SADUN, MD, PHD

6-1 INTRODUCTION This chapter focuses on the most frequently acquired optic nerve diseases: their signs and symptoms, visual ﬁeld ﬁndings, and the required basic workup and management. Acquired optic nerve diseases are often vision threatening and sometimes even life threatening. There is a need for accurate and timely diagnosis. Therefore, it is incumbent on the clinician to identify optic neuropathies, separate them from chronic congenital and hereditary problems, and aggressively pursue the diagnosis and treatment as necessary. In the workup of optic neuropathies, the visual ﬁeld is extremely helpful. All patients with suspected optic neuropathies require careful examination of the visual ﬁelds for detection, characterization, and monitoring. Acquired optic neuropathies include inﬂammatory, ischemic, compressive, metabolic, and central nervous system–reﬂected pathology (papilledema). Inﬂammatory optic neuropathies include optic neuritis and its various etiologies such as demyelination, infective, immune-mediated (atypical), and slowly progressive/ chronic. Ischemic optic neuropathies include nonarteritic ischemic optic neuropathy (NAION) and arteritic ischemic optic neuropathy (AAION). Metabolic optic neuropathies include nutritional and/or toxic etiologies. Compressive optic neuropathies can occur due to mass effect on the disc optic, gliomas, and perioptic meningiomas. Papilledema may be primary (pseudotumor cerebri) or secondary to central nervous system mass effect.

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6-2 OPTIC NEURITIS Optic neuritis is deﬁned as a primary inﬂammation of the optic nerve. It is characterized by central visual loss that worsens over days and usually peaks about 1 to 2 weeks after the onset. It is usually unilateral but may be bilateral, especially in children, following viral infections like measles, mumps, and chickenpox. It occurs most commonly in adults (18-45 years old). Orbital or periocular pain may be present or precede the visual loss and is exacerbated with eye movements. Etiologies include demyelinating diseases/multiple sclerosis;, idiopathic, viral, or bacterial infections (syphilis); contiguous inﬂammation of the meninges, orbit, or sinuses,; granulomatous inﬂammation (tuberculosis, sarcoidosis, and cryptococosis); and autoimmune diseases. It is the most common cause of acute visual loss from optic nerve disease in the young and middle-aged adult group. There is loss of color vision and perception of light intensity. Relative afferent pupilary defect (RAPD) is seen in unilateral or asymmetric cases. Uhtoff’s phenomena (visual deﬁcit with exercise or increase in body temperature) may occur. When it occurs in the intraocular portion of the optic nerve is termed papilitis or anterior optic neuritis, and some degree of disc swelling is seen with or without peripapillary hemorrhages. When the intraorbital part of the optic nerve is affected (majority of cases), it is termed retrobulbar or posterior optic neuritis and usually funduscopy is normal.1-4 Visual ﬁeld ﬁndings include the following: 1. Central scotoma. This involves the central 5° to 20° surrounding ﬁxation. Central scotoma usually indicates damage to the macular retinal ganglion cells [RGCs]or to the papillomacular nerve ﬁbers at or within the optic nerve. If the scotoma incorporates the blind spot, the optic nerve is certainly involved. 2. Paracentral scotoma. This involves defects within 20° of the fovea. 3. Diffuse depression. There is generalized decreased visual sensitivity.5-8 Figure 6-1 shows central depression in a patient with optic neuritis. The asymptomatic fellow eye may show some defect in up to one third of the cases.8 Magnetic resonance imaging (MRI) of the brain should be undertaken to look for signs of optic nerve enhancement (50-80%) and demyelination (up to 30%). An attack of monosymptomatic optic neuritis may precede the development of multiple sclerosis. The natural history of the disease is for visual function to recover in a few weeks. In cases of profound visual loss or where the need for faster improvement is necessary, treatment with IV steroids is recommended (methylprednisolone 1 g/day for 3 days, followed by prednisone 1 mg/kg/day tapered over 11 days). In cases of positive ﬁndings on MRI (three or more T2 hyperintensities), the above protocol should be performed. Based on the Optic Neuritis Treatment Trial, it has been

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Figure 6-1. Central depression in a patient with optic neuritis.

shown that treatment results in a decrease in conversion to multiple sclerosis over the next 2 years compared with no treatment.9-16 In a minority of cases, the vision may not improve over time or even worsen; these are the atypical or “chronic” cases. Additional workup for autoimmune and infective causes should be performed in these patients. In children, it is more common to see bilateral cases; disc edema is also more frequent than in the adult population. It usually follows a febrile prodrome, but it has a lower association with future multiple sclerosis.1

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6-3 ISCHEMIC OPTIC NEUROPATHY

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This is deﬁned as watershed infarction of the optic disc or, less commonly, the retrobulbar portion of the optic nerve. It may be nonarteritic (NAION) or arteritic (AAION). It is the most common cause of nonglaucomatous optic nerve disorder found in patients older than 50 years.17

6-3-1 Nonarteritic Ischemic Optic Neuropathy. NAION is the sudden, painless, usually nonprogressive visual loss of a moderate degree; initially it is unilateral but it may become bilateral. A minority of cases may be progressive, with a second decrease in visual acuity or visual ﬁeld, days or weeks after the initial episode. It usually occurs in adults 40 to 65 years old. A second attack in the same eye is extremely rare. Etiology usually includes vasculopathic causes such as hypertension, diabetes, and/or arteriosclerosis. Signs include pale segmental disc swelling, ﬂame-shaped hemorrhages, afferent pupillary defect (APD), normal erythrocyte sedimentation rate (ESR), decreased color vision, altitudinal or central visual ﬁeld defects, and optic atrophy after the edema resolves. The fellow optic disc usually appears normal, but it is often congenitally full, with a small or absent physiologic cup.17- 23 Visual ﬁeld ﬁndings include the following: 1. Altitudinal. These defects involve the ﬁeld above or below the point of ﬁxation but do not cross the horizontal midline, at least not initially. Altitudinal defects may involve or spare ﬁxation, depending on the underlying pathology. Typically, this type of defect extends to the periphery. 2. Central. This is described in optic neuritis. 3. Nasal steps. It is the beginning of an arcuate scotoma, manifest only at the nasal edge where it respects the horizontal raphe. 4. Arcuate. This is actually a mild form of an altitudinal defect. It does not involve ﬁxation but rather the areas just peripheral to it.17-19 5. Top/bottom An altitudinal visual ﬁeld defect and the optic disc (pallid edema) in a patient with NAION are shown in Figures 6-2 and 6-3, respectively. There is no proved therapy for this entity. Several different treatment modalities have been tried without success. There should be control of vasculopathic risk factors and systemic diseases such as hypertension and diabetes.24,25

6-3-2 Arteritic Ischemic Optic Neuropathy. The visual loss is usually more profound (counting ﬁngers or worse) and may rapidly become bilateral. It usually affects older patients (older than 70 years). Systemic symptoms may include headache, jaw claudication, scalp tenderness, proximal muscle and joint aches (polymyalgia rheumatica), anorexia, weight loss, or fever. Signs include pale swollen disc, often with ﬂame-shaped hemorrhages, that progresses to atrophy when edema resolves; APD; decreased color vision; and sometimes a palpable, tender, and nonpulsatile temporal artery.17,26-29

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Figure 6-2. Altitudinal visual ﬁeld defect in a patient with nonarteritic ischemic optic neuropathy.

Visual ﬁeld ﬁndings include the same ﬁve types described earlier for NAION and severe global depression. Workup should include an immediate ESR (abnormal if greater than 40 mm/hr) and C-reactive protein. Temporal artery biopsy should be obtained if giant cell arteritis (GCA) is based on the symptoms, signs, and/or laboratory tests. Systemic steroids should be administered immediately once GCA is suspected (intravenous methylpredinisolone 1 g/day for 3 days followed by oral prednisone 60-100 mg/day). The tapering should be very slow, and the goal is to maintain

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Figure 6-3. Nonarteritic ischemic optic neuropathy optic disc (pallid edema).

with the minimal oral dose that suppresses the symptoms and keeps the ESR under normal limits. Visual recovery and prognosis are poor.26-29

6-4 METABOLIC OPTIC NEUROPATHIES Etiologies includes malnutrition, toxic exposure (ethanol, methanol, tobacco, chloramphenicol, ethambutol, amiodarone, isoniazid, digitalis, chloroquine, streptomycin, disulﬁran, lead, and others), and vitamin deﬁciency (B group). Other vitamins deﬁciencies also play a role in the pathophysiology in this entity.30-34 In general, metabolic optic neuropathies involve some form of damage to functioning of the mitochondria. Symptoms include a painless, progressive, usually slow, bilaterally symmetric loss of vision. Signs include moderate visual loss (20/50 to 20/400), decreased color vision, temporal disc pallor, optic atrophy, or even normal-appearing disc.35-38 Visual ﬁeld ﬁndings are usually bilateral but symmetric and include: 1. Bilateral cecocentral. This defect extends from the physiologic “blind spot” through and into the point of ﬁxation. Although a central scotoma may also encompass the blind spot, a cecocentral scotoma is smaller and typically dumbbell shaped. 2. Bilateral central. This is described in optic neuritis.30-38 Figure 6-4 shows a typical visual ﬁeld ﬁndings in metabolic optic neuropathy bilateral symmetric visual ﬁeld defect in metabolic optic neuropathy.

6-5 COMPRESSIVE OPTIC NEUROPATHY Etiologies include optic nerve glioma (usually patients younger than 20 years; and positive association with neuroﬁbromatosis), optic nerve sheath meningioma

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Figure 6-4. Cecocentral bilateral symmetric visual ﬁeld defect in metabolic optic neuropathy.

(usually young women; orbital imaging may show an optic nerve mass, diffuse optic nerve thickening, or a railroad track sign, which is an increased contrast of the periphery of the nerve), any intraorbital or intracranial mass (schwannoma, hemangioma, pituitary adenoma, craniopharyngioma, or meningioma), or mass effect in Graves optic neuropathy, because of increased muscle volume or fat and, ﬁnally, by vascular compression as in intracranial aneurysm.39-47 Slowly progressive visual loss is the most common symptom. Signs include RAPD, which may be seen in unilateral and/or asymmetric cases. The optic nerve may be pale, normal, or occasionally swollen. Proptosis and/or optociliary shunt vessels (small vessels around the optic disc that shunt blood from the retinal to the choroidal venous circulation) may be present.39-45 Figure 6-5 shows optociliary shunt vessels. Visual ﬁeld ﬁndings include: 1. Central. This is described in optic neuritis. 2. Altitudinal. This is described in NAION.

Figure 6-5. Optociliary shunt vessels in compressive optic neuropathy.

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3. Junctional scotoma. This is the only situation in which unilateral optic nerve disease results in a bilateral ﬁeld defect. Junctional scotoma is an ipsilateral central scotoma with a contralateral superior temporal quadrantanopsia. It results from damage to the most posterior optic nerve at the chiasmal junction, known as anterior genu of von Wilbrand. Its presence indicates a compressive lesion, most commonly a pituitary adenoma with a postﬁxed chiasm. Workup should include orbital and cranial neuroimaging (computed tomography [CT] or MRI) and vascular studies such as magnetic resonance angiography (MRA). Treatment is controversial, but in general these lesions may be irradiated or followed. If there is progressive proptosis, vision loss, discomfort/pain, or intracranial involvement with risk to the contralateral optic nerve or other vital structures, other treatment options should be considered.39-47

6-6 PAPILLEDEMA Papilledema is deﬁned as bilateral optic disc swelling produced by increased intracranial pressure. Rare exceptions of unilateral disc swelling are usually related to previous optic atrophy or to dysplastic discs. Patients are usually asymptomatic but symptoms may include episodes of transient, usually bilateral, visual obscurations or losses lasting seconds, headaches, double vision, nausea, and vomiting. Signs include bilateral hyperemic disc swelling with blurry margins and obscurations of blood vessels. The retinal nerve ﬁber layer is commonly involved. Peripapillary or papillary ﬂame-shaped hemorrhages, loss of venous pulsations (may occur in up to 20% of normal population), and dilated, tortuous retinal veins may be observed. There is usually a normal visual acuity, pupillary response and color vision. Enlarged physiologic blind spot is the most common ﬁnding in visual ﬁeld exam. Diplopia may develop and is usually due to increased intracranial pressure causing unilateral or bilateral abducens nerve palsies.48,49 Papilledema showing disc swelling with blurry margins and obscurations of blood vessels is represented in Figure 6-6. In chronic papilledema, there is optic atrophy, the hemorrhages resolve, and narrowing of the peripapillary vessels and shunt vessels may develop. Decreased color vision and visual acuity may occur.48,49 Visual ﬁeld ﬁndings include: 1. Enlarged blind spot (reversible) 2. Nasal step; when scotomata occur above and below the ﬁxation point, they meet in the nasal ﬁeld and form a horizontal steplike defect 3. Arcuate (deﬁned in NAION) 4. Bi-arcuates 5. Generalized constriction

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Figure 6-6. Papilledema: disc swelling with blurry margins and obscurations of blood vessels.

6. Central depression plus items 1 through 5 7. Complete blindness 8. Peripheral ﬁeld defect may occur; a temporal island of vision may be preserved before progression to complete blindness.50 Figure 6-7 shows generalized constriction in visual ﬁelds in a patient with papilledema. Etiologies includes primary and metastatic intracranial masses, hydrocephalus, subdural and epidural hematomas (usually secondary to traumas), subarachnoid hemorrhage, brain abscess, meningitis, encephalitis, and idiopathic. Workup should include brain neuroimaging, preferentially MRI. If the scan is normal, lumbar puncture should be performed with recording of opening pressure. Analysis of the cerebrospinal ﬂuid is essential to exclude infectious or neoplastic processes. If this analysis is normal except for increased opening pressure, the patient probably has pseudotumor cerebri or IIH. IIH has a peak incidence in the third decade and is twice as common in women as in men. The patient is often obese and complains of generalized headache, nausea, vomiting, dizziness, and tinnitus. IIH may also present with transient (lasting seconds) visual obscurations and horizontal diplopia (abducens nerve palsy). The etiology is not known, but several disorders may be associated with it, such as obstructed intracranial venous drainage, endocrine and metabolic dysfunctions, exogenous agents (e.g., tetracycline antibiotics), and systemic diseases. Intensity of management is based on severity of headaches, degree of visual ﬁeld loss, and depth of visual acuity loss; it may include medical and surgical procedures. Medical management options include weight loss, serial lumbar punctures, dehydrating agents, diuretics, and corticosteroids. Surgical options include shunting procedures or optic nerve sheath decompression.51-53

A Figure 6-7. Generalized constriction in visual ﬁelds in a patient with papilledema caused by idiopathic intracranial hypertension.

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B Figure 6-7. (Continued)

REFERENCES 1. Beck RW. Optic neuritis. In Miller NR, Newman NJ, eds. Walsh & Hoyt’s Clinical Neuro-Ophthalmology, Vol 1. 5th ed. Baltimore: Williams & Wilkins; 1988:599–647. 2. Katz B. The dyschromatopsia of optic neuritis: a descriptive analysis of data from the Optic Neuritis Treatment Trial. Trans Am Ophthalmol Soc. 1995;93:685–708.

,

204

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3. Cole SR, Beck RW, Moke PS, et al. The National Eye Institute Visual Function Questionnaire: experience of the ONTT. Optic Neuritis Treatment Trial. Invest Ophthalmol Vis Sci. 2000;41:1017–1021. 4. Visual function 15 years after optic neuritis: a ﬁnal follow-up report from the Optic Neuritis Treatment Trial. Optic Neuritis Study Group. Ophthalmology. 2008;115: 1079–1082. 5. Keltner JL, Johnson CA, Spurr JO, et al. Baseline visual ﬁeld proﬁle of optic neuritis. The experience of the Optic Neuritis Treatment Trial. Optic Neuritis Study Group. Arch Ophthalmol. 1993;111:231–234. 6. Keltner JL, Johnson CA, Beck RW, et al. Quality control functions of the Visual Field Reading Center (VFRC) for the Optic Neuritis Treatment Trial (ONTT). Control Clin Trials. 1993;14:143–159. 7. Fang JP, Lin RH, Donahue SP. Recovery of visual ﬁeld function in the Optic Neuritis Treatment Trial. Am J Ophthalmol. 1999;128:566–572. 8. Beck RW, Kupersmith MJ, Cleary PA, et al. Fellow eye abnormalities in acute unilateral optic neuritis. Experience of the Optic Neuritis Treatment Trial. Ophthalmology. 1993;100:691–697. 9. Cleary PA, Beck RW, Anderson MM Jr, et al. Design, methods, and conduct of the Optic Neuritis Treatment Trial. Control Clin Trials. 1993;14:123–142. 10. Beck RW, Cleary PA, Anderson MM Jr, et al. A randomized, controlled trial of corticosteroids in the treatment of acute optic neuritis. The Optic Neuritis Study Group. N Engl J Med. 1992;326:581–588. 11. Anderson MM Jr, Boly LD, Beck RW. Remote clinic/patient monitoring for multicenter trials. Optic Neuritis Study Group. Control Clin Trials. 1996;17:407–414. 12. Chan JW. Optic neuritis in multiple sclerosis. Ocul Immunol Inﬂamm. 2002;10: 161–186. 13. Foroozan R, Buono LM, Savino PJ, et al. Acute demyelinating optic neuritis. Curr Opin Ophthalmol. 2002;13:375–380. 14. Beck RW, Trobe JD, Moke PS, et al. Optic Neuritis Study Group. High- and low-risk proﬁles for the development of multiple sclerosis within 10 years after optic neuritis: experience of the Optic Neuritis Treatment Trial. Arch Ophthalmol. 2003;121: 944–949. 15. Optic Neuritis Study Group. Long-term brain magnetic resonance imaging changes after optic neuritis in patients without clinically deﬁnite multiple sclerosis. Arch Neurol. 2004;61:1538–1541. 16. Optic Neuritis Study Group. Multiple sclerosis risk after optic neuritis: ﬁnal Optic Neuritis Treatment Trial follow-up. Arch Neurol. 2008;65:727–732. 17. Kelman SE. Ischemic optic neuropathies. In Miller NR, Newman NJ, eds. Walsh & Hoyt’s Clinical Neuro-Ophthalmology, Vol 1. 5th ed. Baltimore: Williams & Wilkins; 1988:549–598. 18. Boghen DR, Glaser JS. Ischaemic optic neuropathy. The clinical proﬁle and history. Brain. 1975;98:689–708. 19. Repka MX, Savino PJ, Schatz NJ, et al. Clinical proﬁle and long-term implications of anterior ischemic optic neuropathy. Am J Ophthalmol. 1983;96:478–483. 20. Arnold AC, Hepler RS. Natural history of nonarteritic anterior ischemic optic neuropathy. J Neuroophthalmol. 1994;14:66–69. 21. Beck RW, Savino PJ, Schatz NJ, et al. Anterior ischaemic optic neuropathy: recurrent episodes in the same eye. Br J Ophthalmol. 1983;67:705–709. 22. Beck RW, Servais GE, Hayreh SS. Anterior ischemic optic neuropathy. IX. Cup-to-disc ratio and its role in pathogenesis. Ophthalmology. 1987;94:1503–1508.

,

Acquired Optic Nerve Diseases

205

23. Aiello AL, Sadun AA, Feldon SE. Spontaneous improvement of progressive anterior ischemic optic neuropathy: report of two cases. Arch Ophthalmol. 1992;110:1197–1199. 24. Kelman SE. The Ischemic Optic Neuropathy Decompression Trial. Arch Ophthalmol. 1993;111:1616–1618. 25. Kelman S. Optic nerve decompression surgery for nonarteritic anterior ischemic optic neuropathy (NAION) is not effective and may be harmful. JAMA. 1995;273:625–632. 26. Hayreh SS. Ischemic optic neuropathy. Prog Retin Eye Res. 2009;28:34–62. 27. Hayreh SS, Podhajsky PA, Zimmerman B. Ocular manifestations of giant cell arteritis. Am J Ophthalmol. 1988;125:509–520. 28. Hayreh SS, Zimmerman B, Kardon RH. Visual improvement with corticosteroid therapy in giant cell arteritis. Report of a large study and review of the literature. Acta Ophthalmol Scand. 2002;80:353–354. 29. Danesh-Meyer H, Savino PJ, Gamble GG. Poor prognosis of visual outcome after visual loss from giant cell arteritis. Ophthalmology. 2005;112:1098–1103. 30. Lessel S. Toxic and deﬁciency optic neuropathies. In Miller NR, Newman NJ, eds. Walsh & Hoyt’s Clinical Neuro-Ophthalmology, Vol 1. 5th ed. Baltimore: Williams & Wilkins; 1988:663–680. 31. Rizzo J 3rd, Lessel S. Tobacco amblyopia. Am J Ophthalmol. 1993;116:84–87. 32. Woon C, Tang RA, Pardo G. Nutrition and optic nerve. Semin Ophthalmol. 1995;10:195–202. 33. Iuorno JD, Kolostyak KP, Mejico LJ. Therapies with potential toxicity of neuroophthalmic interest. Curr Opin Ophthalmol. 2003;14:339–343. 34. Kerrison JB. Optic neuropathies caused by toxins and adverse drug reactions. Ophthalmol Clin North Am. 2004;17:481–488. 35. Sadun AA, Martone JF, Muci-Mendoza R, et al. Epidemic optic neuropathy in Cuba. Eye ﬁndings. Arch Ophthalmol. 1994;112:691–699. 36. Sadun A. Acquired mitochondrial impairment as a cause of optic nerve disease. Trans Am Ophthalmol Soc. 1998;96:882–923. 37. Sadun AA. Metabolic optic neuropathies. Semin Ophthalmol. 2002;17:29–32. 38. Carelli V, Ross-Cisneros FN, Sadun AA. Optic nerve degeneration and mitochondrial dysfunction: genetic and acquired optic neuropathies. Neurochem Int. 2002;40:573–584. 39. Shults WT. Compressive optic neuropathies. In Miller NR, Newman NJ, eds. Walsh & Hoyt’s Clinical Neuro-Ophthalmology, Vol 1. 5th ed. Baltimore: Williams & Wilkins; 1988:649–662. 40. Miller NR. Primary tumours of the optic nerve and its sheath. Eye. 2004;18: 1026–1037. 41. McDonnell P, Miller NR. Chiasmatic and hypothalamic extension of optic nerve glioma. Arch Ophthalmol 1983;101:1412–1415. 42. Grill J, Laithier V, Rodriguez D, et al. When do children with optic pathway tumours need treatment? An oncological perspective in 106 patients treated in a single centre. Eur J Pedriatr. 2000;159:692–6. 43. Repka MX, Miller NR, et al. Visual outcomes after surgical removal of craniopharyngiomas. Ophthalmology. 1989;96:195–199. 44. Chicani CF, Miller NR. Visual outcome in surgically treated suprasellar meningiomas. J Neuroophthalmol. 2003;23:3–10. 45. Turbin RE, Thompson CR, Kennerdell JS, et al. A long-term visual outcome comparison in patients with optic nerve sheath meningioma managed with observation, surgery, radiotherapy, or surgery and radiotherapy. Ophthalmology. 2002;109:890–899. 46. Biousse V, Mendicino ME, Simon DJ, et al. The ophthalmology of intracranial vascular abnormalities. Am J Ophthalmol. 1998;125:527–544.

,

206

Visual Fields

47. Kuriyan AE, Phipps RP, Feldon SE. The eye and thyroid disease. Curr Opin Ophthalmol. 2008;19:499–506. 48. Miller NR. Papilledema. In Miller NR, Newman NJ, eds. Walsh & Hoyt’s Clinical Neuro-Ophthalmology, Vol 1. 5th ed. Baltimore: Williams & Wilkins; 1988:487–548. 49. Schirmer CM, Hedges TR 3rd. Mechanism of visual loss in papilledema. Neurosurg Focus. 2007;23:E5. 50. Corbett JJ, Jacobson DM, Mauer RC, et al. Enlargement of the blind spot caused by papilledema. Am J Ophthalmol. 1988;105:261–265. 51. Randhawa S, Van Stavern GP. Idiopathic intracranial hypertension (pseudotumor cerebri). Curr Opin Ophthalmol. 2008;19:445–453. 52. Shah VA, Kardon RH, Lee AG, et al. Long-term follow-up of Idiopathic intracranial hypertension: Iowa experience. Neurology. 2008;70:634–640. 53. Rosa N, Capasso L, Lanza M. Idiopathic intracranial hypertension. J Neuroophthalmol. 2005;25:152.

