Step by Step Minimally Invasive Glaucoma Surgery

Step by Step Minimally Invasive Glaucoma Surgery Step by Step Minimally Invasive Glaucoma Surgery Editors Ashok Garg M...

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Step by Step Minimally Invasive Glaucoma Surgery

Step by Step Minimally Invasive Glaucoma Surgery Editors Ashok Garg MS, PhD, FIAO (Bel) FRSM, ADM, FAIMS, FICA International and National Gold Medalist Medical Director Garg Eye Institute and Research Centre 235-Model Town, Dabra Chowk Hisar-125005 (India)

Shlomo Melamed MD, PhD Profesor of Ophthalmology Sackler Medical School Tel-Aviv University Head and Chairman Sam Rothberg Glaucoma Centre Tel-Hashomer, Israel

Jerome Jean – Phillippe Bovet MD Consultant Ophthalmic Surgeon FMH Clinique de L’oeil 15, Avenyue Du Bois-de-law Chapelle CH-1213, Onex Switzerland

Bojan Pajic MD Chief of Glaucoma Department Chief Corneal and Refractive Surgery Department, Vision Care Klinik Pallas, Louis Giroud Str. 20 4600 Olten, Switzerland

Roberto G Carassa MD Associate Professor of Ophthalmology Director, Glaucoma Service Deptt. of Ophthalmology and Visual Sciences, University Hospital S. Raffaele, Milano, Italy

Tanuj Dada MD Additional Professor of Clinical Ophthalmology RP Centre for Ophthalmic Sciences AIIMS, Ansari Nagar New Delhi-110029, India

Foreword

Robert Jay Weinstock

JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTD New Delhi

Published by Jitendar P Vij

Jaypee Brothers Medical Publishers (P) Ltd EMCA House, 23/23B Ansari Road, Daryaganj, New Delhi 110 002, India Phones: +91-11-23272143, +91-11-23272703, +91-11-23282021, +91-11-23245672 Fax: +91-11-23276490, +91-11-23245683 e-mail: [email protected] Visit our website: www.jaypeebrothers.com Branches • 2/B, Akruti Society, Jodhpur Gam Road Satellite Ahmedabad 380015 Phone: +91-079-30988717 • 202 Batavia Chambers, 8 Kumara Krupa Road, Kumara Park East Bangalore 560 001, Phones: +91-80-22285971, +91-80-22382956, +91-80-30614073 Tele Fax : +91-80-22281761 e-mail: [email protected] • 282 IIIrd Floor, Khaleel Shirazi Estate, Fountain Plaza, Pantheon Road Chennai 600 008, Phones: +91-44-28262665, +91-44-28269897 Fax: +91-44-28262331 e-mail: [email protected] • 4-2-1067/1-3, Ist Floor, Balaji Building, Ramkote Cross Road Hyderabad 500 095, Phones: +91-40-55610020, +91-40-24758498 Fax: +91-40-24758499 e-mail: [email protected] • 1A Indian Mirror Street, Wellington Square, Kolkata 700 013 Phones: +91-33-22456075, +91-33-22451926 Fax: +91-33-22456075 e-mail: [email protected] • 106 Amit Industrial Estate, 61 Dr SS Rao Road, Near MGM Hospital Parel, Mumbai 400 012 Phones: +91-22-24124863, +91-22-24104532, +91-22-30926896 Fax: +91-22-24160828 e-mail: [email protected] • “KAMALPUSHPA” 38, Reshimbag, Opp. Mohota Science College, Umred Road, Nagpur 440 009 (MS) Phones: +91-712-3945220, + 91-712-2704275 e-mail: jpmednagpur @rediffmail.com

Step by Step Minimally Invasive Glaucoma Surgery © 2006, Editors All rights reserved. No part of this publication and interactive DVD ROM should 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 written permission of the editors and the publisher. This book has been published in good faith that the material provided by contributors is original. Every effort is made to ensure accuracy of material, but the publisher, printer and editors will not be held responsible for any inadvertent error(s). In case of any dispute, all legal matters are to be settled under Delhi jurisdiction only. First Edition: 2006 ISBN 81-8061-738-6 Typeset at JPBMP typesetting unit Printed at Paras Press

Dedications • My Respected Param Pujya Guru Sant Gurmeet Ram Rahim Singh Ji for his blessings & motivation. • My Respected Parents, teachers, my wife Dr. Aruna Garg, son Abhishek and daughter Anshul for their constant support and patience during all these days of hard work. • My dear friend Dr. Amar Agarwal, a leading International Ophthalmologist from India for his continued support and guidance. Dr. Ashok Garg • To my loving wife Shuvit.

Dr. Shlomo Melamed

• Yveric, Luc and Fanny Laure. • Silvio Korol, who was not only a teacher but also an intellectual guide and a friend. Dr. Jerome Bovet • To my son Valentin Aleksandar.

Dr. Bojan Pajic

• To my collaborators Dr. Marina Fiori and Dr. Paolo Bettin, for their constant help and support in my clinical work and research. Dr. Roberto G Carassa • The Revered Sufi Saint Hazoor Maharaj Gurmeet Ram Rahim Singh Ji, Dera Sacha Sauda Ashram, Sirsa, Haryana, India. Dr. Tanuj Dada

CONTRIBUTORS Ahmed Galal MD, Ph D

Vissum/Instituto Oftalmologico De Alicante Alicante Spain Amar Agarwal

Bojan Pajic MD Chief, Cornea and Refractive Surgery Deptt., Vision Care Klinik Pallas Louis Giroud Str. 20 4600 Olten, Switzerland Cyres K Mehta

MS, FSVH, FAGE MS, FRCS, FRC Ophth. Director & Consultant

Director Dr. Agarwal’s Eye Hospital 19, Cathedral Road Chennai-600086 India André Mermoud MD Prof. of Ophthalmology Jules Gonin Eye Hospital CH-1004 Lausanne Switzerland Ashok Garg MS, Ph D, FRSM

Medical Director Garg Eye Institute & Research Centre 235-Model Town Dabra Chowk Hisar-125005 (India)

Mehta International Eye Institute Seaside, 147, Colaba Road Mumbai-400005, India Daljit Singh MS, DSC 57, Joshi Colony Amritsar-143001, India Ehud I Assia MD Deptt. of Ophthalmology Meir Hospital Sapir Medical Centre Tsharnihovski St. 44281, Kafar, Saba Israel Guillérmo Avalos-Urzua MD Terranova No. 676-101 Col. Providencia Guadalajara, Jal Mexico CP-44630

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Harsh Kumar MD Chief Glaucoma Service Centre for Sight Safdarjung Enclave New Delhi, India J Agarwal MS Director Dr. Agarwal’s Eye Hospital Pvt. Ltd. 19, Cathedral Road Chennai-600086, India Jens Funk MD Prof. of Ophthalmology AugenklinikUniversitatsklinikum Killianstr. 5 79106 Freiburg Germany Jerome Bovet MD Consultant Ophthalmic Surgeon, FMH Clinique de I’oeil 15, Avenue du Bois-de-laChapelle CH-1213 Onex Switzerland Jorge L Alió MD, PhD Director Instituto Oftalmologico De Alicante Avda. Denia 111, 03015 Alicante Spain

Jose L Rodriguez - Prats MD Instituto Oftalmologico De Alicante Avda. Denia 111, 03015 Alicante Spain JT Lin PhD 4532, Old Carriage Trail OVIEDO Florida 32765 USA Kamaljeet Singh MS Associate Professor Ophthalmology 4A/7, Panna Lal Road Allahabad, India Kaweh Mansouri MD Jules Gonin Eye Hospital Lausanne, Switzerland Keiki R Mehta MS, DO, FIOS

Chairman & Medical Director Mehta International Eye Institute 147, Shahid Bhagat Singh Road Colaba Road Mumbai-400005, India Khristo Takhchidi MD Director General, S.N. Fyodorov Eye Microsurgery Complex Moscow, Russia

Contributors

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Mordechai Goldenfeld MD The Sam Rothberg Glaucoma Centre Goldschleger Eye Institute Sheba Medical Centre Tel-Hashomer Israel

Roberto G Carassa MD Director Glaucoma Service Deptt. of Ophthalmology and Visual Sciences University Hospital S. Raffaele via Olgettina 60 20132 Milano, Italy

Mona Pache MD AugenklinikUniversitatsklinikum Killianstr. 5 79106 Freiburg Germany

Shlomo Melamed MD Prof. of Ophthalmology Sackler Medical School Tel Aviv University Head and Chairman Sam Rothberg Glaucoma Centre Goldschleger Eye Institute Sheba Medical Centre Tel-Hashomer, Israel

Nikolai Ereskin MD Consultant, S.N. Fyodorov Eye Microsurgery Complex, Moscow, Russia Pascal Rozot MD Clinique Monticelli Marseilles France

Subrata Mandal MD Dr. RP Centre for Ophthalmic Sciences, AIIMS New Delhi, India Sunita Agarwal MS, DO, PSVH

Ranjit H Maniar MS 17, Vithal Court, 6th Floor 151, August Kranti Marg Mumbai-400036, India Richard J Fugo MD, PhD 100, West Fornance Street The Fugo Building Norristown, PA-19401 USA

Dr. Agarwal’s Eye Hospital 19, Cathedral Road Chennai-600086, India 15, Eagle Street, Langford Town, Bangalore, India Sylvian Roy MD Jules Gonin Eye Hospital CH 1004, Lausanne Switzerland

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Tanuj Dada MD Associate Professor Dr. R.P. Centre for Ophthalmic Sciences AIIMS, Ansari Nagar New Delhi-110029, India T Agarwal FORCE, DO, FICS

Director Dr. Agarwal’s Eye Hospital 19, Cathedral Road Chennai-600086, India

Vivek Kadambi MD, DOMS Director Kadambi Laser Vision Clinic & Research Foundation Pvt. Ltd. 157, Defence Colony 4th Main Road, Indira Nagar Bangalore-560038 India

FOREWORD One of the most wonderful and stimulating aspects of modern ophthalmology is the continued spirit of ingenuity in advancing the treatment of ophthalmic disease. This is manifested by continuous research in both medical and surgical techniques in the quest to improve our patient’s vision and prevent and treat eye disease. The ophthalmic subspecialty of glaucoma continues to be one of the most interesting and dynamic areas of ophthalmology with numerous improvements in not only the pharmacologic treatment of glaucoma but also the surgical arena. Traditionally glaucoma has been managed with medications until the disease has progressed to a significantly advanced state requiring more than pharmacologic therapy. However, recent trends indicate that surgeons throughout the world are transitioning to a more aggressive mind set with quicker movement towards interventional glaucoma procedures and techniques that reduce intraocular pressure and treat the disease surgically. Dr. Ashok Garg and his colleagues have compiled a brilliant book with concentration on the most novel and successful glaucoma procedures and surgeries available today. The authors, who hail from a diverse international population, have managed to come together and present a

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thorough analysis of the latest technological modalities for treating glaucoma. Through advancements in communication and technology over the past decade these surgeons have been able to share their experiences and technologies leading to the rapid advancement of minimally invasive glaucoma surgery. It is rare to find a text with such a complete and thorough analysis of all the different possible treatment technologies available today. I commend the editors for their diligence in assembling such a diverse and comprehensive text of glaucoma therapy and surgery. Their tireless efforts has enabled surgeons, worldwide, to assemble and share their knowledge and skills in one of the most advanced treatises on glaucoma to date. This book serves not only as an excellent core book on treatment modalities for glaucoma but also serves to introduce and educate all glaucoma specialists to up and coming progressive technologies that they will be using for years to come. I am sure you will enjoy this book as much as I have and in this new era of minimally invasive glaucoma surgery you will come away with a tremendous amount of knowledge and hope for the future of our glaucoma patients. Dr. Robert Jay Weinstock MD The Eye Institute of West Florida 148 13th Street SW Largo, Florida 33770 , USA Tel. (727) 585-6644

PREFACE Glaucoma is a complex multifactorial slowly progressive neurodegenerative disorder associated with raised intraocular pressure leading to death of retinal ganglion cells and degeneration of their connected optic nerve fibers and subsequent visual loss. The aim of Modern Glaucoma Treatment is to preserve visual function with minimal side effects. Effective management of Glaucoma requires a reduction of intraocular pressure to a level appropriate for the stage of disease. There is tremendous improvement in Medical Management of Glaucoma with newer drugs but burden of daily treatment, cost factor, possible side effects and inconvenience and poor compliance leads to progression of disease inspite of early diagnosis and prompt treatment. There are lot of surgical procedures available for Glaucoma management but they have their own postoperative complications which are sometimes difficult to treat leading to the frustration of the patient. In last 5 years tremendous advances have been made specially in minimally invasive glaucoma surgery with minimal postoperative complications and better visual results. This step by step book has been written specially to acquaint ophthalmologist with latest minimally invasive glaucoma surgical techniques. Seventeen chapters of this book are written by International known Glaucoma specialists covering MIGS specially Excimer Laser Trabeculotomy, Sclerothalamotomy, Trans-scleral Diode Laser Cyclophotocoagulation, Milling Trabeculoplasty, VDSCI, Customized Laser Assisted Filtration Surgery (CLAFS), SLT, Pneumatic Trabeculoplasty, Femtosecond Lasers and Neuroprotective Therapeutic approach. These

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are all high techniques with excellent visual results available in this single Internatioonal book. An added attraction of this book is interactive CD showing all latest MIGS techniques. We are highly grateful to Shri Jitendar P Vij (Chairman and Managing Director), Mr. Tarun Duneja, General Manager (Publishing) and all staff members of our publisher M/s Jaypee Brothers Medical Publishers (Pvt) Ltd. who took active interest in this project and prepared this handy high quality book in a short time. We are quite certain this step by step MIGS book shall be a useful companion to every ophthalmologist who do Glaucoma work. Editors

CONTENTS 1. Minimally Invasive Glaucoma Surgery (MIGS) – A New Approach ........................................................ 1 Ashok Garg (India) 2. YAG Laser Iridotomy ................................................ 9 Kamaljeet Singh (India) 3. Laser Sclerotomy ....................................................... 23 J Agarwal, T Agarwal, Sunita Agarwal, Ashok Garg (India) 4. Laser Trabeculoplasty .............................................. 33 Kamaljeet Singh (India) 5. Laser Treatment in Glaucomas .............................. 43 Andre Mermoud, Sylvian Roy (Switzerland) 6. Miscellaneous Laser Applications ........................ 81 Harsh Kumar, Tanuj Dada (India) 7. Trabecular Meshwork Ablation as an Alternative to Invasive Glaucoma Surgery ........ 97 Mona Pache, Jens Funk (Germany) 8. Sclerothalamotomy ab Interno a Minimally Invasive Glaucoma Surgery ................................. 113 Bojan Pajic (Switzerland) 9. Laser Surgical Treatment of Glaucoma by Excimer Laser with 193 nm Wavelength ........... 135 Khristo Takhchidi, Nikolai Ereskin (Russia)

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10. Topical Anesthetic and the Subconjunctival Bubble in Glaucoma and Combined Operations ................................... 147 Jérôme Bovet (Switzerland) 11. Cyclophotocoagulation ......................................... 161 Tanuj Dada, Subrata Mandal (India) 12. Milling Trabeculoplasty: A New Technique for Non-penetrating Glaucoma Surgery ........... 197 Jose L Rodriguez-Prats, Jorge L Alió, Ahmed Galal (Spain) 13. Deep Sclerectomy with T-flux Implant with “Outside In” Drainage ...........................................225 Ranjit Maniar (India) 14. Viscocanalostomy ................................................... 247 Roberto G Carassa (Italy) 15. Pneumatic Trabeculoplasty – A Noninvasive Glaucoma Treatment ............................................. 261 Guillérmo Avalos-Urzua (Mexico) 16. Selective Laser Trabeculoplasty ..........................271 Mordechai Goldenfeld, Shlomo Melamed (Israel) 17. Customized Laser Assisted Filtration Surgery (CLAFS) Using a Solid-State UV Laser ..............281 JT Lin (USA), Vivek Kadambi (India) 18. Non-penetrating Filtration Surgery with the CO2 Laser .................................................297 Ehud I Assia (Israel) 19. Open Angle Filter Surgery for Glaucoma: Deep Sclerocanalostomy (DSC) – A New Technique ................................................... 309 Jerome Bovet (Switzerland)

Contents

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20. Bimanual Microphaco and Deep Sclerocanalostomy (BMP and DSC) – A New Technique ................................................... 327 Jerome Bovet (Switzerland) 21. Very Deep Sclerectomy — or How to Increase Uveoscleral Outflow .............................. 345 Kaweh Mansouri, André Mermoud (Switzerland) 22. G-Probe as Primary Glaucoma Procedure in Cases of Coexisting POAG and Cataract ..... 357 Cyres K Mehta, Keiki R Mehta (India) 23. Combined Phacoemulsification and Deep Sclerectomy with T-Flux® ...................................... 373 Pascal Rozot (France) 24. Glaucoma Surgery Techniques with the Fugo Blade® .............................................................................. 387 Daljit Singh (India), Richard J Fugo (USA) Index ........................................................................... 425

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INTRODUCTION Glaucoma is a complex disorder to treat. Increased intraocular pressure (IOP) accompanied with optic nerve damage requires a life long mandatory treatment to maintain IOP level at acceptable level with visual acuity preservance. Medical management of glaucoma is usually first line of defence which has its own side effects and complications on prolonged use. Second line of treatment is conventional glaucoma surgery – Trabeculectomy which has its own postoperative complications specially bleb leakage. In last one decade intensive research work has been done in glaucoma surgery. When conventional methods fail patients can be well served by innovative new surgical techniques specially non-penetrating glaucoma surgery also known as minimally invasive glaucoma surgery. These new techniques clear the way for restored fluid passage through the eye. These infrastructure improvements are essentially extraocular techniques which has improved visual success rate with minimum postoperative complications. CLASSIFICATION Minimally invasive glaucoma surgery (MIGS) are broadly classified in following groups : a. Surgical-based MIGS or NPGS. b. Laser-based MIGS or NPGS. c. Scleral expansion bands. Here, I am giving broad outlines as the details are described in different chapters of this book.

Minimally Invasive Glaucoma Surgery — A New Approach

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Surgical Based MIGS Surgical based MIGS have made tremendous strides in last one decade. It includes viscocanalostomy, deep sclerectomy, milling trabeculoplasty, sclerothalamotomy ab interno and deep sclero-canalostomy (DSC). Viscocanalostomy Viscocanalostomy introduced by Dr. Robert Stegmann (South Africa) in early nineties increases the aqueous outflow through different mechanism of action. It creates a bypass by which aqueous humor can reach Schlemm’s canal skipping the trabecular meshwork which is the site of the increased outflow resistance in OAG. Viscocanalostomy has several potential advantages over conventional trabeculectomy the major being the absence of external filtration thus independent of conjunctival and episcleral scarring. Postoperative management is comparatively easy with minimal complications. However, this technique is technically strong and requires a long learning curve. Deep Sclerectomy Deep sclerectomy is another non-penetrating glaucoma surgery which has offered excellent results. This techniques has been advocated with the implantation of a collagen drainage device. Dr. Andre Mermoud (Switzerland) has shown the excellent results of deep sclerectomy alone and very deep sclerectomy with collagen implant (VDSCI) which is relatively a new technique. It has been clinically documented that deep sclerectomy significantly lowers the complication rates of glaucoma surgery.

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Milling Trabeculoplasty Milling trabeculoplasty developed by Dr. Jorge L. Alio (Spain) is considered a variation of deep sclerectomy with more refining. This technique provides the opportunity to perform a non-penetrating glaucoma surgery with greater attention for the dissection of the deep scleral flap or the deroofing of the Schlemm’s canal with the additional advantage that is being much faster. Certainly milling trabeculoplasty is an evolving technique for sclapel free NPGS. It is a promising technique specially for surgical management of POAG. Sclerothalamotomy (STT) Sclerothalamotomy ab interno is a new NPGS technique developed by Dr. Bojan Pajic (Switzerland). STT ab interno circumvents the trabecular meshwork resistance by creating a drainage canal in the sclera but the site of perforation is reached from inside and four sclerectomy sites are created using a special high frequency diathermy probe. STT is certainly a promising technique which ensures an efficacy and longevity of filtration. Deep Sclerocanalostomy (DSC) Deep sclerocanalostomy technique has been shown by Dr. Jerome Bovet (Switzerland). This combined new technique of NPGS is all connected with dissection or injection of the Schlemm canal. DSC allows a synthesis of the three main surgical techniques for non-penetrative Filter surgery. This reduces the risks of each while increasing the long-term chances of such in term of IOP control.

Minimally Invasive Glaucoma Surgery — A New Approach

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Laser-Based MIGS Besides the conventional laser techniques in glaucoma management, a number of new techniques are on the horizon with better IOP control and visual acuity management. Research ophthalmologists have shown new techniques with the use of Excimer Laser, Infrared Laser, CO2, Laser and Selective Laser Trabeculoplasty (SLT). Excimer Laser Trabeculotomy Excimer laser trabeculotomy ab interno (ELT) developed by Jens Funk (Germany) is a minimally invasive procedure that uses an excimer laser to ablate pores in the trabecular meshwork of patients with open angle glaucoma. As this procedure uses photoablation, no thermal effect is generated thus helps in thermal necrosis and scar formation potentially allowing a persistent effect over the years. ELT is certainly effective as monotherapy. Prof. Khristo Takhchidi (Russia) has designed a special excimer laser unit with 193 nm wavelength for glaucoma surgery. This new technique of NPGS that uses the excimer laser can reduce the risk of perforating the trabeculodescemetic membrane. With this technique the ablation is precise and homogenous. Titanium Sapphire Laser Trabeculoplasty Dr. Gabriel Simon (Spain) has evolved a new technique of titanium Sapphire Laser Trabeculoplasty (TiSaLT) using infra red laser. In this techniques laser energy targets and is absorbed by pigment inciting shock waves through the tissue ablating the tissue and unclogging blocked passage ways. This procedure causes minimal thermal damage and can be repeated.

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Non-penetrating Glaucoma Surgery with the CO2 Laser Dr. Ehud Assia (Israel) has shown a new technique of nonpenetrating glaucoma surgery with the CO2 laser. The clinical studies have shown that CO2 laser can effectively ablate the dry tissue without tissue perforation. In this procedure deep ablation down to the trabecular meshwork and Descemet’s membrane leaving a microthin wall 30u-50u thick with no perforation. This promising procedure enables accurate dissection of the scleral wall and unroofing of the Schlemm’s canal without penetration into the anterior chamber. Selective Laser Trabeculoplasty Selective laser trabeculoplasty (SLT) is another promising MIGS technique Dr. Mark. A Latina (USA) has pioneered this technique. In this procedure we can selectively treat the trabecular meshwork. With an Nd : YAG laser without creating a thermal burn. This procedure has been developed as an alternative to argon laser trabeculoplasty (ALT). In SLT ophthalmic surgeon selectively target pigmented trabecular meshwork cells instead of complete photocoagulation of the trabecular meshwork which is not necessary. SLT is certainly a better procedure with minimal side effects with good efficacy at lowering of IOP over a longer period. Scleral Expansion Bridge (SEB) Scleral expansion bridge (SEB) best known for their use in presbyopia has been recently shown to be useful in glaucoma management. The cornerstone behind use of SEBs is the Schachar theory of accommodation. This procedure is in early stages of development with essential

Minimally Invasive Glaucoma Surgery — A New Approach

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principle of increasing the effective working distance of the lens by expanding the sclera which shall reverse presbyopia and increase the tension of the longitudinal muscle improve aqueous outflow and thus reduces intraocular tension. The scleral expansion band offers a new potentially reversible, safe surgical alternative to the management of ocular hypertension and primary open angle glaucoma. By these state of Art MIGS techniques, in near future we can indeed personalize an operation for every given glaucoma patient with maximal visual acuity preservance, effective IOP control and minimum complications. Certainly glaucoma customization holds great future.

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INTRODUCTION Meyer Schwickerath reported for the first time the use of Xenon arc photocoagulator in cracking a hole in the iris.1 But the heat produced by xenon led to corneal and lenticular damage.1,2 Ruby laser was tried for some time without much success.3 The first successful laser iridotomy by argon laser was reported in 1970s.4-7 In 1980 the laser iridotomy replaced the surgical iridotomy. Later Nd:YAG laser was found more successful for this procedure.8-10 It is now most commonly applied laser for iridotomy. INDICATIONS • Acute/subacute angle closure glaucoma with symptoms • Chronic congestive glaucoma with anterior synechiae • Occludable angles with positive provocative tests • Occludable angle with signs of previous attack/ critically narrrow angle • Fellow eye • Iris bombe • Subluxated or luxated lens with intact vitreous face • Phacomorphic glaucoma with pupillary block mechanism • Aphakic/pseudophakic pupillary block • Nanophthalmos • Incomplete surgical iridectomy • Mixed mechanism glaucoma if filtering surgery is not required • Aqueous miss direction syndrome • Phakic IOLs • Plateau iris syndrome • Pigmentary glaucoma • To deepen narrow angle before laser trabeculoplasty

YAG Laser Iridotomy

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CONTRAINDICATIONS • • • • •

Opaque or cloudy cornea Widely dilated pupil Flat anterior chamber with iridocorneal touch Active inflammation Rubeosis irides

ABRAHAM CONTACT LENS Abraham contact lens is most commonly used lens for performing this procedure.11 It has a 66 planoconvex button bounded in the front surface of the lens. When laser beam falls on this lens its size is reduced to half of the original size on the iris and doubles the original size on cornea. This increases the power density on the iris and decreases power density to one-fourth on cornea. This helps immensely during the argon laser iridotomy. Same lens is very useful for YAG laser iridotomy also. A high magnification up to 40X should be used on slit-lamp for performing this procedure (Fig. 2.1). Contact lens helps in the following ways: 1. The lids remain separated. 2. Chances of corneal epithelial burns are reduced as the lens absorbs heat energy by acting as a heat sink. 3. The eye movements can be controlled by the lens. PREOPERATIVE PREPARATION Pilocarpine eye drops are instilled preoperatively. It stretches the iris, which thins the iris stroma and also facilitates in the penetration of laser beam because cutting a well-stretched thin paper is easier than cutting a loose paper.