7 Visual Field Defects in Chorioretinal Disorders RON A. ADELMAN, MD, MPH, FACS, AND PATRICIA PAHK, MD

7-1 INTRODUCTION Pathologic processes involving the retina or choroid can present with a wide variety of visual ﬁeld defects. Usually visual ﬁeld defects of retinal diseases directly correlate with the fundus ﬁndings. Visual ﬁeld changes are often the result of damage to the retina or scarring but, in conjunction with other clinical ﬁndings, they may help narrow the differential diagnosis. Most of the macular lesions result in visual ﬁeld defects that do not respect the vertical or horizontal midline. Occasionally inﬂammatory disorders result in visual ﬁeld defects that do not directly correlate with the retinal ﬁndings. For example, patients with multiple evanescent white dot syndrome (MEWDS) may have an enlarged blind spot.

7-2 MACULAR DISEASES Macular disorders can cause central or paracentral scotomas depending on the location of the lesion. Causes of macular pathology include drusen, atrophy from dry age-related macular degeneration (AMD), retinal hemorrhage, choroidal neovascular membrane, macular edema, macular hole, macular scar, pathologic myopia, and macular dystrophies of the retina or choroid (Figures 7-1 through 7-5). Central serous chorioretinopathy (CSCR) can show a relative defect that is anatomically correlated with the area of subretinal or sub RPE (retinal pigment epithelium) ﬂuid accumulation. Residual pigmentary changes in inactive CSCR can also cause a relative depression in the corresponding visual ﬁeld. Pathologic myopia can present with a variety of visual ﬁeld defects depending on the retinal

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Figure 7-1. Dry AMD (A) Dry age related macular degeneration (ARMD). Humphrey visual ﬁeld (HVF) 24-2 with nonspeciﬁc central changes in both eyes. (B) & (C) Fundus photo, right and left eye show multiple drusen.

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Figure 7-1. (Continued)

ﬁndings, such as posterior staphyloma or choroidal neovascular membrane (Figure 7-4,7-5). AMD may show nonspeciﬁc changes in the central or paracentral visual ﬁeld that correlate with the structural damage to the retina and choroid (see Figure 7-1). Geographic atrophy in dry AMD can cause a dense scotoma correlated with the pattern of the atrophy. Choroidal neovascular membranes can cause a depression in the correlating visual ﬁeld due to edema or hemorrhage. Disciform scars in endstage AMD can also cause a dense scotoma (see Figure 7-2). Macular holes may cause a small central scotoma (Figure 7-3). Pattern dystrophies are a family of disorders with a common pathology at the level of the RPE. Butterﬂy dystrophy, an autosomal dominant disorder, and Sjögren reticular dystrophy, an autosomal recessive disorder, are two examples of pattern dystrophies. Often, patients with pattern dystrophies maintain excellent vision, unless atrophy compromises their central visual ﬁeld. Electrophysiologic testing often shows normal electroretinographic (ERG) testing with mildly abnormal electro-oculography (EOG) results, reﬂecting the RPE disturbance. Pathologic myopia has a ﬁeld defect that is correlated with fundus lesions (see Figures 7-4 and 7-5).

7-3 VASCULAR DISEASES Vascular diseases can present with more localizing defects. Artery and vein occlusions will have defects that correlate with the area that has abnormal circulation. Macular edema caused by diabetic retinopathy or vein occlusions will cause a central or paracentral defect (Figures 7-6 through 7-8). Macroaneurysms can cause localized changes from blockage from hemorrhage or edema. Retinal emboli, regardless of composition (ﬁbrin, cholesterol, or calcium), may cause anything from a sectoral to a full ﬁeld defect.

A Figure 7-2. Disciform scar, end stage AMD. (A) HVF 24-2 of both eyes show bilateral central scotomas. (B) and (C) Fundus photo, right and left eye.

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Figure 7-2. (Continued)

7-4 CONGENITAL AND GENETIC DISEASES Retinitis pigmentosa (RP) represents a family of diseases with variable inheritance (autosomal dominant, autosomal recessive, or X-linked). Patients with RP may have poor vision in dim light, rod and cone dysfunction by ERG, and bone spicules in the periphery. Patients classically present with mid peripheral scotomas that coalesce into a ring-shaped scotoma. Later in the course of the disease, the scotoma progresses and involves the central vision or leaves a small central visual ﬁeld. This pattern can be seen in patients who have the typical bone spicules and in those who do not (sine pigmente). Cystoid macular edema may be associated with RP and will cause changes to the central or paracentral visual ﬁeld. Because of the progressive degenerative changes and the signiﬁcant impact of the disease, it is important to evaluate patients suspected of having RP to rule out masqueraders such as syphilis, uveitis, old vascular occlusion, or drug toxicity. It is also important to evaluate patients for systemic metabolic disorders, particularly treatable conditions such as Refsum disease or abetalipoproteinemia. Choroideremia, an X-linked recessive disease, is characterized in the advanced stages by total atrophy of the choriocapillaris, choroid, and RPE. Fundus changes begin with pigmentary mottling at the equator that evolve into atrophy and migrate peripherally as well as centrally. Patients often have diffuse peripheral visual ﬁeld defects with central sparing until late in the course of the disease (Figure 7-9). ERG recordings are reduced and progress to unrecordable in the late stages. Gyrate atrophy, a rare autosomal recessive disorder, causes choroidal and retinal atrophy with progressive loss of peripheral and central vision. The defective gene, ornithine aminotransferase, leads to high levels of serum ornithine. Treatment is targeted at reducing ornithine levels such as through an arginine-restricted diet.1 Such treatment has been shown to slow the progression of disease as measured by serial visual ﬁeld testing and ERG.

A Figure 7-3. Macular hole. (A) HVF 10-2 demonstrates a central scotoma. (B) Fundus photo, left eye. (C) Red free photo, left eye. The outline of the macular hole is clearer on red free imaging. (D) Stratus OCT, left eye. There is full thickness discontinuity of the retinal layers with adjacent macular edema.

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D Figure 7-3. (Continued).

Fundus ﬂavimaculatus, or Stargardt disease, is an autosomal recessive disease that has been localized to mutations in the ABCR gene, which encodes a transmembrane transporter protein in the rod outer segment. Patients with early stages of Stargardt disease can have central scotomas despite minimal ﬁndings on ophthalmoscopy. Patients can have a primarily macular presentation or peripheral changes, or a combination of both. Patches of atrophy can give a beaten bronze appearance of the macula. Pisciform ﬂecks can be found in the macula or in the periphery. Fluorescein angiography can be helpful with the classic ﬁnding known as a “silent choroid.” Advanced disease can show peripheral degenerative changes that are reﬂected in depressed ERG testing. Vitelliform dystrophy, or Best disease, often have well-preserved central vision despite abnormal appearing maculae. Typically of dominant inheritance, the mutation is identiﬁed on the VMD2 gene on chromosome 11. The initial appearance of a yellow macular lesion is often associated with good vision, until

A Figure 7-4. Pathologic myopia. (A) HVF 24-2 shows diffuse nonspeciﬁc depression in both eyes. (B) and (C) Fundus photo, right and left eye. Note the atrophy of the retinal pigment epithelium with the underlying choriocapillaris visible. Signiﬁcant peripapillary atrophy with tilted optic nerves are also seen.

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Figure 7-4. (Continued)

atrophy causes a central scotoma. ERG testing is usually normal; however, Best disease classically has an abnormal EOG with an Arden ratio of less than 1.5. A distinction is made between Best disease and adult-onset vitelliform lesions, such as adult vitelliform foveomacular dystrophy, which is also characterized by bilateral yellow subfoveal lesions but with normal ERG and EOG testing. Patients usually are asymptomatic or have mild metamorphopsia. Distinguishing these diseases is important for genetic counseling. Ocular albinism presents clinically with photophobia and on examination shows iris tranillumination defects as well as a hypoplastic fundus and fovea (Figure 7-10). Visual ﬁeld defects are associated with the areas of hypoplasia, notably in the peripapillary distribution. A hallmark of the disease is the presence of abnormal retinogeniculostriate projections of temporal nerve ﬁbers traveling to the contralateral hemisphere. One study indicated that there is no abnormality in visual ﬁeld testing associated with the projection abnormality.2 In pathologic studies, oculocutaneous albinism is associated with a reduction in the amount of melanin in melanosomes, whereas ocular albinism has a reduction in the total number of melanosomes. Oculocutaneous albinism is usually inherited in an autosomal recessive pattern, although ocular albinism is often X-linked. There are two systemic conditions associated with albinism—Chediak-Higashi syndrome, which is associated with increased susceptibility to infections, and Hermansky-Pudlak syndrome, which is common in children of Puerto Rican descent and is characterized by platelet abnormalities. It is important to clinically distinguish these two syndromes so that appropriate hematologic consultation can be arranged. Patients with cone dystrophy may present with a central ﬁeld defect (Figure 7-11).

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B Figure 7-5. Pathologic myopia. (A) and (B) Goldmann visual ﬁeld of right and left eye show central scotoma. (C) and (D) Fundus photo, right and left eye.

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Figure 7-5. (Continued)

7-5 INFLAMMATORY/INFECTIOUS DISEASES Inﬂammatory diseases can cause visual ﬁeld changes due to structural sequelae of the underlying inﬂammation, such as vitritis, macular edema, or optic disc edema. Lesions in the choroid and retina will also cause visual ﬁeld defects. Several of the “white dot syndromes” are associated with classic visual ﬁeld ﬁndings that help distinguish one from another. Multiple evanescent white dot syndrome (MEWDS) and acute zonal occult outer retinopathy (AZOOR) may present with an enlarged blind spot without evidence of optic disc edema.3,4 MEWDS is a unilateral acute-onset syndrome, often associated with a viral prodrome that presents with multiple white spots. Fluorescein angiography often demonstrates early punctate hyperﬂuorescence with a “wreathlike” conﬁguration that stains late. Symptoms usually resolve within 2 months. AZOOR, in contrast, may have few initial fundus ﬁndings but is characterized with an insidious, progressive loss of outer retinal function and irreversible ERG changes. Large visual ﬁeld defects may develop and correlate with late fundus ﬁndings of loss of RPE and attenuated vessels.5 Ocular histoplasmosis has a ﬁeld defect that is correlated with fundus histo lesions (Figure 7-12). Serpiginous choroidopathy often presents with subretinal lesions that begin in the peripapillary region and spread in a centrifugal fashion. The resulting “serpentine” lesions block early and stain late on ﬂuorescein angiography. Active lesions will present with absolute scotomas, which can involve central ﬁxation if the fovea is involved. Birdshot chorioretinopathy (BSCR) is a chronic uveitic condition that is characterized by bilateral yellowish ovoid spots in the mid periphery associated with a mild vitritis. Visual loss from BSCR often results from recurrent cystoid macular edema or progressive retinal dysfunction with constriction of the peripheral visual

A Figure 7-6. Diabetic macular edema. (A) HVF 24-2 of both eyes show nonspeciﬁc changes. (B) Fundus photo, right eye. (C) Fluorescein angiogram, left eye. Late phase shows diffuse leakage in macula with multiple microaneurysms and macular ischemia. (D) Stratus OCT shows retinal thickening with associated cystic spaces.

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A Figure 7-7. Central retinal vein occlusion (CRVO). (A) HVF 24-2, right eye, with inferior central depression. (B) Fundus photo, right eye. Note diffuse intraretinal hemorrhages and macular edema. (C) Fluorescein angiogram, right eye. Late phase shows enlarged foveal avascular zone with macular and perivascular leakage. (D) Stratus OCT shows cystoid macular edema.

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A Figure 7-8. Branch retinal vein occlusion (BRVO). (A) Branch retinal vein occlusion (BRVO). HVF 24-2, left eye, with superior depression. (B) Fundus photo, left eye. Intraretinal hemorrhages and exudates in inferior macula. (C) Stratus OCT. Note diffuse retinal thickening.

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A Figure 7-9. Choroideremia. (A) HVF 10-2, both eyes, with bilateral dense defects and relative central sparing. (B) and (C) Goldmann visual ﬁeld, right and left eye. (D) and (E) Fundus photo, right and left eye. Choroideremia is characterized by diffuse atrophy of the choriocapillaris, choroid, and retinal pigment epithelium.

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Figure 7-9. (Continued)

ﬁelds.6 Treatment with immunosuppressive medication can limit the visual ﬁeld loss and reduce the risk of developing cystoid macular edema.

7-6 TOXICITY Hydroxychloroquine (Plaquenil) toxicity may present with pigmentary changes or a bull’s-eye maculopathy on fundoscopic examination associated with a paracentral scotoma. While no gold standard for screening for hydrochloroquine toxicity exists, a standard panel of screening tools includes color vision testing, Amsler grid monitoring, fundoscopy, and Humphrey Visual Field Analyzer 10-2. Fluorescein angiography can help distinguish suspected cases of toxicity. Development of central or paracentral scotomas on Humphrey Visual Field Analyzer 10-2 is highly suspicious for hydroxychloroquine-related maculopathy, even if disruption of RPE is not detected on ophthalmoscopy or ﬂuorescein angiography. Because the scotomata are irreversible, there is often a low threshold to discontinue the medication. The usual recommendation is that patients with normal renal function take no more than 6.5 mg/kg/day, although the incidence of retinopathy at lower doses still exists. As a result, annual screening is very important to detect subtle changes. Other modalities that are being investigated include multifocal ERG testing, high-resolution optical coherence tomography (OCT), and preferential hyperacuity perimetry (PHP).

7-7 PERIPHERAL RETINA Peripheral retinal abnormalities can also cause visual ﬁeld changes. Retinal detachments will have relative ﬁeld defects that correlate with the area of

A Figure 7-10. Oculocutaneous albinism. (A) HVF 24-2, both eyes. Visual ﬁeld depression particularly prominent in peripapillary distribution. (B) and (C) Fundus photo, right and left eye, with areas of hypoplasia, notably in the peripapillary area. Note central hemorrhage in right eye.

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Figure 7-10 (Continued)

detachment. This is in contrast to retinoschisis, which cause an absolute ﬁeld defect (Figure 7-13). Peripheral tumors such as ocular melanoma can cause peripheral visual ﬁeld changes. Cancer-associated retinopathy (CAR) can cause retinal dysfunction and loss of peripheral and central vision without pigmentary changes. CAR is associated with a rapidly progressive loss of peripheral and central vision. Initial fundus ﬁndings can be minimal, often with arterial narrowing. ERG can show severe reduction of rod and cone responses. Eye symptoms can precede the diagnosis of the primary tumor and is often associated with small cell lung carcinoma. Melanoma-associated retinopathy (MAR) has a similar presentation of nonspeciﬁc visual ﬁeld changes

A Figure 7-11. Cone dystrophy. (A) Fundus photo, right eye. Fundus ﬁndings can include a subtle bull’s eye maculopathy. (B) HVF 24-2, right eye. Cone dystrophy often presents with central visual ﬁeld changes.

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A Figure 7-12. Ocular histoplasmosis (A) HVF 24-2, right eye, with nasal depression. (B) Ocular. Fundus photo, right eye. There is a central scar and peripapillary changes.

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A Figure 7-13. Retinoschisis. (A) Goldmann visual ﬁeld, with superior depression. (B) Fundus photo montage, left eye, with corresponding inferior retinoschisis.

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B Figure 7-13. (Continued)

that is speciﬁcally associated with malignant melanoma. Unlike CAR, MAR is often found in patients who have already been diagnosed with melanoma. In MAR, ERG ﬁndings can show a preserved a wave with loss of b waves. Both CAR and MAR are associated with antiretinal antibodies.

REFERENCES 1. Kaiser-Kupfer MI, Caruso RC, et al. Use of an arginine-restricted diet to slow progression of visual loss in patients with gyrate atrophy. Arch Ophthalmol. 2004;122:982–984. 2. Hoffman MB, Seufert PS, Schmidtborn LC. Perceptual relevance of abnormal visual ﬁeld representations: static visual ﬁeld perimetry in human albinism. Br J Ophthalmol. 2007;91:509–513. 3. Reddy CV, Brown J Jr, Folk JC, et al. Enlarged blind spots in chorioretinal inﬂammatory disorders. Ophthalmology. 1996;103:606–617. 4. Gross NE, Yannuzzi LA, Freund KB, et al. Multiple evanescent white dot syndrome. Arch Ophthalmol. 2006;124:493–500. 5. Fine HF, Spaide RF, Ryan EH Jr, et al. Acute zonal occult outer retinopathy in patients with multiple evanescent white dot syndrome. Arch Ophthalmol. 2009;127:66–70. 6. Thorne JE, Jabs DA, Kedhar SR, et al. Loss of visual ﬁeld among patients with birdshot chorioretinopathy. Am J Ophthalmol. 2008;145:23–28.

8 Optic Chiasm Field Defects CHRISTINE E. LIN AND JEFFREY G. ODEL, MD

8-1 HISTORY AND OVERVIEW The optic chiasm has been a topic of much interest since the ﬁrst century A.D., when Galen described the union of the optic nerves as a “shape…very much like the letter chi.”1 In the centuries that followed, many scientists and physicians studied the structural aspects of the optic chiasm, starting with Isaac Newton, who in 1706 ﬁrst explained that the partial decussation of the optic nerve ﬁbers was necessary for binocular vision.1 Abraham Vater and J.C. Heinicke provided the ﬁrst clinical evidence of hemidecussation in 1723, when they described cases of transient “halved vision” (homonymous hemianopia), presumably of migrainous origin, and concluded that the optic nerves decussate before uniting into the optic tracts because “without decussation of ﬁbers in these nerves divided vision can in no way be explained.”1 The ﬁrst diagram of decussating ﬁbers was published in 1750 by “Chevalier” John Taylor, an itinerant eye surgeon, notorious for his charlatan ways and a practice “deeply tainted with the dishonest arts of the quack.”2 In 1824, a century after Vater and Heinicke’s work on hemidecussation, William Wollaston reported experiencing two episodes of half vision in each eye. He concluded that this necessitated hemidecussation of the optic nerves at the chiasm.2 The growing body of knowledge of chiasmal anatomy and visual ﬁelds culminated in the work of Harvey Cushing on the diagnostic recognition and surgical management of pituitary tumors. In December 1901, a 16-year-old girl was referred to Cushing by Sir William Osler. She had headaches and loss of vision

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and was short, obese, and sexually underdeveloped, appearing as a child of 12. Cushing missed the possible connection of the patient’s symptoms and appearance to the chiasm and the pituitary. After the young girl developed papilledema, Cushing operated ﬁrst to decompress one cerebral hemisphere and then the other. When both operations failed to restore her vision, he operated a third time on the cerebellum, but the patient died several days later. At autopsy, a large pituitary cyst was discovered. Around the same time, Alfred Frohlich, a friend of Cushing’s from his research days, reported a similar patient from Vienna. Unlike Cushing, Frohlich made the correct localization, and the syndrome of obesity, retarded sexual development, and pituitary tumor was named after him. Embarrassed before his mentor, William Osler, Cushing then made the pituitary body and its relation to the chiasm, visual ﬁelds, and optic atrophy subjects of intense personal interest. He went from missing the diagnosis in 1901 to publishing the seminal work on the topic, The Pituitary Body and Its Disorders, in 1912. He also published a series of papers on visual ﬁelds and optic atrophy, several with his ophthalmologic colleague Clifford Walker. Through this work, Cushing contributed substantially to our current understanding of chiasmal lesions and their associated effects on the visual ﬁelds of patients.3 Evidence of chiasmal dysfunction alerts the ophthalmologist to an intracranial process causing visual loss, possibly neurologic and endocrine dysfunction, and in some cases, loss of life. Since intracranial mass lesions are the cause of the vast majority of chiasmal visual ﬁeld defects, variants of bitemporal hemianopia require the ophthalmologist to switch gears and inquire about endocrine, neurologic, and systemic symptoms and to obtain a scan of the chiasm or refer the patient to the appropriate consultant.

8-2 ANATOMY OF THE CHIASM 8-2-1 Gross Anatomy. The optic chiasm (transverse diameter of 10 to 20 mm, anteroposterior width of 4 to 13 mm, thickness of 3 to 5 mm) is located above the sella turcica at an incline between 15° and 45° from the horizontal.4,5 In 79% of people, the optic chiasm is located above the diaphragma sella, the dural covering of the sella turcica (Figure 8-1). The chiasm may also be positioned above the tuberculum sella in a “preﬁxed” position (Figure 8-2) (12%) or above the dorsum sella in a “postﬁxed” position (Figure 8-3) (4%).6,7 Depending on the position of the chiasm, a space of approximately 10 mm separates the chiasm from the diaphragma sella; variability in chiasm position partially accounts for the range of visual ﬁeld defects experienced by patients with upwardly expanding pituitary adenomas.8 Anterior to the chiasm is the chiasmatic cistern. Superiorly, the lamina terminalis extends upward from the chiasm to the anterior commissure. Laterally, the internal carotid arteries emerge from the cavernous sinuses pointed towards the posterior optic nerves and chiasm. Just posterior, the interpeduncular cistern contains the infundibulum descending through the diaphragma sella, the hypothalamus, and the third nerves as they emerge from the basis pedunculi. The third ventricle is also

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B Figure 8-1. Normal chiasm. The prechiasmal space is 8 mm long, and the tuberculum sella is 5 mm long. (A) Sagittal section of normal chiasm above diaphragma sella. (B) Photograph, top view. (Source: A redrawn by permission from Rhoton AL Jr, Harris FS, Renn WH. Microsurgical anatomy of the sellar region and cavernous sinus. In: Glaser JS, ed. Neuro-Ophthalmology Symposium of University of Miami and Bascom Palmer Eye Institute. St. Louis: CV Mosby; 1977:75–105. B reprinted by permission from Bergland RM, Ray BS, Tornack RM. Anatomical variations in the pituitary gland and adjacent structures in 225 human autopsy cases. J Neurosurg. 1968;28:93–99.)

present posteriorly; the proximity to the third ventricle explains the vulnerability of the chiasm to compression or inﬁltration by lesions within the ventricle or an expanded ventricle.4 The anterior cerebral and anterior communicating arteries of the circle of Willis course above the chiasm, while the posterior communicating arteries, the posterior cerebral arteries, and basilar artery pass below.9 Branches from all of these surrounding vessels supply the optic chiasm both superiorly and inferiorly, and there is often signiﬁcant collateralization, making chiasmal infarct a rare event (Figure 8-4A). Bergland and Ray theorized that the blood supply to the crossing

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B Figure 8-2. Preﬁxed chiasm. The prechiasmal space is 3 mm long, and the chiasm overlies the tuberculum sella. (A) Sagittal section of preﬁxed chiasm above tuberculum sella. (B) Photograph, top view. (Source: A redrawn by permission from Rhoton AL Jr, Harris FS, Renn WH. Microsurgical anatomy of the sellar region and cavernous sinus. In: Glaser JS, ed. Neuro-Ophthalmology Symposium of University of Miami and Bascom Palmer Eye Institute. St. Louis: CV Mosby; 1977:75-105. B reprinted by permission from Bergland RM, Ray BS, Tornack RM. Anatomical variations in the pituitary gland and adjacent structures in 225 human autopsy cases. J Neurosurg. 1968;28:93-99.)

ﬁbers of the chiasm is compromised by compression as in a pituitary adenoma, resulting in bitemporal hemianopia, which may be reversible if the compression is relieved early enough (Figure 8-4B).9 The proximity of these vessels can also produce other pathologic conditions. Aneurysms of the anterior cerebral and internal carotid arteries can impinge on the optic chiasm, producing visual loss. More uncommonly, the carotid arteries and the anterior cerebral arteries may produce pathologic grooving of the chiasm as they cross above.

8-2-2 Nerve Fiber Anatomy. A large percentage of both crossed and uncrossed chiasmal ﬁbers come from the macular region (Figure 8-5). These ﬁbers are generally

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B Figure 8-3. Postﬁxed chiasm. Prechiasmal space is 12mm long, and tuberculum sella is 6 mm long. Chiasm overlies dorsum sella. (A) Sagittal section of postﬁxed chiasm above dorsum sellae. (B) Photograph, top view. (Source: A redrawn by permission from Rhoton AL Jr, Harris FS, Renn WH. Microsurgical anatomy of the sellar region and cavernous sinus. In: Glaser JS, ed. Neuro-Ophthalmology Symposium of University of Miami and Bascom Palmer Eye Institute. St. Louis: CV Mosby; 1977:75–105. B reprinted by permission from Bergland RM, Ray BS, Tornack RM. Anatomical variations in the pituitary gland and adjacent structures in 225 human autopsy cases. J Neurosurg. 1968;28:93–99.)

located in the dorsal and central regions of the chiasm, and lesions affecting the anterior visual pathways can often be detected on automated perimetry, which tests the central 30° of vision.5 The proportion of crossed ﬁbers is greater than that of uncrossed ﬁbers, usually with a ratio of approximately 53 crossed to 47 uncrossed.10 Detailed microscopic anatomy of the ﬁber paths within the chiasm is based on a limited number of studies, typically with small numbers of specimens. Normal anatomy has been best studied in nonhuman primates and extrapolated to humans, where the conclusions may be fanciful. The crossed and uncrossed ﬁbers separate just as the ﬁbers reach the chiasm. Uncrossed ﬁbers continue laterally

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Figure 8-4. (A) The visual pathways pass through the circle of Willis. ACA = anterior cerebral arteries; PCA = posterior cerebral artery; BA = basilar artery; ICA = internal carotid artery. (B) The visual pathways distorted by pituitary tumor. (Source: Reprinted by permission from Bergland RM, Ray BS. The arterial supply of the human chiasm. J Neurosurg. 1969;31:327-334.)