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Fig. 2.1: Slit lamp

If the patient has already had an attack of acute congestive glaucoma, first medical treatment is carried out (Box 2.1). This will reduce the corneal edema. In addition, the pupil can be easily constricted by pilocarpine. The steroid drops should also be instilled if iritis is present for a couple of days before proceeding for laser iridotomy. If acute attack does not abort, one can proceed with iridotomy. So, preoperatively pilocarpine eye drops are instilled one hour prior to constrict the pupil to maximum. Apraclonidine 1 percent is instilled one hour prior to the procedure to prevent postoperative pressure spike.12 Topical proparacaine 0.5 percent is instilled just before the procedure to anesthetize the conjunctiva and cornea. THE SELECTION OF IRIDOTOMY SITE It is usually superonasal between the peripheral and middle third of iris. The reasons for this are (a) the superior

YAG Laser Iridotomy

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Box 2.1 We follow the New York Eye and Ear Infirmary approach1 to acute angle closure glaucoma, which is as follow: 1. Careful history of symptoms relating to intermittent angle closure attacks, attacks in the other eye, use of prescription or nonprescription drugs which may precipitate attacks, and type of activity precipitating the attack. 2. Examination of the affected eye and other eye with attention to central and peripheral anterior chamber depth as well as shape of the peripheral iris. 3. Administration of oral isosorbide, acetazolamide as aqueous suppressants, and even intravenous mannitol at our place. 4. The patient lies supine to permit the lens to fall posteriorly with vitreous dehydration. 5. The eye is reassessed after 1 hour. IOP is usually decreased, but the angle usually remains appostionally closed. One drop of 2 or 4 percent pilocarpine is given and patient is reexamined 30 minutes later. 6. If IOP is reduced and the angle is open, the patient may be treated medically with topical low dose pilocarpine, aqueous suppressants and steroids, until the eye quiets and laser iridotomy may be performed. 7. If IOP is unchanged or elevated and angle remains closed. Lens related angle closure should be suspected, further pilocarpine is withheld and the attack broken by argon laser peripheral iridoplasty. Peripheral iridoplasty does not eliminate pupillary block and is not a substitute for laser iridotomy, which must be performed as soon as the eye is quiet. However, even in eyes with extensive synechial closure, IOP is lowered sufficiently for a few days for the inflammation to resolve. Peripheral iridoplasty is much safer than attempting surgical iridectomy on an inflammed eye with elevated IOP. The risks of intraoperative surgery are avoided and even if malignant glaucoma is present the angle remains open long enough for inflammation to clear. Peripheral iridoplasty is highly effective in ameliorating attacks of angle closure glaucoma in Asian eyes. 1. Kramer P, Ritch R. The treatment of angle closure glaucoma revisited (editorial). Ann Ophthalmol 1984;16:1101-03.

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site remains covered by the lid (b) the nasal side remains away from the macula preventing foveal burn (c) the junction of middle and peripheral third helps in easy penetration. (d) crypt is selected because here the iris is thinnest and easy to penetrate (e) the iris should be examined for any strands. If present, they should be avoided, as they are difficult to penetrate. (f) the lower site is chosen in silicon filled eye because the silicon oil floats and can go to upper site and block the iridotomy. LASERS USED Several lasers can be used. But the commonly used lasers are Nd: YAG and argon. We will describe here the YAG laser iridotomy. Nd: YAG Laser Iridotomy This is most frequently applied method for laser iridotomy. There are several advantages of using YAG laser. This produces extremely high energy, which acts by mechanical disruption. When compared to argon laser, it does not require pigment for absorption for its thermal effect. The spot size is usually fixed to one size (50-75 um) in lasers from different companies. The pulse duration is also fixed for each instrument. The energy levels can be varied. Depending on the color of iris the required energy levels for penetration can be between 5-15 mJ. More energy is required for brown iris. The pulses can be between 1 to 3, which depends largely on the choice of surgeon. YAG laser penetrates simultaneously the iris stroma and pigment epithelium. The only problem with YAG laser iridotomy is bleeding from iris capillaries, which should be avoided if visible.

YAG Laser Iridotomy

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After selecting the site and applying the Abraham’s lens the laser shot is placed at the iris surface after properly focusing the laser beam. Usually one shot is sufficient for blue iris, but at times more than may be required. In brown iris more shots may be needed and the required energy levels may be also be high. The created opening should not be less than 150-200 um,13 otherwise there are chances of its closure. If some difficulty is experienced in enlarging the hole another site may be chosen. Two sites, even if small, are less likely to close (Fig. 2.1). Argon and YAG Laser Combined My technique is first using low intensity large size 200 um argon laser burns to create a crator and then utilizing single pulse low intensity shot of Argon laser also coagulates the capillaries thus reducing the chances of iris bleed.14 POST-LASER TREATMENT • Steroid drops are given to prevent mild iritis. • Pilocarpine eye drops are advised to keep the pupil constricted so that the opening remains patent. COMPLICATIONS 1. Common complications — Transient IOP rise — Iridocyclitis 2. Others — Closure of iridotomy — Hyphema — Corneal damage cataract formation 3. Rare complications — Retinal burns — Malignant glaucoma

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— Monoocular blurring — Endothelial cell loss — Posterior synechia Common Complications Transient Rise of IOP This is commonest complication. The rise of IOP occurs due to decrease in aqueous outflow facility, although aqueous outflow facility gets reduced.15 Other studies suggest that it could be because of release of prostaglandins16-18 and prostaglandin like substances into the aqueous,19 which occurs due to breakdown in the blood aqueous barrier. The blood plasma and fibrin are also released, which may also block the iridotomy site or angle leading to IOP rise. For preventing this rise 1 percent apraclonidine eye drops should be instilled one hour prior to laser iridotomy and also immediately after the procedure. Iridocyclitis As a reaction to YAG laser insult a mild iritis can occur.20 This can easily be managed by giving steroid drops for 3-5 days. However, rarely severe iridocyclitis,21 cystoid macular edema22 and even endophthalmitis23 have been reported. Other Communications Hyphema If the laser beam hits iris capillaries, the blood may be seen leaking from them.8,9 This bleeding can be easily managed by applying pressure with the help of contact lens. If

YAG Laser Iridotomy

17

previous to the YAG laser, Argon laser is utilized the chances of bleeding are reduced as it coagulates the capillaries. Closure of Iridotomy The size of iridotomy should be about 150-200 um,13 because small iridotomy may close due to pigment granules and debris release from the iris by YAG laser disruption. For keeping the iridotomy patent pilocarpine should be instilled postoperatively. If it seems to the clinician that confirmation of patency is required, a provocative mydriatic test should be done after stopping pilocarpine drops. Although most of the time a slit-lamp evaluation done under high magnification confirms the patency, wherein anterior capsule’s visibility suffices. Long-term patency rates of YAG laser iridotomy are very good in dark Asian irides in line with other studies in white and AfroCaribbean eyes.24-26 Cataract Formation The incidence of cataract formation is much less with YAG laser than with argon laser iridotomy. It is said that they are non-progressive. Laser peripheral iridotomy disrupts the natural flow of aqueous in the eye and results in significant increase in lens-iris contact.27 Theoretically, this may predispose to a more rapid development of cataract since less aqueous is in contact with the lens epithelium. Several studies have attempted to look at this issue, but follow-up has been short, no lens grading system was used, and no acceptable control groups were studied.28-29 Focal lenticular opacities seen after argon laser peripheral iridotomy are said not to progress, but once again, followup has been short in published reports.

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Step by Step Minimally Invasive Glaucoma Surgery

Rare Complications Retinal Burns Retinal burns may occur due to YAG laser iridotomy since the laser beam may hit the retina. If the precautions mentioned previously are not taken it may also hit the fovea and cause sudden diminution of vision. The best way of avoiding this complication is by choosing the superonasal site. Some authorities believe that using the Abraham lens also prevents damage to fovea. Malignant Glaucoma This is also rarely described complication and has been reported in one eye and both eyes too. Endothelial Cell Loss One study documented a higher rate of endothelial cell loss after argon laser peripheral iridotomy than after YAG laser peripheral iridotomy.24 Posterior Synechia Another potential complication of laser peripheral iridotomy is the development of posterior synechiae following laser iridotomy.25 Posterior synechiae can both limit vision in dim environments and make later cataract surgery more challenging. Failure of Iridotomy Several studies demonstrate a relation between the extent of angle closure by PAS and failure of iridotomy to control IOP and progression of glaucoma. 30-32 Iridectomy or

YAG Laser Iridotomy

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iridotomy is less effective in eyes with glaucomatous visual field loss and further surgical or medical treatment is often required to control IOP.33,34 REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Meyer-Schwickerath G. Erfahrungen mit der lichokoagulation der Netzhaut und der iris. Doc Ophthalmol 1956;10:91. Hogan MF, Schwartz A. Experimental photocoagulation of the iris of guinea pigs. Am J Ophthalmol 1960;49:629. Perkins AS. Laser iridotomy for secondary glaucoma. Trans Ophthalmol UK 1971;91:777. Khuri CH. Argon laser iridectomies. Am J Ophthalmol 1973;76:490. Anderson DR, Forster RK, Lewis M. Laser iridotomy for aphakic pupillary block. Arch Ophthlol 1975;93:343. Yassur Y, Melamed S, Cohen S, Ben-Sira I. Laser iridotomy in closed angle glaucoma. Arch Opthalmol 1979;97:1920. Pollack IP. Use of argon lasr to produce iridotomies. Ophthalmic Surg 1980;11:506. Latina MA, Puliafito CA, Steinert RR, Epstein DL. Experimental iridotomy with a Q-switched Nd: YAG laser. Arch Ophthalmol 1984;102:1211. Klapper RM. Q-switched Nd: YAG laser iridotomy. Ophthalmology 1984;91:1017. Vernon SA, Cheng H. Freeze frame analysis on high-speed cinematography of Nd: YAG laser explosions in ocular tissues. Br J Ophthalmol 1986;70:321. Abraham RK. Procedure for outpatient argon laser iridectomies for angle closure glaucoma. Int Ophthalmol Clin 1976;16:1. Krupin T, Stank T, Feitl ME. Apraclonidine pretreatment decreases the acute intraocular pressure rise after laser trabeculoplasty or iridotomy. J Glau 1992;1:79. Fleck BW. How large must an iridotomy be? Br J Ophthalmol 1990;74:583.

20 14.

15. 16.

17. 18. 19. 20.

21. 22. 23. 24. 25.

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Del-Priore LV, Robin AL, Pollack IP. Neodymium: YAG and argon laser iridotomy. Long-term follow-up in a prospective, randomized clinical trial. Ophthalmology 1988;95:1207-11. Wetzel W. Ocular aqueous humour dynamics after photodisruptive laser surgery. Ophthalmics Surg 1994;25: 298. Sugiyama K, Kitazawa Y, Kawai K, Enya T. Biphasic intraocular pressure response to Q-switched Nd: YAG laser irradiation of the iris and the apparent mediatory role of prostaglandins. Exp Eye Res 1990;51:531. Gailitis R, Peyman G A, Pulido J, et al. Prostaglandin release following Nd: YAG iridotomy in rabbits. Ophthalmic Surg 1986;17:467. Joo CK, Kim JH. Prostaglandin E in rabbit aqueous humour after Nd: YAG laser photodisruption of iris and the effect of topical indomethacin pretreatment. 1992;33: 1685. Weinreb RN, Weaver D, Mitchell MD. Prostanoids in rabbit aqueous humour: effect of the laser photocoagulation of the iris. Invest Ophthalmol Vis Sci 1985;26:1087. Schrems W, van Dorp HP, Wendel M, Krieglstein GK. The effect of YAG laser iridotomy on the blood aqueous barrier in the rabbit. Graefes Arch Clin Exp Ophthalmol 1984;221: 179. Cohen JS, Biblar L, Tucker D. Hypopyon following laser iridotomy. Ophthalmic Surg 1984;15:604. Margo CE, Lessner A, Goldey SH, Sherwood M. Lensinduced endophthalmitis after Nd: YAG laser iridotomy. Am J Ophthalmol 1992;113:97. Choplin NT, Bene CH. Cystoid macular oedema following laser iridotomy. Ann Ophthalmol 1983;15:172. Schwartz LW, Moster MR, Spaeth GL, et al. NeodymiumYAG laser iridectomies in glaucoma associated with closed or occludable angles. Am J Ophthalmol 1986;102:41-44. Canning CR, Capon MRC, Sherrard ES, et al. Neodymium: YAG laser iridotomies short-term comparison with

YAG Laser Iridotomy

26.

27. 28. 29. 30. 31. 32. 33. 34.

21

capsulotomies and long-term follow-up. Graefes Arch Clin Exp Ophthalmol 1988;226:49-54. Del-Priore LV, Robin AL, Pollack IP. Neodymium: YAG and argon laser iridotomy. Long-term follow-up in a prospective, randomized clinical trial. Ophthalmology 1988;95:1207-11. Caronia RM, Liebmann JM, Stegman Z, et al. Increase in iris-lens contact after laser iridotomy for pupillary block angle closure. Am J Ophthalmol 1998;122:53-57. Robin AL, Pollack IP. A comparison of neodymium: YAG and argon laser iridotomies. Ophthalmology 1984;91:101116. Quigley HA. Long-term follow-up of laser iridotomy. Ophthalmology 1981;88:218-24. Salmon JF. Long-term intraocular pressure control after Nd: YAG laser iridotomy in chronic angle-closure glaucoma. J Glaucoma 1993;2:291-96. Yamamoto T, Shirato S, Kitazawa Y. Treatment of primary angle-closure glaucoma by argon laser iridotomy: a longterm follow-up. Jpn J Ophthalmol 1985;29:1-12. Kim YY, Jung HR. Dilated miotic-resistant pupil and laser iridotomy in primary angle-closure glaucoma. Ophthalmologica 1997;211:205-08. Gelber EC, Anderson DR. Surgical decisions in chronic angle-closure glaucoma. Arch Ophthalmol 1976;94:148184. Richardson P, Cooper RL. Laser iridotomy. Aust NZ J Ophthalmol 1987;15:119-23.

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INTRODUCTION Lasers have been in use for the treatment of glaucoma for the last few decades. A bloodless sutureless technique of using the Nd:Yag laser has been started by the authors (SA) to treat glaucoma. This is called laser sclerotomy. If the patient has a cataract then one can do the cataract removal with the Laser Phakonit technique followed by either a Rollable or Foldable IOL implantation. HISTORY The author first performed this technique on a diabetic patient who was already undergoing hemodialysis as a result of renal failure. His renal failure made the use of acetazolamide an absolute contraindication. Using the ND:Yag laser of the Paradigm machine which is also used for cataract surgeries by the author, the author performed the laser sclerotomy. In this, the idea was to create a hole via the clear corneal incision in the trabecular meshwork. The hole passes through and through to exit the sclera forming a filtering channel into the subconjunctival space. ND:YAG LASER It is a solid state laser having an ionizing effect causing photodisruption, thermal effect causing photovaporization, photocoagulation and photocarbonization. The laser fiberoptic (Fig. 3.1) has a Helium Neon aiming beam with the diameter of the optic end being 380 μ. This fiberoptic is encased within a silicon sleeve. The ‘male socket’ connects the fiberoptic to the laser machine. The laser machine the author advocates is the Paradigm Photon machine which works at 3 Watts.

Laser Sclerotomy

25

Fig. 3.1: Nd:YAG laser fiberoptic (1) laser fiberoptic (2) male socket (3) diameter of ocular end of laser fiberoptic is 380 (4) helium neon aiming beam

LASER SCLEROTOMY WITH ND:YAG – INSTRUMENTATION • 0.9 mm diamond blade: Custom made diamond blade similar to the one used in laser Phakonit. • Viscoelastic: Hydroxy methyl cellulose used for maintenance of anterior chamber with protection of corneal endothelium. • Nd:Yag laser fiberoptic. • Paradigm laser machine. SURGICAL TECHNIQUE Paracentesis The anterior chamber is filled initially with viscoelastics to facilitate a smooth incision (Fig. 3.2). Hydroxymethyl propyl cellulose (viscon) is the preferred viscoelastic. The site of paracentesis is preferably 45 degrees away from the main incision so that a repository may be used later on for control of the eye ball during the procedure.

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Fig. 3.2: Paracentesis with viscoelastic injection

Clear Corneal Incision A keratome/diamond blade of 0.9 mm size (Fig. 3.3) is used to make a clear corneal incision superiorly depending on the site planned for sclerotomy. The entry point may be directly opposite the planned site of sclerotomy or juxtaposed to the planned site of sclerotomy. Depending on the surgeon’s preferences the director of the blade may be adjusted accordingly with the initial entry point parallel to the limbus and the tunnel incision varying according to the planned site of sclerotomy. Recently the author has opted for a variation in the conventional corneal tunnel with the initial entry point parallel but about 2 mm away from the limbus and the tunnel directed towards the limbus. The sclerotomy is then performed in the same area. Laser Sclerotomy After the corneal incision is made the anterior chamber is filled with more viscoelastic (Fig. 3.4) and then the laser

Laser Sclerotomy

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Fig. 3.3: 0.9 mm diamond blade for clear corneal incision

Fig. 3.4: Anterior chamber filled with viscoelastic

fiberoptic (Fig. 3.5) is introduced through the clear corneal incision. A short burst of laser is given directly opposite the intended site of sclerotomy (Fig. 3.6). The procedure is

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Fig. 3.5: Laser fiberoptic introduced through main incision and repositor is used to support the laser fiberoptic

Fig. 3.6: Laser ablation through the trabecular meshwork

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performed without the need of an operative goniolens using just the aiming beam as a guide. When the aiming beam is seen about 1.5 mm (Fig. 3.7) from the limbus a short burst of laser brings the laser fiberoptic out of the scleral bed and under the conjunctiva. Following this the fiberoptic is removed and the anterior chamber washed with BSS to remove traces of viscoelastic. BSS is injected near the sclerotomy site and sub-conjunctival bleb formation (Fig. 3.8) is looked for to assess the patency of the sclerotomy. Peripheral Iridectomy Depending on whether a PBI was done before or not a peripheral iridotomy (Fig. 3.9) may be done near the area of sclerotomy using the laser itself but preferably only in pseudophakic or aphakic patients lest the crystalline lens gets damaged inadvertently.

Fig. 3.7: Laser ablation carried through the sclera 1.5 mm from corneal limbus

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Fig. 3.8: BSS is injected into the anterior chamber to form bleb

Fig. 3.9: Peripheral iridectomy is made in the area of sclerotomy using ND:Yag laser or iris scissors

Laser Sclerotomy

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Closure of Incision The clear corneal incision is closed by stromal hydration (Fig. 3.10). Laser Phakonit and IOL Implantation If the patient has a cataract then one can perform the cataract extraction with the Laser Phakonit technique followed by an IOL implantation. This concludes a triple procedure which is less traumatic than performing a triple procedure with trabeculectomy. Phakic Laser Sclerotomy Laser sclerotomy has been performed safely in phakic individuals. Care has to be exercised when the laser is used, to prevent inadvertent damage of the crystalline lens with

Fig. 3.10: Anterior chamber is reformed and incision sealed with stromal hydration

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Step by Step Minimally Invasive Glaucoma Surgery

the laser energy. Iris pigmentation of the lens is the only complication seen in 20 percent of the phakic patients treated. Laser Sclerotomy in Pseudophakia and Aphakia About 55 percent of the patients who underwent laser sclerotomy were already operated for cataract. Results varied according to the degree of pre-operative IOP and the type of glaucoma. A case of keratoplasty with pseudophakos was treated with this procedure. When impending ciliary staphyloma formation conventional trabeculectomy could not be performed. Also long-term use of anti-glaucoma medication has resulted in subconjunctival fibrosis. The laser sclerostomy in this case was useful.

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INTRODUCTION Zwing and Flocks in 1961 introduced for the first time the concept of using selectively Xenon Arc photocoagulation in the filtration angle of animals and reported lowering of intraocular pressure (IOP). Several workers tried this by different techniques of creating holes in trabecular meshwork (TM), but failed as the holes closed due to fibrous scarring. It goes to the credit of Wise and Witter in 1979, who described the successful protocol of laser trabeculoplasty. ARGON LASER TRABECULOPLASTY Indications • Chronic open-angle glaucoma as initial treatment and as a supplement to maximum tolerable medical therapy • Exfoliation syndrome • Pigmentary glaucoma • Open-angle glaucoma in aphakia and pseudophakia • Previous history of single operation failed trabeculoplasty. The best laser for trabeculoplasty is Green laser. A gonio prism having antireflective coating on the front surface is best for visualizing the angle. Goldmann three mirror or single mirror lens can be used, but both of these require rotation of lens for viewing the 360° of angle. A Thorpe four-mirror gonioscopy lens can also be used. In this lens all the mirrors are inclined at 62°. The best lens, however is Ritch trabeculoplasty laser lens. It has two mirrors inclined at 59° for viewing the inferior quadrants and the other two at 64° for viewing the superior angle. It also has 17 D plano-convex button lens over the mirrors. This provides ×1.4 magnification and also reduces the 50 um

Laser Trabeculoplasty

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spot to 35 um. Therefore we get a 35 um burn on the trabeculum. This produces a burn, which is slightly more than 35 um. Whereas, a 50 um spot produces a burn of 70 um or more, which causes more damage to TM and surrounding structures. The Technique Before beginning actual treatment with argon laser, the instrument should be made parfocal with the surgeon’s eyes. This can be accomplished by placing a paper as target at the same distance where patient’s eye is usually placed. The surgeon then focuses each eye separately on the paper. The aiming beam should make a round circle without any distortion. This makes the instrument parfocal with the surgeon’s eyes. The slit-lamp should be used with ×25 magnification. Too high a magnification can reduce the field whereas, too less magnification will provide with a reduced detail. Preoperatively, Apraclonidine eye drops are instilled to reduce the chances of post-laser spike of IOP. Paracaine eye drops instilled immediately before the procedure is sufficient to give adequate anesthesia for placing Gonio lens in the eyes. The laser settings are 50 um spot, 0.1 sec, energy of 400600 mw. In heavily pigmented trabeculum more energy may be required. The aim is to get a depigmentation spot or a gas bubble at the focussed site. The laser beam is applied in between the pigmented and nonpigmented trabeculum. A posterior placement will burn iris and is likely to produce anterior synechia. Whereas, an anterior placement of the aiming beam can lead to corneal burn. We prefer to apply 50 laser shots on the inferior 180° and then watch the IOP for about three

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Step by Step Minimally Invasive Glaucoma Surgery

months for its control. If the IOP is not well controlled, the superior portion is lasered as second stage procedure (Fig. 4.1). How Does ALT help? Argon laser improves the outflow of aqueous by photocoagulation of the trabecular meshwork (TM). A number of theories have been proposed to explain this effect of ALT on aqueous outflow. The most widely accepted are the mechanical and cellular theories. According to the mechanical theory, ALT causes coagulative damage to the trabecular meshwork, which results in collagen shrinkage and subsequent scarring of the TM. This tightens the meshwork in the area of each burn and reopens the adjacent, untreated intertrabecular spaces.2-4 The cellular theory proposes that in response to coagulative necrosis induced by the laser, there is migration

Fig. 4.1: Argon laser trabeculoplasty: 1, 2, 3 are correct reaction 1: Blenching 2: Small bubble, 3: Large bubble with pigment fallout, 4: Posterior placement of reaction leading to anterior synechia formation

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of macrophages, which phagocytose debris and thus clear the TM. Complications Transient Rise of IOP This is the most commonly encountered complication after laser trabeculoplasty. In majority of the patients a mild rise of IOP occurs, which may remain high for a period for 24 hours only. The pressure starts rising with in 2 hours of trabeculoplasty. Therefore IOP should be rechecked within hours of the procedure. The next day usually the pressure comes down. Special care should be observed for those patients, who have advanced glaucoma. Apraclonidine 1 percent eye drops 1 hour prior and immediately after the procedure is instilled to prevent this complication. Transient Mild Iritis This is also a commonly seen complication in early postoperative period, especially in exfoliation syndrome and pigmentary glaucoma. Postoperatively, steroid eye drops prednisolone or fluoromethalone are given 6 hourly for at least 5-7 days. Other Complications • Corneal burn causing change in the size of corneal endothelial cells • Formation of anterior synechia. Results The 5 years success rate with ALT is reported to be 50 percent, with a decrease of 6 to 10 percent per year. The

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reduction in IOP is between 6 and 9 mmHg. The pressure reduction starts occurring after first day and continues for a period of one month. After this, usually the pressure reduction does not occur. The reduction caused by ALT may be sufficient for some eyes. But in others, it can only help in reducing the number eye drops that the patient is instilling in his eyes. Factors Influencing the Response of ALT 1. Higher the pretreatment IOP more is the response. But if initial pressure has been more than 30 mmHg the response may not be very good. 2. Type of glaucoma. Good Responders • Chronic open-angle glaucoma • Exfoliation syndrome • Pigmentary glaucoma. Fair Responders • Open-angle glaucoma in aphakia and pseudophakia • Previous history of single operation failed trabeculoplasty. Poor Responders • Previous history of multiple surgery • Glaucoma associated with uveitis angle recession glaucoma • Congenital or juvenile glaucoma • Angle recession glaucoma.

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Repeat Trabeculoplasty If 360° ALT has already been done and the desired reduction is not obtained a repeat trabeculoplasty may not be of any use. But if reduction has been achieved once, and the effect has reduced over a period of time, a repeat trabeculoplasty may be beneficial in some patients. Comparison of Selective Laser Trabeculoplasty and ALT Selective laser trabeculoplasty (SLT) is an alternative laser treatment introduced by Latina et al in 1995. SLT utilizes a Q switched, frequency doubled NdYAG laser ( = 532 nm) that selectively targets the pigmented TM cells without adversely affecting the TM in vitro, rendering the TM architecture more preserved. There have been a number of studies that compared the efficacy of ALT and SLT based on post-treatment IOP reduction, and all reported that SLT is as effective as ALT in terms of IOP lowering. In general, both modalities lower IOP an average of 5 mm of mercury 6 months post-treatment. Furthermore, compared to ALT, SLT did not cause ablation craters at the border of pigmented and non-pigmented cells in the TM, and the cellular changes induced by SLT did not extend beyond the Schlemm’s canal as it would after ALT. In addition, SLT appears not to cause the membrane formed by migrating endothelial cells in the necrotic TM seen after ALT treatment. SLT allows the use of 80 to 100 times lower levels of energy and less laser spots on the TM, causing less damage to the TM. Based on the above observations and results, SLT appears to be less destructive and may be more repeatable clinically than ALT.

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BIBLIOGRAPHY 1.

2. 3.

4.

5. 6.

7.

8.

9.

Agarwal HC, Sihota R, Das C, Dada T. Role of argon laser trabeculoplasty as primary and secondary therapy in openangle glaucoma in Indian patients. British J Ophthalmol 2002;86:733-36. Alexander R, Grierson I. Morphological effects of argon laser trabeculoplasty upon the glaucomatous human meshwork. Eye 1989;3:719-26. Cvenkel B, Hvala A, Drnovsek-Olup B, et al. Acute ultrastructural changes of the trabecular meshwork after selective laser trabeculoplasty and low power argon laser trabeculoplasty. Lasers Surg Med 2003;33:204-08. Damji KF, Shah KC, Rock WJ, et al. Selective laser trabeculoplasty vs argon laser trabeculoplasty: A prospective randomized clinical trial. Br J Ophthalmol 1999;83: 218-22. Feldman RM, Katz LJ, Spaeth GL, et al. Long-term efficacy of repeat argon laser trabeculoplasty. Ophthalmology 1991;98:1061-65. Hollo G. Argon and low energy, pulsed Nd:YAG laser trabeculoplasty. A prospective, comparative clinical and morphological study. Acta Ophthalmol Scand 1996;74:12631. Koller T , Sturmer J, Reme C, et al. Membrane formation in the chamber angel after failure of argon laser trabeculoplasty: Analysis of risk factors. Br J Ophthalmol 2000;84:48-53. Kramer T, Noecker R. Comparison of the morphologic changes after selective laser trabeculoplasty and argon laser trabeculoplasty in human eye bank eyes. Ophthalmology 2001;108:773-79. Martinez-de-la-Casa J, Garcia-Feijoo J, Castillo A, et al. Selective vs argon laser trabeculoplasty: Hypotensive efficacy, anterior chamber inflammation, and postoperative pain. Eye 2004;18:498-502.

Laser Trabeculoplasty

10. 11.

12.

13.

14. 15. 16. 17. 18.

19. 20.

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Melamed S, Pei J, Epstein D. Short-term effect of argon laser trabeculoplasty in monkeys. Arch Ophthalmol 1985;103: 1546-52. Mermound A, Herbort CP, Schnyder CC, et al. Comparison of the effects of trabeculoplasty using the Nd:YAG laser and argon laser. Klin Monatsbl Augenheilkd 1992;200:40406. Odberg T, Sandvik L. The medium and long-term efficacy of primary argon laser trabeculoplasty in avoiding topical medication in open-angle glaucoma. Acta Ophthalmol Scand 1999;77:176-81. Popiela G, Muzyka M, Szelepin L, et al. [Use of YAG-selecta laser and argon laser in the treatment of glaucoma] (abstract only; article in Polish). Klin Oczna 2000;102:12933. Reiss GR, Wilensky JT, Higginbotham EJ. Laser trabeculoplasty. Surv Ophthalmol 1991;35:407-28. Ritch R, Liebmann J, Robin A, et al. Argon laser trabeculoplasty in pigmentary glaucoma. Ophthalmology 1993;100:909-13. Shingleton BJ, Richter CU, Dharma SK, et al. Long-term efficacy of argon laser trabeculoplasty. A 10-year followup study. Ophthalmology 1993;100:1324-29. The Glaucoma Laser Trial Research Group. The Glaucoma Laser Trial (GLT), II: Results of argon laser trabeculoplasty vs topical medicines. Ophthalmology 1990;97:1403-13. Weinreb RN, Tsai CS. Laser trabeculoplasty. In: Ritch R, Shields MB, Krupin T, (Eds): The glaucomas: Glaucoma therapy, 2nd ed. Missouri: Mosby-Year Book, 1996;III: 157579. Wise JB, Witter SL. Argon laser therapy for open-angle glaucoma. Arch Ophthalmol 1979;97:319-22. Zweng HC, Flocks M. Experimental photocoagulation of the anterior chamber angle: A priliminary report. Am J Ophthalmol 1961;52:163.

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LASER PRINCIPLE AND INTRODUCTION The word laser was first used in the 60s when light was generated by stimulated emission of radiation. The word LASER is an abbreviation for Light Amplification by Stimulated Emission of Radiation.9 The physical and wavelength characteristics of the laser light were so specific that they gained rapid interest in the field of medical treatment. Laser light is monochromatic and spatially and temporally coherent. This results in a laser beam that is highly directional with little divergence, thus enabling focusing of the beam into a very small spot of high power per unit area. Monochromaticity means that the laser beam is composed of almost a single wavelength, which has great consequences in the surgical eye treatment. This allows light to be effectively absorbed by the pigments contained in the ocular tissues, e.g. the melanin, hemoglobin or the xanthophyll pigments.4 The molecules in biologic tissues are not transparent to wavelength shorter than 300 nm or greater than 100 nm. Between this range, the molecules absorb selectively the light depending on the spectral absorption characteristic of the pigments in the tissues. Laser effects in tissues can be summarized into three groups: photochemical, thermal and ionization effects. The photochemical effect results in photon absorbtion by molecules inducing chemical reactions. A thermal effect is present when photon absorbtion by electrons increases the molecular vibrations to a temperature peak that results in denaturation of proteins in biologic tissues. When the temperature reaches 60°C, the weak van der Waals forces that maintain the molecular bonds are broken and denaturation of the several intracellular proteins occurs.1 If laser energy is strong enough to tear electrons from the outer orbit, the atoms or molecules become ionized and relax this metastable state

Laser Treatment in Glaucomas

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by producing mechanical (pressure) waves (photodisruption effect).7 The efficiency of laser beam onto biological tissues depend on the absorption spectra of cellular pigments.5 Melanin best absorbs wavelengths between 400 and 100 nm. Hemoglobin, naturally presents a red appearance that strongly reduces its absorption characteristics in the long wavelengths above 650 nm. Xanthophyll absorbs very well in the short wavelengths below 500 nm. The laser delivery systems used in laser glaucoma treatments are divided into two groups: non-contact and contact laser source.8 The non-contact delivery system produces a beam that is focused onto the area to be treated via a slit-lamp biomicroscope. It may be useful to place a contact lens to stabilize the eye and the lids, to reduce the optical aberrations of the anterior surface of the cornea and to gain access to structures that are otherwise invisible without a contact lens. The contact delivery system consists of laser source and optical guidance device such as fiberoptic and delivery tip that directly apply onto the tissue to be treated.10,11 The energy distribution of the laser beam can be set on two different modes.7 The fundamental mode gives a sharp focus spot with maximum energy at the focus point and minimum energy anterior or posterior to that point. The mode locking produces a series of brief spikes of photon, with a peak of energy that is much higher than the average energy of equivalent photon bursts that are delivered in a continuous flow. It is also possible to modulate the production of the laser light before delivery by placing an electronic shutter that keeps the excited molecules to a high energy level before relaxation. When the shutter opens, an extremely brief pulse (20 ns) of high energy is produced (Q-switch mode).7

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Step by Step Minimally Invasive Glaucoma Surgery

Several wavelengths are used in ophthalmic laser photocoagulators. Krypton lasers produce red light (647 and 676 nm). Argon lasers produce green light (514.5 nm) and green and blue light (514.5 and 488 nm). Both are used in photocoagulation,14 whereas Nd:YAG lasers deliver infrared light (1064 nm) which is used with Q-switch mode in photodisruption. Diode lasers deliver red (640 nm) and infrared light (800-820 nm) that can be guided through a fiberoptic device for contact photocoagulation. A new type of laser has recently been developed to enhance the photodissociative effect of the YAG laser in intraocular surgery. It is made by combination of a classic YAG laser on which an erbium component has been added to produce fragmentation effects. The wavelength of 2940 nm is longer than Nd:YAG, thus water absorbs most of the energy with an important water absorption photothermal effect.6 The transfer of heat to the adjacent tissue is therefore reduced. The beam is directed through a fiberglass tip with a ceramic end. The first attempts have been made in cataract surgery to replace the ultrasonic emulsification currently used.13 But technical problems regarding the safety of this method in respect to the posterior capsule have not yet been completely solved. New attempts have been made in glaucoma therapy to increase the aqueous outflow by disrupting the trabecular meshwork and inner wall of Schlemm’s canal by an ab-interno approach. A quartz fiber contact endoprobe (320 micron core-diameter, 385 micron coating-diameter) applying single neighboring laser pulses (5-7 mJ) to the trabecular meshwork. The procedure was gonioscopically visualized. Although IOP lowering effect of erbium:YAG laser trabecular ablation did not prove as effective as in filtering procedures. LTA might be a valuable alternative in glaucoma surgery especially in order to avoid conjunctival scarring and postoperative hypotony.3-5 It is

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not known whether this new technique can be widely used in the field of glaucoma laser surgery to add new prospectives or replace existing and efficient laser technique and procedure that will be explained in more details in the subsequent chapters. The physical properties of the laser beam are such that safety aspects should always be considered when using or being in close proximity to laser devices. Every laser delivery system protects the operator from direct damages when using the laser by shutting off the beam with a filter. But this is not the case for personnel being nearby and staring at the laser system, for the filter will not prevent hazardous direct or reflected beam from reaching the retina of the observers.12 LASER IRIDOTOMY Laser iridotomy is a laser surgical procedure by which a small aperture through the iris is created to treat several forms of angle-closure glaucomas and more recently pigmentary glaucoma.25,31 It was introduced in the 80’s with the development of laser surgeries.21 The indication for laser iridotomy is given in the case of acute angle-closure glaucoma when the acute attack has been medically controlled, and the cornea is clear enough to allow sufficient penetration of the laser beam into the anterior chamber without excessive scattering.5,26 In the case of chronic angleclosure glaucoma, or eyes with peripheral anterior synechia, laser iridotomy may reduce the intraocular pressure (IOP) and allow the angle structures to resume a wider space, by deepening the anterior chamber.24 Pupillary block may be relief thus allowing a better control of the IOP. In aphakic or pseudophakic eyes, pupillary block from pockets of aqueous behind the iris plane could be relieved by adequate

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laser iridotomy.1,6,30 In eyes with intumescent cataracts, or in the fellow eye of an acute angle-closure glaucoma eye, prophylactic laser iridotomy can be performed in order to avoid an attack of angle-closure glaucoma.30 In eyes with narrow angle, good visualization of the angle structures may be rendered difficult by the geometric disposition of the iris over the angle. This situation could prevent the performance of laser trabeculoplasty in such eyes. To avoid this complication, laser iridotomy can be performed to open a too narrow angle. In the plateau iris syndrome, anteriorly located ciliary processes support the peripheral iris. Variation in the angle values between dark and light are solely related to changes in iris thickness. Pilocarpine produces iris thinning and is an effective method of opening the angle.18 General disturbance of the geometry of the eye, like in the case of nanophthalmos, have greater risks for developing angle-closure glaucoma. A prophylactic laser iridotomy could reduce the incidence of such complications. In pigment dispersion syndrome, the iris often presents a marked concavity, forming an inverted pupillary block. Accommodation increases iris concavity in some patients with pigment dispersion syndrome. The most likely explanation is an accommodation-induced relative increase in anterior chamber pressure, secondary to anterior movement of the lens surface. Iridotomy prevents change in the iris profile with accommodation.19 In this case too, performance of laser iridotomy would reduce the pressure differential between the anterior and posterior plane of the iris, by creating a channel through the iris.2,4,7,12,22 In the field of refractive surgery, the placement of an intraocular contact lenses (ICL) in the posterior chamber in front of the anterior capsule of the lens reduces the angle and increases the risk for angle-closure glaucoma. Laser iridotomy performed before refractive surgery prevents the likelihood

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of such complications.22 Conversely, in the presence of strong hypermetropic eyes, the current IOL may not have sufficient refractive power for the intended emmetropization. Two intraocular lenses (piggyback) have been placed simultaneously in the capsular bag, thus also reducing the depth of the chamber. In that case too, a laser iridotomy will prevent an attack of angle-closure glaucoma.14 Laser iridotomy is contraindicated in any situation where the angle-closure is not mechanicaly reversible by deepening the anterior chamber, for instance, a flat anterior chamber, synechial closure of the angle by uveitis, neovascular glaucoma or by iridocorneal endothelial syndrome (ICE). In this situation they are absolute contraindications for laser iridotomy. Any corneal edema or opacities will strongly reduce the quality of the transmission of the laser, and are relative contraindications for the performance of the treatment. A gonioscopic contact lens, like the Goldmann is placed on the cornea of the patient after topical anesthesia. It sometimes happens that the iris is not contracted enough to present a smooth surface and thin stroma. Only a few shallow crypts are visible. The use of pilocarpine will contract the sphincter iridae and enlarge the angle of view before treatment. In some cases, the IOP rises a few hours after laser iridotomy.3,27 To prevent the peak of pressure, an alpha agonist such as apraclonidine can be given preand perioperatively.28 The location of the iridotomy should be either the 11 or 1 O’clock positions, so that the upper lid will cover the aperture made by the laser and prevent monocular diplopia (Fig. 5.1).11,16 A crypt should be selected if possible to facilitate the creation of the crater. As laser light is absorbed by ocular pigments, very light iridies are more difficult to perforate than darker. Conversely, very dark pigmented iris have generally thicker stroma and are

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Fig. 5.1: Iris aspect after Nd:YAG laser iridotomy located at 12 O’clock position. Note the depigmentation of the anterior surface of the stroma around the aperture

also difficult to penetrate.13 Laser energy used will then depend on color and density of irides pigments. Current power level for argon type laser ranges from 500 upto 1500 mW for a duration of 0.1 sec. Spot size is set at 50 μm. Nd:YAG laser energy level is set between 2.0 and 8.0 mJ with single burst mode. Small bubbles form around the spot site and, in case of dark brown pigmented iris, some pigments will be released into the anterior chamber. This can severely reduce visibility of the treated area and preclude the completion of the treatment. In such case, a break between laser applications should be made. When passing through the posterior plane of the iris, clouds of pigments burst in the iridotomy crater may appear. As soon as the iris stroma has been totally penetrated, a flow of aqueous humor “leaks” through the aperture and the iris

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stroma moves slightly backwards. Retroillumination through the pupil will reveal a red reflex via the iridotomy. Care should be exercised not to be overconfident in the patency of the iridotomy, as red reflex is not enough to ensure complete burn of iris stroma. Some very thin transparent membranes could still be present, preventing aqueous from freely flowing through the iridotomy. Gonioscopy should always be performed in doubtful cases. Ultrasound biomicroscopy will show an increase in the iridocorneal angle after completion of a successful iridotomy (Fig. 5.2). Corneal edema and epithelial erosion can occur when performing laser iridotomies. Such complications generally resolve in a few days. Endothelial cell can be affected by Nd:YAG laser, caused by the shock waves produced during the treatment. Endothelial cells count have shown that proper application of laser burn with Nd:YAG laser does

Fig. 5.2: Ultrasound biomicroscopy of the anterior chamber angle after patent iridotomy through the iris stroma, the angle is wider

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not significantly increase the endothelial cells lost.15,17,23 Nevertheless, caution should be exercised not to focus the laser beam onto the Descemet’s membrane. The iris stroma is strongly vascularized by arteries from the major iris circle, and injury to arterioles cause instant bleeding in the anterior chamber. When this complication occurs, a gentle pressure with the contact glass will temporarily increase the IOP and promote hemostasis. Dramatic hyphema have been reported after such laser procedures.29 Argon laser, or Nd:YAG laser set on multi-mode iridotomy, generally prevent such complications, as the thermal effect of the laser burns coagulates the vessels and avoids bleeding when hitting a vascular branch.13 The stroma and iris pigment epithelium dispersion phenomena observed during completion of laser iridotomies increase the amount of particles in the anterior chamber. Inflammation and anterior uveitis are generally present after the procedure. To prevent extension and persistence of this inflammation, topical steroids are given and tapered in a few days. Posterior synechiae may develop as a result of prolonged inflammation.10 As mentioned before, the IOP rises in the next few hours after laser therapy. Close monitoring of the IOP is mandatory and adequate medication given in case of persistent elevated values. Some case of damages to the lens have been reported as the result of excessive laser application to the capsule behind the iris plane.32,33 Care should therefore be exercised when applying laser energy on an patent iridotomy. LASER TRABECULOPLASTY When laser burns are applied on the trabecular meshwork, persistent IOP reduction is followed. 30,31 The pathophysiology of the laser burns on the trabecular

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meshwork was hypothesized as follows: Thermal effect of the burns induces collagen shrinkage and scarring of the meshwork. This leads to mechanical traction on the adjacent intertrabecular space that becomes open, thus increasing the outflow facility.5,27 Argon blue-green laser (488 nm) was the laser of choice for this procedure. This has been named argon laser trabeculoplasty (ALT). It can be used in several forms of open-angle glaucoma. A Nd:YAG laser trabeculoplasty (YLT) has also been used as an alternative to the ALT. In case of hypopigmented trabeculum meshwork, YLT is a safe and effective alternative technique to perform laser trabeculoplasty, which is especially useful in poorly pigmented angles where ALT is known to be less effective.14 A non-contact laser delivery system coupled with a slitlamp, is used for the ALT procedure. To gain access to the entire angle structure, a contact lens with a gonioscopic mirror (CGI from LASAG, Bern, Switzerland) is placed on the cornea of the patient after topical anesthesia. In some cases, when the angle is too narrow to allow a good visibility of the trabecular meshwork, use of pilocarpine may enlarge the angle to enable the treatment. Laser spot parameters are set commonly with 50 μm spot size, 0.1 sec. of duration and 800 mW of power. The correct effect of the laser burns should be a blanching of the trabecular meshwork. When too much power is applied, a bubble will form and intense blanching and scarring will result. The power should then be reduced just enough to get blanching with minimal bubble creation. The amount of power required to get this result may vary with the degree of pigmentation of the trabecular meshwork.20 It is important to readjust the power setting throughout the laser session to get homogeneous treatment all over the treated quadrants. The laser beam spot must be kept on focus over

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the entire portion of the treated zone. The spots should be placed evenly over the anterior half portion of the trabecular meshwork (Fig. 5.3). Attention should be paid not to burn adjacent structures of the meshwork such as the ciliary body, the iris processes or the cornea. Correct placement of the spot minimize the possibility of early postoperative IOP rise25 and peripheral anterior synechiae formations.23 Should hemorrhage occur during the laser treatment, it could be kept under control by gently applying a slight pressure to the globe through the contact lens. This relatively rare event might be the result of an inadvertent burn of a peripheral iris vessel from the ciliary circle. Caution should also be exercised not to damage the structure of the cornea. The corneal epithelium may be inadvertently removed when placing or moving the contact lens. The resulting corneal abrasion will heal within hours often without treatment. Corneal endothelium lesions are of greater importance and may lead to permanent corneal lesions. Corneal edema results from insult to the corneal endothelium and may persist for several months, severely impairing the visual outcome of the patient. Pre-existent

Fig. 5.3: Artist’s view of gonioscopic aspect of laser burns after argon and Nd:YAG laser trabeculoplasty, and complication of peripheral anterior synechiae (Courtesy Dr A Mermoud)

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endothelial pathology such as Fuch’s endothelial dystrophy or cornea guttata have greater risks to induce complications of the corneal endothelium.28 Care should be given not to treat too many areas of the trabecular meshwork. An experimental glaucoma model in rhesus monkey has been created by giving a large number of long duration laser burns.8 Postoperative IOP rise peak may also depend on the number of burns.25 Generally, 50 to 70 burns over 180° are enough to create a sustained consistent IOP drop overtime.13,26 It should be kept in mind that the long-term overall outcome of ALT is about 50 percent after 5 years.18,19 Most of the patients will probably require other types of treatment, for instance a filtration surgery. In order not to compromise the result of further filtrating surgery, it is advisable not to treat the upper quadrant, and to leave the trabecular meshwork untouched. It is not uncommon to encounter some pressure spike after argon ALT. To prevent or avoid the extension of such pressure rise, α-2 agonist may be given before and/or just immediately after the laser treatment.17 Apraclonidine or brimonidine are the therapy of choice.1,2,4 Even with an adequate postoperative therapy, the IOP sometimes remains elevated several weeks after the ALT. It should be emphasized that the ALT produces or enhance inflammation in the anterior chamber and over the trabecular meshwork.15 Inflammatory cells and inflammation products collect into the trabecular meshwork and dramatically reduce the outflow facility, resulting in persistent IOP elevation. This inflammatory reaction is thought to be the result of transient breakdown of the bloodaqueous barrier and is correlated with the type of glaucoma. Pigmentary and pseudoexfoliative glaucoma show the greatest inflammatory reaction after ALT compared with chronic open-angle glaucoma.

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Beside the inflammatory reaction, the ALT can also induce other reactions or changes in the anterior chamber. Laser burns placed too posteriorly result in creation of peripheral anterior synechiae.19 This complication does not happen when burns are placed in the anterior trabecular meshwork. It is still unclear whether peripheral anterior synechiae play a role in the long-term outcome of ALT or not.12 The long-term results of the ALT is relatively modest. A mean success rate of 45 percent 5 years after ALT has been reported in several studies.3,6,18,19 Despite this rate, the ALT might be indicated in patients where classical filtrating surgeries cannot be performed for general health state reasons, for ophthalmological reasons, or because of nonmotivated patients.7,9,11,29 Primary ALT gives a longlasting and favorable effect in chronic open-angle glaucoma where 2/3 of the eyes were still managed without additional medication for 8 years. The success in pseudoexfoliation glaucoma was even higher the first 3 years, and stayed above 50 percent for 10 years.3,16,22 In young patients below 50 years, the overall results without additional medication is even higher.10 Some variations in the efficiency of the ALT may be seen between individuals having different intensity in the pigmentation of the trabecular meshwork. The caucasian patients have generally less pigmented meshwork in comparison to the black African patients, and the former may respond poorly to the ALT.21,24 LASER PERIPHERAL IRIDOPLASTY Not every angle-closure glaucoma may be relieved by laser iridotomy. Structural modifications of the anterior chamber angle, like appositional angle closure in the plateau-iris syndrome, peripheral anterior synechiae or attacks of

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severe acute angle-closure glaucoma with corneal edema, anterior chamber flattening and inflammation, will prevent laser iridotomy to be effective.4,5 In case of narrow anterior chamber angle induced by lens intumescence or anterior chamber crowding as the result of short anteroposterior axis eyes (hypermetropia or nanophthalmos), the trabecular meshwork might be also difficult to see through the gonioscopic mirror. In such situations, alternative laser procedures on the iris could be performed to open the angle.5,7,10 Localized heat application onto biological tissues induces protein coagulation and shrinkage around the burn spot. This produces contractions of the tissue fibers and can be used as mechanical retractors. The argon laser peripheral iridoplasty consists of using the thermal effect of argon laser burns of large spot size, long duration and low power applied at the iris periphery to promote contractions of the iris stroma that will retract the iris root and open the angle.8,6,10,11 The treatment is performed with a contact lens under topical anesthesia. In order to have maximum efficiency, the iris surface should be as smooth as possible. To stretch the iris stroma, pilocarpine 4 percent is given one hour before initiating the procedure. Alpha-agonist is also recommended to avoid postoperative rise of the IOP. The laser is set at 500 μm, 0.5 sec and 400 mW of power, depending on the irides coloration. Excess power results in bubble formation and pigment dispersion. In that case, power should be reduced. Enough power should be applied to produce a noticeable stromal contraction. Lighter irides require more power than darker, as pigments are less dense in the former and absorb less power at a time. Location of the burns must be at the most peripheral part of the iris to produce better results. Should the burns

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be placed less peripherally, the contraction would not be acting directly against the iris root and the resulting effect would be much less effective. For instance, placement of burns in the mid-periphery would lead to failure of this procedure. The effect of laser burns on tissues is almost immediate and iris stroma shrinkage is followed by local opening of the anterior angle and local deepening of the anterior chamber. The spots are placed around the circumference of the iris over 360 degrees with two to three spot diameters inbetween. Postoperative treatment consists of an alpha-agonist like apraclonidine given once just after the laser session and topical steroids 3 times a day for a week. Caution should be given to the IOP rise in the early hours and adequate medication be administered accordingly. Complications are relatively seldom and consist in mild iritis lasting no longer than a few days. Corneal burns and endothelial decompensation might occur as the laser beam strikes the iris plane with a narrow angle in the case of plateau iris and shallow anterior chamber. Contrary to laser iridotomy, the iris is not cut through the entire stromal portion and the lens or retina will not suffer from damages linked to laser application. 2,3,9 A case of malignant glaucoma has been reported.1 CYCLOCOAGULATION WITH YAG AND DIODE LASER The intraocular pressure can be lowered not only by enhancing the outflow through the trabeculum meshwork, but also by reducing the production of aqueous humor from the ciliary body.1,18,21 During the era when laser techniques were not currently used, cyclodestruction was made by applying either an intense and focal heat onto the ciliary body, a procedure called cyclodiathermy, or by freezing