Figure 8-5. A very substantial portion of the entire chiasm is composed of macular ﬁbers.

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through the chiasm into the ipsilateral optic tract and the lateral geniculate nucleus (LGN). Superior and inferior ﬁbers from the retina and nerve retain their orientation in the chiasm. Crossed ﬁbers from the upper nasal retinal quadrant cross dorsally in the posterior portion of the chiasm; crossed ﬁbers from the lower nasal quadrant tend to cross in the anterior portion of the chiasm (early-crossing ﬁbers). It was previously thought that some of the early-crossing ﬁbers from the inferonasal retina swept into the contralateral optic nerve in a structure known as “Wilbrand’s knee,” although recent experiments suggest that the crossed ﬁbers continue directly into the contralateral optic tract and LGN.11 In 1904 and 1915, Hermann Wilbrand reported his observations, based on two pathologic human specimens after long-standing monocular enucleation, of a bundle of optic nerve ﬁbers arising from the infranasal retina of the good eye, which traveled 1 to 2 mm into the contralateral atrophic optic nerve after entering the optic chiasm to decussate into the contralateral optic tract (Figure 8-6).12 He called these ﬁbers the “knee” of the optic chiasm and theorized that lesions compressing an optic nerve medially, just anterior to the chiasm, would result in a contralateral superior temporal visual ﬁeld defect due to injury to the “knee ﬁbers” from the contralateral optic nerve. He further theorized that the compression of the ipsilateral nerve would additionally result in an ipsilateral temporal defect or complete blindness. J. Lawton Smith expanded this concept in his popular lectures; he taught that in patients with decreased vision in one eye, the most important part of the workup was to check the other eye’s visual ﬁeld for an upper temporal defect.”19 This particular combination of visual ﬁeld loss due to a compression

Figure 8-6. Case E from Wilbrand showing a human chiasm sectioned horizontally after longstanding monocular enucleation of one eye. Nerves are at the bottom, and tracts are on top. The nerve on the right is atrophic following enucleation, showing knee ﬁbers marked K that come from the nerve on the left.

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of the optic nerve–chiasm junction is often referred to as an “anterior chiasmal syndrome”, and the upper temporal defect in the eye contralateral to the lesion is referred to as a “junctional scotoma.” Recent work suggests that Wilbrand’s knee is actually an artifact of mononuclear enucleation rather than a structural component of normal chiasmal anatomy. In 1997, Jonathan Horton reported a series of experiments in nonhuman primates and humans in which a radioactive tracer was injected into a single eye of both normal nonhuman primates and those that underwent mononuclear enucleation. No evidence of Wilbrand’s knee appeared in normal subjects; the “knee” could, however, be found to form after long-term mononuclear enucleation (more than 6 months). In his anatomic studies in humans, Horton found that at 6 months after enucleation, crossed ﬁbers from the intact eye were drawn closer to the junction of the atrophic optic nerve and the chiasm. At 27 months post-enucleation, a modest Wilbrand’s knee had formed, and by 28 years after enucleation, a well-developed Wilbrand’s knee of 1 to 2 mm could be seen.11 Horton’s work has since been supported by the notable absence of patients developing a junctional scotoma after surgical resection of the optic nerve at the nerve–chiasm junction.14 One possible explanation for the formation of Wilbrand’s knee is that the optic nerve atrophy following enucleation causes the optic chiasm to shrink, thereby shortening the distance traversed by normal decussating ﬁbers. As a result of their extra slack, the ﬁbers gradually herniate into the contralateral optic nerve. The “anterior chiasmal syndrome,” previously interpreted as compression of the “knee” ﬁbers is now speculated to occur from combined compression of the ipsilateral optic nerve and the body of the chiasm.

8-3 TESTS FOR FIELD DEFECTS Automated threshold perimetry has become the standard visual ﬁeld testing technique for diagnosis of chiasmal lesions. It affords several advantages, such as objectivity, reproducibility, and capacity for quantitative analysis. While useful, automated visual ﬁelds must be carefully interpreted in the context of the patient, and all test parameters, such as ﬁxation losses and false-positive and false-negative responses, need to be carefully considered. In patients with unreliable results from automated perimetry, confrontation testing, tangent screen, or Goldmann perimetry may be preferable. Testing with multifocal visual evoked potentials may provide an objective measure of visual ﬁeld function.15 Confrontation techniques remain an essential part of evaluating the patient and can reveal clues that suggest the diagnosis of a chiasmal disorder. Such ﬁndings include a patient’s missing temporal letters in each eye, color desaturation of the red Amsler grid in the temporal region, and corrected acuity of less than expected. Subtle central bitemporal hemianopia may be revealed by having the patient compare the relative redness of a red object, such as a red mydriatic bottle cap, across the vertical midline while ﬁxating the examiner’s nose at 1 or more meters. Other ﬁndings in the physical examination may suggest bitemporal ﬁeld defects such as chiasmatic post-ﬁxation blindness or hemiﬁeld slide phenomenon.16 Chiasmatic post-ﬁxation

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blindness occurs when the patient with bitemporal hemianopia converges his eyes to look at near. The object of interest is at the convergence of the optic axes of the two eyes, and if the optic axes are projected through the object of interest, they form a triangle beyond ﬁxation; the post-ﬁxational triangle is in the temporal ﬁeld of each eye. Thus, these patients may experience an area of blindness in the post-ﬁxational triangle. Patients experiencing this may report difﬁculty with precision tasks such as threading needles, and diminished depth perception, or may report that objects disappear in the area behind ﬁxation. Patients with bitemporal hemianopia may also experience hemiﬁeld slide phenomenon, a condition caused by the absence of a physiological linkage between their two nasal half ﬁelds. The difﬁculty in maintaining the two half ﬁelds juxtaposed is accentuated in the presence of exophoria, esophoria, or hyperphoria, which can respectively produce the intermittent perception of objects appearing to overlap, separate horizontally, or diverge vertically.

8-4 CHIASMAL VISUAL FIELD DEFECTS Starting at the anterior junction of the chiasm with the optic nerve and continuing along the chiasm, optic tract, geniculate body, optic radiation, and occipital lobe, the hallmark of visual pathway involvement on the visual ﬁeld is that the defect respects the vertical midline. This means that the defect is clear on one side and either normal or markedly better on the other side. A vertical step of neurologic origin does not slope across the vertical; that would be a sign of a retinal disorder or a disc anomaly. Vertical defects or steps reﬂecting chiasmal or further posterior visual pathway involvement typically demonstrate the greatest disparity immediately across the midline. On confrontation, the patient notes a distinct difference in the appearance of the stimulus as it immediately crosses the vertical midline. This is best demonstrated by moving the stimulus from the defective ﬁeld across the midline to the seeing ﬁeld. The classic presentation of damage to the optic chiasm is a bitemporal defect, but a variety of visual ﬁeld defects may suggest chiasmal involvement. 1. At the anterior angle of the chiasm, small lesions nasal to an optic nerve at the junction of the nerve and chiasm may produce an ipsilateral monocular temporal scotoma respecting the vertical midline. Harry Moss Traquair, who called it a “junctional scotoma,” ﬁrst identiﬁed this monocular temporal scotoma with careful tangent screen testing.17 It is now referred to as the “junctional scotoma of Traquair” (Figure 8-7).5 Traquair, who practiced prior to the availability of computed tomography, referred to these defects in 1927, saying, “I have termed this type ‘junction’ scotoma on account of the probable situation of the lesion at the junction of nerve and the chiasm.” He accounted for these lesions, theorizing that “[i]f on careful analysis hemianopic features are found, indicating that either the crossed or uncrossed macular ﬁbers are purely or mainly affected, it may be inferred that the lesion is situated at a point where these fasciculi are anatomically separated… .”

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A

B

C Figure 8-7. (A) Traquair’s illustration of a series of tangent screen visual ﬁelds from a patient with a resolving junctional scotoma. (B) Tangent screen visual ﬁeld demonstrating monocular central temporal defect in the left eye ipsilateral to a pituitary adenoma compressing the junction of left optic nerve and chiasm (junctional scotoma of Traquair). The right eye is normal. (C) Coronal MRI scan demonstrating the pituitary adenoma compressing the junction of the left optic nerve and chiasm causing the visual defect from B.

2. The other junctional scotoma syndrome is an upper temporal visual ﬁeld defect contralateral to a cecocentral scotoma or large central scotoma incorporating the blind spot or other optic nerve type defect. Prior to Horton’s work on Wilbrand’s knee, the upper temporal defect (scotoma) was attributed to injury to knee ﬁbers that were originating from the contralateral optic nerve. Since Horton, we believe the body of the chiasm and the optic nerve ipsilateral to

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the central defect are compressed. Whatever the anatomical point, one of the most important practical concepts in visual ﬁeld testing as emphasized by J. Lawton Smith is that in a patient with decreased vision in one eye, extra care should be taken to look for an upper temporal defect in the contralateral eye as this would localize the lesion to the anterior chiasmal region. (See Figure 8-10 for left eye demonstrating a junctional scotoma.) 3. Lesions affecting the body of the chiasm often produce bitemporal hemianopia that may be peripheral, central, or a combination of both with or without splitting of the macula (Figures 8-8 and 8-9). Visual acuity may or may not be affected.5 4. Lesions at the posterior angle of the chiasm typically produce bitemporal hemianopic scotomas. Lesions here may also involve the optic tracts and result in homonymous hemianopia.5,18 5. At the lateral aspect of the chiasm, compression from internal carotid artery aneurysms or other lesions can produce a distinctive pair of ﬁeld defects.

A Figure 8-8. (A) Humphrey 24-2 visual ﬁeld OS from patient with a craniopharyngioma compressing the body of the chiasm from below showing marked temporal defect which is densest below with intact foveal sensation. (B) Humphrey 24-2 OD from same patient as in A.

B Figure 8-8 (Continued).

Figure 8-9. Coronal T2-weighted MRI image of patient from Figure 8-8 demonstrating craniopharyngioma distorting the chiasm roughly in the midline.

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The eye ipsilateral to the lateral chiasmal compression has an upper and lower nasal defect and an inferior temporal defect, but the upper temporal ﬁeld is relatively spared because the ﬁbers from the ipsilateral inferior nasal retina have crossed early or anteriorly in the chiasm and have avoided the compression. The early-crossing ﬁbers from the contralateral eye have crossed already and are exposed to the compression (Figure 8-10).19

A Figure 8-10. (A) Humphrey 24-2 visual ﬁeld from the left eye of a patient with right lateral chiasmal compression from a meningioma demonstrating subtle upper temporal defect from compression of the early crossing ﬁbers, originating in the left inferior nasal retina, as they cross in the anterior chiasmal region. (B) Humphrey 24-2 visual ﬁeld from right eye of patient in A. This ﬁeld demonstrates an upper and lower nasal defect from compression of uncrossed ﬁbers originating in the right temporal retina passing through the chiasm laterally. It also demonstrates relative sparing of the upper temporal quadrant caused by sparing of the ﬁbers from the inferior nasal retinal that have crossed to the left anteriorly at the optic nerve junction and chiasm. (C) Axial T1-weighted MRI with contrast; bold arrow points to enhancing meningioma lateral to chiasm indicated by thin arrow.

B

C Figure 8-10. (Continued).

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8-5 CHIASMAL REGION LESIONS 8-5-1 Common Lesions Affecting the Optic Chiasm. Common lesions affecting the optic chiasm include the following: 1. 2. 3. 4. 5. 6.

Pituitary tumors Meningiomas Craniopharyngiomas Aneurysms Dilatation of the third ventricle Miscellaneous lesions: traumatic injuries, metastatic tumors, radiation necrosis, sarcoidosis, multiple sclerosis, arachnoid cysts, empty sella syndromes, and others (Table 8-1)4,20

8-5-2 Pituitary Tumors. Pituitary adenomas are the most common lesions occurring in the sellar region, accounting for 6-10% of all symptomatic intracranial tumors.21 Pituitary carcinoma is exceedingly rare. Secreting tumors, which secrete prolactin, growth hormone, adrenocorticotropic hormone, or thyroid-stimulating hormone, are frequently detected as endocrinopathies. Secreting tumors are therefore often diagnosed as microadenomas (less than 10 mm in greatest diameter).22 Visual symptoms are usually absent with prolactinomas and ACTH-secreting adenomas because these are typically diagnosed while they are small lesions.4 Growth hormone–secreting adenomas are less often detected as microadenomas and may present with accompanying visual ﬁeld deﬁcits. Last, thyrotroph adenomas, which are very rare, tend to be larger growths and more frequently associated with visual loss.4 Nonsecreting tumors often go undetected until they have grown large enough to produce secondary symptoms such as visual symptoms, headaches, or pituitary insufﬁciency. Pituitary adenomas characteristically produce bitemporal hemianopia, with ﬁeld defects initially occurring in the superior temporal quadrants as adenomas compress

Table 8-1. Chiasmal Region Lesions Traumatic

Iatrogenic

Intrinsic Lesions

Extrinsic Lesions

Motor vehicle accident Skull fracture

Radiation Surgical injury Fat packing Empty sella Dopamine agonists

Glioma Demyelination Chiasmal inﬂammation/ inﬁltration (sarcoidosis, leukemia, and lymphoma) Ganglioglioma Cavernoma Histiocytosis Ischemia

Pituitary adenoma Craniopharyngioma Meningioma Aneurysm Mucocele Lymphocytic hypophysitis Hydrocephalus Arachnoid cyst Epithelial cyst Dysgerminoma Metastasis

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the chiasm from below. As the compression continues, the inferior temporal ﬁelds may become involved. With time, the inferior nasal visual ﬁeld and ﬁnally the superior nasal visual ﬁeld become involved. Patients may present with reduced acuity and loss of color vision.5 As mentioned previously, loss of the bilateral temporal visual ﬁelds may also lead to postﬁxation blindness or hemiﬁeld slide phenomenon. Although the prognosis for the recovery of vision varies, marked improvement is seen in many patients within 24 hours after surgery.4 Pituitary apoplexy is a life-threatening condition characterized by headache, visual loss, ophthalmoplegia, and altered mental status, from hemorrhage into or infarction of a pituitary tumor or gland.23 Depending on the direction in which the hematoma or necrotic mass expands, patients may also present with stiff neck, fever, diabetes insipidus, adrenal insufﬁciency, seizure, or cerebrospinal rhinorrhea. Although the pathologic mechanism is not yet clearly understood, some authors have suggested that as a pituitary adenoma expands, it outgrows its blood supply, leading to ischemic necrosis and hemorrhage. Another theory posits that the tumor directly compresses the pituitary infundibulum and obstructs blood ﬂow from the portal vessels.23 However, because pituitary apoplexy is not relegated only to patients with evidence of pituitary adenomas, other mechanisms involving extrinsic factors such as abnormal vasculature, medications, procedures, or systemic diseases may play a role as well.

8-5-3 Meningiomas. Intracranial meningiomas represent about 20% of all primary intracranial tumors4 and have a signiﬁcant predominance in women. Meningiomas occurring in one of three regions may affect the chiasm: 1. Suprasellar (tuberculum sella meningiomas) 2. Suprachiasmatic (olfactory groove meningiomas) 3. Parasellar (sphenoid wing meningiomas)

8-5-3-1 Suprasellar Meningiomas. Suprasellar meningiomas constitute 3-10% of all meningiomas and usually arise from the dura overlying the chiasmatic sulcus or tuberculum sella.24 Visual loss is frequently bilateral and usually bitemporal, although variations in clinical presentation depend on the anatomic position of the chiasm in the individual patient and direction of extension of the particular tumor. Headaches are another common symptom accompanying visual loss. In 1930, Cushing described a syndrome of optic atrophy and bitemporal hemianopia where the sella turcica appeared normal on plain x-ray ﬁlm. This syndrome, known as “Cushing’s syndrome of the chiasm,” is often associated with suprasellar meningiomas but may also appear in patients with aneurysms and craniopharyngiomas.4,24 These tumors may compress the chiasm from below. The sella turcica on plain radiographs would appear normal because there was no tumor arising within it to expand it or erode an anterior clinoid process. However, with the advancement of neuroimaging (e.g., magnetic resonance imaging and computed tomography), abnormalities of the soft tissues in the sellar region are better appreciated.

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8-5-3-2 Suprachiasmatic Meningiomas. Olfactory groove meningiomas are slowly progressing tumors that often remain clinically silent until they reach a certain size. Along with a depressed sense of smell, olfactory groove meningiomas may also produce visual loss as the mass compresses the chiasm. In about 30-70% of cases, patients will also present with optic atrophy, which may be unilateral or bilateral and is often asymmetric.5,25 8-5-3-3 Parasellar Meningiomas. Meningiomas originating from the lesser wing of the sphenoid are particularly close to the optic chiasm and may cause visual ﬁeld defects even as small lesions.5 These tumors characteristically produce initial unilateral vision loss. As the mass expands, a temporal ﬁeld defect in the contralateral eye can also develop. 8-5-4 Craniopharyngiomas. Craniopharyngiomas are the most common type of nonglial intracranial neoplasm,26 having peak incidences in the ﬁrst to second decade and the sixth to seventh decade.27 Thought to arise from remnants of Rathke’s pouch, craniopharyngiomas are often located in the suprasellar region, although they may compress the optic chiasm from any direction depending on their size and location. In children, loss of vision is a frequent symptom associated with craniopharyngiomas (54%),28,29 but visual loss can go undetected because very little or no optic atrophy may be visible on fundus examination. The cystic structure of the craniopharyngioma may cause conduction block prior to axonal death, delaying the diagnosis until profound optic atrophy and irreversible loss of vision have occurred. This is one of the reasons why the visual ﬁeld examination, looking for variants of bitemporal hemianopia, is important in the workup of visual loss. Adult patients usually experience progressive visual loss over the course of months to years.5,28 The most typical pattern of visual loss in both children and adults is bitemporal hemianopia.29 Of note, the most common cause of optic tract homonymous hemianopia is craniopharyngioma. 8-5-5 Aneurysms. Intracranial aneurysms are usually found in the internal carotid artery (ICA) or the anterior circulation of the circle of Willis, often occurring at the junction of the ICA and the posterior communicating artery (40%), at the junction of the anterior cerebral artery and the anterior communicating artery (35%), and at the bifurcation of the middle cerebral artery (20%). Most aneurysms (90%) remain asymptomatic until the time of rupture. In the remaining 10% of cases, patients with unruptured aneurysms may present with paresis of the third nerve or visual loss from a “giant” aneurysm that is larger than 25 mm. Aneurysms compressing the third nerve are usually found at the junction of the ICA and the posterior communicating artery, whereas aneurysms from the anterior communicating artery may compress the optic nerve or optic chiasm to produce visual loss. This visual loss is usually unilateral and may be acute or progressive.30 Giant suprasellar aneurysms may cause lateral chiasmal compression as mentioned previously.

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8-5-6 Dilatation of Third Ventricle. Dilatation of the third ventricle may cause stretching of the chiasm and results in headache, papilledema, nausea/vomiting, or bitemporal ﬁeld defects. A number of conditions may obstruct outﬂow from the third ventricle, including such third ventricle tumors as colloid cysts.5 8-5-7 Miscellaneous Lesions. Other causes of chiasmal visual defects include intrinsic and inﬁltrative and inﬂammatory processes, such as gliomas, arteriovenous malformations, radiation necrosis, multiple sclerosis, sarcoidosis, and histiocytosis. These processes should also be kept in mind in the appropriate setting in the patient presenting with bitemporal hemianopia (see Table 8-1). 8-6 PSEUDO TEMPORAL AND BITEMPORAL HEMIANOPIA Visual ﬁeld defects that respect the vertical midline localize the causative lesion to the junctional region of the anterior chiasm, chiasm, optic tract, geniculate body, optic radiation, or occipital lobe. Bitemporal hemianopia that respects the vertical midline as discussed in this chapter indicates chiasmal dysfunction. The clinician, when faced with apparent vertical steps or vertical visual ﬁeld cuts, must inspect the ﬁeld defect for strict respect for the vertical. Abnormalities that affect the nasal retina may on superﬁcial inspection appear to give temporal visual ﬁeld defects, but if the defect is carefully inspected, it may be found that it slopes across or towards the vertical midline or does not even closely approach the midline. Retinal problems such as nasal retinal detachment, sectoral pigmentary retinal degeneration, acute idiopathic blind spot enlargement syndrome, acute zonal occult outer retinopathy, and multiple evanescent white dot syndrome may present with relative temporal defects or defects that slope across or toward the vertical midline. Congenital and acquired disorders of the optic nerve such as tilted discs, optic nerve colobomas, morning glory discs, papilledema, and pseudopapilledema may cause visual defects that are temporal and related to an enlarged optic nerve or to a refractive change.

REFERENCES 1. Glaser J. Romancing the chiasm: vision, vocalization, and virtuosity. J Neuro-ophthalmol. 2008;28:131–143. 2. Rucker C. The concept of a semi-decussation of the optic nerves. AMA Arch Ophthalmol 1958;59:159–171. 3. Fulton JF. Harvey Cushing: A Biography. Springﬁeld, Ill: Charles C Thomas; 1946. 4. Miller N, Newman NJ, Biousse V, Kerrison JB, eds. Walsh and Hoyt’s Clinical Neuroophthalmology. Philadelphia: Lippincott Williams & Wilkins; 2005. 5. Anderson JR, et al. Neurology of the pituitary gland. J Neurol Neurosurg Psychiatry. 1999;66:703–721. 6. Bergland RM, Ray BS, Torack RM. Anatomical variations in the pituitary gland and adjacent structures in 225 human autopsy cases. J Neurosurg. 1968;28:93–99. 7. Schaeffer J. Some points in the regional anatomy of the optic pathway, with especial reference to tumors of the hypophysis cerebri: and resulting ocular changes. Anat Rec. 1924;28:243–279.

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8. Walker A. The neurosurgical evaluation of the chiasmal syndromes. Am J Ophthalmol. 1962;54:563–581. 9. Bergland RM, Ray BS. The arterial supply of the human optic chiasm. J Neurosurg. 1969;31:327–334. 10. Kupfer C, Chumbley L, et al. Quantitative histology of optic nerve, optic tract and lateral geniculate nucleus of man. J Anat. 1967;101(Pt 3):393–401. 11. Horton J. Wilbrand’s knee of the primate optic chiasm is an artefact of monocular enucleation. Trans Am Ophthalmol Soc. 1997;95:579–609. 12. Wilbrand H, Saenger A. Die Neurologie Des Auges: III- 1 and VI. Weisbaden: Verlag Von J.F. Bergman; 1904, 1915. 13. Lawton Smith J. Neuro-Ophthalmology Tapes. http://library.med.utah.edu/NOVEL/ Smith/ 14. Lee J. Wilbrand’s knee: does it exist? Surg Neurol. 2006;66:11–17. 15. Seiple W, Holopigian K, et al. The multifocal visual evoked potential: an objective measure of visual ﬁelds? Vision Res. 2005;45:1155–1163. 16. Kirkham TH. The ocular symptomatology of pituitary tumours. Proc R Soc Med. 1972;65:517–518. 17. Traquair HM. An Introduction to Clinical Perimetry. London: Henry Kimpton; 1927. 18. Foroozan R. Chiasmal syndromes. Curr Opin Ophthalmol. 2003;14:325–331. 19. Berson EL, Freeman MI, Gay AJ. Visual ﬁeld defects in giant suprasellar aneurysms of internal carotid. Arch. Ophthal. 1966;76:52–58. 20. Mejico LJ, Miller RN, et al. Clinical features associated with lesions other than pituitary adenoma in patients with an optic chiasmal syndrome. Am J Ophthalmol. 2004;137:908–913. 21. Ironside J. Pituitary gland pathology. J Clin Pathol. 2003;56:561–568. 22. Aron DC, Tyrrell JB, et al. Pituitary tumors. Current concepts in diagnosis and management. West J Med. 1995;162:340–352. 23. Biousse V, Newman NJ, et al. Precipitating factors in pituitary apoplexy. J Neurol Neurosurg Psychiatry. 2001;71:542–545. 24. Cushing H. The chiasmal syndrome of primary optic atrophy and bitemporal ﬁeld defects in adults with a normal sella turcica. Arch Ophthalmol. 1930;3:505–551. 25. Bakay L. Olfactory meningiomas: the missed diagnosis. JAMA. 1984;251:53–55. 26. Ohmori K, Collins J, et al. Craniopharyngiomas in children. Pediatr Neurosurg. 2007;43:265–278. 27. Stripp DCH, Maity A, et al. Surgery with or without radiation therapy in the management of craniopharyngiomas in children and young adults. Int J Radiat Oncol Biol Phys. 2004;58:714–720. 28. Bartlett JR. Craniopharyngiomas: a summary of 85 cases. J Neurol Neurosurg Psychiatry. 1971;34:37–41. 29. Karavitaki N, Brufani C, et al. Craniopharyngiomas in children and adults: systematic analysis of 121 cases with long-term follow-up. Clin Endocrinol. 2005;62:397–409. 30. Biousse V, Mendicino ME, et al. The ophthalmology of intracranial vascular abnormalities. Am J Ophthalmol. 1998;125:527–544.