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the ciliary processes with the help of a cryoprobe applied close to the limbus.3,19 The laser technique used to destroy the ciliary body belongs to the group of cyclophotocoagulation, a way of reducing the activity of the ciliary body by the means of light as a vector of energy. Nd:YAG laser and diode laser are both used to achieve this goal. The laser delivery system can be of contact or non-contact type, if the laser beam has to be directed through a fiberoptic end probe or applied through the air to the globe via the optic devices of a slit lamp. The latter has the advantage that the end part of the delivery system does not carry the risk of transmitting infectious diseases and does not need to be sterilized, while the former can be more compact and easier to use on a patient in a bed. The energy delivery mode can be set on a pulse mode, whereas during short time intervals a predetermined burst of energy is emitted, or the beam is continuously emitted from the laser source during a preset time. The Nd:YAG laser produces a laser beam of 1064 nm, that is well below the lowest visible wavelengths. The pulse-wave mode creates a mechanical photodisruption that is concentrated in the pigment epithelium of the ciliary body. The continuous wave mode gives a very high level of energy that is mostly absorbed thermally over the ciliary body and partially absorbed in the sclera.16 The effects of Nd:YAG laser application onto the ciliary body result in destruction of tissue, inflammation fibrosis and coagulation necrosis. At the end stage, the production of aqueous humor is markedly reduced, thus lowering the IOP.12,20 The patient is given a retrobulbar injection of anesthetic to reduce the pain induced by the laser treatment and to avoid unexpected eye movements during the procedure. With a non-contact delivery system, the patient is seated

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in front of a slit-lamp. The laser beam is set with the maximum offset value to separate the aiming beam from the Nd:YAG beam. The energy is set between 5 and 10 J/ pulse, the duration of the continuous mode is 20 ms. The beam is pointed between 1 and 2 mm from the limbus and burns are made around evenly spaced. The number of burns varies between 20 and 40. When using a contact delivery system, the probe is placed at less than 1 mm from the limbus and the energy level limited to 5 J. The diode laser produces a laser beam of 810 nm which is slightly lower than the lowest visible wavelength.15,22 There is only one mode, the continuous-wave mode. Two delivery systems can equally be used, the contact and noncontact, in the same way the Nd:YAG laser is being used (Fig. 5.4). The effects on the ciliary body are mostly due to the thermal action of the laser beam absorbed by the melanin pigments of the ciliary epithelium. Coagulation necrosis and tissue shrinkage are the main changes observed after diode laser cyclophotocoagulation.8 The patient is prepared according to the same protocol used for the Nd:YAG treatment. The power level for non-contact

Fig. 5.4: Diode cyclophotocoagulation probe for contact cyclocoagulation

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diode treatment is set between 1000 and 2000 mW, the duration is 2 sec, and the spot size varies between 150 and 500 μm.9 In the contact mode, the duration is slightly longer, giving a power level of 2000 mW.17 The laser beam or the diode probe are placed 1 mm behind the limbus and 20 to 40 burns are made over the entire 360 degrees of the limbus (Fig. 5.5).7,10,13 A new technique for controlling refractory glaucoma has been developed that acts directly from inside the eye instead of acting through the sclera. One reason for failure of trans-scleral cyclophotocoagulation, particularly in congenital glaucoma, may be the displacement of the ciliary processes. This displacement does not permit the indirect treatment to reach the appropriate area. Because endoscopic laser cyclophotocoagulation allows direct visualization of the processes, treatment can be accurately

Fig. 5.5: Inflammation is noticeable after Nd:YAG cyclophotocoagulation, with mixed perilimbal conjunctival injection. The laser burns are clearly visible around the limbus as white scars evenly spaced

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applied to the very individual ciliary processes.6,14 Endoscopic cyclophotocoagulation treatment encompassed 180 to 360 degrees of the ciliary body circumference and is performed through a limbal incision. An 810 nm pulsed continuous-wave diode laser capable of 1.2 W output is being used. Generally, 800 mW are being used for less than 1 second, for a total of 0.8 J per treatment. Early results suggest that endoscopic cyclophotocoagulation is a safe and effective therapeutic modality for refractory glaucomas.11 The postoperative care of patients undergoing cyclophotocoagulation consists of patching the eye for one day with topical steroids to control the postoperative inflammatory stage (Fig. 5.5). The steroids are gently tapered and antiglaucoma medication adjusted according to the postoperative examinations. The conjunctiva is frequently burned and uveitis is present after every laser treatment but subsides with steroids application. The pain might be moderate to severe, generally lasting no longer than a few days. The most severe complication implies prolonged hypotony and phthisis bulbi, a feared event that had already occurred in several cases after cyclocryocoagulation.5 These complications tend to be less frequent when using the diode laser cyclophotocoagulation.2 The pressure lowering effect of laser cyclophotocoagulation is variable but values of 15 to 30 mm Hg might be achieved, and results overtime remain quite stable. Nd:YAG and diode laser cycloablations are relatively safe and effective at controlling IOP in eyes with advanced refractory glaucoma in the short and medium term.4 Glaucoma medications are generally also reduced after one or more laser sessions. Repeated treatments are nevertheless required in some patients when the intended lowering effect is not reached at the first session.

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LASER TREATMENTS AFTER FILTERING SURGERY After classical filtering surgery that has been performed without complications, it may happen that filtration progressively decreases. The IOP rises again to values measured before surgery. The main cause for such failure is an overscarring of the filtration bleb. The trabeculectomy technique requires a good closure of the scleral flap to prevent excessive aqueous outflow resulting in hypotony and shallow anterior chamber. But a too tight closure of the scleral flap may result in excessive elevation in IOP in the postoperative period. To prevent prolonged elevation in the IOP, it is possible to selectively cut some sutures to release the tension of the scleral flap.7,9 Scleral flap sutures are made of nylon or polypropylene sutures that are either black or deep blue. The thermal effect of argon laser is efficient in lysis of such material through the conjunctiva. Technically, the procedure is performed with a contact glass applied to the conjunctiva, using the Hoskins or the Ritch lens. 4,11 This allows a better visualization of the suture by flattening the Tenon and conjunctiva layers. It is better not to perform ocular massage immediately before the laser lysis, as the massage brings some subconjunctival fluid that will scatter laser light and reduce visibility and accessibility to the suture. The laser setting is 50 μm for the spot size, with a duration of 0.1 sec and power of 300 to 500 mW. The laser beam is focused on the suture and shots are applied until the suture is being cut. Intraocular pressure is then measured to ascertain the degree of efficiency reached. Gentle massage of the globe might also be performed to promote the outflow. Caution should be exercised not to excessively treat by cutting too many sutures resulting in hypotony, shallow anterior chamber, choroidal effusion, optic disk

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and macular edema.1 The ideal time to perform suture lysis is 1 to 2 weeks after surgery in case of elevated IOP. After this period, the result is less prone to be efficient, probably because of scarring of the scleral flap.3 Other causes of elevated pressure like iris incarceration into the internal sclerostomy or malignant glaucoma, should be investigated and eliminated accordingly. Overfiltration on the other hand is a troublesome complication that requires efficient treatment. Overfiltrating bleb can be brought to a less effective size by enhancing the fibrosis. Invasive techniques like autologous blood injection in the bleb have been reported to be efficient. Noninvasive methods using laser techniques can also be developed to prevent persistent hypotony and create some local subconjunctival bleeding. By applying gentle laser spots onto the conjunctiva with a Nd:YAG laser, the conjunctival vessels are disrupted and bleeding occurs.2 The idea is to create adhesion scars between the conjunctival bleb and the Tenon shield that reduce the size and efficiency of the bleb. It is also possible to physically promote scarring of the subconjunctival space and Tenons and mechanically tighten the two layers. To achieve this goal, several burns are made at the edge of the bleb by using the Hoskins or the Ritch lens to depress the conjunctiva. The spot size is set between 50 and 100 μm, with a duration of 0.1 sec, a power of 200 to 400 mW. The beam is focused on the Tenon or slightly deeper to avoid perforation of the conjunctiva, and the spots are evenly spaced all around the bleb. Power should not be excessive as this will result in conjunctival buttonhole or formation of subconjunctival bubbles that will increase the bleb size instead of helping scar formation.6 Laser treatment in the postoperative period can also be used in conjunction with other surgical techniques used

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to treat refractory glaucoma. In this case, drainage devices are being used to create an effective outflow from the anterior chamber to the subconjunctival and sub-Tenon’s space. But this technique requires an adequate control of the outflow that can be achieved by placing a stent suture around the tube. In the postoperative period, the IOP is monitored and the suture may be released should the pressure be elevated.8 It may also happen that the tube opening in the anterior chamber becomes blocked by fibrin clots and this results in failure of the shunt technique. Nd:YAG laser membranectomy will clean the tube and thus restore a patent drainage to the external plate.12 In the new non-perforating techniques, like deep sclerectomy with collagen implants or viscocanalostomy, the trabecular meshwork remains untouched and only the inner wall of Schlemm’s canal and the juxtacanalicular meshwork are removed. 5,13 A very thin membrane prevents the anterior chamber to collapse during the filtering surgery. But after a few weeks or months, the trabeculodescemetic membrane may become fibrotic because of elevated IOP and should be open to allow better outflow. This procedure is called goniopuncture, and can easily be done with a Nd:YAG laser. The goal of this technique is to perforate the remaining trabecular meshwork at the surgery site by performing an internal trabeculotomy or descemetomy. A gonioscopic contact glass is set on the eye of the patient after topical anesthesia to gain access to the anterior chamber angle. The trabecular meshwork at the surgery site appears as a thin less pigmented membrane, some light from the sclerectomy being transmitted through the wall (Fig. 5.6). The laser beam is pointed to this membrane and several impacts are shot. The power level is set at 5 mJ. Some air-bubbles may be generated during the treatment. It is sometimes difficult

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to ascertain the patency of the trabeculotomy, as the perforation diameter is very small, being less than 70 μm and the edge barely distinguishable from the surrounding poorly pigmented trabecular tissue. In such case, it is best advisable to measure the pressure a few days later and perform a second session if necessary. The postoperative treatment consists of topical corticosteroids 3 times a day, tapered in a few days. The hypotensive medication if required before goniopuncture, should be continued or stopped after laser treatment according to the IOP lowering effect achieved.10 SCLEROSTOMIES The technical approach of glaucoma surgery is based on the creation of a fistula that drains into a filtering bleb.

Fig. 5.6: Gonioscopic view of the anterior chamber, and inner aspect of the trabeculodescemetic membrane after Nd:YAG goniopuncture. Note the black suture used to secure the collagen implant

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Mechanical techniques that involve the use of cutting blades, blunt dissection, tissue removal and titrated sutures promote inflammatory responses that will modulate the healing and scarring processes. Overacting fistulas or inefficient filtering blebs result from variation of standard procedure and lead to the need of complementary surgery or adjunctive treatment. Laser, by its physical property, is a very useful tool that can provide calibrated beams at various energy levels. By developing adequate delivery systems to the trabecular meshwork, it is possible to perform a direct fistula through the tissue, a so-called sclerostomy.7 The advantages of such techniques are that the fistula diameter can be better predicted, tissue trauma could be less extended, especially regarding the development of the filtering bleb.3 Three methods have been developed to achieve this goal. All are based on the kind of delivery system being used to apply laser energy to create a channel through the sclera and trabecular meshwork. Basically there are two approaches possible, from outside the eye, the ab-externo procedure, or from inside, the ab-interno procedure. The latter can further be divided into two categories, invasive or non-invasive procedure. To perform a non-invasive ab-interno sclerostomy, a modification of the current laser technique has to be made before completion of the treatment. A pulse-dye laser is used to get a beam for the non-contact delivery system connected to the slit-lamp. A gonioscopy lens is applied on the eye to allow good visualization of the angle structures. The laser produces a beam at 660 nm, set at 200 μm spot size, 10 μsec duration and 200 to 400 mJ energy level. In order to get the most effects from the beam at that wavelength, the site of sclerostomy must be dyed with methylene blue dye with an iontophoresis marker.14 The

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beam is then directed to the blue patch that is visible in the gonioscopic lens. Shots are given repetitively until the whole sclera has been drilled and the anterior chamber shallows and the conjunctival bleb develops.8 The invasive ab-interno sclerostomy consists of introducing an endolaser probe in the anterior chamber to deliver laser beam directly to the trabecular meshwork.11 The main advantage consists of leaving the conjunctiva untouched avoiding scar formation. Disadvantages of this technique are those related to any intraocular approach; the infectious risks, trauma to the endothelium, the iris structures and the lens. Thermal damages due to accumulation of heat at the impact site are also related to this technique. To introduce the endolaser probe, a paracentesis is performed on the cornea and the anterior chamber is filled with a viscoelastic agent. The fiberoptic probe is introduced and the tip is brought into perpendicular contact with the corneoscleral tissue, taking care to avoid the posterior trabecular meshwork. Laser beam is actuated and tissue ablation begins. The probe is moved forward as ablation removes tissue leaving space for further ablation. The end of the procedure is determined when the tip is seen through the conjunctiva, and the aqueous humor and viscoelastic agent flow into the bleb.1 The ab-externo sclerostomy consists in creating a channel through the sclera to the anterior chamber.12,13 A contact probe is placed at the limbus to guide the laser beam. The conjunctiva is cut 15 mm away from the intended treatment site to allow the probe to be placed correctly thus allowing an adequate contact with the sclera. A holmium:YAG laser is used to produce the energy required to ablate the tissue. The energy level is set at 100 mJ/pulse. The beam is applied to the sclera and can be seen through the cornea into the anterior chamber. Progression of creation of the channel can therefore be

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monitored until completion. At that stage, aqueous humor flows through the fistula into the subconjunctival space.10 After removal of the probe, the conjunctival incision is closed with a single suture and topical antiinflammatory medication given.2,5,6,9 REFERENCES Laser Principle and Introduction 1.

Birngruber R. Thermal modeling in biological tissues. In Hillenkamp F, Praetesi R, Sacchi CA (Eds): Laser in Biology and Medicine Plenum: New York, 1980. 2. Dietlein TS, Jacobi PC, Krieglstein GK. Ab-interno infrared laser trabecular ablation: Preliminary short-term results in patients with open-angle glaucoma. Graef’s Arch Clin Exp Ophthalmol 1997;235(6):349-53. 3. Dietlein TS, Jacobi PC, Krieglstein GK. Erbium: YAG laser trabecular ablation (LTA) in the surgical treatment of glaucoma. Lasers Surg Med 1998;23(2):104-10. 4. Hillenkamp F. Interaction between laser radiation and biological systems. In Hillenkamp F, Praetesi R, Sacchi CA (Eds): Laser in Biology and Medicine. Plenum: New York, 1980. 5. L’Esperance FA Jr. Ophthalmic Laser: Photocoagulation, Photoradiation and Surgery (3rd edn): Mosby: St. Louis 1989. 6. Loertscher H, Shi WQ, Grundfest WS. Tissue ablation through water with erbium: YAG lasers. IEEE Trans Biomed Eng 1992;39:86-88. 7. Mainster MA, Sliney DH, Blecher CD, et al. Laser photodisruptors: Damage mechanisms, instrument design and safety. Ophthalmology 1983;90:973-91. 8. Mainster MA, Ho PC, Mainster KJ. Argon and krypton laser photocoagulators. Ophthalmology 1983;90: 48-54. 9. Ready JF. Industrial applications of lasers. Academic Press: New York, 1978.

70

Step by Step Minimally Invasive Glaucoma Surgery

10.

Schuman JS, et al. Experimental use of semiconductor diode laser in contact transscleral photocoagulator in rabbits. Arch Ophthalmol 1990;108:1152-57. 11. Schuman JS, et al. Energy levels and probe placement in contact transscleral semiconductor diode laser cyclophotocoagulation in human cadaver eyes. Arch Ophthalmol 1991;109:1534-38. 12. Sliney DH, Mainster MA. Potential laser hazards to the clinician during photocoagulation. Am J Ophthalmol 1987;103:758-60. 13. Wetzel W, Brinkmann R, Koop N, et al. Photofragmentation of lens nuclei using the Er: YAG laser: Preliminary report of an in vitro study. Ger J Ophthalmol 1996;5(5): 281-84. 14. Wieder M, Pomerantzeff O, Schnieder J. Retinal vessel photocoagulation: A quantitative comparison of argon and krypton laser effects. Invest Ophthalmol Vis Sci 1981;20:418-24.

Laser Iridotomy 1.

Anderson DR, Forster RK, Lewis ML. Laser iridotomy for aphakic pupillary block. Arch Ophthalmol 1975;93:343-46. 2. Breingan PJ, Esaki K, Ishikawa H, et al. Iridolenticular contact decreases following laser iridotomy for pigment dispersion syndrome. Arch Ophthalmol 1999;117(3):32528. 3. Brooks AMV, Harper CA, Gillies W. Occurrence of malignant glaucoma after iridotomy. Br J Ophthalmol 1989;73:617-20. 4. Carassa RG, Bettin P, Fiori M, et al. Nd:YAG laser iridotomy in pigment dispersion syndrome: An ultrasound biomicroscopic study. Br J Ophthalmol 1998;82(2):150-53. 5. Fleck BW, Wright E, Fairley EA. A randomised prospective comparison of operative peripheral iridectomy and Nd:YAG laser iridotomy treatment of acute angle closure glaucoma: 3-year-visual acuity and intraocular pressure control outcome. Br J Ophthalmol 1997;81(10):884-88.

Laser Treatment in Glaucomas

6. 7. 8.

9. 10. 11. 12. 13.

14. 15. 16. 17.

71

Forman JS, et al. Pupillary block following posterior chamber lens implantation. Ophthalmic Laser Ther 1987;2:85-88. Gandolfi SA, Vecchi M. Effect of a YAG laser iridotomy on intraocular pressure in pigment dispersion syndrome. Ophthalmology 1996;103(10):1693-95. Janiec S, Rzendkowski M, Bolek S, et al. The effect of Nd:YAG laser iridotomy on irido-corneal angle width assessed with ultrasound biomicroscopy in patients with primary open-angle glaucoma. Klin Oczna 1998;100(1):1518. Kim YY, Jung HR. Dilated, miotic-resistant pupil and laser iridotomy in primary angle-closure glaucoma. Ophthalmologica 1977;211(4):205-08. Kraemer C, Gramer E. Posterior synechiae after Nd:YAG laser iridotomy. A clinical study. Ophthalmologe 1998;95(9):625-32. Kublin J, Simmons RJ. Use of tinted soft contact lenses to eliminate monocular diplopia secondary to laser iridectomies. Ophthalmic Laser Ther 1987;2:111-13. Lagreze WD, Mathieu M, Funk J. The role of YAG-laser iridotomy in pigment dispersion syndrome. Ger J Ophthalmol 1996;5(6): 435-38. Lim L, Seah SK, Lim AS. Comparison of argon laser iridotomy and sequential argon laser and Nd:YAG laser iridotomy in dark irides. Ophthalmic Surg Lasers 1996;27(4):285-88. Masket S. Piggyback intraocular lens implantation. J Cataract Refract Surg 1998;24(4):569-70. Meyer KT, Pettit TH, Straatsma BR. Corneal endothelium damage with neodymium: YAG laser. Ophthalmology 1984;91:1022-28. Murphy PH, Trope GE. Monocular blurring: a complication of YAG laser iridotomy. Ophthalmology 1991;98:1539-42. Panek WC, Lee DA, Christensen RE. The effects of Nd: YAG laser iridotomy on the corneal endothelium. Am J Ophthalmol 1991;111:505-07.

72 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28.

29. 30. 31.

Step by Step Minimally Invasive Glaucoma Surgery

Pavlin CJ, Foster FS. Plateau iris syndrome: Changes in angle opening associated with dark, light, and pilocarpine administration. Am J Ophthalmol 1999;128(3):288-91. Pavlin CJ, Macken P, Trope GE, et al. Accommodation and iridotomy in the pigment dispersion syndrome. Ophthalmic Surg Lasers 1996;27(2):113-20. Pesando PM, Ghiringhello MP, Tagliavacche P. Posterior chamber collamer phakic intraocular lens for myopia and hyperopia. J Refract Surg 1999;15(4):415-23. Pollack IP. Use of argon laser energy to produce iridotomies. Ophthalmic Surg 1980;11:506-15. Potash SD, et al. Ultrasound biomicroscopy in pigment dispersion syndrome. Ophthalmology 1994;101:332-39. Power WJ, Collum LMT. Electron microscopic appearances of human corneal endothelium following Nd:YAG laser iridotomy. Ophthalmic Surg 1992;23:347-50. Quigley HA. Long-term follow-up of laser iridotomy. Ophthalmology 1981;88:218-24. Ritch R, Podos SM. Argon laser treatment of angle-closure glaucoma. Perspect Ophthalmol 1980;4:129-34. Ritch R, Solomon IS. Glaucoma surgery. In L’Esperance FA (Ed): Ophthalmic Lasers (3rd edn): Mosby: St Louis, 1989. Robin AL. Intraocular pressure rise after iridotomy (letter). Arch Ophthalmol 1986;104:1117. Robin AL, Pollack IP, DeFaller JM. Effects of topical ALO 2145 (p-aminoclonidine hydrochloride) on intraocular pressure rise following argon laser iridotomy. Arch Ophthalmol 1987;105:1208-11. Rubin L, Arnett J, Ritch R. Delayed hyphema after argon laser iridectomy. Ophthalmic Surg 1984;15:852-53. Samples J, et al. Pupillary block with posterior chamber intraocular lenses. Am J Ophthalmol 1987;105:335-37. Schwartz LW, et al. Argon laser iridotomy in the treatment of patients with primary angle-closure or pupillary block glaucoma: A clinicopathologic study. Ophthalmology 1978;85:294-309.

Laser Treatment in Glaucomas

32. 33. 34.

73

Wollensak G, Eberwein P, Funk J. Perforation rosette of the lens after Nd:YAG laser iridotomy. Am J Ophthalmol 1997;123(4):555-57. Zadok D, Chayet A. Lens opacity after neodymium: YAG laser iridectomy for phakic intraocular lens implantation. J Cataract Refract Surg 1999;25(4):592-93. Zaldivar R, Davidorf JM, Oscherow S. Posterior chamber phakic intraocular lens for myopia of ~8 to ~19 diopters. J Refract Surg 1998;14(3):294-305.

Laser Trabeculoplasty 1. 2.

3.

4. 5. 6. 7. 8.

Barnebey HS, et al. The efficacy of brimonidine in decreasing elevation in intraocular pressure after laser trabeculoplasty. Ophthalmol 1993;100:1083-88. Barnes SD, Campagna JA, Dirks MS, et al. Control of intraocular pressure elevations after argon laser trabeculoplasty: comparison of brimonidine 0.2 percent to apraclonidine 1.0 percent. Ophthalmology 1999;106(10): 2033-37. Bergea B, Bodin L, Svedbergh B. Primary argon laser trabeculoplasty vs pilocarpine. IV Long-term effects on optic nerve head. Acta Ophthalmol Scand 1995;73(3):21621. Brown RH, et al. ALO 2145 reduces the IOP elevation after anterior segment surgery. Ophthalmol 1988;95:378-84. Brubaker RF. Liesegang TJ. Effect on trabecular photocoagulation on the aqueous humor dynamics of the human eye. Am J Ophthalmol 1983;96:139-47. Chen TC, Wilensky JT, Viana MA. Long-term follow-up of initially successful trabeculectomy. Ophthalmology 1997;104(7):1120-25. Damji KF, et al. Selective laser trabeculoplasty vs argon laser trabeculoplasty: A prospective randomised clinical trial. Br J Ophthalmol 1999;83(6):718-22. Gaasterland D, Kupfer C. Experimental glaucoma in rhesus monkey. IOVS 1974;13:455-57.

74 9.

10.

11.

12.

13. 14.

15. 16.

17. 18.

Step by Step Minimally Invasive Glaucoma Surgery

Guzey M, et al. Effects of frequency-doubled Nd:YAG laser trabeculoplasty on diurnal intraocular pressure variations in primary open-angle glaucoma. Ophthalmologica. 1999;213(4):214-18. Jacobi PC, Dietlein TS, Krieglstein GK. Primary trabeculectomy in young adults: Long-term clinical results and factors influencing the outcome. Ophthalmic Surg Lasers 1999;30(8):637-46. Jampel HD. Initial treatment for open-angle glaucomamedical, laser, or surgical? Laser trabeculoplasty is the treatment of choice for chronic open-angle glaucoma. Arch Ophthalmol 1998;116(2): 240-41. Koller T, Sturmer J, Reme C, et al. Membrane formation in the chamber angle after failure of argon laser trabeculoplasty: Analysis of risk factors. Br J Ophthalmol 2000;84(1):48-53. Lustgarten J, et al. Laser trabeculoplasty: A prospective study of treatment parameters. Arch Ophthalmol 1984;102:517-19. Mermoud A, Herbort CP, Schnyder CC, et al. Comparison of the effects of trabeculoplasty using the Nd-YAG laser and the argon laser. Klin Monatsbl Augenheilkd 1992; 200(5):404-06. Mermoud A, Pittet N, Herbort CP. Inflammation patterns after laser trabeculoplasty measured with the laser flare meter. Arch Ophthalmol 1992;110:368-70. Odberg T, Sandvik L. The medium and long-term efficacy of primary argon laser trabeculoplasty in avoiding topical medication in open angle glaucoma. Acta Ophthalmol Scand 1999;77(2):176-81. Robin AL. Argon laser trabeculoplasty medical therapy to prevent the intraocular pressure rise associated with argon laser trabeculoplasty. Ophthalmic Surg 1991;22:31-37. Shingelton BJ, et al. Long-term efficacy of argon laser trabeculoplasty. Ophthalmol 1987;94:1513-19.

Laser Treatment in Glaucomas

19. 20. 21. 22. 23.

24. 25. 26. 27. 28. 29. 30. 31.

75

Schwartz AL, Love DC, Schwartz MA. Long-term followup of argon laser trabeculoplasty for uncontrolled openangle glaucoma. Arch Ophthalmol 1985;103:1482-84. Schwartz LW, et al. Variation of techniques on the results of argon laser trabeculoplasty. Ophthalmol 1983;90:78184. The Advanced Glaucoma Intervention Study (AGIS): 4. Comparison of treatment outcomes within race. Sevenyear-results. Ophthalmology 1998;105(7):1146-64. Ticho U, Nesher R. Laser trabeculoplasty in glaucoma. Tenyear-evaluation. Arch Ophthalmol 1989;107(6):844-46. Traverso CE, Greenidge KC, Spaeth GL. Formation of peripheral anterior synechiae following argon laser trabeculoplasty: A prospective study to determine relationship to position of laser burns. Arch Ophthalmol 1984;102:861-63. Varma R. Trabeculoplasty, trabeculectomy, and race: Is there a difference in response to treatment between blacks and whites? Ophthalmology 1998;105(7):1135-36. Weinreb RN, et al. Immediate intraocular pressure response to argon laser trabeculoplasty. Am J Ophthalmol 1983;95:279-86. Weinreb RN, et al. Influence of the number of laser burns administered on the early results of argon laser trabeculoplasty. Am J Ophthalmol 1983;95:287-92. Wickham MG, Worthen DM, Binder PS. Physiologic effects of laser trabeculectomy in rhesus monkey eyes. IOVS 1977;16:624-28. Wilensky JT, Jampol L. Laser therapy for open-angle glaucoma. Ophthalmol 1981;88:213-17. Wise JB. Ten-year-results of laser trabeculoplasty. Does the laser avoid glaucoma surgery or merely defer it? Eye 1987;1(Pt 1):45-50. Wise JB, Witter SL. Argon laser therapy for open-angle glaucoma: A pilot study. Arch Ophthalmol 1979;97:31922. Wise JB. Status of laser treatment of open-angle glaucoma. Ann Ophthalmol 1981;13:149-50.

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Laser Peripheral Iridoplasty 1. 2.

3. 4.

5.

6. 7. 8. 9. 10. 11.

Fourman S. “Malignant” glaucoma post laser iridotomy. Ophthalmology 1992;99(12):1751-52. Karjalainen K, Laatikainen L, Raitta C. Bilateral nonrhegmatogenous retinal detachment following neodymium-YAG laser iridotomies. Arch Ophthalmol 1986;104:1134. Karmon G, Savir H. Retinal damage after argon laser iridotomy. Am J Ophthalmol 1986;101:554-60. Lai JS, Tham CC, Lam DS. Limited argon laser peripheral iridoplasty as immediate treatment for an acute attack of primary angle closure glaucoma: A preliminary study. Eye 1999;13(Pt 1):26-30. Lam DS, Lai JS, Tham CC. Immediate argon laser peripheral iridoplasty as treatment for acute attack of primary angle-closure glaucoma: A preliminary study. Ophthalmology 1998;105(12):2231-36. Ritch R, Liebmann JM. Argon laser peripheral iridoplasty. Ophthalmic Surg Lasers 1996;27(4):289-300. Ritch R. Plateau iris is caused by abnormal positioned ciliary processes. J Glaucoma 1992;1:23-27. Sassani JW, et al. Histopathology of argon laser peripheral iridoplasty. Ophthalmic Surg 1993;24:740-45. Shapiro A, Tso MO, Goldberg MF. Argon laser-induced cataract. Arch Ophthalmol 1984;102:579-83. Verma N, Fromberg G. Combined argon laser iridoplasty and trabeculoplasty in the management of open angle glaucomas. Indian J Ophthalmol 1986;34:221-23. York K, Ritch R, Szmyd LJ. Argon laser peripheral iridoplasty: Indications, techniques and results. IOVS 1984;25(Suppl): 94.

Cyclocoagulation with YAG and Diode Laser 1.

Albaugh CH, Dunphy EB. Cyclodiathermy. Arch Ophthalmol 1942;27:543.

Laser Treatment in Glaucomas

2. 3. 4.

5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

77

Azuara-Blanco A, Dua HS. Malignant glaucoma after diode laser cyclophotocoagulation. Am J Ophthalmol 1999;127(4): 467-69. Bietti G. Surgical intervention on the ciliary body: New trends for the relief of glaucoma. JAMA 1950;142:889. Bloom PA, Tsai JC, Sharma K, et al. “Cyclodiode”. Transscleral diode laser cyclophotocoagulation in the treatment of advanced refractory glaucoma. Ophthalmology 1997; 104(9):1508-19. Brindley G, Shields MB. Value and limitation of cyclocryotherapy. Graefe’s Arch Clin Exp Ophthalmol 1986;224: 545-48. Chen J, Cohn RA, Lin SC, et al. Endoscopic photocoagulation of the ciliary body for treatment of refractory glaucomas. Am J Ophthalmol 1997;124(6):787-96. Detry-Morel M, Gilon B. Treatment of refractory glaucoma with trans-scleral cyclophotocoagulation using a diode laser. Bull Soc Belge Ophthalmol 1999;272: 45-52. Hennis HL, Stewart WC. Transcleral cyclophotocoagulation using a semiconductor diode laser in cadaver eyes. Ophthalmic Surg 1991;22:274-78. Kida K, et al. Non-contact transscleral semi-conductor diode laser cyclophotocoagulation for refractory glaucoma. IOVS 1992;33 (Suppl): 1267. Linsen MC, Mannes C, Zeyen T. Diode laser cyclophotocoagulation in refractory glaucoma. Bull Soc Belge Ophthalmol 1998;270:69-73. Mora JS, et al. Endoscopic diode laser cyclophotocoagulation with a limbal approach. Ophthalmic Surg Lasers 1997;28(2):118-23. Nassise MP, et al. Inflammatory effects of continuous-wave Nd:YAG laser cyclocoagulation. IOVS 1992;33:2216. Oguri A, Takahashi E, Tomita G, et al. Trans-scleral cyclophotocoagulation with the diode laser for neovascular glaucoma. Ophthalmic Surg Lasers 1998;29(9):722-27. Plager DA. et al. Intermediate-term results of endoscopic diode laser cyclophotocoagulation for pediatric glaucoma. J AAPOS 1999;3(3):131-37.

78 15. 16. 17.

18. 19.

20. 21. 22.

Step by Step Minimally Invasive Glaucoma Surgery

Schlote T, Kreutzer B, Kriegerowski M, et al. Diode laser cyclophotocoagulation in treatment of therapy refractory glaucoma. Klin Monatsbl Augenheilkd 1997;211(4):250-56. Schubert HD, Agarwal A. Quantitative CW Nd:YAG pars plana trans-scleral photocoagulation in postmortem eyes. Ophthalmic Surg 1990;21:835-39. Schuman JS, et al. Energy levels and probe placement in contact trans-scleral semiconductor diode laser cyclophotocoagulation in human cadaver eyes. Arch Ophthalmol 1991;109:1534-38. Stocker FW. Response of chronic simple glaucoma to treatment with cyclodiathermy puncture. Arch Ophthalmol 1945;34:181. Vogt A Versuche zur intraokularen Druckherabsetzung mittels Diathermieschadigung des corpus ciliare (Zyklodiatermiestichelung) Klin Monatsbl Augenheilkd 1936;97:672. Weekers R, et al. Effects of photocoagulation of ciliary body upon ocular tension. Am J Ophthalmol 1961;52:156. Weve H. Die Zyklodiatermie das corpus ciliare bei Glaukom Zentralbl Ophthalmol 1933;29:256. Wong EY, Chew PT, Chee CK, et al. Diode laser contact trans-scleral cyclophotocoagulation for refractory glaucoma in Asian patients. Am J Ophthalmol 1997;124(6): 797-804.

Laser Treatments After Filtering Surgery 1.

Bardak Y, Cuypers MH, Tilanus MA, et al. Ocular hypotony after laser suture lysis following trabeculectomy with mitomycin C. Int Ophthalmol 1997-98;21(6):325-30. 2. Bettin P, Carassa RG, Fiori M, et al. Treatment of hyperfiltering blebs with Nd:YAG laser-induced subconjunctival bleeding. J Glaucoma 1999;8(6):380-83. 3. Chopra H, et al. Early postoperative titration of bleb function: Argon laser lysis and removable sutures in trabeculectomy. J Glaucoma 1992;1:54.

Laser Treatment in Glaucomas

4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

79

Hoskins HD Jr, Migliazzo C. Management of failing filtering blebs with the argon laser. Ophthalmic Surg 1984;15:731. Karlen ME, Sanchez E, Schnyder CC, et al. Deep sclerectomy with collagen implant: Medium term results. Br J Ophthalmol 1999;83(1):6-11. Lanzl IM, Katz LJ, Shindler RL, et al. Surgical management of the symptomatic overhanging filtering bleb. J Glaucoma 1999;8(4):247-49. Lieberman MF. Suture lysis by laser and goniolens. Am J Ophthalmol 1983;95:257. Liebmann J, Ritch R. Intraocular suture ligature to reduce hypotony following Molteno seton implantation. Ophthalmic Surg 1992;23:51. Macken P, Buys Y, Trope GE. Glaucoma laser suture lysis. Br J Ophthalmol 1996;80(5):398-401. Mermoud A, Karlen ME, Schnyder CC, et al. Nd:YAG goniopuncture after deep sclerectomy with collagen implant. Ophthalmic Surg Lasers 1999;30(2):120-25. Ritch R, Potash SD, Liebmann JM. A new lens for argon laser suture lysis. Ophthalmic Surg 1994;25:126. Singh K, Eid TE, Katz LJ, et al. Evaluation of Nd:YAG laser membranectomy in blocked tubes after glaucoma tubeshunt surgery. Am J Ophthalmol 1997;124(6):781-86. Stegmann R, Pienaar A, Miller D. Viscocanalostomy for open-angle glaucoma in black African patients. J Cataract Refract Surg 1999;25(3):316-22.

Sclerostomies 1. 2. 3.

Berlin MS, Rajacich G, Duffy M, et al. Excimer laser photoablation in glaucoma filtering surgery. Am J Ophthalmol 1984;103:713-14. Friedman DS, Katz LJ, Augsburger JJ, et al. Holmium laser sclerostomy in glaucomatous eyes with prior surgery: 24month results. Ophthalmic Surg Lasers 1998;29(1):17-22. Haring G, Behrendt S, Wetzel W. Evaluation of laser sclerostomy fistulas using ultrasound biomicroscopy. Int Ophthalmol 1997-98;21(5):261-64.

80 4. 5. 6. 7.

8. 9. 10. 11. 12. 13.

14.

Step by Step Minimally Invasive Glaucoma Surgery

Iwach AG, Hoskins HD Jr. Laser sclerostomy for the management of glaucoma. Curr Opin Ophthalmol 1993;4(2):85-92. Iwach AG, Hoskins HD Jr, Drake MV, et al. Subconjunctival THC:YAG (“Holmium”) laser thermal sclerostomy abexterno. A one year report. Ophthalmol 1993;100:356-65. Jacobi PC, Dietlein TS, Krieglstein GK. Prospective study of ab externo erbium: YAG laser sclerostomy in humans. Am J Ophthalmol 1997;123(4):478-86. Kendrick R, Kollarits CR, Khan N. The results of ab-interno laser thermal sclerostomy combined with cataract surgery versus trabeculectomy combined with cataract surgery 6 to 12 months postoperatively. Ophthalmic Surg Lasers 1996;27(7):583-86. Latina MA, Melamed S, March WF, et al. Gonioscopic abinterno laser sclerostomy: A pilot study in glaucoma patients. Ophthalmol 1992;99:1736-44. Luntz MH, Fliegler RD, Mastrobattista J. Subconjunctival THC:YAG laser sclerostomy under a partial thickness flap. Eur J Ophthalmol 1996;6(3):268-72. Mannino G, et al. Ultrasound biomicroscopy in the clinical evaluation of ab-externo holmium: YAG laser sclerostomies. Ophthalmic Surg Lasers 1998;29(2):157-61. Melamed S, Neumann D. Internal sclerostomy with laser: A new approach to glaucoma surgery. Lasers Surg Med 1991;11(5):440-44. Onda E, Ando H, Jikihara S, et al. Holmium YAG laser sclerostomy ab-externo for refractory glaucoma. Int Ophthalmol 1996-97;20(6):309-14. Spiegel D, Wetzel W, Birngruber R. Ab-externo erbium YAG laser sclerostomy versus conventional trabeculectomy. Treatment of glaucoma patients. Ophthalmologe 1998;95(8):537-41. Wang Y, Cohen RE, Schuman JS. Iontophoresis of indocyanine green and monastral blue B for gonioscopic diode laser sclerectomy. Ophthalmic Surg Lasers 1996; 27(6):484-87.

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NEODYMIUM YAG LASER IRIDOLENTICULAR SYNECHIOLYSIS Presence of a bound down pupil in patients of granulomatous uveitis is a well known phenomenon. This can lead to an obstruction to aqueous and secondary glaucoma. A sizeable percentage, especially from the poorer socioeconomic strata where medical attention is neither sought nor easily available tends to have the bound down pupil or ring synechiae with the pupil bound down in the miosed position. Most of these cases also have a complicated cataract in the posterior subcapsular area resulting in a profound visual loss. Many authors have reported using the argon laser photomydriasis in such cases but Nd:YAG laser has seldom been used for sectioning of iridolenticular adhesions are very few (Fig. 6.1).

Fig. 6.1: Bound down pupil with iridolenticular adhesions

Miscellaneous Laser Applications

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Pre-laser Workup All patients are initially given a trial of pupillary dilatation by 2 percent homatropine and 10 percent phenylephrine eye drops (rule out hypertension) after which additional dilatation is tried by tropicamide 1 percent eye drops. One percent Atropine eye ointment is used in twice daily dosage on a long-term basis in these patients. Informed consent must be obtained. Technique of Laser Therapy They are seated on a Q-switched Nd:YAG laser machine and an Abraham type of iridotomy lens is used. The synechiae are cut by 1mJ of power by focusing the laser towards the iris rather than the lens surface starting in the inferior quadrant so that the debris and hemorrhage are not dispersed in the anterior chamber, impeding further laser. If excess debris and hemorrhage are dispersed in the anterior chamber then the next sitting is tried after 30 minutes and if again visualization is inadequate then the procedure is carried out after 48 hours. Postoperatively IOP is recorded hourly for 4 hours, then at 12 hours and thereafter daily till 7 days. It is also recorded subsequently whenever patient visits the outpatient department. Dilatation is tried by putting 2 percent homatropine and 10 percent phenylephrine drops starting immediately after laser at every 5 minutes for 30 minutes (Fig. 6.2). Patients are continued on antiglaucoma medications of 0.25 percent timolol maleate BD along with 1 percent tropicamide eye drops four times daily for 2 weeks. Postoperatively pupillary diameter, change in visual acuity along with any lenticular damage is recorded.

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Fig. 6.2: Dilatation of pupil after YAG laser synechiolysis

Clinical Results A study was conducted at Dr RP Centre for Ophthalmic Sciences, New Delhi (unpublished data) to evaluate the above technique. Fifteen patients of chronic granulomatous uveitis with bound down pupil or presence of ring synechiae where dilatation was not possible by pharmacological means were chosen for the study. Shallow anterior chamber, hazy cornea, active anterior uveitis and secondary glaucoma formed the contraindications to such a laser therapy. Each patient also has an associated complicated cataract in the posterior subcapsular zone with pigment dispersal on lens and cornea contributing to the visual loss. Each patient had a full work up and was under constant medical supervision at our uvea clinic. Every patient was given a choice of surgery or laser but all the

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first 15 cases opted for an initial laser procedure after having been explained the possible complications and risks involved with such a procedure. The mean age of 15 patients was 31.80 ± 9.52 years. The mean pre-laser IOP was 22.61 mm Hg while the average post-laser IOP was 17.33 ± 3.59 mm Hg at 4 weeks followup. The average pre-laser pupillary size was 3.6 ± 1.0 mm while the average post-laser pupillary size was 5.06 ± 1.50 mm (p<0.001). An average of 45.93 ± 14.31 shots were used. More than 2 line increase in visual acuity occurred in 6 eyes (40%), while no eye had a loss of best corrected acuity. The complications included hemorrhage (15/15), mild hyphema (7/15) and mild to moderate uveitis in all 15 patients. IOP spikes were less than 25 mmHg in all patients treated. Iridolenticular adhesions with totally pharmacologically non-dilating pupil are not an uncommon entity in ophthalmic practice. It may result in iris bombe formation with peripheral anterior synechiae, and is commonly associated with cataract. It may interfere with vision, fundus visualization and evaluation for glaucoma becomes difficult. In all such cases, sectioning of adhesions should provide relief. Laser surgery being an outpatient procedure is obviously preferable. Our main purpose for trying synechiolysis in these cases was trying for visual improvement by increasing the pupillary diameter which could bypass the obstruction posterior subcapsular cataractous changes. The obvious additional advantage is that a number of these cases in time would go in for cataract surgery and performing an anterior capsulotomy is much easier along with aspiration of cortex without having to mechanically dilate the iris which could result in unwanted excess pigment dispersal and fibrinoid reaction postoperatively.

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The results clearly reveal that this procedure is no panacea as only 6 out of 15 cases achieved any gain in visual acuity along with dilatation of pupil. However, as most of these patients have chronic inflammation and cataract, surgery is also fraught with complications and any gain of visual acuity which can postpone surgery is very welcome to the patient. All cases had an associated micro hemorrhage along with pigment dispersal in anterior chamber. However, it was usually self limiting and one had to only apply some pressure with the contact lens to abolish the hemorrhage. Though hemorrhage and pigment may cause short-term deterioration of visualization, in none of our patients did it result in a long-term deterioration of vision. The elevation of intraocular pressure was definitely present but was easily controlled on single anti-glaucoma medication. Thus overall no case showed any significant complication or any obvious lenticular damage on biomicrosocpy. Considering the advantages and relative safety, we recommend this procedure for routine use but by an experienced laser microsurgeon. Long-term results of visual benefit by this procedure must be reviewed in terms of further complications related to primary disease which can lead to enhancement of cataract, uveitis, retinal and optic nerve damage. Modified Technique for Nd: YAG Laser Iridolenticular Synechiolysis This technique differs from the above-mentioned technique of synechiolysis in the fact that instead of direct photodisruption, it utilizes the shock waves generated in aqueous to release the synechia. The aiming beam is focused at the center of the broad base synechia towards the side of iris. This is followed by slight anterior defocusing

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of the aiming beam. A power of 1-2 millijoules is used. Shock waves were generated in the aqueous and immediate lysis of the whole of the synechiae is observed, with mild pigment dispersion. Post-laser treatment regimen includes topical 1 percent prednisolone acetate eye drops four time daily, 0.5 percent timolol maleate eye drops twice daily for four days and 1 percent tropicamide eye drop four times daily for one week. In an initial technique (Nd:YAG iridolenticular synechiolysis) direct cutting of the synechiae with Nd:YAG laser, and the beam is directed at the synechia just at the junction of iris and lens was used. Though with Nd:YAG iridolenticular synechiolysis we did not observe any lens damage or clinically significant flare up of the inflammation but the theoretical possibility of lens damage does exist. Few cases where bleeding occurred, it was transient and could controlled easily and had no untoward effects. The new modified technique differs from the previous one in the fact that instead of direct photodisruption it utilizes the shock wave generated in aqueous to release the synechia. Thus this technique actually combines the virtues of YAG sweeping with lysis, therefore making lysis easier at points where a broad based synechiae are available. As the laser was aimed onto the iris at the center of the synechiae, possibility of lens damage is almost eliminated. Additionally, slight anterior defocusing of the aiming beam helps to eliminate the risk of iris damage. However, with misalignment and malfocusing of the laser, it may hit the crystalline lens. Accidental hitting of the lens with low-power Nd:YAG may not have an untoward effect, however, theoretically it may lead to lens damage and focal opacification of lens. This procedure also carries the theoretical risk of bleeding in presence of new vessels in the synechiae.

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Thus, this method appears to be a relatively safe technique for iridolenticular synechiolysis. Larger studies with longer follow-up are required to establish the complete safety and efficacy of this technique. LASER SUTUROLYSIS During trabeculectomy nylon sutures are applied to secure the scleral flap and to regulate the aqueous flow through the bleb. To avoid immediate postoperative hypotony and its complication especially in eyes with advanced glaucoma, tight sutures are preferred. However, if the intraocular pressure (IOP) is too high and anterior chamber is deep, laser suturolysis may be required. Lens: The Hoskins lens is used for this purpose. However, in case this special lens is not available, then one can use the edge of a regular gonioscope or a four mirror gonioscope to press on the conjunctiva overlying the suture and thus helping in visualization. Laser: Argon laser or frequency doubled Nd:YAG laser (532 nm) are the commonly used lasers. Laser parameters: Spot size — 50 microns, power — 250 to 750 mW, duration — 0.1 second. Technique Patient is seated on the slit-lamp. Conjunctival sac is anesthetized with 0.5 percent proparacaine / 4 percent xylocaine. In case the conjunctiva is hyperemic and congested, it is a good option to decongest the same using the phenylepherine eye drops (10%), instilled two to three times at 10 minutes interval. Hoskins lens is applied over the bleb area. It helps to visualize the underlying suture and also protects the conjunctiva from thermal injury. Laser

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spot is applied over the visible suture arm. If there is accompanying subconjunctival hemorrhage or pigmentation, krypton red laser (600 nm) may be used in order to avoid damage to the conjunctiva as melanin, hemoglobin and nylon suture have absorption spectrum near 532 nm. Following suturolysis mild bleb massage is given and immediate lowering of IOP with mild shallowing of anterior chamber and bleb formation is noted. Suturolysis is generally performed within 2 weeks of surgery but can be performed up to 4 weeks, if adjunctive anti-fibrotic agents have been used. This technique is not effective at a later stage when the fibrosis has already set in. LASER-ASSISTED BLEB REMODELING Large overhanging bleb is a well documented complication of trabeculectomy, especially if Mitomycin C has been used. It can be associated with complications like over-filtration, hypotony and extremely large blebs can result in foreign body sensation, discomfort, decreases in visual acuity due to astigmatism, and dellen formation. These blebs are also predisposed to late onset leaks, blebitis, and endophthalmitis. Various therapeutic modalities like surgical repair, injection of autologous blood, cryotherapy, have been employed for treating this problem. The presumed mechanism through which the laser treatment works is based on the fact laser generates thermal energy which results in tissue protein denaturation. This causes shrinkage of the collagen tissue, and as the laser beam selectively affects the inner surface of the bleb leading to inflammation and fibrosis without damaging the overlying conjunctiva, this results in remodeling or shrinkage of the bleb.

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Laser: Argon laser, frequency doubled Nd:YAG laser. Laser parameters: 300-500 mW power, 500 microns size and 0.1 seconds duration. Technique The eye is anesthetized with one drop of 0.5 percent proparacaine, and the patient is seated in front of the slitlamp mounted with laser. Heat absorption by epithelial surface can be promoted by application of a dye. The bleb surface is painted with gentian violet using sterile cotton tipped applicator. Another option is to use vital dyes like rose bengal and methylene blue dye, which require light epithelial abrasion. 25-50 spots are applied on the surface of bleb in the area of maximum height. An immediate shrinkage in the elevation of bleb is noticed. At follow-up apart from IOP monitoring, the bleb area is examined for any evident leak. Repeat treatments may be performed if required. Complications include bleb failure due to over treatment and iatrogenic perforation leading to wound leak. Bleb leaks due to laser induced perforation occur with over treatment, especially with thin and transparent blebs. Nd:YAG GONIOPUNCTURE Goniopuncture of the trabeculo-Descemet’s membrane complex is performed in cases with operated nonpenetrating deep sclerectomy (NPDS), where postoperative bleb functioning is inefficient and the IOP remains high. The laser treatment is performed with Q-switched Nd:YAG laser to puncture the Descemet’s membrane and convert the NPDS into a penetrating procedure. This significantly enhances the success of NPDS.

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Lens: Lasag 15 gonioscopy contact lens (CGA1). Laser settings: Energy 2 to 4 mJ. Studies have shown that goniopunctures decreases the mean IOP with an immediate success rate of 70-85 percent. Apart from the eyes with operated NPDS with insufficient IOP control. Nd:YAG goniopuncture may also be performed as primary procedure along with deep sclerectomy in eyes with Sturge-Weber syndrome. This is a two staged technique described by Hara et al. In Stage 1, under conjunctival and thin scleral flaps, the deep (4 × 2 mm) scleral block containing the outer wall of Schlemm’s canal is removed. Stage 2, the puncturing of the remaining trabeculum with Q-switched Nd:YAG laser, is performed the next day. This helps to avoid hemorrhagic choroidal detachment which frequently occur in these eyes following a penetrating filtering surgery. Complications Iris synechia is a potential complication that may cause elevated IOP after laser goniopuncture in patients having NPDS. Occasionally a spontaneous iris prolapse may also occur leading to IOP elevation. ERBIUM-YAG LASER-ASSISTED DEEP SCLERECTOMY Lasers have been increasingly used for scleral ablation during NPDS. Laser decreases the mechanical or thermal damage resulting in decreased scarring. Both excimer laser and Erbium:YAG laser have been used for this purpose. Theoretically speaking Erbium:YAG laser (2940 nm/11 mJ, 7 Hz) provides extra safety by eliminating the possibility of ultraviolet light related cyto-toxicity and retinal toxicity.