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9 Optic Tract and Lateral Geniculate Body Field Defects THOMAS R. HEDGES III, MD

9-1 OPTIC TRACT FIELD DEFECTS Lesions affecting the optic tracts can cause a variety of neuro-ophthalmic signs. Not only are the visual ﬁeld defects distinctive, but they are also associated with ﬁndings that encompass pupillary physiology and retinal nerve ﬁber anatomy as well as central and peripheral ocular motor function. For example, a patient with a lesion in the region of an optic tract might have: incongruous, macular splitting hemianopia, the details of which require careful performance and interpretation of the visual ﬁelds; band atrophy of the optic nerve and retinal nerve ﬁber layer; a relative afferent pupillary defect; and a third nerve palsy. Indeed, much of neuroophthalmology can be learned from a thorough understanding of lesions involving the optic tracts.1,2 Therefore, a review of the neuro-anatomy of this region is very important. After the ﬁbers of the retinal ganglion cells decussate in the chiasm, they pass into the optic tract. The pupillary ﬁbers leave the tract before the lateral geniculate body and travel to the midbrain. On magnetic resonance imaging (MRI) scans the hilum of the lateral geniculate nucleus (LGN) can be seen where it abuts the lateral recess of the ambient cistern. The lateral and superior borders of the LGN are sharply deﬁned by the white matter of the optic radiations.3 As the visual ﬁbers make their way through the tract, there is a 90° nasal rotation. As a result, the two groups of homonymous ﬁbers from both upper retinas, which represent the lower ﬁeld, rotate to a medial position in the tract. The lower homonymous retinal ﬁbers rotate laterally. The macular ﬁbers (which are the vast majority) occupy a

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wedge-shaped area between the medial and lateral portions. The ﬁbers from the corresponding retinal areas begin to associate themselves as they progress through the optic tract. The midbrain is nearby and the third cranial nerve lies just below the optic tract. Because of this imperfect match of corresponding retinal areas from each eye in the tract, the ﬁeld defects due to lesions affecting the optic tract are incongruous— that is, the defect is different in each eye when demonstrated by the same-size test object (Figures 9-1 and 9-2). As mentioned in Chapter 1, congruity is always measured by performing central ﬁelds, rather than peripheral ﬁelds; in homonymous defects, the nasal ﬁeld of one eye is always smaller than the homonymous temporal ﬁeld of the other eye. If the peripheral ﬁeld were used to measure incongruity, all homonymous ﬁeld defects would be incongruous no matter where the defect was located. A complete homonymous ﬁeld defect caused by an optic tract lesion is no different from such a defect in the optic radiation and is indistinguishable on that basis alone. In a total hemianopia, congruity cannot be evaluated; it can be tested only if the defect is not complete. Wernicke’s hemianopic pupillary sign is a real sign of optic tract disease, but it cannot be reliably produced. Because pupilary ﬁbers are in the tract, it would seem reasonable that not only visual ﬁbers but also pupillary ﬁbers would be affected. Wernicke4 postulated that a light shone into the hemianopic side of the retina would produce a defective pupillary response that would not be present if the light

A

B Figure 9-1. (A) Tangent screen depicting a defect to a 1-mm white test object is different in each homonymous ﬁeld, representing incongruity from an optic tract lesion. (B) Similar ﬁndings involving the left hemiﬁeld from a different patient with an optic tract lesion demonstrated by automated perimetry.

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A

B Figure 9-2. (A) Automated visual ﬁelds showing incongruous right hemianopia from a 38-year-old man found to have vision loss out of proportion to keratoconus by cornea specialist. (B) MRI showing a pituitary adenoma as the cause.

were shone into the side of the retina where the normal ﬁeld was located. This is something that can be demonstrated with special light, but it is impractical and difﬁcult to show in a clinical setting. However, a relative afferent pupillary defect contralateral to the lesion can be found in most cases.1,2 A relative afferent pupillary defect is more easily found when the asymmetry between the two eyes is at its greatest. This is the best way to clinically differentiate an optic tract lesion from a lesion in the lateral geniculate body. Many years ago, Behr5 postulated that if an optic tract were involved, more pupillary ﬁbers from the contralateral eye would be affected, resulting in a larger

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contralateral pupil. Because there is equal output from the Edinger-Westfall nucleus, this is unlikely and such pupil size inequality has not been reliably seen in optic tract disease. There is the possibility of pupillary size asymmetry if a lesion affecting an optic tract is large enough to affect the sympathetic ﬁbers in the midbrain or if it were to compress the nearby third cranial nerve. Optic tract lesions can produce speciﬁc ophthalmoscopic ﬁndings. Because the tract has ﬁbers from both eyes, any retrograde atrophy will be seen in both optic nerve heads.6 The atrophy, however, will be on the temporal side of the ipsilateral eye and on the nasal side of the contralateral eye—which is usually a striking asymmetric type of atrophy. This type of band atrophy can be seen using red-free light7 during ophthalmoscopy or fundus photography. It is also nicely demonstrated by optical coherence tomography either with retinal nerve ﬁber analysis or by retinal thickness measurements8 (Figure 9-3). Other associated ﬁndings include pyramidal tract signs, as well as hemianesthesia ipsilateral to the hemianopia. These are similar to ﬁndings seen in patients with lateral geniculate body visual ﬁeld defects (see later). The most common causes of optic tract lesions are pituitary tumors (Figure 9-2), craniopharyngiomas, and meningiomas of the skull base. Aneurysms of the posterior part of the circle of Willis can compress the optic tract. Occasionally, tumors from the medial portion of the temporal lobe compress the tract. Rarely, optic tract neuritis occurs as a result of demyelinating disease9 (Figure 9-4). Various infections can affect the optic tract including bacterial and fungal abscesses as well as cytomegalovirus and cryptococci.

A Figure 9-3. (A) Automated visual ﬁelds from a 30-year-old nurse who developed memory loss and fatigue showing incongruous left homonymous hemianopia. (B) Optical coherence tomography (OCT) showed a pattern consistent with band optic atrophy. (C) MRI showing a craniopharyngioma causing the ﬁndings.

B

C Figure 9-3. (Continued)

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A

B Figure 9-4. (A) Automated visual ﬁelds from a 41-year-old man who noted a left homomymous visual ﬁeld defect to the left 4 years after having had optic neuritis. (B) Computed tomography scan showing a probable demyelinating lesion involving the right optic tract.

9-2 LATERAL GENICULATE BODY FIELD DEFECTS As stated previously, the optic tract ﬁbers, which rotate nasally 90° and which represent upper retinal ﬁbers (lower ﬁeld), make their way to the medial part of the lateral geniculate body. Those from the lower quadrants move to the lateral part of the lateral geniculate body. The macular ﬁbers are wedged in between. Although the lateral geniculate body is rarely the site of an isolated ﬁeld defect, lateral geniculate anatomy allows for lesions affecting it to result in some very interesting visual ﬁeld defects.

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Of the six layers of the lateral geniculate body, layers 1, 4, and 6 receive crossed retinal ﬁbers from the contralateral eye, whereas layers 2, 3, and 5 receive uncrossed ﬁbers from the ipsilateral eye. Corresponding retinal areas are vertically represented as well and include all six layers.10,11 This gives a three-dimensional representation of the ﬁelds in the lateral geniculate body. Because the layers are not exactly alternating and because a lesion could also affects more bands coming from one eye than the other, visual ﬁeld defects from partial lesions of the lateral geniculate body are not congruous, and they tend to have a sectoral quality.12-15 When the lateral geniculate body is affected, frequently the damage is partial, with some layers being affected more than others16 because two separate arteries supply it. The anterior and lateral aspects of the nucleus and anterior ﬁbers are supplied by the anterior choroidal artery. Occlusion of that artery produces an upper and a lower sector defect (Figure 9-5).

A

B Figure 9-5. Occlusion of the anterior choroidal artery produces and loss of the upper and lower quadrants, with sparing of the central part of the visual ﬁeld and is the same to all test objects in this case. (A) Goldmann representation. (B) Automated representation.

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The remainder of the nucleus, which receives primarily macular input, is supplied by the lateral choroidal artery and occlusion of that artery produces a homonymous horizontal “sectoranopia”14,17-19 (Figure 9-6). These defects are usually incongruous, but congruous lesions have been found in a few cases.15,17,20,21 Lesions of the optic radiations can mimic a geniculate lesion.18 Involvement of the medial portion of the lateral geniculate body produces a congruous homonymous lower quadrantanopia to the opposite side. Similar involvement of the lateral portion produces a congruous homonymous upper quadrantanopia to the opposite side.19 Involvement of the pyramidal tracts nearby the lateral geniculate body may produce associated contralateral weakness. Concomitant effects on the thalamus may produce a hemianesthesia or, on rare occasions, Déjérine-Roussy syndrome (pain, dysesthesia, paresthesia). In addition to atherosclerotic occlusion, the branches of the posterior cerebral and anterior choroidal arteries can be compressed

A

B Figure 9-6. Occlusion of the lateral choroidal artery produces loss of the central ﬁeld up to the ﬁxation point and spares the upper and lower quadrants. (A) Goldmann representation. (B) Automated representation.

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as they pass between the hippocampal gyrus and the base of the lateral geniculate body, and these vessels can be compressed by the ﬁrm tentorial edge, either by a tumor displacing the brain or by brain swelling from trauma or hypoxia.

REFERENCES 1. Newman SA, Miller NR: Optic tract syndrome: neuro-ophthalmologic considerations. Arch Ophthalmol. 1983;101:1241–1250. 2. Savino PJ, Paris M, Schatz NJ, et al: Optic tract syndrome: a review of 21 patients. Arch Ophthalmol. 1978;96:656–663. 3. Horton JC, Landau K, Maeder P, Hoyt WF. Magnetic resonance imaging of the human lateral geniculate body. Arch Ophthalmol. 1990;47:1201–1206 4. Wernicke C: Ueber hemiopische Pupillen-reaction. Fortschr Med. 1883;1:49–53. 5. Behr C: Die Untersuchungsmethoden, II: die Lehre von Pupillenbewegungen. In: Graefe A, Saemisehe I, eds: Handbuch der gesamtem Augenheilkunde. Leipzig: Engelmann; 1924:115–117. 6. Hoyt WF, Rios-Montenegro EN, Behrens MM, et al: Homonymous hemioptic hypoplasia: fundoscopic features in standard and red-free illumination in three patients with congenital hemiplegia. Br J Ophthalmol. 1972;56:537–545. 7. Hoyt WF, Schlicke B, Eckelhoff RS: Fundoscopic appearance of a nerve-ﬁbre-bundle defect. Br J Ophthalmol. 1972;56:577–583. 8. Vedel-Jensen N: Optic tract neuritis in multiple sclerosis. Acta Ophthalmol. 1959; 37:537. 9. Moura FC, Medeiros FA, Montiero MLR. Evaluation of macular thickness measurements for detection of band atropy of the optic nerve using optical coherence tomography. Opthalmology. 2007;114:175–181. 10. Minkowski M: Über den Vertauf die endigung und die zentrale Repräsentation von gekreuzten und ungerkreuzten schnerven Fasern bei einigen Saugertieren und beim Menschen. Schweiz. Arch Psychiatr Nervenkr. 1920;6:201–252; 1921;7:268–303. 11. Mackenzie I, Meighan S, Pollock EN: On the projection of the retinal quadrants on the lateral geniculate bodies and the relationship of the quadrants to the optic radiations. Trans Ophthalmol Soc UK. 1933;53:142–169. 12. Gunderson CH, Hoyt WF: Geniculate hemianopia: incongruous homonymous ﬁeld defects in two patients with partial lesions of the lateral geniculate nucleus. J Neurol Neurosurg Psychiatry. 1971;34:1–6. 13. Fite DJ: Temporal lobe epilepsy: association with homonymous hemianopsia. Arch Ophthalmol. 1967;77:71–75. 14. Smith JL, Nashold BS, Kreshoan MJ: Ocular signs after stereotactic lesions in the pallidum and thalamus. Arch Ophthalmol. 1961;65:532–535. 14. Shacklett DE, O’Connor PS, Dorwart RH, et al: Congruous and incongruous sectoral visual ﬁeld defects with lesions of the lateral geniculate nucleus. Am J Ophthalmol. 1984;98:283–290. 16. Lindenberg R, Walsh FB: Vascular compressions involving intracranial visual pathways. Trans Am Acad Ophthalmol Otolaryngol. 1964;68:677–694. 17. Frisén L: Quadruple sectoranopia and sectorial optic atrophy: a syndrome of the distal anterior choroidal artery. J Neurol Neurosurg Psychiatry. 1979;42:590–594. 18. Carter JE, O’Connor P, Shacklett D, et al: Lesions of the optic radiations mimicking lateral geniculate nucleus visual ﬁeld defects. J Neurol Neurosurg Psychiatry. 1985;48:982–988.

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19. Helgason C, Caplan LR, Goodwin J, Hedges TR. Anterior choroidal artery-territory infarction. Arch Neurol. 1986:43:681–686. 20. Frisén L, Holmegaard L, Rosencrantz M: Sectorial optic atrophy and homonymous, horizontal sectoranopia: a lateral choroidal artery syndrome? J Neurol Neurosurg Psychiatry. 1978;41:374–380. 21. Donahue SP, Kardon RH, Thompson HS: Hourglass-shaped visual ﬁelds as a sign of bilateral lateral geniculate myelinolysis. Am J Ophthalmol. 1995;119:378–380.

10 Retrogeniculate Visual Field Defects THOMAS R. HEDGES III, MD

10-1 TESTING FOR RETICULOGENICULATE VISUAL FIELD DEFECTS Automated perimetry has changed visual ﬁeld testing considerably in recent years. What was considered an art has become an exercise in interpreting a set of data points obtained mechanically. Automated perimetry saves ophthalmologists time, which ideally should allow for more visual ﬁelds to be obtained on patients with unexplained vision loss. However, one must still keep in mind that automated perimetry still depends on the subjective responses from the patient. More important, automated perimetry has made interpretation of visual ﬁeld defects, especially those due to occipital lesions, more difﬁcult.1 For example, macular sparing may not be reﬂected, especially with programs limited to the central 24° or 30°. A 10° ﬁeld may be required to show macular sparing. Also, sparing or involvement of the temporal crescent will not be shown with 24° or 30° visual ﬁelds. The limitation of most programs may lead to the appearance of incongruity when in fact the ﬁeld is indeed congruous. Sometimes, a small homonymous hemianopic scotoma will be detected when one eye is tested but will be completely missed when the other eye is tested, giving the false impression that the visual loss is monocular. This is especially problematic if the patient also falsely interprets his or her homonymous loss of vision as monocular. Such individuals may complain of loss of vision in one eye when in fact it is one half of their visual ﬁeld that is defective. The strategy of automated testing on either side the vertical and horizontal meridians may lead to the false impression that ﬁeld defects respect the vertical or horizontal meridian when they do not.

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Automated perimetry should make it possible to test more patients with unexplained vision loss, but all automated visual ﬁelds must be interpreted with caution and, when necessary, substantiated with some other method, such as the tangent screen, which remains the most powerful method of detecting the size, shape, and density of visual ﬁeld defects. Because most ophthalmologists no longer use tangent screen testing, at least an Amlser grid should be used to qualify the nature of a paracentral visual ﬁeld defect.

10-2 LOCALIZATION AND CONGRUITY OF OPTIC RADIATION AND CALCARINE CORTEX VISUAL FIELD DEFECTS Localizing the site as well as cause of a lesion in the optic radiations and occipital lobe depends on certain characteristics of the visual ﬁeld as well as associated neurological signs and symptoms. In one series of 100 consecutive cases of homonymous hemianopia, 24% were due to lesions in the temporal lobe, 33% were due to lesions in the parietal lobe, 39% were due to lesions in the occipital lobe, and the remaining 4% were due to lesions in the optic tract and the lateral geniculate body.2 In a later series of 104 cases, occipital lobe cases accounted for 62%.3 Tumors occurred in 18% of the occipital lobe cases,3 as opposed to only 3% in a previous series.2 There were also differences in the incidence of congruity and in sparing versus splitting. The fact that the investigators used different patient selection techniques may have caused differences in the results. One can conclude that the exact cause and anatomic location may not always be ascertained merely by conducting the ﬁeld, ﬁnding a homonymous hemianopia, and depending on statistical guidelines. In each of the three lobes through which the visual ﬁbers pass, there are not only speciﬁc characteristics of the hemianopia but other neurologic signs that may help in localizing the responsible lesion. A complete homonymous hemianopia has only lateralizing value. Loss of the left half of the ﬁeld of each eye signiﬁes loss of function of the right half of the visual pathway somewhere behind the chiasm but gives no more information than that. Figure 10-1 shows the perimetric ﬁelds of a patient who had a vascular infarction of the left occipital lobe. All this chart discloses, however, is that the right half of the visual pathway is completely interrupted by the lesion. It gives no information as to whether the difﬁculty lies in the tract, the radiation, or the occipital lobe. Some of the characteristics of hemianopias that have localizing value include congruity and the presence or absence of macular sparing. It should be noted that, with the almost constant use of automated perimetry in current use, many of the subtleties of classic perimetry, either Goldmann or tangent screen, are not usually seen, or they are less apparent. When judging whether a ﬁeld defect is congruous or incongruous, the defect must be incomplete. If it is complete, any test object, large or small, will show the same complete, homonymous hemianopic ﬁeld defect as demonstrated in Figure 10-1. Looking at the peripheral ﬁeld in Figure 10-2, one’s initial impression might be of “incongruity,” because one half-ﬁeld is about two times the size of the defect in the other eye. To determine of there is congruity, the ﬁeld defect must spare some

A

B Figure 10-1. A right homonymous hemianopia is the same to all test objects; it is absolute. It can be seen in complete lesions of the optic tract, lateral geniculate body, optic radiation, or visual cortex. Under these conditions and with splitting of the macula, there are no distinguishing features to localize the ﬁeld defect to any one of these anatomical locations. (A) Tangent screen representation. (B) Computerized representation.

A

B Figure 10-2. Peripheral ﬁelds from both eyes were performed with a 1-mm white test object. The homonymous ﬁeld in the right eye is larger than the ﬁeld from the left eye and appears to be incongruous. However, this is only apparent; the temporal visual ﬁeld of the right eye is normally larger than the right nasal visual ﬁeld. (A) Tangent screen representation. (B) Computerized representation.

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of the peripheral visual ﬁeld (Figure 10-3). With automated perimetry, it is often difﬁcult to judge congruity, unless the patient is very good at performing visual ﬁeld testing. Occasionally, even with the best intentions, limitations inherent in the automated visual ﬁeld program may create the false impression of incongruity, and an alternate method of visual ﬁeld testing may be required.1 The issue of whether lesions of the anterior retrochiasmal visual pathways were less congruent than lesions near the occipital lobe was addressed in one study in which incongruent homonymous hemianopia was found in about one third of the occipital cases, in

A

B Figure 10-3. (A) Automated visual ﬁelds from a patient who underwent resection of a temporal lobe tumor showing left incongruous superior quadrantanopia. (B) MRI showing the surgical defect in the right temporal lobe.

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about two thirds of optic radiation lesions, and in less than half of optic tract lesions. However, in this study, only automated and technician Goldmann visual ﬁelds were used, again indicating the importance of judging the quality of visual ﬁelds with caution.4 Retrochiasmal visual ﬁeld defects are generally expected to respect the vertical meridian. Occasionally, one encounters a patient whose ﬁeld is canted several degrees away from the vertical meridian either superiorly or inferiorly. This ﬁnding is frequently ignored or explained by a muscle imbalance or a shifting of the patient’s eyes. One observer concluded that the shifting of the vertical hemianopic line was not an artifact but a true ﬁnding, that it is unlikely that the developmental process would consistently separate the retina in the same place in everyone, and that some variations of the vertical meridian are likely.5 With automated perimetry, one also ﬁnds ﬁelds that are shifted slightly into the normal hemiﬁeld. This is an artifact of ﬁxation in most cases.

10-3 TEMPORAL LOBE FIELD DEFECTS The ﬁbers emerging from the ventrolateral portion of the lateral geniculate body form the lower ﬁbers of the optic radiation in the temporal lobe. A lesion in these ﬁbers produces a defect in the upper ﬁeld. The ﬁbers enter the temporal lobe, turn rostrally, and spread out around the anterior tip of the lateral ventricle, forming Meyer’s loop. This loop of visual ﬁbers varies considerably from person to person. In one relatively recent study, it was determined that there is at least 20 cm from the anterior temporal lobe cortex to the anterior portion of Meyer’s loop.6 In another study, the anterior limit of Meyer’s loop was found to be 24 to 28 mm from the anterior temporal pole and there was involvement of the lower quadrant when resections reached 70 to 79 mm.7 The ﬁbers continue around the lateral aspect of the ventricle and enter the calcarine cortex. The ﬁbers emerging from the dorsomedial aspect of the lateral geniculate body take a different route in the temporal lobe. They do not spread out but rather travel as a thin bundle medially over the horn of the ventricle and enter the upper portion of the calcarine cortex. These ﬁbers subserve the lower ﬁelds and the monocular temporal crescent. They also subserve the central ﬁelds and come to lie in the middle third of the radiation. The difference in course, as well as the location of the two groups of ﬁbers, is important in appreciating the characteristic way in which a temporal lobe ﬁeld defect develops. The typical ﬁeld defect caused by a lesion in the temporal lobe is a homonymous, upper altitudinal, incongruous quadrantanopia (see Figure 10-3). This has been called a “pie-in-the-sky” defect. The defect is sector shaped and begins in the upper quadrants. The defect is always densest at the upper vertical meridian.8-10 Because the majority of tumors of the temporal lobe begin in the anterior tip, a patient may have symptoms of temporal lobe disease without interference with the ﬁbers of Meyer’s loop. Repeated experiments measuring visual ﬁelds before and after temporal lobectomy have shown that a signiﬁcant lesion may exist in the anterior tip of the temporal lobe without even the most subtle ﬁeld defect. When a defect

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does occur, it is densest at the vertical meridian, and the apex of the defect points toward the ﬁxation point (see Figure 10-3). If the initial test object does not show that the defect reaches the ﬁxation point, smaller or more subtle test objects will enlarge the defect toward ﬁxation. The Chamlin step technique (see Chapter 1) is valuable in situations where the defect is subtle and splits the vertical meridian and, thus, is useful in temporal lobe disease (see Figures 1-19 and 1-20 in Chapter 1). If the Chamlin step is suggestive, but not conclusive, of a defect with small white test objects, the use of red test objects may further enlarge the defect (see Figure 1-21). Because the ﬁbers of Meyer’s loop spread out, the ﬁeld defect progresses through the upper quadrant of the ﬁeld in a stepwise fashion.11 The ﬁbers of the lower ﬁeld, which are in a tight bundle, are affected as a group. The ﬁeld in the lower quadrant is lost as a unit—a phenomenon that differentiates the defect from one in the upper quadrant, where-the ﬁeld is lost progressively from the vertical meridian down to the horizontal raphe. The pace of loss of the lower quadrant is different from that of the upper quadrant because of a difference in anatomy, rather than a difference in the growth of the tumor (Figure 10-4). Most temporal lobe visual ﬁeld defects are incongruous. The nasal defect tends to be about 15% greater than the temporal defects for all degrees of quadrantanopia.7 One reason for this may be that the ﬁbers leaving the lateral geniculate body rearrange themselves into an incongruous pattern. As the ﬁbers proceed farther into the optic radiation, they rearrange themselves again into a congruous pattern.12 Another possibility is that, when temporal lobe tumors cause incongruous ﬁeld defects, they do so by pressing medially on the optic tract. Thus, the ﬁeld defect results more from the tract than from the temporal lobe radiation. Many ﬁeld defects in temporal lobe disease have sloping margins, which are indicative of lack of proximity of ﬁbers from corresponding points in the two visual ﬁelds in the temporal lobe as opposed to the calcarine cortex, and perhaps also due to the higher incidence of tumors, which cause more diffuse damage than vascular lesions.2,3 Temporal lobe lesions are accompanied by other neurologic deﬁcits. If an infarction of the dominant hemisphere involves the posterior limb of the internal capsule and the temporal isthmus, not only will there be a hemianopia but also agraphia, alexia, hemiplegia, and a supranuclear type of facial weakness. The aphasia may mask some of the other signs, as well as the hemianopia; in that situation, only the threat type of ﬁeld testing may suggest a defect. If the infarction involves a similar area on the nondominant hemisphere, hemianopia and hemiplegia also occur, as well as anosognosia (the inability to recognize which side of the body is involved). It is important to elicit other signs of temporal lobe disease when trying to localize a hemianopic ﬁeld defect that is not entirely diagnostic on its own. For example, if the lesion is limited to the temporal lobe, the optokinetic nystagmus (OKN) response will be normal.13 Hallucinations are not infrequent in temporal lobe lesions and, theoretically, are usually formed; those occurring in the occipital lobe are unformed, as are those seen in the scintillating scotomas of the migraine syndrome. However, visual hallucinations can be produced in any part of the brain.14,15

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A

B

C Figure 10-4. (A–C) Progression of visual ﬁeld defects from right, superior, homonymous, sector loss to (B) right, superior, homonymous quadrantanopia to (C) right, homonymous hemianopia in a patient with a progressively growing temporal lobe tumor.