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Laser parameters: Energy of 40-100 mJ, Frequency of 1-10 Hz, spot size 500 microm and 1 mm (divergent beam). Technique After creating a superficial scleral flap (4.0 × 4.0 mm); a deep scleral ablation (3.0 × 3.0 mm) is performed with the pulsed Er:YAG laser to remove 220±40 microns thick deep scleral tissue. Schlemm’s canal is removed, and the cornea is dissected to Descemet’s membrane until aqueous humor percolates. This is followed by a water tight closure of scleral flap and conjunctiva. Study by Verges C et al showed a decrease in mean IOP from 28.3± 6.1 mmHg preoperatively to 16.3±4.2 mm Hg at 3 months, and 15.3±2.7 mm Hg at 15 months post-operatively. There were no significant complications. The success rate (IOP < or =18 mm Hg without medication) was 93.47 percent at 1 month and 84.78 percent at 15 months. Deep sclerectomy using the Er:YAG laser may be considered as a safe and effective in eyes with POAG, with significantly lower complications compared to trabeculectomy. Studies with a larger sample size and longer follow-up are needed to establish its efficacy. ANTERIOR HYALOIDOTOMY In eyes with aphakic and pseudophakic malignant glaucoma, Nd:YAG laser rupture of the anterior hyaloid phase directly, brings a dramatic cure due to release of the trapped aqueous. This procedure results in immediate deepening of the anterior chamber and relieves acute pain and provides sudden symptomatic relief to the patient. This procedure requires careful handling and should be done by experience laser surgeons only. The trick is to go deep and try and break the vitreous phase from behind

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forward using 1-2mj of energy since chamber is very shallow therefore, chances of corneal damage are very high. However, even if the endothelium gets damaged at one place, we should try it at other place since this is much more convenient then going in for a vitrectomy which is a more difficult affair. LYSIS OF VITREOUS STRAND IN THE CATARACT WOUND It is well known that any strand of vitreous incarcerated in the wound can result in complications. The strand forms a route from where infection can travel into the eye. Also when a person goes from bright light to dim light the pupil size changes and this causes a pull on the strand. This can result in a retinal detachment. Lysis of such a strand can easily be carried out using the energy of 1-1.5 mJ of Nd:YAG spot focused directly on the strand to lyse it (Fig. 6.3).

Fig. 6.3: Vitreous strand going to the wound site which can be cut with YAG laser

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BIBLIOGRAPHY Neodymium YAG Laser Iridolenticular Synechiolysis 1. 2. 3. 4. 5.

Fankhauser F, Kwasniewska S, et al. Neodymium Q-Switched YAG laser lysis of irisens synechiae. Ophthalmology 1985;92:790-92. James WA Jr, Roeth Jr, et al. Argon Laser Photomydriasis. Am J Ophthalmol 1976;81:6270. Kumar H, Sony P. A new technique for Nd:YAG iridolenticular synechiolysis (In press) Ophthalmic Surgery Lasers and imaging. L’Esperance FA Jr, James WA Jr. Argon Laser Photocoagulation of iris abnormalities. Trans Am Acad Ophthalmol Otolaryngol 1975;79:321-39. Obstbaum SA, Barasch KR, Galin MA, et al. Laser Photomydriasis in pseudophakic pupillary block. Am Intraocul Implant Soc J 1981;7:28-30.

Laser Suturolysis 1.

2. 3. 4. 5.

Akova YA, Dursun D, Aydin P, Akbatur H, Duman S. Management of hypotony maculopathy and a large filtering bleb after trabeculectomy with mitomycin C: Success with argon laser therapy. Ophthalmic Surg Lasers 2000;31:491-94. Day S, Uveal Tract, Taylor D (Eds): Paediatric Ophthalmology, Boston, Blackwell Scientific Publications. 1990; 276-98. Hara T, Hara T. Deep sclerectomy with Nd:YAG laser trabeculotomy ab-interno: Two-stage procedure. Ophthalmic Surg 1988;19:101-06. Liebmann MF. Doide laser suturolysis following trabeculectomy with mitomycin C. Arch Ophthalmol 1996;114:364. Liu Y, Yang W, Li S. Neodymium: YAG laser therapy in aphakic pupillary block glaucoma and aphakic malignant

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6. 7.

8.

9. 10.

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(ciliovitreal block) glaucoma. Yan Ke Xue Bao 1990;6(1-2): 11-6. Melamed S, Ashkenazi I, Glovinski J, Blumenthal M. Tight scleral flap trabeculectomy with postoperative laser suture lysis. Am J Ophthalmol 1990 15;109:303-09. Mermoud A, Karlen ME, Schnyder CC, Sickenberg M, Chiou AG, Hediguer SE, Sanchez E. Nd:Yag goniopuncture after deep sclerectomy with collagen implant. Ophthalmic Surg Lasers 1999;30:120-25. Pallikaris IG, Kozobolis VP, Christodoulakis EV. Erbium: YAG laser deep sclerectomy: An alternative approach to glaucoma surgery. Ophthalmic Surg Lasers Imaging 2003;34:375-80. Sony P, Kumar H, Pushker N. Treatment of overhanging bleb with frequency doubled Nd:YAG laser. Ophthalmic Surg Lasers Imaging. 2004;35:430-32. Verges C, Llevat E, Bardavio J. Laser-assisted deep sclerectomy. J Cataract Refract Surg 2002;28:758-65.

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INTRODUCTION Open-angle glaucoma is the second leading cause of blindness in the world.1,2 Glaucomatous optic neuropathy (GON) is characterized by a loss of retinal ganglion cells and their axons, associated by a tissue remodeling both of the optic nerve head (ONH) and the retina leading to the characteristic ONH cupping. Many glaucoma patients present with elevated intraocular pressure (IOP), most often caused by reduced outflow capacity of aqueous humor. The outflow resistance is localized at the level of the trabecular meshwork, or, more precisely, at the juxtacanalicular meshwork and the inner wall of Schlemm’s canal. Data from several major studies available on this topic, such as the OHTS,3 EGPS,4 CIGTS,5 EMGT6 and the AGIS7 suggest that both development and progression of glaucomatous damage can be mitigated by lowering IOP. Moreover, the NTGS has clearly demonstrated that lowering of the IOP can slow down the progression of the disease even in patients with normal-tension glaucoma (NTG).8 Topical IOP-lowering medication is often the first-line therapy for glaucoma, even though it harbors potential disadvantages such as local and systemic side effects, tachyphylaxis, and, probably most important, compliance problems. Friedman and co-workers recently examined a cohort of 1712 glaucoma suspects and 3623 diagnosed glaucoma patients and found that a large proportion of individuals requiring treatment are falling out of care and are being monitored at rates lower than expected from recommendations of published guidelines because they do not come for follow-up visits and do not ask for a refill of their prescribed glaucoma medication.9 Apart from this disappointing information, it has to be added that local

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medication is also not always sufficient if a very low individual target IOP is required. The CNTGS has shown that a 30 percent reduction in IOP is often only reached by surgical intervention. Another point is that the costs of medical control over a lifetime might also be prohibitive for some glaucoma patients. Glaucoma surgery includes nowadays a number of potential therapies all aiming either to increase the outflow of aqueous humor or to decrease its production. Argon laser trabeculoplasty (ALT), for example, increases the conventional outflow through the trabecular meshwork and is easy to perform. The procedure has, however, a limited efficacy and duration of effect, as ALT produces thermal effects with coagulation of the trabecular meshwork. A successfully performed trabeculectomy shows a much better efficacy, however, a number of potential complications such as hypotony, suprachoroidal hemorrhage, and bleb failure exist. Patients often find the conjunctival bleb uncomfortable, moreover it can become thin and avascular, thus increasing the risk of bleb leaks, blebitis and endophthalmitis. In case of surgery failure, repeated operations can become necessary, however, the chances for success decrease as both sclera and conjunctiva are subjected to repeated surgical insults. Glaucoma drainage devices (tube shunts) have a relatively high success rate in experienced hands, however the patients are at greater risk for complications. In 1996, Vogel and co-workers reported a new IOPlowering operation technique: Using an excimer laser, they managed to ablate trabecular meshwork tissue with minimal thermal effects and necrosis, thus resulting in only minimal scar formation. The authors assumed that it should be possible to create an open connection between the anterior chamber and Schlemm’s canal. The group treated

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6 patients with open-angle glaucoma. In 4 cases intraocular pressure was reduced by 11 mmHg over a follow-up time of 5 months. In 2 cases IOP rose by 2 mmHg in spite of medication.10 ERBIUM-YAG GONIOTOMY Also in 1996, an endoscopic erbium-YAG laser system allowing effects on trabecular tissue comparable to those produced by a 308 nm excimer laser became available. In the following years we could demonstrate a reduction in IOP with this laser system that was comparable to the excimer laser.11 We performed combined cataract surgery and erbium-YAG goniotomy in 24 eyes and compared the IOP results to a control group that underwent cataract surgery. In the combined surgery group, mean IOP dropped from 21.8 to 15.5 mmHg. IOP regulation was successful in 88 percent of these cases. In eyes that underwent only cataract surgery, the IOP reduction was less pronounced (mean IOP preoperative 20.0, postoperative 17.4, success rate 35%). The follow-up in this preliminary study was 4 months (mean 6.5 months, max. 12 months).12 In another non-randominized clinical trial with a 3 years follow-up, we treated 20 eyes of 20 patients suffering from both glaucoma and cataract with combined phacoemulsification and erbium-YAG goniotomy and compared them to a control group that underwent cataract surgery. Main outcome variables were IOP, visual acuity, and number of antiglaucomatous drugs 1 year after surgery. The mean IOP dropped by 30 percent (23.5 to 16.3 mmHg) after 12 months in the laser-treated group and by 9 percent (19.8 to 18.1 mmHg) in the control group. After 3 years, the mean IOP in the laser group was 15.0 mmHg. The mean

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number of antiglaucomatous drugs needed decreased significantly from 1.6 to 0.5 in the laser group and from 1.0 to 0.8 in the control group. Anterior chamber hemorrhage occurred in 12 eyes after laser treatment and resolved within 72 hours in all but 1 patient who was on warfarin sodium therapy. There were no cases of hypotony in either group.13 We also aimed to compare the efficacy of erbium:YAG goniotomy to trabeculectomy, with both methods as adjuncts to cataract surgery. Fifty-nine eyes of 59 glaucoma patients with coexistent cataract underwent combined phacoemulsification and erbium:YAG goniotomy. We compared this prospective treatment arm to a retrospective inclusion-matched control group treated by trabeculectomy and cataract surgery in a single procedure. Primary endpoints were IOP, number of antiglaucomatous drugs, postoperative complications, hospitalization time and visual acuity 1 year after surgery. In the laser-treated group, the mean IOP dropped by 30 percent from 23.4 to 16.3 mmHg after 12 months. Without reoperation, treatment was successful in 71 percent of these eyes. In the control group, the IOP decreased by 33.5 percent from 22.7 to 15.1 mmHg. The success rate without reoperation was 46 percent. The number of antiglaucomatous drugs needed decreased from 1.48 to 0.48 in the laser-treated group and from 2.0 to 0.39 in the controls. Postoperative complications were more frequent in the control group, and postoperative visual acuity was as well. Hospitalization time was shorter in the laser group. It can be concluded from these data that the IOP-lowering effect of combined erbium:YAG goniotomy and cataract surgery is comparable to that of combined trabeculectomy and cataract surgery. Moreover, due to fewer postoperative complications, erbium:YAG goniotomy seems to be superior to standard fistulation

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surgery as the primary approach.14 To date, 3 years followup data of a small pilot group that underwent combined erbium:YAG goniotomy and cataract surgery are available; and the IOP-lowering effect has not diminished over this follow-up period.15 EXCIMER-LASER-TRABECULOTOMY (ELT) Background In the meantime, the CE-certified AIDA excimer laser (TuiLaser AG, Germering, Germany) has become commercially available (Fig. 7.1). We therefore switched from the erbium:YAG system prototype to the certified laser, assuming that it should have a comparable effect. Like the erbium:YAG laser, the AIDA excimer laser reestablishes the outflow of aqueous humor through conventional drainage pathways. By excising a defined

Fig. 7.1: The AIDA excimer laser (TuiLaser AG, Germering, Germany)

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area of trabecular meshwork, juxtacanalicular tissue, and the inner wall of Schlemm’s canal via a fiberoptic probe delivering 308 nm XeCL excimer laser energy, aqueous outflow is re-established.16 The creation of the openings through the trabecular meshwork and the inner wall of Schlemm’s canal is accomplished by using the fiberoptic delivery system LAGO 200 or LAGO 200 ENDO. In detail, the fiberoptic system is positioned across the anterior chamber to contact the trabecular meshwork. Laser pulses remove tissue to create a fistula into Schlemm’s canal. Direct viewing for positioning of the fiber is performed with either a goniolens or an endoscope. The small size of the delivery system (external diameter 0.5 mm for the LAGO 200, 1.3 × 0.95 mm for the LAGO 200 ENDO, coaxial endoscope) ensures access through a self sealing clear cornea incision (Figs 7.2 and 7.3). Twenty laser pulses are adequate to create a permanent opening into Schlemm’s canal. Once the corneal incision is prepared, the actual

Fig. 7.2: Photomontage of the fiberoptic system contacting the opposite trabecular meshwork

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Fig. 7.3: Operative setting: The ELT probe has been inserted via a clear cornea incision and approaches the opposite trabecular meshwork

procedure requires about three minutes. The procedure can easily be combined with cataract surgery. The wavelength of the AIDA laser - 308 nm has been found to ablate the trabecular meshwork without inducing thermal damage, thereby minimizing fibrous tissue healing reactions17-19 (Fig. 7.4). Surgical Procedure ELT can easily be performed through a clear cornea tunnel incision as used for cataract surgery. We constrict the pupil with topical pilocarpine 2 percent or intracameral injection of acetyline chloride (i.e. Miochol ® ), then inject a viscoelastic gel (i.e. Healon) into the anterior chamber and insert the laser probe. We then advance the probe to the

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Fig. 7.4: Histology demonstrated that the wavelength of the AIDA laser ablates the trabecular meshwork without inducing thermal damage, thereby minimizing fibrous tissue healing reactions

opposing chamber angle under gonioscopic or endoscopic visualization. The application of the laser pulses can be controlled when the probe tip is in contact with the trabecular meshwork (Figs 7.5 and 7.6). The probe tip is then repositioned such that ten trabecular meshwork perforations are created to the inferior 180°. Following removal of the probe (and endoscope), the viscoelastic is exchanged by BSS. Postoperatively, all eyes are treated with topical steroids 4x/d tapered over 3 weeks. In case of a persistent fibrin reaction, atropine 1 percent eye drops 2x/d can be added. In case of combined cataract + ELT procedure, we first perform cataract surgery followed by the ELT procedure, which takes about three minutes longer than cataract surgery alone.

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Fig. 7.5: ELT: Endoscopic view showing the fiberoptic delivery approaching the trabecular meshwork

Fig. 7.6: ELT: Two trabeculotomies are already created. Note: The retrograde bleeding from Schlemm’s canal which we take as a sign of successful perforation

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Study Results Pooled data from a number of study groups have demonstrated that ELT is a safe and sufficient IOP-lowering procedure that can easily be combined with cataract surgery.20 In our own clinic, we have retrospectively studied a group of 135 patients with open-angle glaucoma (n = 128) and ocular hypertension (n = 7) that were divided into two groups: (a) ELT as a stand-alone procedure (n=75), (b) combined cataract and ELT procedure (n= 60). Both groups were further divided into 2 subgroups: (1) Preoperative IOP > 22 mmHg, (2) Preoperative IOP • 22 mmHg. KaplanMeier survival curves were calculated. Success criterion was 20 percent decrease of IOP in combinaton with IOP • 21 mmHg and postoperative IOP-lowering medication • preoperative IOP-lowering medication. Follow-up time was 1 year. For group a) ELT, 1. Preoperative IOP > 22 mmHg, 2. Preoperative IOP • 22 mmHg: Kaplan-Meier survival curves showed a success rate of 57 percent in subgroup 1 and of 41 percent in subgroup 2 (Figs 7.7 and 7.8) For group b) Combined cataract and ELT procedure, 1. Preoperative IOP > 22 mmHg, 2. Preoperative IOP • 22 mmHg: Success rate was 91 percent in subgroup 1 and 52 percent in subgroup 2 (Figs 7.9 and 7.10). Side effects of the ELT were rare: In two cases, an iris adhesion at the tunnel occurred, in 3 cases there was a fibroid reaction that responded very well to topical steroids. One patient developed an occlusion of the central retinal vein 5 months after surgery. IOP however was wellcontrolled at that time, indicating that there was no connection between the CRVO and the ELT procedure. Our data indicate that ELT is not only a safe and efficient IOP-lowering procedure, but also that it is most effective

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Fig. 7.7: ELT: Kaplan-Meier-survival curve, preoperative IOP > 22 mmHg

Fig. 7.8: ELT: Kaplan-Meier-survival curve, preoperative IOP • 22 mmHg

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Fig. 7.9: ELT+Phako: Kaplan-Meier-survival curve, preoperative > 22 mmHg

Fig. 7.10: ELT+Phako: Kaplan-Meier-survival curve, preoperative • 22 mmHg

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in patients with a high preoperative IOP. The 2-year-followup data are now available for many patients, and it seems obvious that the IOP-lowering effect of ELT is conserved also after this longer period of time. We have a prospective multicenter study ongoing in this field and are looking forward to its result. Due to its sufficient IOP-lowering effect and the minimal invasiveness of the procedure, ELT has become the therapy of choice for patients who suffer from cataract and glaucoma. We recommend the combined procedure in all cataract patients with an IOP of more than 22 mmHg without therapy. ELT as a stand-alone procedure is performed in patients whose IOP is above 22 mmHg despite maximally tolerated therapy. In patients with low preoperative IOP, such as patients with normal-tension glaucoma, ELT has proven to be less powerful. We assume that in such cases, the episcleral venous pressure limits the chances of success and prefer a trabeculectomy instead. CONCLUSION Excimer-Laser-Trabeculotomy is a promising IOPlowering technique both as a stand-alone procedure and in combination with cataract surgery. It is especially suitable for patients with high preoperative IOP levels and can easily be combined with cataract surgery. REFERENCES 1.

2.

Quigley HA. Proportion of those with open-angle glaucoma who become blind. Number of people with glaucoma worldwide. Ophthalmology 1999;106(11):203941. Quigley HA. Number of people with glaucoma worldwide. Br J Ophthalmol 1996;80(5):389-93.

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3.

4. 5. 6.

7.

8.

9.

10. 11. 12.

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Kass MA, Heuer DK, Higginbotham EJ, Johnson CA, Keltner JL, Miller JP, et al. The Ocular Hypertension Treatment Study: A randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open-angle glaucoma. Arch Ophthalmol 2002;120(6):701-13; discussion 829-30. Miglior S, Zeyen T, Pfeiffer N, Cunha-Vaz J, Torri V, Adamsons I. Results of the European Glaucoma Prevention Study. Ophthalmology 2005;112(3):366-75. Feiner L, Piltz-Seymour JR. Collaborative Initial Glaucoma Treatment Study: A summary of results to date. Curr Opin Ophthalmol 2003;14(2):106-11. Heijl A, Leske MC, Bengtsson B, Hyman L, Hussein M. Reduction of intraocular pressure and glaucoma progression: Results from the Early Manifest Glaucoma Trial. Arch Ophthalmol 2002;120(10):1268-79. The Advanced Glaucoma Intervention Study (AGIS): 7. The relationship between control of intraocular pressure and visual field deterioration.The AGIS Investigators. Am J Ophthalmol 2000;130(4):429-40. Comparison of glaucomatous progression between untreated patients with normal-tension glaucoma and patients with therapeutically reduced intraocular pressures. Collaborative Normal-Tension Glaucoma Study Group. Am J Ophthalmol 1998;126(4):487-97. Friedman DS, Nordstrom B, Mozaffari E, Quigley HA. Glaucoma Management among Individuals Enrolled in a Single Comprehensive Insurance Plan. Ophthalmology 2005. Vogel M, Lauritzen K, Quentin CD. Punktuelle Ablation des Trabekelwerks mit dem Excimer-Laser beim primären Offenwinkelglaukom. Ophthalmologe 1996;93(5):565-68. Funk J, Schlunck G. Endoskopisch kontrollierte ErbiumYAG-Laser-Goniotomie. Erste präklinische Versuche. Ophthalmologe 1998;95(1):33-36. Funk J, Feltgen N, Asbeck D. Augendrucksenkung durch endoskopisch kontrollierte Erbium: YAG-Goniotomie. Ophthalmologe 2000;97(7):473-77.

112 13. 14.

15.

16.

17. 18. 19. 20.

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Feltgen N, Mueller H, Ott B, Frenz M, Funk J. Combined endoscopic erbium:YAG laser goniopuncture and cataract surgery. J Cataract Refract Surg 2003;29(11):2155-62. Feltgen N, Mueller H, Ott B, Frenz M, Funk J. Endoscopically controlled erbium:YAG goniopuncture versus trabeculectomy: Effect on intraocular pressure in combination with cataract surgery. Graefes Arch Clin Exp Ophthalmol 2003;241(2):94-100. Philippin H, Wilmsmeyer S, Feltgen N, Ness T, Funk J. Combined cataract and glaucoma surgery: Endoscopecontrolled erbium:YAG-laser goniotomy versus trabeculectomy. Graefes Arch Clin Exp Ophthalmol 2005. Walker R, Specht H. Theoretical and physical aspects of excimer laser trabeculotomy (ELT) ab-interno with the AIDA laser operating at 308 nm. Biomedizinische Technik 2002;47(5):106-10. Berlin MS. Perspectives on new laser techniques in managing glaucoma. Ophthalmology Clinics of North America 1995;8(2):341-63. Berlin MS. We need a trabecular meshwork procedure that works. American Glaucoma Society Annual Meeting, San Jose 2002. Berlin MS. ELT Eximer Laser Trabeculostomy: Update 2003. ASCRS 2003. Berlin MS, Funk J, Pache M, Wilmsmeyer S, Giers U, Kleineberg L, et al. Excimer Laser Trabeculostomy. A new, minimally invasive surgical procedure for the treatment of open-angle glaucoma. Glaucoma Today 2004;2-6.

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INTRODUCTION The ongoing devote on recent developments in glaucoma surgery reflects that an ideal solution is not available which would promise long-term IOP reduction and eliminate the necessity of supplementary pressurereducing medication at low complication rates. Trabeculectomy, first described in the sixties, 3,9,30 is probably the most widespread approach in glaucoma surgery presently. The intention of trabeculectomy is to bypass the resistance of trabecular meshwork by channelling aqueous humor directly to the Schlemm’s canal. In literature the success rate of trabeculectomy ranges between 32-96 percent.1,4,9,12,14,16-18,21-23,30,32-35 On the other hand, postoperative complications like hypotony and choroidal detachment are reported up to 24 percent.6 Variation of success rates may be explained by different criteria of surgical indications, selection of cases, various diagnoses, the various degrees of surgical experience and variations in postoperative medical treatment. Failure of pressure regulations is associated with the assence of a filtering bleb and depends on the duration of follow-up involved. It has become evident that successful reduction in IOP following trabeculectomy is clearly related to the presence of a filtering bleb.26 The more recent method of non-penetrating deep sclerectomy, was first described by Fjodorov in the eighties.8 This techniques tries to achieves an improved uveoscleral outflow and therefore is not depending on the presence of a filtering bleb. Koslov13 expanded this method by introducing a collagen implant. Literature on nonpenetrating deep sclerectomy indicates a success rate of 58 to 74 percent without collagen implant and 74 to 90 percent with collagen implantation.5,24

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In 1976, Benedikt2 described that the exposure of the ciliary body (i.e. a form of penetrating sclerectomy) was leading to successful long-term IOP regulation in 27 of 38 cases involving hemorrhagic, aphakic and irreversible angle-closure glaucoma after initially failed filtering surgery. This technique was the basis for later development of perforating deep sclerectomy, a method which has been used since 1985 was described previously 20 as “sclerothalamectomy”). Bypassing of the trabecular meshwork is an alternative for aqueous humour outflow from the anterior chamber to the Schlemm canal. It is the principal mechanism for non-penetrating glaucoma surgery, in particular, for deep sclerectomy and viscocanalostomy. These surgical procedures provide effective IOP reduction as well as the elimination of typical filtration bleb complications.7,15,31 So far clinical application of these procedures has been limited by technical difficulties to perform this kind of surgery and a poor predictability of pressure reduction. The concept of trabecular meshwork bypass as a surgical principle for glaucoma treatment evolved from the discovery that pathologic outflow resistance is caused primarily by the juxtacanicular conjunctive tissue of the trabecular meshwork and, in particular, by the inner wall of the Schlemm canal.10,11 A further publication in this area indicates that 35 percent of the outflow resistance arises distally to the inner wall of the Schlemm canal.25 Spiegel et al29 have described a new surgical technique involving the use of an implanted tube, the so-called trabecular meshwork bypass tube shunt, which should provide a direct connection between Schlemm canal and the anterior chamber. This surgical technique avoids technical difficulties of non-penetrating deep sclerectomy, especially the delicate microperforation of the trabecular

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meshwork in order to ensure the permeability of the descemet membrane. Furthermore, these techniques avoid the disadvantages of filtration blebs. All surgical procedures for glaucoma involving the creation of external access may be complicated by the risk of fibroblast proliferation and failure of filtration. The novel procedure published offers a chance to avoid some of the above-mentioned disadvantages. We refer to this technique as sclerothalamotomy ab interno.19 PATIENTS AND METHODS Before beginning the clinical study phase, the tips used for the STT ab interno procedure were developed using a large number of pigs’ eyes. The high-frequency diathermic technique was already very well known in the application for capsulorhexis in cataract surgery. It was important to create a design for optimal application of the STT probe in the iridocorneal angle and to evaluate the characteristic of the achieved deep sclerotomy. By virtue of this results the STT ab interno probe development as describe below. 53 sclerothalamotomies ab interno in 53 patients were carried out in primary open-angle glaucoma between 1 April 2002 and 31 July 2002. Main inclusion criterion into this study was an insufficient response to medical treatment of IOP. Data was documented according to a prospective study protocol. Mean age of patients was 72.3±12.3 years (range: 15-92 years) (Fig. 8.1). 17 patients (32%) were female, 36 patients (68%) male. In 25 cases (47.4%) the right eye in 28 cases (52.6%) the left eye was treated. There was no patient who received bilateral surgery. Snellen visual acuity was 0.7±0.3 (range 0.1 to 1.0) preoperatively. In 5 cases a moderate cataract was observed which didn’t have influence on the visual acuity.