The signiﬁcance of color hallucinations versus black-and-white hallucinations is even more of a mystery. There has been one report of a man with a temporal lobe tumor who saw his black-and-white television in color. When the tumor was removed, he saw it in black and white again.2 Other symptoms of temporal lobe lesions are olfactory or gustatory hallucinations (uncinate ﬁts), déjà vu phenomena, and psychomotor seizures.

10-4 PARIETAL LOBE FIELD DEFECTS Most tumors and vascular lesions are rarely limited to just the parietal lobe. Therefore, “typical” parietal lobe ﬁeld defects are uncommon. The so-called typical parietal lobe ﬁeld defect is a homonymous hemianopia, with the densest

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part occurring in the lower ﬁeld (Figure 10-5). This defect is referred to as a “pieon-the-ﬂoor” defect (Figure 10-6), as opposed to the temporal lobe “pie-in-thesky” defect. Usually, however, the ﬁeld defect is a more complete homonymous hemianopia that is denser neither above nor below the horizontal meridian, and it splits ﬁxation. Usually one identiﬁes the location of the lesion causing the ﬁeld defect in that part of the optic radiation by the associated signs of parietal lobe function. Gerstmann syndrome16-18 includes ﬁnger agnosia, right–left confusion, dyscalculia, and agraphia. If all four signs are found in a patient who is not confused and has

A

B Figure 10-5. (A) Automated visual ﬁeld showing a right lower quadratic defect due to a stroke seen on MRI (B) involving the left parietal lobe from a man who suddenly was unable to ﬁnd his way from the golf course to the clubhouse.

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A

B Figure 10-6. This homonymous defect from a parietal lobe lesion appears congruous and denser below. However, in this case, the automated ﬁeld (B) indicates that it may be more incongruous than depicted by the tangent screen ﬁeld (A).

no increased intracranial pressure, the lesion is probably located in the parietal lobe, especially the angular gyrus of the dominant hemisphere. If only one or two signs are found, the localization of the lesion is not so speciﬁc. When a hemianopia and other signs and symptoms are present, they probably signify more extensive involvement of the cerebral cortex. Nondominant parietal lobe dysfunction may complicate visual ﬁeld testing in two ways: motor impersistence and the extinction phenomenon. Motor impersistence limits the patient’s ability to maintain ﬁxation. Therefore, it is important, in patients with suspected parietal lobe disease, to take this into account during the ﬁeld test and to be careful not to question such patients’ behavior. Also, in any patient who clearly has difﬁculty with ﬁxation, the possibility that they may have nondominant parietal lobe disease should be raised. Suspicions can be conﬁrmed by asking the patient to close the eyes until told to open them. Within seconds, they will open their eyes, even though they admit to understanding the instruction. The defect of motor impersistence is caused by an inability to perform a willed motor act for any length of time, whether it be closing the eyes or ﬁxating steadily on a target. At that point, the perimetrist should try the confrontation ﬁelds outlined in Chapter 1. One can alternately use two hands and project a series of ﬁngers rapidly, ﬁrst into one ﬁeld and then into another, before the patient changes his ﬁxation. At this time, a dense homonymous hemianopia may be demonstrated that previously had eluded more sophisticated testing because of the patient’s inability to ﬁxate adequately. The second sign that affects parietal lobe ﬁeld testing is the extinction phenomenon.19,20 Patients with this sign may not have a true ﬁeld defect, but they pay no attention to one half of the ﬁeld when both sides are simultaneously stimulated.

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They are really ignoring the other half of the body image. This occurs also when the hands or legs are simultaneously stimulated by touch. No matter how careful and exhaustive the testing, the defect will not show up, because only one ﬁeld is tested at a time with the usual techniques. The extinction phenomenon should be considered when no defect is found by the usual means. When a patient is referred from a nonophthalmologist with the diagnosis of a homonymous hemianopia and, after careful routine testing, no suggestion of a ﬁeld defect is found, simultaneous testing of tactile sensation can establish the apparent visual ﬁeld loss as the extinction phenomenon, rather than as a true hemianopia. The localizing value of OKN responses is somewhat controversial. All agree that OKN abnormalities occur in cerebral hemisphere disease. The traditional view is that abnormal OKN responses occur with targets coming out of the hemianopic ﬁeld of parietal lobe lesions but not with lesions creating similar ﬁeld defects from the temporal and occipital lobes.21 On the other hand, others have asserted that the OKN response is only of lateralizing signiﬁcance to one or the other cerebral hemisphere and not to a single lobe of the brain.22 However, many patients with deep lesions affecting the optic radiations have normal OKN, and a normal OKN response does not rule out the parietal location as much as an abnormal response rules it in.

10-5 OCCIPITAL LOBE FIELD DEFECTS One cannot always differentiate between lesions of the occipital cortex and lesions of the calcarine cortex. Improved techniques of arteriography, combined with magnetic resonance imaging (MRI), have allowed clinicians to identify small vascular occlusions in these areas, previously only implied, and to map the vascular supply to these areas with more accuracy. The terminal branches of the basilar artery are the posterior cerebral arteries. These, in turn, form the circum-mesencephalic segment as it crosses around the midbrain and the tentorial edge to become the internal occipital branch of the medial aspect of the occipital lobe. The internal occipital branch divides into terminal parieto-occipital and calcarine branches. The calcarine artery, which is the main blood supply to the calcarine cortex, arises on the lateral aspect of the parieto-occipital branch as one of two trunks. The striate area is frequently supplied with additional blood from the posterior temporal and parieto-occipital branches. It is difﬁcult to predict the size of the ﬁeld defect resulting from an injury of the visual cortex, regardless of its cause. Postmortem23 and reﬁned arteriography24 studies demonstrated collateral circulation to this area, indicating that visual ﬁeld defects from posterior cerebral artery occlusions are much smaller than one might expect. The areas usually spared in posterior cerebral artery occlusion are the macular projection and the far periphery. The former receives additional blood from the posterior temporal and angular branches of the middle cerebral artery from the carotid system in over 50% of cases. The peripheral strip is preserved by its proximity to adjacent pial blood supply. The area most consistently lost through posterior cerebral artery occlusion is the paracentral ﬁeld, which is supplied preponderantly,

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if not exclusively, by the posterior cerebral artery and is in the central part of the calcarine cortex. Angiography has demonstrated that the vascular bed of the occipital cortex is perfused not only by the vertebral basilar system but also by the posterior temporal branch of the middle cerebral artery, accounting for a smaller ﬁeld defect than expected.25-28 There are many causes of the vascular occlusion of one posterior cerebral artery, which, in turn, causes a homonymous hemianopia. The development of a bilateral hemianopia, presumably from bilateral posterior cerebral artery occlusion, is less common but does occur from multiple emboli from a cardiac, vertebral, or basilar arterial source.24 Similar ﬁeld defects can occur during open-heart surgery, particularly if there is any complication such as hypotension or cardiac arrest, no matter how brief. Reﬁned angiographic techniques showing the capillary details shed light on why the macular projection in the striate area is preserved in some of these cases. In cases involving avascularity of the anterior striate cortex, as well as of the posterior occipital pole, the central macular projection is involved. If, in another instance, the same avascular anterior striate area had late capillary ﬁlling of the occipital pole, there is less involvement of the macular area. Late ﬁlling represents collateral ﬁlling from the parieto-occipital and posterior temporal branches of the posterior cerebral artery and through posterior temporal and angular branches of the middle cerebral artery. The anatomy of the visual cortex studied in detail on postmortem specimens has shown variations in the amount of both total visual cortex and exposed visual cortex not buried in the calcarine ﬁssure. An average of 67% of the visual cortex appears to be buried in the calcarine ﬁssure. The deeper areas of the ﬁssure are considered to represent the visual ﬁeld along the horizontal axis.29 Evaluation of visual ﬁelds of patients who had penetrating bullet wounds of the radiation and the visual cortex indicated that the central vision is located in the most posterior tip of the visual striate area and is large in area, covering not only a posterior area but also a posteromedial area. Within the calcarine ﬁssure is the horizontal meridian ﬁeld, which also is located above and below the ﬁssure. The peripheral ﬁeld is located anteriorly in the striate cortex. 24,25,30,31

10-5-1 Types of Occipital Cortex Field Defects. The types of ﬁeld defects seen in the occipital radiation or the striate cortex vary from very small congruous scotomas32 to congruous quadrantanopia and homonymous hemianopia from unilateral occipital lesions (Figures 10-7 through 10-12) and apparent altitudinal hemianopia, severe visual ﬁeld constriction, and even checkerboard quadrantanopia when there are bilateral lesions33 (Figures 10-13 through 10-19). Regardless of the type of visual ﬁeld defect, most lesions are associated with macular sparing from 2° to 10° around the ﬁxation point (see Figures 10-7 and 10-12). Most hemianopic ﬁeld defects that occur from lesions in the optic tract and optic radiations cut directly through ﬁxation and split the macula and only occasionally spare part of ﬁxation. The method of testing for macular splitting is explained in Chapter 1. False sparing of the macula occurs when ﬁxation is poor or shifts a few degrees. This type of sparing is spurious, because it occurs all along

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A

B Figure 10-7. (A) Automated visual ﬁelds showing congruous left inferior quadrantanopia with macular sparing from a 60-year-old man with metastatic carcinoma of the lung to the right occipital lobe shown on MRI (B).

the vertical meridian, not just around ﬁxation. Automated perimetry, especially programs that test the central 30° or 24° of the visual ﬁeld, frequently give the impression of macular splitting, and careful evaluation of the threshold values may be needed to identify macular sparing (see Figure 10-12). One explanation for the phenomenon of macular sparing in occipital lesions is bilateral representation of the macula in the cortex. Proponents of unilateral representation point to failure to produce bilateral geniculate degenerative changes after unilateral removal of the cerebral cortex.34 This evidence seems to indicate that there are no crossing ﬁbers. Also, sectioning the corpus callosum causes no

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B Figure 10-8. (A) Automated visual ﬁeld showing congruous right inferior quadrantic scotoma from a 55-year-old man with a meningioma of the right superior occipital lobe shown on MRI (B).

ocular defect,35 indicating that there are no crossing ﬁbers from one geniculate body to the other through the corpus callosum. On the other hand, one patient has been described who had unilateral occipital lobe destruction, producing a complete homonymous hemianopia with macular sparing. After subsequent surgical resection went as far forward as the splenium of the corpus callosum, the defect changed from one of macular sparing to one of macular splitting.36 Another theory of a chessboard type of foveal innervation with ganglion cells projecting to both ipsilateral and contralateral dorsal lateral geniculate bodies from each side of the fovea has been postulated but not substantiated.36

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B Figure 10-9. (A) Automated visual ﬁelds showing superior and inferior left paracentral hemianopic scotomas from a 52-year-old woman with a meningioma of the right occipital lobe affecting both upper and lower calcarine areas shown on MRI (B).

Studies using neurosonography and horseradish peroxidase has demonstrated that a 1° strip of cells along the vertical meridian of the dorsal lateral geniculate nuclei represented both ipsilateral and contralateral ganglion cells. In the area of foveal representation, this area increased to 3°. These labeled ganglion cells were found along both the nasal and the temporal rims of the foveola, suggesting bilateral representation.39 Most advocates of the bilateral-representation theory point to surgical cases in which unilateral total occipital lobe removal resulted in a complete homonymous hemianopia with sparing.37-39 Correlation of visual ﬁelds and damage to the striate cortex in soldiers with war injuries led to a retinotopic map of the striate cortex that has been the basis of our

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B Figure 10-10. (A) Automated visual ﬁelds showing superior and inferior mid peripheral scotomas from a 70-year-old woman with probable emboli from recurrent atrial ﬁbrillation to the left superior and left inferior calcarine arteries shown on MRI (B).

thinking since the early 1900s.40,41 The authors of these classic studies assigned 25% of the striate cortex to the central 15° of vision. Early computed tomography studies correlating injury to ﬁeld loss seem to correlate closely to those ﬁgures. However, examination in primates like the macaque monkey suggest that some 15% of central vision is represented by more than 70% of the striate cortex.42 Studies using MRI found a close correlation between the human and the macaque striate cortex.42 These ﬁndings compare favorably with estimates that 55% to 60% of striate cortex is devoted to macular vision.43 This has led to the concept of a linear

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B Figure 10-11. (A) Automated visual ﬁelds showing left inferior midperipheral inferior quadrantic defects from a 43-year-old woman with complicated migraine and infarction of the right anterior occipital region shown on MRI (B).

magniﬁcation factor,44 which describes the amount of cortex represented per degree of visual ﬁeld. This ratio begins at 40:1 and decreases toward the periphery. Most injuries to the occipital lobe are vascular (see Figures 10-10 through 10-14). The macular vascular supply is primarily conducted by way of the posterior cerebral artery. In about 25% of patients, a supplemental vascular supply is provided by the middle cerebral artery. If the posterior cerebral artery is occluded, the branch from the middle cerebral artery may preserve a part of the macular projection. This is similar in theory to the cilioretinal artery preserving macular vision when the central artery is occluded. As mentioned, the linear magniﬁcation factor of the macular projection accounted for the preservation of central vision in only a small area of the striate cortex.

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A

B Figure 10-12. (A) Automated visual ﬁelds showing left homonymous hemianopia with macular sparing as seen by preservation of the threshold values to the left of ﬁxation. There is also some preservation of ﬁeld just to the left of the vertical meridian about 15° above ﬁxation. The patient was able to read without difﬁculty. The responsible lesion was an infarct seen on MRI (B). The patient noted persistent ﬂashes of light and also saw objects including hands and stools that were not really present.

Conclusive evidence to explain the phenomenon of macular sparing has not yet been put forward. The dense homonymous hemianopia with splitting of ﬁxation is a common form of occipital lobe ﬁeld defect and usually has a vascular cause. Even if the hemianopia is complete, acuity should remain normal. If acuity is decreased, another cause must be sought. This may represent bilateral, but asymmetric, occipital involvement or disease of the eye itself, such as cataracts or retinal degenerative disease. A bilateral homonymous hemianopia can occur.45,46 When it occurs in the occipital lobes, visual acuity is equal in both eyes. If acuity is not equal, something else is happening, which must be found to explain the discrepancy. In patients who have this sign, the expected site for the lesion is the occipital lobe. A patient with bilateral lesions anywhere else in the radiation would not survive or, at least, would show other defects besides a ﬁeld defect. As mentioned earlier, one of the causes can be multiple emboli from a mural thrombus of the vertebral basilar system or the heart. Another cause can be sudden and severe anoxia such as might occur with

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A

B Figure 10-13. (A) Automated visual ﬁelds showing right superior quadrantanopia with macular sparing, left superior quandrantanopia, left inferior mid peripheral quadrantic loss, and possible peripheral left inferior defects from a 67-year-old woman with bilateral occipital infarcts from an unknown source, presumably cardiac or aortic, shown on MRI (B).

cardiac arrest or drowning. Such patients may have severe loss of visual ﬁeld and acuity, which may recover some vision after many months.47 There are three varieties of bilateral homonymous hemianopia that can occur. The ﬁrst type is represented by the patient who says he is blind or so severely impaired visually that he is functionally blind. The patient says that he is blind and acts as if he is blind. The pupils are essentially normal and so is the fundus

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A

B

C

Figure 10-14. (A) Automated visual ﬁelds showing primarily right superior quadrantic loss as well as left superior quadrantic loss from a 78-year-old man with bilateral strokes involving both occipital regions shown on MRI (B).

examination, as would be expected. The only objective evidence of the severe visual loss is the loss of the blink reﬂex to the threat type of ﬁeld testing. The second type is that found in a patient who has an identical type of ﬁeld defect but does not admit to having blindness. If the deﬁcit is demonstrated to them, they create an excuse for their lack of visual function—there may be a certain Korsakoff-like quality to their personality. This denial of blindness, referred to as Anton syndrome, probably represents involvement not only of the visual cortex of

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area 17 of Brodmann but also of the association areas. The last variety of bilateral homonymous hemianopia is the most misunderstood. Patients with this type say, and act as if, they are functionally blind. They admit to seeing light. They cannot see the largest letters on the chart. The examiner then logically goes to countingﬁngers and ﬁnally to hand-motion tests for visual acuity. At times, however, the patient appears to identify small test objects correctly, which is inconsistent with his inability to see large test objects or to count ﬁngers. The diagnosis of hysteria or of malingering is often considered at this point. The real answer may be that the tip of the visual cortex has been spared from infarction, leaving a ﬁeld remnant of only 3° to 5°. A residual ﬁeld may be too small for the patient to see the entire 20/400 letter “E,” for instance, but he may see a smaller letter if he can ﬁnd it. In situations where this type of defect is suspected, it may be easier to have the patient hold a card. The proprioceptive effect of holding the card will allow the patient to direct his residual ﬁeld to the correct place in space, namely, the handheld card. Using his ﬁnger as a proprioceptive guide, the patient should move his gaze down the card until his residual ﬁeld can encompass the appropriate-size letter. This will distinguish the patient with hysteria from the patient with a residual 3° to 5° central ﬁeld.

10-5-2 Field Defects Unique to the Occipital Cortex. The temporal crescent syndrome is a very rare form of occipital lobe defect.48-50 In each radiation there is an unpaired group of ﬁbers. When these are interrupted, they cause only a monocular defect— probably the only true monocular visual defect behind the chiasm. The ﬁbers of the temporal crescent are not isolated sufﬁciently as a unit until they reach the anterior visual cortex, so they are not affected individually as a unit anterior to that location. The monocular temporal crescent extends from about 60° out to the peripheral ﬁeld. This is the part of the ﬁeld that does not overlap with the other eye. It may either be preserved in the face of an otherwise complete homonymous hemianopia51 (see Figure 10-18) or be lost when the rest of the ﬁeld is preserved52 (see Figure 10-19). The most anterior portion of the calcarine cortex is where information from the temporal crescent is initially processed. This phenomenon demonstrates the value of obtaining peripheral as well as central ﬁelds. If only central ﬁelds were obtained, the defect would be missed, and if only peripheral ﬁelds were done, the impression would be one of a monocular ﬁeld defect, and investigation of the cause would be directed erroneously to the particular eye or optic nerve. The Riddoch phenomenon is a visual ﬁeld sign that has been ascribed to occipital visual ﬁeld defects.53 Riddoch believed that patients with severe ﬁeld loss from occipital lobe involvement perceive form and movement separately. He postulated that perception of movement recovers before perception of form and that this phenomenon was of some prognostic value for recovery of ﬁeld. The phenomenon is illustrated in the patient with an extensive, dense homonymous hemianopia as a result of an occipital lobe lesion: Such a patient cannot see a large stationary object in the blind ﬁeld but can see a much smaller object if it is moving. The Riddoch phenomenon was originally described as a sign of a recovering occipital lobe ﬁeld defect. The patient would perceive movement before light in their peripheral ﬁeld. This can be best demonstrated with the projection type of perimeter. The patient

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perceives the movement of the test light but does not see that same object when projected into that same ﬁeld without movement. However, others have found that the Riddoch phenomenon is not anatomically speciﬁc and can be demonstrated in most ﬁeld defects using kinetic red stimuli.54,55 Postictal hemianopia is rare, whereas postictal (Todd’s) paralysis is not. When postictal visual loss does occur, the duration varies and may be related to cerebral tumor.56 If the occipital seizures are frequent, affected patients can lose vision or visual ﬁeld for periods of days. Transient cerebral blindness after seemingly minor head trauma occurs more frequently in children than in adults.57 It lasts from several minutes to several hours, depending on the degree of trauma, and the patient may have other neurologic deﬁcits. This condition also occurs when there is a history of migraine or epilepsy.58 The latter diagnoses should be kept in mind when there is only minimal trauma. Cortical blindness has also been reported with ventriculography or with ventricular decompression.59 The exact cause is unknown and, fortunately, the condition is rare. One theory holds that there is a shift of the brain when the cerebrospinal ﬂuid is exchanged for air, causing herniation and compression of the blood supply to the occipital cortex.60,61 More commonly seen now is reversible leukomalacia from various drugs and with severe elevations in blood pressure, especially with eclampsia.62 In multiple sclerosis, a homonymous hemianopia is much rarer than optic neuritis. This is not to say that the retrochiasmal pathway is not frequently involved in this disease—an observation made in 1890 by Uhthoff. However, as mentioned previously, small lesions of the radiation and of the striate cortex may not produce any demonstrable ﬁeld defect. A bilateral homonymous hemianopia must be even rarer in multiple sclerosis. In one study of 300 patients, only 4 had a homonymous ﬁeld defect and only 1 had a bilateral homonymous ﬁeld defect.63 The incidence of a homonymous ﬁeld defect in this series was 1.3%. The patients all had multiple sclerosis, diagnosed by other criteria. The site of the lesions causing homonomous hemiaopia in multiple sclerosis may occur anywhere from the optic tracts to the occipital regions.64 Headache can occur in patients with occipital vascular lesions as well as tumors. In one report, the authors commented that headaches occurred more often with a hemianopia in the occipital lobe than in other parts of the radiation. They believed that the headache was caused by irritation of dural branches of the ﬁrst division of the trigeminal nerve.65 The occipital lobe can be affected by more remote lesions. Frontal tumors can displace the brain posteriorly, compressing the blood supply to the visual cortex as the vessel posterior cerebral arteries cross the tentorial edge. The frontal lobe tumor may have been inconspicuous up to that point, but when an infarction of one of the occipital lobes caused a sudden hemianopia, it became symptomatic. There may be confusion when a brain scan shows two widely separated lesions. These may incorrectly be interpreted as metastatic lesions, and tumor resection will not be indicated. In reality, there is only one tumor in the frontal lobe, and it may be accessible surgically. MRI or CT usually shows the different densities of the lesions and indicates whether they have the same cause. A similar mechanism

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of tentorial herniation with compression of the posterior cerebral arteies can occur from epidural hematoma after trauma.66 A false localizing hemianopia in the chiasmal area may also occur when, distant from the chiasm, obstruction of the aqueduct of Sylvius causes enlargement of the third ventricle. This will, in turn, cause compression of the chiasm and the bitemporal type of defect typical of chiasmal lesions.

A

B Figure 10-15. (A) Automated visual ﬁelds from a 75-year-old woman who noted visual loss after resection of an atrial myxoma, showing apparent superior nasal paracentral loss in the right visual ﬁeld and apparent inferior temporal paracentral loss on the left. However, tangent screen ﬁelds (B) show that there really is a congruous, left inferior homonymous paracentral scotoma. This was due to a right posterior occipital infarct associated with other infarcts on the opposite side seen on MRI (C).