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Fig. 8.1: Mean age

A complete ophthalmologic status check was carried out in each patient prior to surgery including: uncorrected and best corrected visual acuity, IOP applanation tonometry, biomicroscopy of anterior segment, funduscopy (in particular, stereoscopic evaluation of the optic nerve head) and computerized visual field testing (Octopus 101, program G2). Complete ophthalmologic follow-up examinations were carried out postoperatively at day 1, 2, 3 and 4, after 1, 2 and 4 weeks, and 2, 3, 6, 12, 15, 18, 21, 24, 27, 30, 33 and 36 months. In a pilot study with at least of 24 months follow-up, 5 patients with therapy-resistant juvenile glaucoma were treated.

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HIGH-FREQUENCY DIATHERMIC PROBE The high-frequency diathermic probe consists of an inner platinum electrode which is isolated from the outer coaxial electrode. The platinum probe tip is 1 mm in length, 0.3 mm high and 0.6 mm width and is bent posteriorly at an angle of 15° (Figs 8.2A and B). The external diameter of

Figs 8.2A and B: STT Glaucoma Tip (Oertli Reference VE 201750)

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the probe measures 0.9 mm. Modulated 500 kHz current generates a temperature of approximate 130°C at the tip of the probe. The set-up provides high frequency power dissipation in close vicinity of the tip. As a result, heating of tissue is locally very limited and is applied as a rotationed ellipsoid. SURGICAL PROCEDURE A clear cornea incision (1.2 mm wide) was placed in the temporal upper quadrant using a diamond knife. A second corneal incision was performed 120° apart from the first followed by injection of Healon GV. The high-frequency diathermic probe (Oertli) was inserted through the temporal corneal insertion (Fig. 8.3). Visual inspection of

Fig. 8.3: Insertion of the high-frequency diathermic probe (Oertli) through the temporal corneal insertion

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the target zone (opposite iridocorneal angle) was observed by a 4-mirror gonioscopic lens (Fig. 8.4). The high frequency tip penetrates up to 1mm nasal into the sclera through the trabecular meshwork and Schlemm canal, forming a deep sclerotomy (i.e. “thalami”) of 0.3 mm high and 0.6 mm width (Figs 8.5 and 8.6). This procedure was repeated 4 times within one quadrant. Healon GV was evacuated from the anterior chamber with bimanual irrigation/aspiration (Fig. 8.7). Tobramycin/Dexamethason eye drops were then applied 3x daily for 1 month and Pilocarpin 2 percent eye drops 3x daily for 10 days. EVALUATION OF THE RESULTS Statistical evaluation of results was calculated with SPSS Program Version 10. Two-tailed Student t-test was used

Fig. 8.4: Visual inspection of the target zone (opposite iridocorneal angle) by a 4-mirror gonioscopic lens

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Fig. 8.5: Penetration of the high frequency tip

Fig. 8.6: Penetration up to 1mm nasal into the sclera through the trabecular meshwork and Schlemm canal

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Fig. 8.7: Healon GV was evacuated from the anterior chamber with bimanual irrigation/aspiration

for statistical evaluation of parametric data. The unit of significance was set at a critical p value of <0.05, including Bonferroni correlation for repetitive use of data sets. Results Mean preoperative IOP in the study population of 53 patients with primary open-angle glaucoma was 25.6 ± 2.3 mmHg (range18 to 48 mmHg). Average IOP was 17.6 ± 2.7 mmHg (range 2 to 36 mmHg) after a follow-up period of 1 day, 14.9 ± 2.4 mmHg (range 2 to 30 mmHg) after 2 days, 15.7 ± 2.4 mmHg (range 4 to 28 mmHg) after 3 days, 16.0 ± 2.6 mmHg (range 4 to 36 mmHg) after 4 days, 19.0 ± 2.6 mmHg (range 12 to 39 mmHg) after 7 days, 16.9 ± 2.5 mmHg (range 9 to 44 mmHg) after 1 month, 15.1 ± 1.8

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mmHg (range 11 to 20 mmHg) after 3 months, 14.7 ± 1.7 mmHg (range 11 to 20 mmHg) after 6 months, 14.8 ± 1.7 mmHg (range 10 to 20 mmHg) after 9 months, 14.7 ± 1.7 mmHg (range 10 to 20 mmHg) after 12 months, 15.5 ± 1.7 mmHg (range 11 to 20 mmHg) after 15 months, 14.1 ± 1.6 mmHg (range 11 to 20 mmHg) after 18 months, 16.5 ± 1.7 mmHg (range 12 to 22 mmHg) after 21 months, 15.0 ± 1.6 mmHg (range 11 to 20 mmHg) after 24 months, 14.7 ± 1.7 mmHg (range 11 to 20 mmHg) after 27 months, 14.7 ± 1.7 mmHg (range 10 to 20 mmHg) after 30 months, 15.5 ± 1.7 mmHg (range 11 to 20 mmHg) after 33 months and 14.6 ± 1.7 mmHg (range 10 to 20 mmHg) after 36 months a result which, at p<0.005, is statistically highly significant (Fig. 8.8). Pressure reduction at any time of standardised follow up was statistically significant compared to preoperative data at a level of α<0.03 (Bonferroni corrected). For all patients the follow-up was 36 months.

Fig. 8.8: Average level of intraocular pressure (IOP) after sclerothalamotomy (STT) ab interno surgery for all 53 cases at the time of scheduled examination

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At month 36, 54.7 percent of patients had an IOP<15 mmHg, 77.4 percent had an IOP<18 mmHg and 83 percent had an IOP<21 mmHg (Fig. 8.9). After 36 months, 86.8 percent achieved >20 percent reduction in IOPs and 77 percent of treated patients achieved >30 percent reductions of the IOP. The complete success rate, defined as an IOP lower than 21 mmHg without medication, was 83 percent at 36 month. Qualified success rate, defined as an IOP lower than 21 mmHg with medication, was 100 percent at 36 month (Fig. 8.10). The average preoperative administration of pressurereducing eye agents was 2.6 ± 1.0. Following surgery, this value was decreased to 0.45 ± 0.72 after 1 month, 0.38 ± 0.60 after 3 months 0.38 ± 0.69 after 6 months, 0.19 ± 0.52 after 12 months, 0.21 ± 0.53 after 24 months and 0.50 ± 0.90 after 36 months (Fig. 8.11). After 36 months, it was necessary to administer IOP reducing medication in only 9 eyes, a figure which corresponds to 17 percent of all cases.

Fig. 8.9: Percentages of patients reaching specified intraocular pressure (IOP) levels

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Fig. 8.10: Preoperative and postoperative level of IOP 36 months of follow-up

Average visual acuity after treatment was 0.69 ± 0.31 (range 0.05 to 1.0). In 6 eyes (11.3%) moderate cataract development after surgery which was without influence of visual acuity. Another 3 eyes (5.7%) developed cataract with decreased visual acuity of one Snellen line. There is no significant difference regarding the cup/ disc ratio at baseline with 0.65±0.18 and at 36 months with 0.66±0.19 (p=0.11) (Figs 8.12A and B).

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Fig. 8.11: Administration of pressure-reducing eye agents during 36 months

Fig. 8.12A: Cup/disc ratio at baseline

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Fig. 8.12B: Cup/disc ratio at 36 months

There is no significant changes comparing the visual field at baseline with mean defect MD 9.45±2.32, loss variance LV 30.0±5.11 and at 36 months with MD 9.29±2.59, LV 31.4±5.66 (p=0.78 for MD, p=0.96 for LV) (Fig. 8.13). Temporary IOP elevation higher than 21 mmHg was observed in 12 of 53 eyes (22.6%). These patients responded well to pressure-reducing treatment with one agent and medication could gradually be withdrawn in all of these patients. A single case of hypotension (1.9%) that lasted for 3 days after surgery was observed. Hyphema was present in 6 cases (11.4%) which disappeared within the first 2 weeks after surgery. One eye (1.9%) exhibited transient fibrin formation at pupillary level. Fibrin was cleared within one day after frequent application of topical Dexamethason (Fig. 8.14).

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Fig. 8.13: Visual field analysis

Fig. 8.14: Complications after sclerothalamotomy (STT) ab interno surgery

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In a pilot study 5 patients with therapy-resistant juvenile glaucoma were treated. We observed an IOP reduction from 41 ± 6.4 mmHg prior to surgery to 12 ± 2.6 mmHg after surgery, a result that has remained stable without any additional pressure-reducing therapy for 24 months. DISCUSSION This study reports long-term results of a new surgical technique for treating open angle glaucoma. The STT ab interno method intends the creation of a direct channel between the anterior chamber and the Schlemm canal. Persistence of the sclerotomy can be investigated with a 3mirror Lens (Goldmann 903). The STT ab interno tip creates a deep sclerotomy with subsequent access of aqueous to the scleral layer. Both aspects may facilitate a bypass effect of aqueous outflow. In light of the fact that about 85 percent of the aqueous humour drains (in physiological terms) trans-trabecularly, we suspect an additional route for aqueous humour absorption in the case of elevated IOP. There is evidence in literature that such bypass effects may be present after surgical intervention which do not lead to the formation of filtering blebs. In a previous study,20 it was ascertained that eyes without filter bleb exhibited very stable long-term IOP regulation postoperatively. In addition to the bypassing of trabecular outflow resistance caused by STT ab interno treatment, outflow resistance may be further reduced by scleral thinning at the base of the thalamus. In addition to that aqueous humour could perhaps be absorbed by the ciliary body.20,27 After early postoperative reduction, the average IOP continued to decline gradually over a period of 6 months before reaching a relatively a constant level. It can be speculated that newly

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formed blood vessel and lymph vessel close to the surgical site, may contribute to the decrease of IOP level during follow up.2 In literature the success rate range for trabeculectomy ranges between 57 and 96 percent,1,4,9,12,14-18,21- 23,30,32-35 for deep sclerectomy without collagen device between 57 and 74 percent, and for deep sclerectomy with collagen device between 58 and 90 percent.1,5,15,24 The STT ab interno technique with a complete success rate of 90.6 percent is comparable with other so far published surgery methods. Advantages of the STT ab interno method, compared with trabeculectomy and perforating and non-perforating deep sclerectomy seem to be a rate of postoperative complications and a constant level of reduced IOP. Hypotension, a frequent finding in trabeculectomy, perforating deep sclerectomy and non-perforating deep sclerectomy, is a relatively rare postoperative complication. The most frequent early complications in trabeculectomy are hyphema (24.6%), shallow anterior chamber (23.9%), hypotony (24.3%), wound leak (17.8%) and choroidale detachment (14.1%). The most frequent late complications are cataract (20.2%), visual loss (18.8%), iris incarceration (5.1%) and encapsulated bleb (3.4%). After STT ab interno cataract development was seen in 17 percent with only 5.7 percent loss of one line of visual acuity after 36 months. Compared with other techniques STT ab interno seems to be a relatively save surgical technique.1,5,6,7,15,16 Transient IOP elevation after STT ab interno may occur in the first 6 weeks and can be effectively brought under control with the use of a topical medication. In most cases, IOP-reducing therapy could be gradually withdrawn after 3 weeks post surgery. It was necessary to continue pressure-reducing therapy in 5 of 53 eyes, in all this cases medication was effective in controlling IOP.

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Problems of scarring to the Tenon’s capsule, fibroblast proliferation and secondary occlusion associated with trabeculectomy which are induced by the surgical procedure itself may the reason behind the practice of antimetabolites applications (Mitomycin C at concentration of 0.2-0.4 mg/ml for 1-5 minutes). Although this practice was conceived to modulate wound healing and thus to counteract scar formation, it often resulted in serious complications, such as scleral necrosis and an increased incidence of avascular filter bleb and their late complications.28 The surgical procedure applied in this study avoids stimulation of episcleral and conjunctival proliferations and may therefore be related with less secondary cell invasion at the filtrating bypass. Preliminary histological investigations of post mortem human eyes following STT ab interno did not indicate signs of indirect necrosis in cell layers adjacent to the thalamus formed by high-frequency diathermy. It is yet unknown, if the inner surface of the thalamus will be covered by endothelial cells of corneal or trabecular origin, and whether the thalamus and its function will remain intact on a much longer time scale. Avantages to STT ab interno include the comparative simplicity and quickness of the surgical procedure itself. This study point out, that the performance of 4 thalami has so far proved sufficient, what corresponds to a resorption surface area of 2.4 mm². The number of 4 thalami was defined empirical. Regarding the results of this study the creation of 4 thalami seems to provide a sufficient longterm decrease of IOP as a low rate of postoperative complications. For a further potentiality of IOP decreasing effect we recommend to perform up to 6 thalami. A randomized multicenter study will be conducted in the future to compare STT ab interno, trabeculectomy, and

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deep sclerectomy for the surgical treatment of primary open angle glaucoma. REFERENCES 1. 2.

3.

4. 5.

6. 7.

8. 9.

10.

Akafo SK, Goulstine DB. Long-term post trabeculectomy intraocular pressure. Acta Ophthalmologica 1990;70:31216. Benedikt O, Hiti H. Die Ziliarkörperfreilegung. Eine neue Operationsmethode zur Behandlung des irreversiblen Winkelblockglaukoms und des Aphakieglaukoms. Klin Monatsbl Augenheilkd 1976;169:711-16. Burian HM. A case of Marfan’s syndrome with bilateral glaucoma. With a description of new type of operation for developmental glaucoma (trabeculotomy ab externo). Am J Ophthalmol 1960;50:1187-92. Cairns JE. Trabeculectomy. Preliminary report of a new method. Am J Ophthalmol 1968;66:673-79. Demailly P, Lavat P, Kretz G, et al. Non-penetrating deep sclerectomy with or without collagen device in primary open-angle glaucoma: middle-term retrospective study. Int Opthalmol 1997;20:131-40. Edmunds B, Thompson JR, Salmon JF, et al. The National Survey of Trabeculectomy. III. Early and late complications. Eye 2002;16:297-303. El Sayyad F, Helal M, El-Kholify H, et al. Nonpenetrating deep sclerectomy versus trabeculectomy in bilateral primary open-angle glaucoma. Ophthalmology 2000;107: 1671-74. Fjodorov SN, Loffe DI, Ronkina TI. Deep sclerotomy: technique and mechanism of new glaucomatous procedure. Glaucoma 1984;6:281-83. Fronimopoulos J, Lambrou N, Pelekis N, et al. Elliot’s trepanation with scleral cover (procedure for protecting the fistula in Elliot’s trepanation with a lamellar scleral cover). Klin Monatsbl Augenheilkd 1970; 156:1-8. Grant WM. Experimental aqueous perfusion in enucleated human eyes. Arch Ophthalmol 1963;69:738-801.

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11. 12. 13. 14. 15.

16. 17. 18. 19.

20.

21. 22.

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Johnson DH, Johnson M. How does nonpenetrating glaucoma surgery work? Aqueous outflow resistance and glaucoma surgery. J Glaucoma 2001;10:55-67. Konstans AGP, Jay JL, Marshall GE, et al. Prevalence, diagnostic feature, and response to trabeculectomy in exfoliation glaucoma. Ophthalmology 1993;100:619-27. Kozlov VI, Bagrov SN, Anisimova SY, et al. Non penetrating deep sclerectomy with collagen. Ophthal Surg 1990;3:44-46. Mermoud A, Salmon JF, Barron A, et al. Surgical management of post-traumatic angle recession glaucoma. Ophthalmology 1993;100:634-42. Mermoud A, Schnyder CC, Sickenberg M, et al. Comparison of deep sclerotomy with collagen implanta and trabeculectomy in open-angle glaucoma. J Cataract Refract Surg 1999;25:323-31. Mills KB. Trabeculectomy: a retrospective long-term follow-up of 444 cases. Br J Ophthalmol 1981;65:790-95. Molteno ACB, Bosma NJ, Honours BSc, et al. Otago glaucoma surgery outcome study. Ophthalmology 1999;106:1742-50. Morell AJ, Searle AET, O’Neill EC. Trabeculectomy as an introduction to intraocular surgery in an ophthalmic training program. Ophthalmic Surg 1992;23:38-39. Pajic B, Pallas G, Gerding H, Böhnke M. A novel technique of ab interno glaucoma surgery: follow-up results after 24 months. Graefes Arch Clin Exp Ophthalmol 2005 Jul; 19: 1-6. Pallas G, Pajic B 1999. Die Sklerothalamektomie (STE): Stabile postoperative Augendruckregulierung beim Offenwinkel- und Kapselhäutchenglaukom. Klin Monatsbl Augenheilkd 2000;216:256-60. Popovic V, Sjöstrand J. Long-term outcome following trabeculectomy: Visual field survival. Acta Ophthalmologica 1991;69:305-09. Roth SM, Spaeth G, Starita RJ, et al. The effects of postoperative corticosteroids on trabeculotomy and the

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23. 24. 25. 26. 27. 28. 29. 30. 31. 32.

33. 34. 35.

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clinical course of glaucoma: Five-year follow-up study. Ophthalmic Surg 1991;22:724-29. Saiz A, Alcuaz A, Maquet JA, et al. Pressure-curve variations after trabeculectomy for chronic primary openangle glaucoma. Ophthalmic Surg 1990;21:799-801. Sanchez E, Schnyder CC, Sickenberg M, et al. Deep sclerectomy: Results with and without collagen implant. Int Ophthalmol 1997;20:157-62. Schuman JS, Chang W, Wang N, et al. Excimer laser effects on outflow facility and outflow pathway morphology. Invest Ophthalmol Vis Sci 1999;40:1676-80. Schwartz AL, Anderson DR. Trabecular surgery. Arch Ophthalmol 1974;92:134-38. Schwenn O, Dick B, Pfeiffer N. Trabekulotomie, tiefe Sklerektomie und Viskokanalostomie. Ophthalmologe 1998;95:835-43. Singh J, O’Brien C, Chawla HB. Success rate and complications of intraoperative 0.2 mg/ml mitomycin C in trabeculectomy surgery. Eye 1995;9:460-66. Spiegel D, Kobuch K. Trabecular meshwork bypass tube shunt: initial case series. Br J Ophthalmol 2002;86:1228-31. Starita RJ, Fellmann RL, Spaeth GL, et al. Short-and longterm effects of postoperative corticosteroids on trabeculectomy. Ophthalmology 1985;92:938-46. Sunaric-Megevand G, Leuenberger PM. Results of viscocanalostomy for primary open-angle glaucoma. Am J Ophthalmol 2001;132:221-28. Tanihara H. Surgical effects of trabeculectomy ab externo on adult eyes with primary open angle glaucoma and pseudoexfoliation syndrome. Arch Opthalmol 1993;111: 1653-61. Vernon SA, Spencer AF. Intraocular pressure control following microtrabeculectomy. Eye 1995;9:299-303. Watson PG, Barnett F. Effectiveness of trabeculectomy in glaucoma. Am J Ophthalmol 1975;74:831-45. Watson PG. When to operate an open angle glaucoma. Eye 1987;1:51-54.

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INTRODUCTION There is an increasing interest in the use of the excimer laser in ophthalmology, particularly in refractive surgery. The argon fluoride excimer laser (193 nm) ablates tissue with a high precision and without any mechanical or thermal damage to surrounding structures. Within the fiveyear follow-up the intrastromal excimer laser ablation (ISELA) was smooth and regular and there was no evidence of inflammation or thermal damage. Our study demonstrates a beneficial effect of the excimer laser (193 nm) during the non-penetrating glaucoma surgery. BACKGROUND AND OBJECTIVE The initial application of excimer lasers has been oriented to the cornea and to refractive surgery.2,14 Today, different types of lasers have been used in the treatment of glaucoma (the Holmium laser, Erbium:YAG laser, Carbondioxide laser and Excimer lasers).3,8-10 All authors use well-known «traditional» methods of glaucoma treatment, but apply for this purpose the excimer laser with 193 nm wavelength: external trabeculoectomy, sclerostomy, trans-scleral sinusotomy, filtering sclerostomy, deep sclerectomy, NPDS, etc.1,4,5,17 The argon fluoride excimer laser ablates the tissue with a high precision (1 micron per pulse) and without mechanical or thermal damage to surrounding structures and also has a cytostatic effect (Figs 9.1 and 9.2).6,12,18 The current technology does not allow the 193 nm wavelength to transmit through the fiber optics, which limits the endo-ocular use of this laser. We designed a special excimer laser unit with 193 nm wavelength for glaucoma surgery in 1999. It is possible to use this device in the standard operating room under the

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Fig. 9.1: Light photomicrograph and scanning electron microscopy of the stroma of rabbit cornea after excimer laser

Fig. 9.2: Light photomicrograph and scanning electron microscopy of rabbit cornea after surgical incision

operating microscope. Portable in dimensions it has a special mobile manipulator to deliver the laser energy to the operating field. The laser beam works in “eraser mode” without the necessity of a special mask. The focal distance between the manipulator and the ocular tissues is about several millimeters, the beam area in the focal point is 0.5 × 1 mm (Fig. 9.3). This study was conducted to find out the effectiveness and longevity of non-penetrating glaucoma surgery (NPDS) 7 with the use of excimer laser with 193 nm wavelength.7,15,16 PATIENTS AND METHODS In a non randomized prospective study there were 160 eyes of 154 patients aged from 18 to 88 years, between March

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Fig. 9.3: A special mobile manipulator for a surgeon, that delivers the laser energy to the operating field of the eye

2000 and May 2005. The majority of patients had advanced and far-advanced stages of open-angle and narrow-angle glaucoma. Laser iridotomy was performed in 44 patients with narrow-angle glaucoma to enlarge the profile of the anterior chamber angle. Intraocular pressure (IOP) was

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recorded preoperatively and postoperatively at 1, 7, 14 days, at 1, 3, 6 and thereafter every 6 months. SURGICAL TECHNIQUE We describe a new technique of non-penetrating glaucoma surgery that uses the excimer laser to reduce the risk of perforation the trabeculo-descemet’s membrane. With this technique the ablation is precise and homogeneous. The procedure can be performed with topical anesthesia. Excimer laser surgery consists of: • fornix-based conjunctival flap 2.0-2.5 mm in the upper quadrant; • minimal episcleral cautery; • dissection of a superficial corneal groove; • dissection of a 2.5 × 2.5 mm rectangular in half thickness lamellar scleral flap; • excimer laser ablation; • closure of scleral flap and conjunctival closure with a running 8.0 silk suture. The deep layers of sclera were evaporated layer by layer with laser energy of a 150 mJ/cm2 density until vessels of ciliary body appeared (Fig. 9.4). Then the Schlemm’s canal was covered with a protector, and the deep layers of corneal stroma were removed by laser up to the Descemet’s membrane until the moment of the aqueous humor drop appearance (energy density 50 mJ/cm2) (Fig. 9.5). Postoperative treatment consisted of antibiotics and dexamethasone drops instilled four times a day during 2 weeks. RESULTS AND DISCUSSION As a result of intrastromal excimer laser ablation (ISELA) the ophthalmotonus normalization was achieved in all

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Fig. 9.4: The deep layers of sclera were evaporated by excimer laser until vessels of ciliary body appeared

Fig. 9.5: The deep layers of corneal stroma were removed by excimer laser up to the Descemet’s membrane until the moment of the aqueous humor drop appearance

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cases independently of disease stages. The IOP averaged 10±2 mm Hg in the early postoperative follow-up. There were observed no cases of hemorrhagic or other complications, and the postoperative period was notable for a favorable course. All patients did not note any painful sensations both intra- and post-operatively, in this connection this procedure may be transferred to the outpatient category. The B-scanning and ultrasound biomicroscopy were performed thoroughly in patients with hypotonia in order to reveal a choroidal detachment. As the rule, only edema and thickening of choroid by 50-100 μm took place in the first postoperative days that indirectly was evidence of aqueous humor resorption by vessels of ciliary body. The surgical technique supposes a creation of bypass between the Descemet’s membrane and vessels of ciliary body which absorbability is 50 times more than in ordinary capillaries (Fig. 9.6). In our opinion the normalization of intraocular pressure after the intrastromal excimer laser ablation is achieved owing to an improvement of uveal scleral outflow of aqueous humor, an elimination of Schlemm’s canal collapse and a recovery of its functionally maintained sites. As a result there are no sharp IOP fluctuations in the direction

Fig. 9.6: Basic outflow pathways of aqueous humor in ultrasound biomicroscopy: 1- into the intrascleral space and vessels of ciliary body; 2 - into the flat filtering bleb

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of hypotonia that leads to proper complications (hyphema, choroidal detachment, cataract progression, etc.). Preoperatively the outflow facility index (C) did not exceed 0.04 mm3/min/mmHg while after the intervention this index (C) averaged 0.32 ± 0.02 mm3/min/mmHg, i.e. 7-9 times the increase. Moreover a tendency of the aqueous humor production (F) increase is revealed in a part of cases. In the majority of cases (about 70% of eyes) an improvement of visual acuity is noted on an average by 0.1-0.2 obviously due to a decompression of optic disk fibers and a reduction of peripapillary edema that needs a further study. In the long-term follow-up the outflow facility index (C) decreased slightly, but remained within the norm (mean 0.20±0.04 mm 3 /min/mmHg) that provided a compensation of ophthalmotonus on a level of 17.0 ± 2.5 mm Hg (Fig. 9.7). In the long-term follow-up in patients with initial and advanced stages of glaucoma the IOP was compensated in all cases. In the group of patients with the far-advanced stage of disease the YAG laser descemeto-goniopuncture (DGP)11,13 in the intervention area was required within periods from 4 to 6 months in 16 eyes (10% of cases). It

Fig. 9.7: IOP data after excimer laser treatment (ISELA) and NPDS

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allowed to restore aqueous humor outflow pathways and to normalize the IOP (Fig. 9.8). Within the follow-up of 1 year and more a development of cystic filtering bleb was observed in 2 eyes. A monotherapy with the 0.5 percent Betoptic solution instillation one or two times was administered in 12 patients with far-advanced glaucoma. CONCLUSION Thus, the creation of a domestic specialized excimer laser unit with 193 nm wavelength allowed to develop practically a new safe technology of glaucoma surgery that cannot be performed using traditional knife surgery. Small dimensions (portability), presence of manipulator for a surgeon, price of the unit differentiate it advantageously from other foreign excimer laser and also allow to adapt it in conditions of an ordinary operating room. A new technology of glaucoma surgery (ISELA) is developed that allows to restore natural aqueous humor outflow pathways without a destruction of the Schlemm’s canal, to return the greater part of aqueous humor to vessels

Fig. 9.8: The ultrasound biomicroscopy before and after the YAGlaser DGP (descemeto-goniopuncture) to create a microperforation in Descemet’s membrane behind Schwalbe’s line to improve filtration

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of ciliary body. The procedure is especially efficient and safe in patients with initial and advanced stages of disease because allows to normalize ophthalmotonus and to maintain visual functions. REFERENCES 1. 2.