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C Figure 10-15. (Continued)

Visual hallucinations, as mentioned previously, can originate in any part of the visual system. They are not necessarily conﬁned to the temporal and occipital lobe areas.14 The explanation accepted generally is that formed and organized hallucinations are attributed to a temporal lobe location, whereas unformed hallucinations originate in the occipital lobe. A classic example of an unformed hallucination of the occipital lobe is the scintillating fortiﬁcation scotoma in migraine.66 The optokinetic nystagmus response is generally considered to be normal in temporal and occipital lobe lesions associated with a homonymous hemianopia. However, the OKN response can be abnormal in known occipital lobe lesions. However, this more often occurs with a mass lesion, perhaps because tumors are rarely conﬁned to such a small area without involving the parietal lobe (the distance covered by the occipital lobe is only 50 mm).13 Conjugate-gaze deviations in occipital lobe lesions are rarely seen. When they are, they are small and the deviation is toward the side of the lesion or away from the hemianopia. Another explanation for this mild gaze paresis is reticence to look into the hemianopic ﬁeld defect.

10-5-3 Color Field Defects in the Occipital Lobe. Color used as a reduced stimulus for measuring subtle ﬁeld defects is well known. However, lack of appreciation of a colored stimulus can take several other forms. It may also be due to a greater effect of the disease on ﬁbers sensitive to color such as is seen in early stages of optic nerve disease. Another form of color defect is the congenital variety, which is seen to varying degrees in about 6% of the male population. This type of color defect persists throughout the entire visual ﬁeld and should not cause a localized ﬁeld defect. These defects in color testing are commonly known to any perimetrist. A more rarely encountered form is a color loss secondary to a lesion of the central

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Figure 10-16. A true checkerboard defect shows the same two quadrants totally out The other two quadrants have the defect also but in response to a smaller test object. (A) Tangent screen representation. (B) Computerized representation of left eye only; right eye is the same.

Figure 10-17. This patient has all four quadrants of the visual cortex affected and 5º of the macular projection spared.

nervous system.67,68 Central loss of color can be subdivided into two broad groups of patients. One group has an intellectual problem in recognizing or naming colors but has no speciﬁc color defect. The second group is intellectually intact and has excellent acuity to perceive color but has a central color defect (cerebral dyschromatopsia) in the cerebral cortical area that appreciates colored information. Patients with a speciﬁc aphasia for naming colors do exist, but more commonly this aphasia is associated with other forms of aphasia. One can demonstrate that this color-naming aphasia does exist by testing the patient with pseudoisochromatic plates. This patient will see even the most subtle plates if he has no congenital color defect, thus attesting to the fact that his defect is not in seeing colors but rather in naming colors and that it is acquired. Yet, he will miss naming the bright-green

Figure 10-18. (A) If testing of only the central ﬁelds is performed, the hemianopia is congruous and there is no sparing of the ﬁelds within 30º. (B) If peripheral ﬁeld testing is performed on the same patient, a peripheral strip will be preserved in the right eye beyond 60º. (C) Computerized representation of the left eye. (D) Computerized representation of the right eye. (E) Computerized representation of temporal crescent of the right eye.

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Figure 10-19. These central ﬁelds are completely normal out to 30º. The temporal crescent, however, is affected from 60º out in the right eye only. (A) Tangent screen representation. (B) Computerized representation of the left eye. (C) Computerized representation of the right eye. (D) Computerized representation of the right eye.

color of a large watermelon. This defect appears to be more common with left hemisphere lesions,69 perhaps with a secondary defect in the splenium of the corpus callosum.70 Color agnosia would be distinguished from cerebral dyschromatopsia. Affected patients cannot recognize and name objects but cannot name colors. They see the subtle, hidden symbols in the color plates. They can name the correct color if given other sensory clues, such as associating the color yellow with a banana. Experimental studies in monkeys have demonstrated color-responsive cells in the fourth visual area.71 This area may be considered comparable to an area in the human occipital cortex that has been implicated in cerebral dyschromatopsia. In the few case studies postmortem, the comparable area in humans involves the fusiform and lingual gyri. In cerebral dyschromatopsia, the color defect is random and does not follow any pattern such as protanopia or deuteranopia. If patients with cerebral

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dyschromatopsia are tested with pseudoisochromatic plates, they do not see the confusion numbers.72 Patients with cerebral dyschromatopsia have ﬁeld defects. The defects, however, cannot account for their extensive loss of color appreciation.73,74

REFERENCES 1. Wong AM, Sharpe JA. A comparison of tangent screen Goldmann and Humphrey perimetry in the detection and localization of occipital lesions. Ophthalmology. 2000;107:527–544. 2. Smith JL. Homonymous hemianopia: a review of one hundred cases. Am J Ophthalmol. 1962;54:616–623. 3. Trobe JD, Borber ML, Schlezinger NS. Isolated homonymous hemianopia: a review of 104 eases. Arch Ophthalmol. 1973;89:377–381. 4. Kedar S, Zhang X, Lynn MJ, et al. Congruency in homonymous hemianopia. Am J Ophthalmol. 2007;143:772–780. 5. Younge BR. Midline tilting between seeing and nonseeing areas. Mayo Clin Proc. 1976;51:562–568. 6. Krolak-Salmon PK, Guenot M, Tiliket C, et al. Anatomy of optic nerve radiations as assessed by static perimetry and MRI after tailored temporal lobectomy. Br J Ophthalmol. 200;84:884–889. 7. Barton JJ, Hefter R, Chang B, et al. The ﬁeld defects of anterior lobectomy: a quantitative reassessment of Meyer’s loop. Brain. 2005;128:2123–2133. 8. Fox JC, German WJ. Macular vision following cerebral resection. Arch Neurol Psychiatry. 1936;35:808–817. 9. Bjork A, Kugelberg E. Visual ﬁeld defects after temporal lobectomy. Acta Ophthalmol. 1957;35:210–215. 10. Falconer MA, Wilson JL. Visual ﬁeld changes following anterior temporal lobectomy: their signiﬁcance in relation to “Meyer’s loop” of the optic radiation. Brain. 1958;81:1–14. 11. Kravitz D. The value of quadrant ﬁeld defects in the localization of temporal lobe tumors. Am J Ophthalmol. 1931;14:781–785. 12. Harrington DO. Visual ﬁeld character in temporal and occipital lobe lesions: localizing values of congruity and incongruity in incomplete homonymous hemianopia. Arch Ophthalmol. 1961;66:778–792. 13. Cogan DG, Loeb DR: Optokinetic response and intracranial lesions. Arch Neurol Psychiatry. 1949;61:183–187. 14. Weinberger LM, Grant FC. Visual hallucinations and their neuro-optical correlates. Arch Ophthalmol. 1940;23:166–199. 15. Horrax G. Visual hallucinations as a cerebral localizing phenomenon. Arch Neurol Psychiatry. 1923;10:532–547. 16. Gerstmann J. Some notes on the Gerstmann syndrome. Neurology. 1957;7:866–869. 17. Benton AL. The function of the “Gerstmann syndrome.” J Neurol Neurosurg Psychiatry. 1961;24:176–181. 18. Critchley M. The enigma of the Gerstmann’s syndrome. Brain. 1966;89:183–198. 19. Bender MB, Furlow LT. Phenomenon of visual extinction in homonymous ﬁelds and psychologic principles involved. Arch Neurol Psychiatry. 1945;53:29–33. 20. Nathan PW. On simultaneous bilateral stimulation of the body in a lesion of the parietal lobe. Brain. 1946;69:325–334. 21. Smith JL, Cogan DG. Optokinetic nystagmus in cerebral disease: a report of 14 autopsied cases. Neurology. 1960;10:127–137.

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22. Davidoff RA, Atkin A, Anderson PJ, et al. Optokinetic nystagmus and central disease. Arch Neurol. 1966;14:73–81. 23. Beevor CF. On the distribution of the different arteries supplying the human brain. Philos Roy Soc Lond (Biol). 1909;40:1–16. 24. Kaul SN, DuBoulay GH, Kendall BE. Relationship between visual ﬁeld defect and arterial occlusion in the posterior cerebral circulation. J Neurol Neurosurg Psychiatry. 1974;37:1022–1030. 25. Hoyt WF, Newton TH. Angiographic changes with occlusion of arteries that supply the visual cortex. N Z Med J. 1970;72:310–317. 26. Weiskrantz L. Residual vision in a scotoma. Brain. 1987;110:77–92. 24. Weiskrantz L. Contour discrimination in a young monkey with striate cortex ablations. Neuropsychologia. 1963;1:145–164. 27. Weiskrantz L. Behavioral analysis of the monkey’s visual nervous system. Proc Roy Soc Lond. 1972;182:427–455. 28. Stensaas SS, Eddington OKL, Dobelle WH. The topography and variability of the primary visual cortex in man. J Neurosurg. 1974;40:747–755. 30. Spalding JMK. Wounds of the visual pathway, I: the visual radiation. J Neurol Neurosurg Psychiatry. 1952;15:99–107. 31. Spalding JMK. Wounds of the visual pathway, II: the striate cortex. J Neurol Neurosurg Psychiatry. 1952;15:169–181. 32. Bender MB, Battersby WS. Homonymous macular scotomata in cases of occipital lobe tumor. Arch Ophthalmol. 1958;60:928–938. 33. Felix CH. Crossed quadrant hemianopia. Br J Ophthalmol. 1926;10:191–195. 34. Polyak S. Projection of the retina upon the cerebral cortex, based upon experiments with monkeys. J Mt Sinai Hosp. 1942;9:698–707. 35. Akelaitis AJ. Studies on the corpus callosum, II: the higher visual functions in each homonymous ﬁeld following complete sections of the corpus callosum. Arch Neurol Psychiatry. 1941;45:788–796. 36. Penﬁeld W, Evans JD, MacMillian JA. Visual pathways in man: with particular reference to macular representation. Arch Neurol Psychiatry. 1935;33:816–834. 37. Huber A. Homonymous hemianopia after occipital lobectomy. Am J Ophthalmol. 1962;54:623–629. 38. Bunt AH, Minckler DS. Foveal sparing. Arch Ophthalmol. 1977;95:1445–1447. 39. Stone J, Leicester L, Sherman SM. The nasotemporal division of the monkey’s retina. J Comp Neurol. 1973;150:333–348. 40. Inouye T. Die Sehstörungen bei Schussverletzungen der kortikalen Sehsphäre: Nach Beobachtungen an Verwundeten der letzten japanischen Kriege. Leipzig: Engelmann; 1909. 41. Holmes G, Lister WT. Disturbances of vision from cerebral lesions with special reference to the cortical representation of the macula. Brain. 1916;39:34–73. 42. Horton JC, Hoyt WF. The representation of the visual ﬁeld in human striate cortex: a revision of the classic Holmes map. Arch Ophthalmol. 1991;109:816–824. 43. Van Essen DC, Newsome WT, Maunsell JH. The visual ﬁeld representation in striate cortex of the macaque monkey: asymmetries, anisotropies, and individual variability. Vision Res. 1984;24:429–448. 44. Daniel DM, Whitteredge D. The representation of the visual ﬁeld on the cerebral cortex in monkey. Physiology. 1961;159:203–221. 45. Kearns TP, Wagener HP, Millikan CH. Bilateral homonymous hemianopia: relationship to thrombosis of the basilar artery. Arch Ophthalmol. 1955;53:560–565.

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46. Symonds C, Mackenzie I- Bilateral loss of vision from cerebral infarction. Brain. 1957;80:415–455. 47. Hoyt WF, Walsh FB- Cortical blindness with partial recovery following acute cerebral anoxia from cardiac arrest. Arch Ophthalmol. 1958;60:1061–1069. 48. Kronfeld PC- The temporal half–moon. Trans Am Ophthalmol Soc. 1932;30: 431–456. 49. Bender MB, Strauss I. Defects in visual ﬁeld of one eye only in patients with a lesion of one optic radiation. Arch Ophthalmol. 1937;17:765–787. 50. Walsh T. Temporal crescent or half–moon syndrome. Ann Ophthalmol. 1974;6: 501–505. 51. Landau K, Wichmann W, Valavanis A. The missing temporal crescent. Am J Ophthalmol. 1995;119:345–349. 52. Lepore FE. The preserved temporal crescent; the clinical implications of an “endangered” ﬁnding. Neurology. 2001;57:1918–1921. 53. Riddoch G. Dissociations of visual perceptions due to occipital injuries with especial reference to appreciation of movement. Brain. 1917;40:15–29. 54. Safran BA, Glaser JS. Statokinetic dissociation in lesions of the anterior visual pathways: a reappraisal of the Riddoch phenomenon. Arch Ophthalmol. 1985;98:291– 295. 55. Zappia RJ, Enoch JM, Stampers R, et al. The Riddoch phenomenon revealed in nonoccipital lobe lesions. Br J Ophthalmol. 1971;55:416–420. 56. Salmon JH. Transient postictal hemianopia. Arch Ophthalmol. 1968;79:523–525. 57. Dodge PR, Grifﬁth JF. Some transient ocular manifestations of neurologic disease in children. In: Smith JL, ed. Symposium of the University of Miami and the Bascom Palmer Eye Institute. St. Louis: CV Mosby; 1967:chap 16. 58. Greenblatt SH. Posttraumatic transient cerebral blindness association with migraine and seizure diatheses. JAMA. 1973;225:1073–1076. 59. Rinaldi I, Bolton JE, Troland CE. Cortical visual disturbances following ventriculography and/or ventricular decompression. J Neurosurg. 1962;19:568–571. 60. Lindgren E. Radiologic examination of the brain and spinal cord. Acta Radiol. 1957;151(Suppl). 61. Schwartz GA, Rosner AA. Displacement and herniation of the hippocampal gyrus through the incisura tentorii: a clinicopathologic study. Arch Neurol Psychiatry. 1941;46:297–521. 62. Hinchey J, Chaves C, Appignani B, et al. A reversible posterior leukoencephalopathy syndrome. N Engl J Med. 1996;334:494–500. 63. Hawkins K, Behrens MM. Homonymous hemianopia in multiple sclerosis: with report of bilateral case. Br J Ophthalmol. 1975;59:334–337. 64. Plant GT, Kermode AG, Turano G, et al. Symptomatic retrochiasmal lesions in multiple sclerosis. Clinical, visual evoked potential and magnetic resonance imaging. Neurology. 1992;42:68–76. 65. Knox DL, Cogan DG. Eye pain and homonymous hemianopia. Am J Ophthalmol. 1962;54:1091–1093. 66. Bender MB, Kanzer MM. Dynamics of homonymous hemianopias and preservation of central vision. Brain. 1939;62:404–421. 67. Damasio A, Yamada T, Damasio H, et al. Cerebral achromatopsia: behavioral, anatomic and physiologic aspects. Neurology. 1980;30:1064–1071. 68. Critchley M. Acquired anomalies of colour perception of central origin. Brain. 1965;88:711–724.

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69. Gerschwind N, Fusillo M. Color-naming defects in association with alexia. Arch Neurol. 1966;15:137–146. 70. Zihl IG, Von Cramon DJ. Colour anomia restricted to the left visual hemiﬁeld after splenial disconnexion. J Neurol Neurosurg Psychiatry. 1980;43:719–724. 71. Zeki SM. Colour coding in rhesus monkey prestriate cortex. Brain Res. 1973;53:422– 427. 72. Green GJ, Lessell S. Acquired cerebral dyschromatopsia. Arch Ophthalmol. 1977;95:121–128. 73. Zeki SM. Colour coding in the superior temporal sulcus of rhesus monkey visual cortex. Proc R Soc Lond. 1977;197:195–223. 74. Zeki SM. Representation of central visual ﬁelds in prestriate cortex of monkey. Brain Res. 1969;14:271–291.

11 Functional Visual Loss THOMAS J. WALSH, MD

11-1 TYPES OF PATIENTS Functional loss of vision or visual ﬁelds can present some of the most difﬁcult diagnostic challenges, but even more difﬁcult to diagnose are patients who have, in addition to functional visual loss, an organic disease. No matter how functional the symptoms appear, the clinician has to go that extra step to ﬁnd any true pathology. This is why different ﬁeld techniques may be more appropriate than the more sophisticated techniques. A tangent screen, for instance, may be better to control the patient’s response than a Humphrey Visual Field Analyzer. Remember the functional patients get sick, too. Patients with functional ﬁeld loss can be placed into one of three general groups: neurasthenics, hysterics, or malingerers. The neurasthenic patient usually has many complaints, not limited to the visual system or to one set of visual symptoms such as ﬁeld loss. The complaints, as well as the degree of ﬁeld or visual defect, frequently vary from one examination to another, as well as during an examination as fatigue increases. The spiral ﬁeld is often found in neurasthenic patients.1 The patient with hysteria, on the other hand, usually has a single ocular complaint. This chapter discusses the hysterical loss of acuity or ﬁelds.2,3 The usual ﬁeld defect is a severe tubular type of contraction. The spiral ﬁeld is sometimes seen in these patients. The malingerer may be the most difﬁcult patient with functional loss, particularly if he has previously been examined by another physician and has acquired more experience with ﬁeld testing than he had when ﬁrst examined.4

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11-2 TYPES OF FIELD LOSS The spiral ﬁeld is not limited to functional loss; it can also be seen as a fatigue phenomenon in sick patients when the ﬁeld testing is unduly prolonged. Its essential feature is that the ﬁeld becomes progressively smaller as a speciﬁc isopter is tested for a second and third time with the same size of test object. Figure 11-1 shows all the points that were tested with a 3-mm white test object. The limits of the ﬁeld from the ﬁrst test are indicated by the line marked with an X; the ﬁeld areas from the second and third tests are marked by O and V, respectively. Severe contraction, in my experience, is a more common type of ﬁeld defect, especially in hysterical patients. The contraction of the ﬁeld is concentric and severe, and it frequently reduces to 5° or 10° (Figure 11-2). If the contraction is obviously asymmetric, suggesting a bitemporal or homonymous conﬁguration, then one may not be dealing with a purely functional ﬁeld loss. At this point, a careful evaluation of the difference between the two halves of the ﬁeld should be made, using the technique for demonstrating a Chamlin-type defect. If the ﬁelds are severely contracted, testing should be done in reverse, moving the test object from a seeing to a nonseeing area. If the defect is functional, it will usually enlarge signiﬁcantly. Severely contracted ﬁelds tan also be seen in exacting patients who want to be sure they see the object and, therefore, unduly contract the ﬁelds. Fields can also contract when the object is moved from a seeing to a nonseeing area. There is a deﬁnite difference in doing the two ﬁeld tests, suggesting a nonorganic cause for the defect.

Figure 11-1. This is a 3-mm test object for ﬁelds (us marked by X, 0, mid V).

Figure 11-2. This ﬁeld defect is usually this small in response to all sizes of test objects and frequently to all distances from the patient.

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There are pathologic causes of severe contraction besides hysteria. These include cortical blindness with sparing of the macular projections. Monocular causes include advanced glaucoma, central retinal artery occlusion with sparing of the cilioretinal artery, retinitis pigmentosa, and diffuse chorioretinitis with sparing of the macular area.

11-3 TESTS FOR FUNCTIONAL FIELD LOSS Sometimes, severely contracted tubular ﬁelds are termed “gun barrel.” The term is misleading because it gives the impression that the ﬁelds are the same diameter throughout. In reality, the ﬁelds are more like a blunderbuss, which enlarges as it reaches the tip, than a riﬂe. The number of degrees in the ﬁeld does not change with the distance, but the area does. It is like a pie cut at the 90° and 180° meridians. If it is in a 10-inch pie pan, a 90° slice of pie is of a certain size (line A in Figure 11-3); a 90° slice of pie in a 20-inch pan (line B) would have the same angle as the pie in the 10-inch pan but would be a bigger piece. In ﬁeld testing, line A would represent a 1-m screen, and the ﬁeld done to a 3-mm white object would be 10° (Figure 11-3). If a second ﬁeld is done at 2 m, line B should also be 10° (Figure 11-4). What had been the 20° isopter at 1 m would now be the 10° isopter at 2 m. If the distance at which the ﬁelds are done is doubled, the size of the test object must also be doubled so that the exact testing circumstances are duplicated. If the distance is doubled to 2 m and a 3-mm test object is still used, the object size now reduces to one half the size on the retina as it was at 1 m. A dramatic way to use this method is for the examiner to use his or her hand as a test object. If a patient contracts his ﬁelds to 7° to a 3-mm white test object, for example, instead of moving the patient back

Figure 11-3. Line A represents 1 m from ﬁxation, and line B represents 2 m from ﬁxation, but both encompass the same number of degrees.

Figure 11-4. This ﬁeld test is a repeat for the patient shown in Figure 11-2. This time, the ﬁeld is performed at 2 m from the same screen. The size of the test object is doubled also to 6 mm. The meridian marked at 20° is actually the 10° meridian at 2 m. If the defect was still to the meridian marked as 10°, this would be a smaller ﬁeld at 2 m than at 1 m and would be a sign of functional ﬁeld loss.

296

Visual Fields

2 m from the screen, the examiner may move 10 to 12 feet from the patient and use his or her hand as the test object. This test object is grossly larger than the target required for that distance. If the patient sees the hand as the test object at a distance of less than 7°, this will demonstrate the functional nature of the ﬁeld defect. One of the easiest tests for functional visual loss is to compare the distant (20-foot) and the near (14-inch) acuity with the appropriate distant prescription and add as indicated. Distant and near acuities should be essentially the same, or near acuity should be only slightly better than distant acuity because of the magniﬁcation. There should not be a discrepancy of four or ﬁve lines. The next step is to measure the acuity at different distances from the chart. If a patient reads the 20/200 large S-L letters at 20 feet, he should read the original 20/100 O-P-L-D line at 10 feet, which, at the new distance, is equal to the previous 20/200 S-L line. The patient can further be tested at 5 feet or for any line of letters with which he starts. If he continues to read only the original 20/200 S-L at all distances, he may then be considered to have functional visual loss. A variation on the standard refraction is another useful test. The patient is given cycloplegia, and his best refraction is put in the phoropter. A +2.50 lens is then inserted in front of the eye about which he is complaining. If the patient compares both eyes alternately on the distant chart, his vision in the suspected eye will be blurred and he will not be able to read the letters. As long as both eyes are open behind the phoropter, he does not mind reading the distant chart, because he feels he is reading it with the uninvolved eye. The near card is now moved to 16 inches in front of him, and he is asked to read it. Presuming that his uninvolved eye still is doing the reading, the patient reads the near card. Because, however, he is under cycloplegia and only the involved eye has the appropriate +2.50 lens in front of it, he will be reading only with the eye with which he said he could not read the distant 20/200 S-L—an obvious discrepancy. More sophisticated tests can be done with prisms. In these tests, the patient who says he has a monocular defect reads with both eyes open, and supposedly he is reading with the good eye only. If an 8-diopter base-out prism is placed in front of the affected eye and the patient makes a correcting fusional movement, evidence of reasonable vision is indicated. A similar movement in the opposite direction will occur when the prism is withdrawn. If the vision is as poor as the patient claims, there will be no reason for a fusional movement. This test can be reversed by putting a vertical 6-D prism in front of the affected eye. Vertical prisms of this magnitude cannot be fused and will cause diplopia and interruption of reading. If the vision in the suspected eye is so poor that it is not used in reading, the vertical prism will cause no interruption in reading and no diplopia symptoms. The far test with reading is similar to the vertical prism test. The duochrome test can also be used when functional loss is suspected. This test uses the red-green ﬁlter in the projector and red-green glasses either on the patient or in front of the phoropter. If the patient reads both the red and the green letters, it belies his claim that he sees abnormally with one of his eyes, because he is seeing the red letters through the eye with the red lens in front of it and the green letters through the eye with the green lens. The success of this test presupposes that the patient does not close each eye alternately to check with which eye he is seeing.

Functional Visual Loss

297

A clever variation of the duochrome test uses polarizing lenses instead of redgreen glasses. The red-green slide is replaced with a polarizing slide, half of the letters polarized vertically to 90° and the other half horizontally to 180°. A similar orienting glass is placed in front of each eye. As in the duochrome test, the patient can discover which eye sees which half of the line of letters by closing each eye separately. By a twist of the projector knob, however, the examiner can easily interchange the half of the letters having a horizontal orientation and the half having a vertical orientation. At one slight movement, the right eye sees the right half of the line of letters and, in the span of a blink, the left eye sees the same half. If the change of orientation is kept in mind and is done fast enough, the patient may be tricked into reading with his “poor” eye. Several other tests can be used for patients who complain of bilateral visual loss. These tests have some use in unilateral loss as well. If a patient says he can see only light or hand motion, the optokinetic nystagmus and mirror tests are of particular value. The OKN tape is moved in front of the patient at a distance where he says he cannot see anything except, perhaps, light. If his eyes move appropriately as the tape is moved, he must see the tape. This test cannot be used with patients who will not cooperate with ﬁxation. If the patient appears to ﬁxate but no response is forthcoming, the direction of the movement of the tape should be changed from horizontal to vertical. This change may surprise or momentarily confuse the patient, putting him off his guard so that he will give the examiner the proper response. In the mirror test, the examiner holds a mirror at the distance where the patient says he sees nothing. The patient is asked to ﬁxate straight ahead and not to move his eyes, even if he cannot see anything on which to ﬁxate. At this point, the examiner starts a conversation to distract the patient so that he does not realize the test is taking place. The examiner slowly moves the mirror horizontally or vertically. If the patient is ﬁxating steadily on himself, his eyes will move slowly. If he does not see himself, he will have no reason to move his eyes as the mirror is moved. The use of the visual evoked response is another method of testing for the integrity of the visual system, but it is not always available and is rarely needed. Furthermore, the test may not be helpful if a patient does not ﬁxate adequately, such as occurs in young children. There is no one test that is better than another to make the diagnosis. To prove the problem is functional, multiple tests need to be done; the patient only needs to fail only one test. REFERENCES 1. Fames TH: A study of tubular and spiral central ﬁelds in hysteria. Am J Ophthalmol. 1947;30:610–611. 2. Karp JJ: Functional disease in neuro-ophthalmology. Int Ophthalmol Clin. 1972;17: 157–167. 3. Miller B: A review of practical tests for ocular malingering and hysteria. Surv Ophthalmol. 1973;17:241–246. 4. Eggers H: Estimation of uncorrected visual acuity in malingerers. Arch Ophthalmol. 1945;33:23–27.

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Index

NOTE: An f following a page number indicates a ﬁgure, and a t following a page number indicates a table. Abscess in optic tract infection, 256 papilledema, 201 Absolute defect, in ﬁelds, 19, 144, 157 Acquired optic nerve diseases, 193 compressive optic neuropathy, 198–200 ischemic optic neuropathies, 196 arteritic ischemic optic neuropathy (AAION), 196–98 nonarteritic ischemic optic neuropathy (NAION), 196 metabolic optic neuropathies, 198 visual ﬁeld effects of, 198 optic neuritis, 194–95 papilledema, 200–201 Acute zonal occult outer retinopathy (AZOOR), 217, 250 Advanced Glaucoma Intervention Study (AGIS), 132 Afferent ﬁeld defect (APD), 44f, 60, 196, 253, 255 Alcohol and stress, 184 teratogenic agent, for ONH, 178 Altitudinal defects, 16, 59, 72, 73, 179, 181, 196 Altitudinal ﬁeld defects, 42t, 72–75 congruous, 73–75 noncongruous binocular and monocular, 72–73 Altitudinal hemianopia, 273 congruent, 73–74 localized monocular ﬁeld defects, 42t, 44f, 59 nonconguent, 73f Amblyopia, 37, 57, 77, 180 Ametropias, 177 Amsler grid, ﬁeld testing techniques, 36, 226, 240 Aneurysms, 71, 73, 83, 109, 199, 236, 243, 247, 248, 249, 256 Anterior chiasmal syndrome, 240 Anterior choroidal artery, occlusion of, 45f, 61, 63, 259f Anterior genu of von Wilbrand, 200

Anterior visual pathway, 45, 54, 72, 237 Anton syndrome, 281–82 Aphasia, color-naming, 37, 268, 286 Aplasia, 177 Arachnoiditis, optochiasmic, 71 Arc perimeter, 85 Arcuate defect, 27f, 101, 107f, 135f optic nerve and retina, 20 Arcuate ﬁeld defects, localized monocular ﬁeld defects, 52–54 optic nerve head, 53–54 retina, 53 retrobulbar optic nerve, 54 Arcuate scotomas, 16, 52, 58, 100f, 128f, 141, 179, 196 Arcuate temporal retinal ﬁbers, 128 Arteriovenous malformations, 250 Arteritic ischemic optic neuropathy (AAION), 193, 196–98 signs of, 196 visual ﬁeld effects of, 197 Artery occlusions, 209, 259 Artifacts in automated perimetry, 149 in corrective lens, 120 and learning effect, 118 corrective lens/frame artifacts, 120 eyelid and nose effects, 119 media opacities, 119 miosis and mydriasis, 118–19 refractive errors, 119–20 Atrial myxoma, visual loss after, 284f Automated perimetry custom tests, 105–11 FASTPAC algorithm, 95, 108–9 grid size, 108 Nasal Step program, 110 Peripheral 60 and 60-4 program, 110 Programs 30-1 and 24-1, 109 stimulus size option, 111

299

300

Index

Automated perimetry (continued) evaluation of series of tests, 144–61 of single test, 132–44 ﬁeld testing, principles of, 86–94 frequency-of-seeing curves and ﬂuctuations, 92–94 kinetic perimetry, 88–90 static perimetry, 90 follow-up printout, 111–14 change analysis printout, 111–14 glaucoma progression analysis printout, 114 guided progression analysis, 114 overview printout, 111 full threshold test, glaucoma-related advantages of, 129–30 disadvantages of, 130 future of, 161–73 altered stimuli, 161–69 altered strategies, 169–71 interpretive aids, 171–73 in glaucoma automated perimetry options, 129–32 evaluation of series of tests, 144–61 evaluation of single test, 132–44 glaucomatous visual ﬁeld defects, 127–29 historical overview of, 85–86 learning effect and artifacts, 118–20 corrective lens/frame artifacts, 120 eyelid and nose effects, 119 media opacities, 119 miosis and mydriasis, 118–19 refractive errors, 119–20 limitations of, 263–64 single test printout in, 99–105 Glaucoma Hemiﬁeld test, 102–5 global indices, 105 grayscale results, 101 numeric results, 101 pattern deviation, 101 reliability indices, 99–101 test selection, 99 total deviation, 101 test selection and algorithms, 94–99 ﬁxation monitoring, 96–99 foveal threshold, 95 initial values, 95–96 Swedish Interactive Threshold Algorithm (SITA), 94–95 threshold testing, 99 visual ﬁeld technician, role of, 121 visual function speciﬁc perimetric technologies, 114–18 frequency doubling perimetry, 117 high-pass resolution perimetry (HPRP), 117 short-wavelength automated perimetry (SWAP), 117 tendency-oriented perimetry, 118

Automated perimetry, ﬁeld testing principles of frequency-of-seeing curves and ﬂuctuations, 92–94 kinetic perimetry, 88–90 static perimetry, 90 suprathreshold techniques, 90–92 threshold techniques, 92 Automated perimetry, follow-up printout, 111–14 change analysis printout, 111–14 glaucoma progression analysis printout, 114 guided progression analysis, 114 overview printout, 111 Automated perimetry, future of, 161–73 altered stimuli, 161–69 color perimetry, 168–69 ﬂicker perimetry, 165–67 frequency doubling perimetry/frequency doubling technology (FDP/FDT), 165 motion automated perimetry (MAP), 168 pattern-discrimination perimetry, 168 ring perimetry, 167 short-wavelength automated perimetry (SWAP), 161–65, 166–67f, 168–70f altered strategies, 169–71 interpretive aids, 171–73 Automated perimetry, series of tests evaluation, 144–61 artifacts, 149–54 baseline establishment, 146–49 central abnormalities, follow-up of, 159–60 disc hemorrhage, early defect conﬁrmed by, 148f glaucoma, conﬁrmation of, 145–46f glaucoma progression analysis, 157–59 inferior arcuate region, depression in, 147 long-term ﬂuctuation, 155–56 progression criteria for, 155–57 progression, nature of, 149 trend analysis, 159 Automated perimetry, single test evaluation, 132–44 abnormality, criteria for, 140–43, 143t advanced ﬁeld loss, follow-up of, 144 apparent dense peripheral constriction, 137–38f ﬁeld loss, staging of, 143–44 learning effect, recognition of, 141–42f patient reliability, 132–40 false-negative responses, 136 false-positive responses, 133–36 ﬁxation losses, 133 full threshold algorithm, STF on, 136 stimuli number, 136–40 test duration, 133 test selection, 144 true dense peripheral constriction, 139–40f Automated perimetry options, 129–32 full threshold test advantages of, 129–30 disadvantages of, 130

Index Swedish Interactive Threshold Algorithm (SITA), 130–32 Automated threshold perimetry for chiasmal lesion, 240 Automated visual ﬁelds, 255f Bacterial infection, 194, 256 Bacterial infection, in optic neuritis, 194 Bausch & Lomb colored test objects, 25, 31 Bjerrum region, 52 Best disease, 213, 215 “Big pumpkin test,” cecocentral scotoma, 37 Bilateral central depression, in DOA, 187 Bilateral central ﬁeld defects, 42t, 77–78 Bilateral checkerboard scotomas, 42t, 79–80 Bilateral homonymous hemianopias, 42t, 80, 279, 280, 283 Bilateral peripheral ﬁeld defects, 42t, 78–79 Binocular ﬁeld defects altitudinal ﬁeld defects, 72–75 congruous, 73–75 noncongruous binocular and monocular, 72–73 bilateral central ﬁeld defects, 77–78 bilateral checkerboard scotomas, 79–80 bilateral homonymous hemianopias, 80 bilateral peripheral ﬁeld defects, 78–79 binasal ﬁeld defects, 70–72 complete, 70–71 incomplete, 71 bitemporal hemianopias, 67–70 with central depression, scotomatous, 69–70 complete, 67–69 homonymous hemianopias, 60–67 horizontal sectoranopia, 62–63 incomplete incongruous, 65–66 macular sparing, incomplete, 64 macular splitting, complete, 60–62 paramidline-sparing vertical hemianopia, 63 two scotomas, incomplete, 64 unilateral defect of temporal crescent, 67 unilateral sparing of temporal crescent, 66 quadrantanopias, 75–77 inferior homonymous, complete, 76–77 superior homonymous, incomplete, 75–76 Bipolar cells, 12, 45, 46t, 52 Birdshot chorioretinopathy (BSCR), 217–26 Bitemporal hemianopias, 7, 16, 20f, 42t, 44f, 82f, 181, 234, 236, 249, 250 binocular ﬁeld defects, 67–70 with central depression, scotomatous, 69–70 complete, 67–69 by confrontation testing, 240–41 and Cushing’s syndrome, 248 lesions affecting chiasm body, 243 and pituitary adenomas, 247 Bitemporal hemianopia plus, 83

301

Blindness, 281 chiasmatic postﬁxation, 240–41, 248 complete, 16, 201, 239 cortical blindness, 283, 295 retinal lesions, 16 transient cerebral blindness, 283 using suprathreshold techniques, 90 Blind spot, 21, 26f, 27f, 28f, 52, 73, 88, 97f, 98, 99, 217, 242 false-positive responses, 133 Fuchs colobomata, 181 interpretation of, 4 and optical nerve, 194 Blind spot enlargement, 181, 182f, 250 reasons for, 7 Blue-on-yellow perimetry, 117. See also Shortwavelength automated perimetry (SWAP) Bowl perimeter, 86 Brunescent cataract, 32 Calcarine artery occlusions, 64 Calcarine cortex, 14f, 45, 49f, 61f, 62, 78, 267, 268, 283 incomplete incongruous, 66 macular sparing, incomplete, 64 in occipital lobe ﬁeld defects, 272, 273 visual ﬁeld defects, 264–67 Calcarine cortex, anterior, 67 Calcarine cortex, basal superior or inferior, 74–75 Calcarine cortex, posterior, 66 Calcarine ﬁssure, 13, 15, 44, 46, 47, 48, 66, 273 Calcarine sulcus, 50f, 67, 75, 78, 79 Cancer-associated retinopathy (CAR), 228 Cataract, 32, 59, 60, 103, 105, 111, 119, 141–42, 152f, 157, 161, 279 blind spot interpretation, 4 and SITA Standard, 114 Cecocentral defect, 26f optic nerve and retina, 20 Cecocentral scotoma, 16, 38f , 243 in DOA, 186–87 ﬁeld testing, difﬁculty in, 37 Central ﬁeld examination, guidelines for, 27–31 Central ﬁelds exploration, perimetry, 6–7 vascular lesions, identiﬁcation of, 6 in glaucoma patients, 6–7 Central scotoma or depression, 54–56 optic nerve head, 56 retina, 54–56 retrobulbar optic nerve, 56 Central scotoma, 16 in DOA, 186 and ONH, 179 in optic neuritis, 194 Central serous chorioretinopathy (CSCR), 207 Central visual ﬁeld defect, 181, 182f. See also Blind spot enlargement Central visual loss, in optic neuritis, 194

302

Index

Centrocecal scotoma or depression, 42t, 57–58 optic nerve, 57–58 retina, 57 Cerebral artery occlusions, 272, 273 Cerebral dyschromatopsia, 286, 288–89 Chamlin step technique ﬁeld testing, 31–34 temporal lobe ﬁeld defects, 268 Checkerboard scotoma, bilateral, 42t, 79, 80 Chediak-Higashi syndrome, 215 Chiasmal compression, 245, 249 Chiasmal dysfunction, 234, 250 Chiasmal region lesions aneurysms, 249 craniopharyngiomas, 249 dilatation of the third ventricle, 250 meningiomas, 248 parasellar meningiomas, 249 suprachiasmatic meningiomas, 249 suprasellar meningiomas, 248–49 pituitary tumors, 247–48 Chiasmal tumor, 20f, 21f Chiasmal visual ﬁeld defects, 241–46 Chiasmatic postﬁxation blindness, 240–41 Chorioretinal disorders, 207–32 congenital and genetic diseases, 211–17 retinitis pigmentosa (RP), 211 inﬂammatory/infectious diseases, 217–26 acute zonal occult outer retinopathy (AZOOR), 217 birdshot chorioretinopathy (BSCR), 217 Chediak-Higashi syndrome, 215 cone dystrophy, 215 Hermansky-Pudlak syndrome, 215 multiple evanescent white dot syndrome (MEWDS), 217 ocular histoplasmosis, 217 white dot syndromes, 217 macular diseases, 207–9 causes of, 207 pathologic myopia, 207–9 peripheral retinal abnormalities, 226–32 peripheral tumors, 228 toxicity, 226 vascular diseases, 209–11 intraretinal hemorrhages and exudates, 222–23f microaneurysms and macular ischemia, 218f progressive retinal dysfunction, 217 retinal emboli, 209 Choroidal neovascular membrane, 207, 209 Choroideremia, visual ﬁeld defects by, 211 HVF 10-2 showing, 224–25f Circle of Willis, in optical chiasm, 235, 238f, 249, 256 Clinical perimetry, 4, 86 Cloverleaf ﬁeld, 96, 97f, 136, 137 Cocaine, teratogenic agent, for ONH, 178

Coenzyme Q10, mitochondrial energy production, 184 Cogan’s rule, 66 Collaborative Initial Glaucoma Treatment Study (CIGTS), 132 Collaborative Normal Tension Glaucoma Study, 127 Color agnosia, ﬁeld defects, 288 Color blindness, 37 Color perimetry. See Blue-on-yellow perimetry; Short-wavelength automated perimetry (SWAP) Color testing, 36–38, 285 Color vision recording, 5 Compressive optic neuropathy, 193, 198–200 visual ﬁeld ﬁndings of, 199 Computer graphics, understanding retinotopic projection, 46 Computerized ﬁeld examination of arcuate defect, 27f of bitemporal hemianopia, 20f of cecocentral defect, 26f of chiasmal tumor, 21f incongruous ﬁeld defect., representation of, 17–19f, 22f of paracentral defects, 26f and tangent screen, 3 Computerized perimeter advantage of, 27 use of, 6, 10–11f in central ﬁeld exploration, 6 in neuro-ophthalmic patients, 9–10 Computerized representation of homonymous hemianopia, 265f Computerized visual ﬁeld assessment, 85 Cone dystrophy, 228–29f visual ﬁeld defect, 215–16 Conﬂuent central ﬁeld loss, 171f Confrontation testing for chiasmal lesion, 240–41 Congenital and genetic diseases, 211–17 Congenital color defect, 32 Congenital optic disc anomalies, 177–82 anomalous disc elevations, 180–81 aplasia and dysplasia, 177–79 optic nerve colobomas and pits, 179–81 Congruity, visual ﬁeld testing, 264–67, 267f incongruous superior quadrantanopia, 266f temporal lobe visual ﬁeld defects, 268 Congruous defects, 16 Congruous left inferior quadrantic scotoma, 275f Congruous quadrantanopia, 273 with macular sparing, 274f Congruous scotomas, 273 Conjugate-gaze deviations, and occipital lobe lesions, 285 Contraction, as ﬁeld defect, 294 Corneal scar, 119

Index Corrected pattern standard deviation (CPSD), 105 glaucomatous visual ﬁeld defects, 129 Cortical blindness, 283, 295 Craniopharyngioma, 64, 68–69, 199, 243, 244f, 247, 248, 249 optic tract lesions, 256 Cushing’s syndrome of the chiasm, 248 Custom tests, automated perimetry, 105–11 FASTPAC algorithm, 95, 108–9 grid size, 108 Nasal Step program, 110 Peripheral 60 and 60-4 program, 110 Programs 30-1 and 24-1, 109 stimulus size option, 111 Cycloplegia, 296 Cystoid macular edema, 211, 217, 226 HVF 24-2 showing, 220f Dazzle test and papillary responses, 5 de Morsier syndrome. See Septo-optic dysplasia Defects in ﬁelds, interpretation of, 16–21 anatomic locations, types of defects, 16 computerized perimetry, use of, 9 margin, deﬁnition of, 20 in optic nerve and retina, 20–21 tangent screen representation in, 17–19f Déjérine-Roussy syndrome, 260 Differential light sensitivity, static perimetry, 87 Diffuse depression, in optic neuritis, 194 Dilatation of the third ventricle, 250 Dominant optic atrophy (DOA), 185–88 visual ﬁnding of, 186 Double-ring sign, 178, 178f Drusen, macular pathology, 207 Duochrome test, for functional loss, 296–97 Dyscalculia, 23, 270 Dyschromatopsia, 37–38, 182, 288–89 in color testing, 37 in dominant optic atrophy (DOA), 186 in LHON, 183 Early Manifest Glaucoma Trial (EMGT), 157 Early-crossing ﬁbers, 239 Edinger-Westfall nucleus, 256 Electro-oculography (EOG), macular diseases, 207, 215 Electroretinographic (ERG) testing, macular diseases, 207, 215 and cancer-associated retinopathy (CAR), 228 melanoma-associated retinopathy (MAR), 232 Embolic disease, 49 multiple emboli, 273, 279 retinal emboli, 209 Energy depletion, 183 Enlarged blind spot, in papilledema, 200 Enlarged physiologic blind spot, 56–57 optic nerve, 57 peripapillary retina, 56–57

303

Equatorial annular scotoma or depression, 58–59 equatorial retina, 58 preretinal media, 58 Esophoria, 241 Exophoria, 241 Extrinsic lesion, 247t Eyelids, and nose effects, 119 False-negative responses automated perimetry in glaucoma, 136 False-positive responses automated perimetry in glaucoma, 133–36 False-positive errors, 133–36 superimposed on glaucomatous defects, full threshold test, 135f FASTPAC algorithm, 95, 108–9 Field testing, techniques of, 21–38 Amsler grid, 36 central ﬁeld technique, 24–31 central ﬁeld examination, 27–31 No. 966 Eagle Prismacolor pencil, 29–31 paracentral defects, 26f spherical test object, 25 tangent screen representation, 25f Chamlin step technique, 31–34 homonymous ﬁelds, 34 color testing, 36–38 big pumpkin test, cecocentral scotoma, 37 confrontation technique, 21–24 tangent screen examination, 22f temporal and nasal ﬁelds, comparison of, 23–24 ﬁnger counting method, 23 for peripheral ﬁeld defect, 31 peripheral ﬁeld technique, 34–35 Riddoch phenomenon, 35 temporal and nasal ﬁelds, comparison of, 35f Finger counting, 23 Finger movement technique, 23 Fixation losses, 136 Flat test object, 25 Folate, mitochondrial energy production, 184 Frequency-of-seeing curves and ﬂuctuations, ﬁeld testing principles, 92–94 Fuchs colobomata, 181 Full threshold testing strategy, 129–30 Functional MRI (fMRI), understanding retinotopic projection, 46, 48 Functional visual loss ﬁeld loss types, 294–95 patient types, 293 tests for, 295–97 Fundus ﬂavimaculatus, 213. See Stargardt disease Fundus photography, band atrophy, 256 Fungal infection, 256 Fusion testing, macular area evaluation, 5

304

Index

General contraction, 16 Generalized constriction papilledema, 201, 202–3f Generalized defects, monocular ﬁeld defects, 59–60 generalized depression or peripheral contraction, 59–60 Generalized depression or peripheral contraction, 59–60 optic nerve, 60 preretinal media, 59–60 retina, 60 Geniculocalcarine ﬁbers, visual pathway, 13 Geographic atrophy mimicking paracentral glaucomatous ﬁeld loss, patient with, 156–57f Gerstmann syndrome, 270–71 Giant aneurysm, 250 Glaucoma hemiﬁeld test (GHT) abnormally high sensitivity, display of, 134 Glaucoma, 295 progression analysis printout, 115f Glaucomatous cupping, 128 Glaucomatous ﬁeld loss, single ﬁeld printout, 100f deviation and the pattern standard deviation, 107f Glaucomatous scotomas, detection of by manual perimetry, 128 Glaucomatous visual ﬁeld loss, and automated perimetry, 127–29 advanced ﬁeld loss, 150–51f age-related macular degeneration, 156 dense superior and inferior arcuate-type defects, 158–59f diagnosing acquired glaucomatous damage, 144t early glaucomatous generalized depression, 130–31f and elevated mean deviation, 129 evaluation of series of tests, 144–61 artifacts, 149–54 baseline establishment, 146–49 central abnormalities, follow-up of, 159–60 glaucoma progression analysis, 157–59 long-term ﬂuctuation, 155–56 progression, criteria for, 155–57 progression, nature of, 149 trend analysis, 159 evaluation of single test, 132–44 abnormality, criteria for, 140–43, 143t advanced ﬁeld loss, follow-up of, 144 ﬁeld loss, staging of, 143–44, 149t patient reliability, 132–40 test selection, 144 full threshold test advantages of, 129–30 disadvantages of, 130 generalized depression on, 130–31f

and glaucoma management, identiﬁcation of, 127 high pass resolution perimetry in, 173f central scotomas, occurrence of, 129 multiple confounding variables, 152–55f ocular hypertension, 160f Gliomas, 193, 198–99, 247t, 250 Goldmann perimeter, 4, 11, 86, 111 advantage of, 27 central ﬁeld exploration, 6 for chiasmal lesion, 240 for peripheral ﬁeld technique, 34–35 and tangent screen, 3 Goldmann visual ﬁeld with superior depression, peripheral retinal abnormalities, 231–32f Guided Progression Analysis (GPA), 157, 162–65f PROGRESSOR trend analysis, 165f Gun barrel ﬁeld, 295 Gustatory hallucinations, 269 Gyrate atrophy, visual ﬁeld defects by, 211 Hallucinations occipital lobe ﬁeld defects and, 285 temporal lobe ﬁeld defects and, 268–69 gustatory hallucinations, 269 Halved vision, 233 Headache in dilatation of third ventricle, 250 in papilledema, 200, 201 in pituitary tumor, 233 inarteritic ischemic optic neuropathy, 196 nonsecreting tumors, 247 pituitary apoplexy, 248 suprasellar meningiomas, 248–49 Heijl-Krakau blind spot monitoring technique, 96 Hemianesthesia, 61, 256, 260 Hemianopia, 179, 256 Hemianopic pupillary sign, 254 Hemianopsia, 16 and Chamlin step technique, 32 Hemiﬁeld slide phenomenon, 240–41 Hemiretinal suppression, 31 Heredodegenerative optic atrophies, 182–83 dominant optic atrophy (DOA), 185–88 Leber’s hereditary optic neuropathy (LHON), 183–85 recessive optic atrophy (ROA), 189 Hermansky-Pudlak syndrome, oculocutaneous albinism, 215 High-resolution optical coherence tomography (OCT), 226 Histiocytosis, 247t, 250 Homonymous defects, incongruous, 16 Homonymous hemianopia, 16. See also Halved vision occipital cortex ﬁeld defects, 273 with macular sparing, 275 bilateral, 280–81

Index Homonymous hemianopias horizontal sectoranopia, incomplete congruous, 62–63 incomplete incongruous, 65–66 macular sparing, incomplete, 64 macular splitting, complete, 60–62 paramidline-sparing vertical hemianopia, 63 two scotomas, incomplete, 64 unilateral defect of temporal crescent, incomplete, 67 unilateral sparing of temporal crescent, incomplete, 66 Homonymous hemianopic scotoma detection of, 263 multiple sclerosis and, 283 Horizontal sectoranopia, incomplete congruous, 62–63 Hormone-secreting adenoma, 247 HRR plates, 37, Humphrey 24-2 visual ﬁeld, 243–44f, 245f Humphrey perimeter, 9 depicting variations, ﬁelds defects, 19 Humphrey Visual Field Analyzer, 85, 88, 93, 95, 293 ﬁxation monitoring by, 96–99 graytone symbols, use of, 87f visual threshold, measurement of, 88f Hydroxychloroquine toxicity, 226 Hyperphoria, 241 Hyperplasia, 177 Hypoplasia, 177, 178, 179, 215 Hysteric patients, 293 Iatrogenic lesion, 247t Idiopathic blind spot, 250 Idiopathic intracranial hypertension (IIH), 193 and papilledema, 201 Illuminance, measurement of light, 87 Incomplete incongruous, binocular ﬁeld defects, 65–66 anterior optic tract, 65 occipital lobe, 66 optic radiation, 65–66 Internal carotid artery (ICA) aneurysms, 243 Intracranial aneurysm, 199, 249 Intraretinal hemorrhages and exudates, HVF 24-2, 222–23f Intravenous steroids in arteritic ischemic optic neuropathy (AAION), 197 in optic neuritis, 194 Intrinsic lesion, 247t Ipsilateral optic tract, 239 Ischemic optic neuropathies, 193 Isopter clinical perimetry, 4 perimetry chart, 85

305

Junctional ﬁeld defects, 80–83 bitemporal hemianopia plus, 83 complete monocular plus incomplete contralateral ocular, 80–81 homonymous hemianopia plus, 81–83 Junctional scotoma, 241, 242f Kinetic perimetry, 5 ﬁeld testing principles, 88–90 visual ﬁeld, localized shallow depressions of, 89f Kinetic stimuli, measurement of light, 87 Kinetic testing, blind spot interpretation, 4 Kjer’s optic neuropathy. See Dominant optic atrophy (DOA) Knapp’s description, and blind spot, 7 Kollner’s law, in color testing, 36 Lateral choroidal artery, occlusion of, 260f Lateral geniculate body ﬁeld defects, 258–61 Lateral geniculate nucleus (LGN), 239, 253 L-carnitine, mitochondrial energy production, 184 Learning effect and artifacts, automated perimetry, 118–20 corrective lens/frame artifacts, 120 eyelid and nose effects, 119 media opacities, 119 miosis, 118–19 mydriasis, 118–19 refractive errors, 119–20 Leber’s hereditary optic neuropathy (LHON), 183–85 characteristics of, 183 dense central visual ﬁeld defect, 185f Light, measurement of, 87 Linear magniﬁcation factor, 277–78 Localization, visual ﬁeld testing, 264–67 of hemianopic ﬁeld defect, 268 Localized defects, monocular ﬁeld defects, 48–59 altitudinal hemianopia, 59 arcuate and paracentral ﬁeld defects, 52–54 central scotoma or depression, 54–56 centrocecal scotoma or depression, 57–58 enlarged physiologic blind spot, 56–57 equatorial annular scotoma or depression., 58–59 wedge-shaped temporal ﬁeld defect, 48–52 Localized scotoma, 105, 106f, 111, 129, 130f, 133 Los Angeles Latino Eye Study, 127 Luminance, measurement of light, 87 Macroaneurysm, 209 Macular area, evaluation of, 5 Macular degeneration, dry age-related, 36f, 57, 156, 207, 208f, 209f geographic atrophy in, 209 Macular diseases, visual ﬁeld defects by, 207–9

306

Index

Macular edema, macular pathology causing visual ﬁeld defect, 207 cystoid, associations with RP, 211 by diabetic retinopathy, 209 Macular ﬁbers, 13, 14f, 15 Macular hole, 207 Macular scar, 207 Macular sparing automated perimetry, limitation of, 263 congruous left inferior quadrantanopia with, 274f homonymous hemianopia with, 275 incomplete, binocular ﬁeld defects, 64 in occipital lesions, 273–74 Macular splitting, complete, 61–62 calcarine cortex, 62 lateral geniculate body, 61 optic peduncle, 61 optic radiation, 61–62 optic tract, 61–62 Magnetic resonance imaging (MRI), occipital lobe ﬁeld defects paracentral hemianopic scotoma on, 276f striate cortex, studies on, 277f superior and inferior mid-peripheral scotomas, 277f vascular occlusions identiﬁcation on, 272 Male population color defect in, 285 LHON in, 183 Malingerers, 293 Maternal diabetes, an ONH, 178 Mean deviation (MD), single ﬁeld printout, 105 glaucomatous ﬁeld loss, 107f Melanoma-associated retinopathy (MAR), 228 in patients with melanoma, 232 Meningiomas, 248 optic tract lesions, 256 parasellar meningiomas, 249 suprachiasmatic meningiomas, 249 suprasellar meningiomas, 248–49 Metabolic optic neuropathies, 182, 193, 198 Meyer’s loop temporal lobe ﬁeld defects, 267 visual pathway, 13 Microaneurysm, 218t and macular ischemia, HVF 24-2, 218f Microangiopathy, in LHON, 183 Miosis, 6, 129 in blind spot interpretation, 4 and mydriasis, 118–19 Mirror tests, 297 Mitochondrial DNA (mtDNA) in optic neuropathies, 182 Mitochondrial function and inherited optic neuropathies, 182 Monocular ﬁeld defects generalized defects, 59–60 generalized depression or peripheral contraction, 59–60

localized defects in, 48–59 altitudinal hemianopia, 59 arcuate and paracentral ﬁeld defects, 52–54 central scotoma or depression, 54–56 centrocecal scotoma or depression, 57–58 enlarged physiologic blind spot, 56–57 equatorial annular scotoma or depression, 58–59 wedge-shaped temporal ﬁeld defect, 48–52 Morning glory syndrome, 179–80, 180f Moth-eaten visual ﬁeld, 133 MRI, understanding retinotopic projection, 46, 50f Multifocal visual evoked potentials, 240 Multiple evanescent white dot syndrome (MEWDS), 207, 217, 250 Multiple sclerosis, 250 Mydriasis and miosis, 118–19 Nasal step defects, defects in ﬁelds, 16 Nausea in dilatation of third ventricle, 250 ND1, role in LHON, 183 ND4, role in LHON, 183 ND6, role in LHON, 183 Nerve ﬁber layer swelling, in LHON, 183 Nerve ﬁbers, visual pathway, 12–13, 14f, 15 Neurasthenic patients, 293 Neurologic deﬁcits accompaniment, temporal lobe ﬁeld defects, 268 Neuro-ophthalmic signs, 253 Neurosonography, 276 Newer techniques, patient’s reliability in, 3 No light perception (NLP), 189 Nonarteritic ischemic optic neuropathy (NAION), 193 signs of, 196 visual ﬁeld effects of, 196 Nondominant parietal lobe dysfunction, 271 Normal chiasm, 235f Normal pattern standard deviation (PSD), 129 Nuclear gene OPA1, cure for DOA, 187 No. 966 Eagle Prismacolor pencil, ﬁeld testing, 29–31 Nystagmus, 178, 189 optokinetic (OKN), 66 Occipital lobe ﬁeld defects, 272–89 color ﬁeld defects in, 285–89 aphasia, color-naming, 287 cerebral dyschromatopsia, 288–89 color agnosia, 288 conjugate-gaze deviations, 285 occipital cortex, ﬁeld defects unique to, 282–85 lesions, impacts of, 283–84 open-heart surgery, ﬁeld defects by, 273 types of, 273–82 Anton syndrome, 281–82 congruous left inferior quadrantic scotoma, 275f

Index congruous scotomas, 273 horseradish peroxidase, 276 linear magniﬁcation factor, 277–78 neurosonography, 276 occipital lobe injuries, 277f, 278f, 279f, 280f, 281f paracentral hemianopic scotoma, 276f superior and inferior mid peripheral scotomas, 277f tentorial herniation, 283–84 Occipital lobe injuries, 277f, 278f, 279f, 280f, 281f Occipital lobe lesions, 46–48 Occlusion, retinal arterioles, 50 Ocular histoplasmosis HVF 24-2 showing, 230–31f visual ﬁeld defect, 217 Ocular melanoma, peripheral visual ﬁeld changes by, 228 Oculocutaneous albinism, visual ﬁeld defects by, 215 Older techniques, importance of, 3 Olfactory groove meningiomas. See Suprachiasmatic meningiomas 11778 mtDNA mutation, 183 14484 mtDNA mutation, 183, 184 Ophthalmoscopy, band atrophy, 256 Optic chiasm, 44f, 45 visual pathway, 12–13, 14f Optic disc drusen, 181, 182f blind spot enlargement in, 182f Optic disc pit, 180f, 180–81 arcuate bundle scotoma, 181 Fuchs colobomata, 181 Optic nerve hypoplasia (ONH), 178 ﬁeld defects of, 178 altitudinal defects, 179 central depression, 179 generalized constriction, 179 hemianopias, 179 nasal wedges, 178 temporal wedges, 179 Optic nerve, defects affecting, 20–21 Optic neuritis, 194–95 visual ﬁeld ﬁndings, 194 Optic radiation, 273 and calcarine cortex visual ﬁeld defects, 264–67 homonymous hemianopia, 265f incongruous superior quadrantanopia, 266f visual pathway, 13, 14f Optic tract ﬁeld defects, 253–58 Optical chiasm, 233–34 anatomy of, 234 gross anatomy, 234–36 nerve ﬁber anatomy, 236–40 bitemporal hemianopia, 250 chiasmal region lesions aneurysms, 249 craniopharyngiomas, 249 dilatation of third ventricle, 250

307

meningiomas, 248 pituitary tumors, 247–48 chiasmal visual ﬁeld defects, 241–46 ﬁeld effects, tests for, 240–41 pseudo temporal hemianopia, 250 Optochiasmic arachnoiditis, 71 Optociliary shunt vessels in compressive optic neuropathy, 199 Optokinetic nystagmus (OKN), 66, 268, 297 in cerebral hemisphere disease, 272 in occipital lobe lesions, 285 Oxidative phosphorylation, 182, 183 Pantograph, 9 Papilledema, 56–57, 200–201, 234, 250 optic nerve and retina, 20 signs of, 200 Paracentral defect, 26f, 209 Paracentral ﬁeld defects, 52–54 optic nerve head, 53–54 retina, 53 retrobulbar optic nerve, 54 Paracentral ﬁeld loss, 171f Paracentral hemianopic scotoma, 276f Paracentral scotoma, 16, 54, 85, 108, 128, 129, 226, 284f in DOA, 186 in optic neuritis, 194 Paramidline-sparing vertical hemianopia, 63 Parasellar meningiomas, 249 Parietal lobe ﬁeld defects, 269–72 Gerstmann syndrome, 270–71 nondominant parietal lobe dysfunction, 271 pie on-the-ﬂoor defect, 270 Parvocellular (P) cells, 56, 117, 161, 167 Pathologic myopia, 207–9 macular pathology causes, 207 Pattern standard deviation (PSD), single ﬁeld printout, 103f, 105, 129, 144t glaucomatous ﬁeld loss, 107f localized scotoma, representation of, 106f Percipient elements, edematous elevations of, 7 Pericecal ﬁeld defect. See Physiologic blind spot Perichiasmal lesions, retrochiasmal lesions, 46 Perimetry, overview of central ﬁelds, exploration of, 6–7 in glaucoma patients, 6–7 quantitative perimetry, 7 vascular lesions, identiﬁcation of, 6 experience, learning from, 3 function of perimetry, 4 peripheral ﬁelds, exploration of, 5–6 tangent screen test in, 6 physiologic blind spot, 7 recording ﬁelds, 7–12 artiﬁcial illumination, use of, 7–8 coding device, colors, 9 visual ﬁelds, examination and interpretation of, 10–12f visual ﬁelds charts, 8f

308

Index

Peripheral defects, Chamlin step technique, 31 Peripheral ﬁelds exploration, perimetry, 5–6 tangent screen test in, 6 Peripheral retina abnormalities, 226–32 Peripheral retinal abnormalities, 226–32 Phenytoin, teratogenic agent, for ONH, 178 Phoropter, 296 Physiologic blind spot, 7, 42t, 47f, 48, 49, 56, 143t, 200 bilateral cecocentral, 198 enlarged, 56–57 nasal wedge, 178 optic nerve, 57 peripapillary retina, 56–57 temporal wedge, 179 Pie on-the-ﬂoor defect, 270 Pie-in-the-sky defect, 267 Pituitary adenoma, 69, 70, 199, 200, in anatomy of chiasm, 234, 236, 242f chiasmal region lesion, 247–48 in optic tract ﬁeld defect, 255f Pituitary apoplexy, 248 Pituitary tumors, 233, 247–48 optic tract lesions, 256 pituitary adenomas, 247–48 pituitary apoplexy, 248 pituitary carcinoma, 247 secreting tumors, 247 thyrotroph adenomas, 247 Posterior cerebral artery occlusion, 272–73 Posterior optic neuritis. See Retrobulbar optic neuritis Posterior visual pathway, 45 Posteromedial occipital lobe, schematic representation showing, 51f Postﬁxed position, of chiasm, 234, 237f Postictal hemianopia, 283 Prednisone in arteritic ischemic optic neuropathy (AAION), 197 in optic neuritis, 194 Preﬁxed position, of chiasm, 234, 236f Primary open-angle glaucoma defects versus normal-tension glaucoma defects, 129 Primary visual ﬁeld, representation of, 47 Primary visual sensory pathway, 45 Prism tests, for functional loss, 296 Programs 30-1 and 24-1, 109 Progressive retinal dysfunction, 217 Projection perimeter machines, 27 Pseudo temporal hemianopia, 250 Pseudopapilledema, 181 visual ﬁeld defects of, 181 Pseudotumor cerebri. See Idiopathic intracranial hypertension (IIH) Pyramidal tract signs, 256

Quadrantanopias, binocular ﬁeld defects, 16, 42t, 44f, 68, 81, 260, 267, 268, 269, 274, 280 inferior homonymous, complete, 76–77 superior homonymous, incomplete, 75–76 Quadrantic defects, retina, 20–21, 278f Qualitative perimetry, central ﬁeld exploration, 7 Quantitative perimetry, central ﬁeld exploration, 7 Quinine, teratogenic agent, for ONH, 178 Radiation necrosis, 250 Reactive oxygen species (ROS), 183 Recessive optic atrophy (ROA), 189 Red color test object, for central scotoma, 33 Relative afferent pupilary defect (RAPD) in optic neuritis, 194 in compressive optic neuropathy, 199 Relative defect, defects in ﬁelds, 19 Respiratory chain dysfunction, in LHON, 183 Retina, functional microanatomy of, 45 Retinal artery occlusions, 295 Retinal displacement, blind spot enlargement, 7 Retinal elevation of percipient elements, blind spot enlargement, 7 Retinal emboli, visual ﬁeld defects by, 209 Retinal hemorrhage, macular pathology causes, 207 Retinal nerve ﬁber layer, lesions of, 46 Retinal pigment epithelium (RPE), macular diseases, 207, 214f, 224f Retinal problems, in temporal defects, 250 Retinal sensitivity, central ﬁeld exploration, 6 Retrobulbar optic neuritis, 194 Retrochiasmal lesions, neural territory, 46 Retrochiasmal visual ﬁeld defects, 267 Retrogeniculate visual ﬁeld defects, 263–89 occipital lobe ﬁeld defects, 272–89 color ﬁeld defects in, 285–89 occipital cortex, ﬁeld defects unique to, 282–85 open-heart surgery, ﬁeld defects by, 273 types of, 273–82 optic radiation and calcarine cortex visual ﬁeld defects, 264–67 homonymous hemianopia, tangent screen representation of, 265f incongruous superior quadrantanopia, 266f parietal lobe ﬁeld defects, 269–72 Gerstmann syndrome, 270–71 pie on-the-ﬂoor defect, 270 temporal lobe ﬁeld defects, 267–69 neurologic deﬁcits accompanying, 268 pie-in-the-sky defect, 267 testing for, 263–64 Riddoch phenomenon, 35 and occipital visual ﬁeld defects, 282, 283

Index Sarcoidosis, 250 Scotoma, blind spot interpretation, 4, 17, 16 and central ﬁeld exploration, 6 computerized representation of, 12f identiﬁcation of, 6 and physiologic blind spot, 7 Scotoma, macular diseases, 209 central Goldmann visual ﬁeld showing, 216–17f HVF 10-2 demonstration, 212–13f paracentral, 207 Sectoranopia, 42t, 62, 260 Seidel scotomas, glaucoma, 128 Sensorineural hearing loss, in DOA, 187 Septo-optic dysplasia, 178 Short-term ﬂuctuation (STF) full threshold testing strategy, 129 visual ﬁeld thresholds, 93 and seed-point locations, 96f Short-wavelength automated perimetry (SWAP) altered stimuli, automated perimetry future of, 161–65 visual function speciﬁc perimetric technologies, 117 Single test printout, automated perimetry, 99–105 Glaucoma Hemiﬁeld test, 102–5 global indices, 105 numeric results and grayscale results, 101 pattern deviation, 101 reliability indices, 99–101 test selection, 99 total deviation, 101 SITA Fast claim, 136 SITA Standard 24-2, for glaucoma patients, 144 Sloping, ﬁeld defects, 19 Snellen acuity, visual ﬁeld interpretation, 4–5, 99, 111, 119 Sphenoid wing meningiomas. See Parasellar meningiomas Spherical test object, advantage of, 25 Standard automated perimetry, 85 custom tests, 105–11 FASTPAC algorithm, 95, 108–9 grid size, 108 Nasal Step program, 110 Peripheral 60 and 60-4 program, 110 Programs 30-1 and 24-1, 109 stimulus size option, 111 ﬁeld testing, principles of, 86–94 frequency-of-seeing curves and ﬂuctuations, 92–94 kinetic perimetry, 88–90 static perimetry, 90 follow-up printout, 111–14 change analysis printout, 111–14 glaucoma progression analysis printout, 114 guided progression analysis, 114 overview printout, 111

309

historical overview of, 85–86 learning effect and artifacts, 118–20 corrective lens/frame artifacts, 120 eyelid and nose effects, 119 media opacities, 119 miosis and mydriasis, 118–19 refractive errors, 119–20 single test printout in, 99–105 Glaucoma Hemiﬁeld test, 102–5 global indices, 105 numeric results and grayscale results (raw data), 101 pattern deviation, 101 reliability indices, 99–101 test selection, 99 total deviation, 101 test selection and algorithms, 94–99 ﬁxation monitoring, 96–99 foveal threshold, 95 initial values, 95–96 Swedish Interactive Threshold Algorithm (SITA), 94–95 threshold testing, 99 visual ﬁeld technician, role of, 121 visual function speciﬁc perimetric technologies, 114–18 frequency doubling perimetry, 117 high-pass resolution perimetry (HPRP), 117 short-wavelength automated perimetry (SWAP), 117 tendency-oriented perimetry, 118 Stargardt disease, 213 Static automated threshold perimetry for glaucoma patients, 86 Static perimetry, 5, 10f, 85, in differential light sensitivity, 86–87 suprathreshold techniques, 90 visual threshold, measurement of, 90f Static stimuli, measurement of light, 87 STATPAC, Humphrey perimeter, 101, 141f in glaucoma progression analysis, 114 and global indices, 105 in stimulus size option, 111 Stiles-Crawford effect, blind spot enlargement, 7 Succinate, mitochondrial energy production, 184 Superior nasal paracentral loss, 284f Suprachiasmatic meningiomas, 249 Suprasellar meningiomas, 248–49 Suprathreshold techniques, in static perimetry, 90–92 Swedish Interactive Threshold Algorithm (SITA) automated perimetry options, 130–32 conﬂuent central and paracentral ﬁeld loss, follow-up testing, 171–72f for glaucoma patients, 144 standard, versions of, 94, 95

310

Index

Tangent screen representation of arcuate defect, 27f of bitemporal hemianopia, 20f of cecocentral defect, 26f for chiasmal lesion, 240 of chiasmal tumor, 21f and computerized perimetry and static perimetry, comparison of, 10–11f evaluating visual system by, 5 and Goldmann perimeter, 3 of homonymous hemianopia, 265f of incongruous ﬁeld defect, 17–19f, 22f of paracentral defects, 26f Temporal lobe ﬁeld defects, 267–69 hallucinations, 268–69 neurologic deﬁcits accompaniment, 268 optokinetic nystagmus (OKN), 268 pie-in-the-sky defect, 267 temporal lobe tumor, 269 progression of visual ﬁeld defects, 266f, 268, 269f Temporal retinal ﬁbers, 127–28 Temporal wedge defect in glaucoma, 129 in ONH, 179 Tentorial herniation, 283–84 Test selection and algorithms, automated perimetry ﬁxation monitoring, 96–99 foveal threshold, 95 initial values, 95–96 Swedish Interactive Threshold Algorithm (SITA), 94–95 threshold testing, 99 Testing algorithms, evolutions in, 130–32 Thiamine, mitochondrial energy production, 184 3460 mtDNA mutation, 183 Threshold-related test, suprathreshold techniques, 91f Thyrotroph adenoma, 247 Tilted discs, 7 with crescent, 181 optic nerve disorder, 250, Toxicity, 211, 226 Transient cerebral blindness, 283 Traumatic lesions, 247t Tributary retinal veins, thrombosis, 50 Tuberculum sella meningiomas. See Suprasellar meningiomas Tübingen perimeter, 86 Tumors, central ﬁeld exploration, 6 Two scotomas postchiasmal visual pathway, 64 Uhtoff’s phenomena, 194 Unilateral occipital lesions, 273, 275

Vascular diseases, visual ﬁeld defects by, 20–21, 209–11 Vein occlusions, 209 Ventricular decompression, cortical blindness with, 283 Ventriculography, cortical blindness with, 283 Viral infection inﬂammatory diseases, 217 in optic neuritis, 194 Visual agnosia, color testing, 37 Visual evoked response, 297 Visual ﬁeld defects in chorioretinal disorders, 207–32 congenital and genetic diseases, 211–17 macular diseases, 207–9 peripheral retina abnormalities, 226–32 toxicity, 226 vascular diseases, 209–11 Visual ﬁeld defects, anatomic basis and differential diagnosis, 42t binocular ﬁeld defects, 60–80 altitudinal ﬁeld defects, 72–75 bilateral central ﬁeld defects, 77–78 bilateral checkerboard scotomas, 79–80 bilateral homonymous hemianopias, 80 binasal ﬁeld defects, 70–72 bitemporal hemianopias, 67–70 homonymous hemianopias, 60–67 quadrantanopias, 75–77 categories of, 41–43 junctional ﬁeld defects, 80–83 bitemporal hemianopia plus, 83 complete monocular plus incomplete contralateral ocular, 80–81 homonymous hemianopia plus, 81–83 monocular ﬁeld defects, 48–60 generalized defects, 59–60 localized defects, 48–52 related to anatomy of visual pathway, 44f Visual ﬁeld technician, role of, 121 Visual ﬁeld testing and automated perimetry, 263 nondominant parietal lobe dysfunction, complications by, 271–72 Visual function speciﬁc perimetric technologies, 114–18 frequency doubling perimetry, 117 high-pass resolution perimetry, 117 short-wavelength automated perimetry (SWAP), 117 tendency-oriented perimetry, 118 Visual pathway anterior visual pathway, 45 arterial supply of, 45f location of, 13

Index overview of, 43–48 occipital lobe, 46–48 related disease, computer-assisted perimetry, 10–11f structure of, 12–15 macular ﬁbers in, 13, 14f nerve ﬁbers in, 12–13 optic radiation, 13 territories of, 43–46, 46t neural territory, 46 preretinal territory, 43–46 Visual system, evaluation of, 5, 86–87, 98–99, 285, 293, 297

Vitamins deﬁciency of, 198 in mitochondrial energy production, 184 Vitelliform dystrophy, 213–15 Wedge-shaped temporal ﬁeld defect, 42t, 48 optic nerve head, 52 retina, 49–52 retrobulbar optic nerve, 52 White dot syndromes, 207, 217, 250 White scotomas, 133, 134f Wilbrand’s knee, 81, 239, 240, 242

311