3. 4. 5. 6.

7.

8.

9.

Argento C, Sanseau AC, Basoza D, et al. Deep sclerectomy with a collagen implant using the excimer laser. J Cataract Refract Surg 2001;Apr.27(4):504-06. Aron-Rosa DS, Boutnoy JL, Carré F, et al. Excimer laser surgery of the cornea: qualitative and quantitative aspects of photoablation according to the energy density. J Cataract Refract Surg 1986;12:27-33. Beckman H, Fuller TA. Carbon dioxide laser scleral dissection and filtering procedure for glaucoma. Am J Ophthalmol 1979;88:73-77. Berlin MS, Martinez M, Papaioannou T, et al. Goniophotoablation: excimer laser glaucoma filtering surgery. Lasers Light Ophthalmol 1988;2:17-24. Brooks AM, Samuel M, Carroll N, et al. Excimer laser filtration surgery. Am J Ophthalmol 1995;119:40-47. Ereskin NN, Takhchidi KP, Vartapetov SK, et al. Advantages of a new excimer laser for glaucoma surgery. 4th International Glaucoma Symposium-I.G.S. Barcelona, Spain,19-22 March 2003;P-28. Fyodorov SN, Kozlov VI, Timoshkina NT, Sharova AB, Ereskin NN, Kozlova EE. Non-penetrating deep sclerectomy in open angle glaucoma. Ophthalmosurgery 1989;34:52-55. Iwach AG, Hoskins HD, Mora JS, et al. Update on the subconjunctival THC:YAG (holmium) laser sclerostomy Abexterno clinical trial: a 4-year report. Ophthalmic Surg Lasers 1996 Oct;27(10):823-31. Jacobi PC, Dietlein TS, Krieglstein GK. Prospective study of ab externo erbium: YAG laser sclerostomy in humans. Am J Ophthalmol 1997, Apr; 123(4):478-86.

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10. 11.

12. 13. 14. 15.

16.

17.

18.

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Klink T, Lieb W, Grehn F. Erbium-YAG laser-assisted preparation of deep sclerectomy. Graefes Arch Clin Exp Ophthalmol 2000 Sep;238(9):792-96. Kozlov V, Magaramov D, Ereskin N. Laser surgery for open-angle glaucoma in eyes with intraocular pressure elevation after non-penetrating deep sclerectomy. Ophthalmosurgery 1990;4:62-66. Marshall J, Trokel S, Rothery S, et al. An ultrastructural study of corneal incisions induced by an excimer laser at 193 nm. Ophthalmol 1985;92:749-58. Mermoud A, Karlen ME, Schnyder CC, et al. Nd:YAG goniopuncture after deep sclerectomy with collagen implant. Ophthalmic Surg Lasers 1999 Feb; 30(2):120-25. Puliafito CA, Steinert RF, Deutsch TF, et al. Excimer laser ablation of the cornea and lens. Ophthalmol 1985;92(6): 741-48. Takhchidi KP, Ereskin NN. Surgical treatment of glaucoma by excimer laser with 193 nm wavelength. Intraocular Implant and Refractive Society, India. 2005 May;1(5):1113. Takhchidi KP, Ereskin NN, Doga AV, et al. A new microinvasive technology of glaucoma surgery by excimer laser. 5-th International Glaucoma Symposium-I.G.S. Cape Town, South Africa, 30 March-April 2,2005; P-A24. Traverso CE, Murialdo U, Dilorenzo G, et al. Photoablative filtration surgery with the excimer laser for primary openangle glaucoma: a pilot study. Int Ophthalmol 1992;16:45,363-5. Schuman JS, Chang W, Wang N, et al. Excimer laser effects on outflow facility and pathway morphology. Inves. Ophthalmol Vis Sci 1999;40:1676-80.

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OBJECTIVE AND INTRODUCTION The arrival of glaucoma surgery into the framework of deep sclerectomy or cataract surgery using bimanual phacoemulsification, allows surgery to be performed on a closed anterior chamber. It was evident that these microinvasive techniques would use the same topical anesthesia technique. Topical anesthesia is used in ambulatory surgery where the patient must be able to return home immediately without any risk to health or from postoperative risks.5 Another advantage of using this anesthesia in glaucoma surgery, is that it becomes possible to position the eye on the exact axis to enable dissection of the scleral flap. This is easier for the surgeon than when using retrobulbar or peribulbar anesthesia. which paralyze the external muscles, or - worse - place the eye in an unsuitable position. In our experience, it appears that the length of hospitalization is about one hour:2 the amount of time needed to prepare and carry out the surgical operation. This is as long as the patient is kept calm and relaxed, which is simpler than it appears to be. When caring for the patient, we must ensure his optimum comfort and that the stress inherent in any operation is kept to the minimum.6 Topical anesthesia is not necessarily enough. It depends on the type of the operation and also the type of patient. This anesthesia, in the course of years, has been improved or, rather, completed by various surgeons and anesthetists. Glaucoma surgery is different from cataract surgery in that, at the beginning of the operation, an 12 mm incision is made in the conjunctiva with a perpendicular conjunctival cut. This dissection has to be made up to the tenon in order to find the sclera. It is sometimes necessary to use a cauter to coagulate the superficial vessels. For this

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reason, topical anesthesia is sometimes not sufficient, making a subconjunctival bubble during glaucoma surgery that allows mobility to be maintained. This is very convenient, as it allows the operated eye to be kept in the best position for microdissection of successive layers. HISTORICAL BACKGROUND At the beginning of the twentieth century, we see the appearance of topical anesthetics, among them, cocaine.19 In 1910, Julius Hirschberg presented a cataract operation using a 2 percent solution of cocaine as a topical anesthetic.14 In 1988, Robert Smith presented a anesthesia technique for cataract surgery in EEC, using 1 percent drops of amethocaine and a superior conjunctival injection of a bubble of 2 percent lidocaine.18 More recently, in 1991, R Fischman reported using tetracaine as drops for a phacoemulsification cataract operation. 17,10 C Williamson, in 1992, used lidocaine 4 percent in topical anesthesia, 4 drops before emulsification.25 In 1996, J P Gills improved the technique by introducing an introcamerular injection of lidocaine, diluted at 0.5 percent, which did away with the deep pains occurring with mobilization of the iris or the capsule.11,13 ANATOMICAL REVIEW OF CORNEAL INNERVATION The cornea is the most innervated tissue. This innervation is supplied mainly by the ciliary branches of the ophthalmic division of the trifacial nerve. It enters the cornea radially at the level of the stroma moyenne, forming a dense plexus under the Bowmann membrane. The central epithelium receives terminal axones from this plexus. There is a small sympathetic innervation which is probably at the origin of the cellular proliferation.23

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Contrary to earlier theories, corneal innervation is made at the central level by the plexus which goes through the Bowmann membrane and, on the periphery, by a more superficial conjunctival tract. The innervation of the ciliary muscles and of the iris that generate during the deep pain occurring with mobilization of the globe. This comes from the plexus. This necessitates using a different anesthesia to get rid of the pains. The innervation of the tarsal and bulbar conjunctives also come from the trifacial nerve but by way of a different route to the cornea. PHARMACOLOGY The ideal topical anesthetic must have neither local nor systemic, nor a corneal toxicity. It must not bring about an epithelial edema. Whilst working fast without causing pain when introduced, it must work for an adequate period of time. There are several types of topical anesthetics. The most frequently used are cocaine, proparacaine, tetracaine and lidocaine. All topical anesthetic drops sting when they are put in. Cocaine and proparacaine have been abandoned because of significant bulbar and epithelial toxicity. Tetracaine is much less toxic but it doesn’t provide deep enough corneal anesthesia, and it becomes necessary to repeat the instillation of drops during the operation. This often causes an epithelial edema. 17 This group of anesthetics includes an ester, increasing their solubility in water and diminishing cellular penetration. Tetracaine has been preferred in the United States for a long time, because it was the only preservative free solution.15 Lidocaine belongs to the amide group. It is lipid soluble which allows greater tissue penetration and has a longer

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period of action. For corneal anesthesia, this anesthetic gives satisfactory anesthesia from 30 minutes to one hour, depending on the patient. At a concentration of 2 percent, it doesn’t present any toxicity problems and does not entail epithelial edema.21 Lidocaine given by intracamerula injection, at a dosage of not more than 0.5 percent, is not toxic for the human endothelium. This has been proved by multiple random prospective clinical studies.15 A study using rabbits has demonstrated that an injection of lidocaine can be toxic for the endothelium, but the dosage used and the conditions under which that study was done were far removed from those used in human microsurgery.16 DESCRIPTION OF TOPICAL ANESTHESIA TECHNIQUES Cataract Before disinfection, a drop of oxybuprocaine (Novésine) is put in. Five minutes before the operation, five drops of lidocaine 2 percent without preservative (Astra) is put in. Topical anesthesia is completed by an intracamerular injection of 1cc lidocaine 0.5 percent without preservative, done after the paracenteses and during hydrodeliniationhydrodissection. This gets rid of the deep pain during mobilization of the iris or the capsule.11,13 Glaucoma The initial stages of a glaucoma operation are similar to that of a cataract operation. Firstly, before disinfection, drops of oxybuprocaine are put in. Then, five minutes before the arrival of the patient in the operating theater, lidocaine 2 percent is put in. Then, instead of intracamerula

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injection, using a swab, lidocaine 2 percent is put in on the conjunctiva. After this, 2 cc-3 cc of lidocaine 2 percent is injected under the conjunctiva with a 25G yellow needle to form a perfect bubble on the dissection surface of the scleral flap. This bubble must cover at least a quadrant of the eye. The anesthetic will take effect in about two minutes, after which the patient is asked to orientate his eye in the direction of the flap that is to be made. Usually, this presents no problem, and patient collaboration is excellent (Figs 10.1 and 10.2). Combined Cataract/Glaucoma Although the principle is the same in a combined glaucoma/cataract operation, the timing will vary, depending on how the surgery progresses. Firstly, five minutes before the arrival of the patient in the operating theater, drops of lidocaine 2 percent are put in. Then, the bubble is created by injecting lidocaine 2 percent under the conjunctiva. During the cataract operation an intracamerular injection of lidocaine at 0.2 percent dilution is made to reduce the deep pain. Generally, no additional topical anesthetic is needed to complete the second flap and the closure of the conjunctiva, but it can always be added, if needed. COMPLEMENTARY SEDATION USING INTRAVENOUS INJECTION It is always possible that sedation will need to be administered before or during the operation. The onset and rise of anxiety has always a contextual aspect. The role and the attitude of the surgeon and other participants cannot be underestimated in the onset and rise of patient anxiety. At the beginning of the operation and depending on the

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Fig. 10.1: Subconjunctival bubble of anesthesia lidocaine 2%

Fig. 10.2: Conjunctival dissection with wescoat under subconjunctival anesthesia lidocaine 2%

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type of patient and their anxiety level, an intravenous dose of propofol can be administered at the same time as the subconjunctival injection is made. If the build up of patient anxiety cannot be controlled, a very slow and progressive intravenous injection of benzodiazepines (midazolamDormicum 0.5 to 1.5 mg) and/or opiates with a short halflife (alfentanil-Rapifen 50-100 mcg) can be made.3,7,8 PREPARATION OF THE PATIENT Preoperative Preparation The patient meets his surgeon and his anesthetist,9 and it is important, during this consultation, that all the patient’s questions are discussed. It is vital that the patient clearly understands the stages and procedures of the operation, so that trust is established and that he can follow his operation well. On the day of the operation, an assistant checks that the patient clearly recalls and understands all stages and procedures. It is imperative that the patient goes to the toilet before the operation to empty his bladder, thus allowing him not to be worried by external matters during the operation. Eye dilation is carried out by the patient at home. This reduces the waiting time before the operation begins – a time full of anxiety for the patient. Five minutes before going into the operating theater, the patient is given 5 drops of 2 percent lidocaine on the cornea. Great care must be taken at this point not to allow the cornea to dry out thorough small blinks of the eyelid. At this point, the anesthetist has an important role in verbally soothing the patient.21

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Preparation during the Operation Once the patient is settled comfortably in the operating theater, the operating field is rapidly applied. It is important to tell the patient what is going to happen before each action is carried out, so as to avoid undue alarm. The microscope light is very dazzling and it is experienced as painful by the patient.4 It is paramount, to accustom the patient, to start with a weak light and increase its strength progressively. Once the operating field is stuck on the face, the eyelid retractor is placed into position and then opened delicately, so that there is no eyelid akinesia. Once the eyelid retractor is in position, the surface of the conjunctiva is swabbed with 2 percent lidocaine, then a subconjunctival injection of lidocaine is made a little behind the site of the flap, so that the conjunctiva is not damaged and a high-quality anesthesia is achieved (Figs 10.3 and 10.4). After this, the operation proper can proceed as normal, always speaking to the patient so that he is not alarmed or surprised and does not move. Postoperative Care and Patient’s Home Return Once the operation is finished, there is in the patient an extreme sense of relief, and a natural relaxation, as patients always imagine that an eye operation will be much more painful than any other. Once the operation is finished, the patient must be taken care of by the nurse - especially in the case of an ambulatory patient who must not have a sense of being abandoned. The nurse offers him light refreshments, tea or coffee. The patient is discharged about thirty minutes after the end of the operation. The patient must go home with all

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Fig. 10.3: Positioning the globe to see the flap at the end of the operation

Fig. 10.4: Motility of the globe under topical and a conjunctival bubble of anesthesia

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the instructions he has to follow for his postoperative treatment and a follow-up appointment for the next day, to check the operation. He must be given a contact telephone number for the nurses and the surgeon, in case he is worried. CONCLUSION: ENVIRONMENT UNDER WHICH THE OPERATION TAKES PLACE Topical anesthesia in cataract operations has proved itself. In the case of glaucoma operations, subconjunctival anesthesia allows the mobility of extrinsic muscles to be kept intact and for the operating field to be placed exactly where the surgeon needs (Figs 10.3 and 10.4). For a successful topical anesthesia to be done, it is imperative that the surroundings should be familiar to the patient and that he does not feel suffocated. In ambulatory surgery, the patient must feel that he is in a caring, warm and professional environment.1,22 The team which takes charge of the patient must bond together well, be friendly but not familiar. Stress does not diminish the pain threshold! Since 1996, we have been practising this type of anesthesia regularly on all our patients, without any major complications. REFERENCES 1. 2. 3.

Bovet JJ. Minimal standard needs for out-patient surgery Abstract first ESOPES congress Vienna 1993. Bovet JJ, Molnar I, Baumgartner J-M, Bruckner J-C. Outpatient surgery comparing with In patient surgery round table Ascona symposium abstract April 1995. Bovet JJ, Baumgartner JM, Bruckner JC, Ilic V, Paccolat F, Maroni O, Bovet F. Chirurgie de la cataracte en topique intracamérulaire Abstract SSO-SOG. Sept 1997.

158 4. 5. 6. 7. 8. 9. 10. 11. 12.

13. 14. 15. 16. 17.

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Bovet JJ, Lebuisson DA. Le microscope opératoire in Laroche L, Lebuisson DA, Montard M Chirurgie de la cataracte chap 7 pp81-8ed Masson 1996. Bruckner JC. Option zéro Abstract 2th ESOPES congress Genève 1994. Bruckner JC. Abstract 15e Asia-Pacific congress Honk kong mars 1995. Bruckner JC. Out-patient cataract surgery: yet another backseat role for the anesthetist? abstract 3th ESOPES congress postdam 1996. Esteve C, Lebuisson DA, Montin JF. Anesthésie topique dans la chirurgie de la cataracte par phakoémulsification de l’adulte Ophtalmologie 1997;11:246-8. Fraser SG, Siriwadena D, Jamieson H, Girault J, Bryan SJ. Indicators of patient suitability for topical anesthesia. J Cataract Surg 1997;23:781-3. Fischman, R ASCRS abstract, April 1992. JP Gills. Ocular surgery news abstract 1996. Gills JP, Cherchio M Raanan MG. The use of intraoperative unpreserved lidocaïne to control discomfort during IOL surgery under topical anesthesia. J Cataract Refract Surg 1997;23:527-35. Gills JP, Martin RG, Cherchio M. Topical anesthesia and intraocular lidocaïne in Cataract surgery the state of the art Gills JP chap 2 pp9-17 Slack inc 1998. Hirschberg J. History of ophtalmology 1910;284. Hustead RF, Hamilton RC. Pharmacology. In Gills JP, Hustead RF, Sanders DR. Ophthalmic Anesthesia chap 2 pp69-102 Slack inc ed 1993. Judge AJ, Najafi K, Lee DA, Kevin MM. Corneal endotheliale toxicity of topical anesthesia. Ophthalmology 1997;104:1373-9. Kershner RM. Cataract surgery technique using topical anesthesia In Fine I H, Fichman R A, Grabow H B. Clear Cornea Cataract Surgery and Topical Anesthesia. chap 11: pp141-153 Slack inc ed 1993.

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18. 19. 20.

21. 22.

23. 24. 25.

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Klyve P, Nicolaissen B. Surgery of strabismus performed during topical anesthesia using adjustable suture. TidssrkNor-laegeferen 1992;112:774-5. Knapp H. On cocaïne and its use in ophthalmic and general surgery. Arch Ophthalmol 1884;13:402-3. Lebuisson DA, Bovet JJ. Le concept opératoire pour patients ophtalmologiques ambulants in Laroche L, Lebuisson DA, Montard M Chirurgie de la cataracte chap 6 pp61-74ed Masson 1996. Lebuisson DA, Chevaleraud E, Bovet JJ. Les anesthésies locales in Laroche L, Lebuisson DA, Montard M Chirurgie de la cataracte chap10 pp109-127ed Masson 1996. Lebuisson DA, Bovet JJ. Principle d’hygiène au bloc opératoire ophtalmolgique in Laroche L, Lebuisson DA, Montard M Chirurgie de la cataracte chap 5 pp39-58ed Masson 1996. Martin XY, Safran AB. Corneal hypoesthesia Survey Ophtal 1988;33:28-40. Smith R. Cataract extraction without retrobulbar injection Brit J Ophthalmol 1990;205-107. Williamson CH. Cataract keratotomy with topical anesthesia. Ocular Surgery News 1992;10:44.

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INTRODUCTION Cyclodestructive procedures are generally used for refractory glaucomas. Previously it has been carried out by various methods like surgical excision of ciliary body,1 cyclodiathermy,2,3 cycloirradiation,4 cycloelectrolysis,5 cyclocryotherapy, 6-9 ultrasound, 10 microwave cyclodestruction,11 and currently by cyclophotocoagulation. Laser cyclophotocoagulation has now become the principal method of cyclodestructive procedures. Various laser has been used for this purpose which includes ruby, Nd:YAG, argon, krypton and diode laser, etc. Beckman and Sugar first popularized the use of transscleral cyclophotocoagulation (TSCPC) by ruby laser in early 1970s.12,13 Later they discovered that Nd:YAG laser was more effective in penetrating sclera and energy absorbed by ciliary body is also optimum.13 Secondary glaucomas like postpenetrating keratoplasty glaucomas, aphakic/pseudophakic glaucomas, neovascular glaucomas and glaucoma following trauma are examples where cyclodestructive procedures are favored due to a poor response to standard filtering procedures.14-16 INDICATIONS OF CYCLODESTRUCTIVE PROCEDURES 1. 2. 3. 4. 5.

Refractive primary ACG, OAG Neovascular glaucoma (NVG) Post-traumatic glaucoma Aphakic/pseudophakic glaucoma Severe congenital glaucoma with multiple failed surgeries 6. Postpenetrating keratoplasty glaucoma 7. Postretinal detachment surgery glaucoma

Cyclophotocoagulation

8. 9. 10. 11. 12. 13. 14.

163

Silicone oil-induced glaucoma Inflammatory glaucoma Glaucoma with severe conjunctival scarring. Failed trabeculectomy and drainage implants Medical condition precluding invasive surgery Patients’ refusal to undergo invasive surgery In emergent situation (i.e. acute onset NVG).

MECHANISM OF ACTION Various theories have been described regarding mechanism of cyclophotocoagulation. Decreased Aqueous Production • Destruction of the ciliary epithelium resulting in decreased aqueous production. • Destruction of ciliary blood vessels and coagulative necrosis also contributes in decreasing aqueous production.17 • Intraocular inflammation is also thought to be responsible for short-term hypotension.19 For both of these mechanisms presence of ciliary body pigment is important in absorbing laser energy.18 The diode laser (810 nm) has greater melanin absorption compared to the Nd:YAG laser (532 nm). Increased Aqueous Outflow • Nd:YAG laser also produces a neuroepithelial defect resulting in increase outflow which is related to the extent of treatment. In an in-vitro perfusion model, laser lesions placed 6 mm posterior to limbus had an equivalent effect on outflow to that of laser lesions directed towards ciliary process.20

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Animal study 21 suggests that the decrease of the intraocular pressure after pars plicata cyclocoagulation resulted from the reduction of aqueous secretion, whereas that after pars plana cyclocoagulation resulted from enhancement of the uveoscleral outflow through the enlarged extracellular space from the anterior chamber into the suprachoroidal space. CYCLOPHOTOCOAGULATION Trans-scleral Cyclophotocoagulation with the Nd: YAG Laser In pulsed mode Nd:YAG laser focuses very intense laser energy into small area for a short period which produces mechanical photodisruption. But in continuous mode it creates 1000 folds greater energy than used for routine photodisruption. These high energy levels alter the ciliary body thermally and are used for trans-scleral cyclophotocoagulation.22 Trans-scleral cyclophotocoagulation with the Nd: YAG laser can be performed both as continuous and pulsed laser system. It may be a contact and non-contact procedure.23-25 Contact system uses hand-held probe, which is placed on conjunctiva to allow energy transmission directly to the ocular surface. Non-contact laser system transits the laser energy through air from a slit-lamp delivery system. Contact procedure requires a lesser energy than the non contact procedures. The commonly used settings in the thermal mode of Nd: YAG non-contact method employs 8 Joules for 20 msec, 32-40 spots over 360o. In comparison the contact technique requires 7 Watts for 0.7 seconds for each spot; 32-40 spots being applied over 360o (Table 11.1). In non-contact method laser applications have been placed 1 to 3 mm from limbus.

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Whereas in case of contact method anterior edge of probe is placed 0.5 to 1 mm posterior to limbus. However, the YAG laser is bulky, expensive and requires careful maintenance. The success rate of Nd:YAG laser cyclophotocoagulation in various studies is listed in Table 11.2. Results of Clinical Trials In a large series of 500 patients by Shields MB et al26 suggests that noncontact trans-scleral Nd:YAG cyclophotocoagulation is the cyclodestructive procedure of choice. It Table 11.1: Treatment parameters for Nd:YAG laser cyclophotocoagulation

Energy Duration Number Circumference Spot size

Non-contact

Contact

4-8 J 10-20 msec 32 spots 360o Fixed, 70 um

4-9 watts 0.5-0.7 seconds 32 spots 360o Fixed, Quartz probe

Table 11.2: Success rates in various studies using Nd:YAG cyclophotocoagulation

Authors

No. Follow- Success Success Retreatof up Definition rate ments eyes (months) (mm Hg) (%) (eyes)

Phelan MJ et al28 Delgado MF et al29 Beiran I et al30 Schuman JS et al31 Schuman JS et al32 Miyazaki et al33 Hampton c et al34 Brancato et al35 Klapper et al36

10 115 52 116 140 26 106 23 30

15 27 12 12 6 10 6 8.6 6

21 22 21 22 5-22 22 7-20 25 22

50 65 70 65 59 77 51 66 86

7 33 — 31 16 12 29 13 7

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offers a reasonable surgical option in patients with neovascular glaucoma, glaucomas with active uveitis, glaucomas in aphakia or pseudophakia, and other cases in which filtering surgery has failed or is felt to have a low chance for success. Satisfactory intraocular pressure reduction was achieved in 62 percent of the patients with one treatment session and with multiple treatments in 94 percent. However, visual loss remains a significant postoperative complication occurring in 39 percent of the study population. Patients with neovascular glaucoma had the greatest percentage of visual loss at 46 percent, compared with 34 and 38 percent for patients with glaucomas in pseudophakia and aphakia, respectively. But it is not known how many of these cases of visual loss were a direct result of the cyclophotocoagulation. A prospective study by Lin P et al27 of 68 eyes of 64 patients with advanced, uncontrolled glaucoma who received cyclophotocoagulation showed a significant reduction of IOP after surgery at 1, 5, and 10 years of followup; however, 51.5 percent of eyes failed by the end of 10 years, with most failures occurring within the first year (40%). Ten eyes of pediatric glaucoma was treated by Phelan MJ et al 28 with Nd:YAG contact trans-scleral laser cyclophotocoagulation. Five patients (50%) achieved IOP of less than 21 mm but Hg was in, retreatment was required in 7 of 10 eyes. Loss of vision was seen in four patients, and one case of phthisis bulbi was noted. Delgado MF et al 29 did noncontact trans-scleral Nd:YAG cyclophotocoagulation treatment for neovascular glaucoma in 115 eyes of 111 subjects treated. Success rate was 65.0 percent at 1 year, 49.8 percent at 3 years, and at 34.8 percent 6 years. Phthisis developed in 8.6 percent of the eyes.

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Results of noncontact trans-scleral Nd:YAG cyclophotocoagulation in the treatment of postpenetrating keratoplasty refractory glaucoma is also promising. In Beiran’s series of fifty-two eyes, the mean post-treatment IOP was 15.8+/-9.7 mm Hg, pretreatment IOP being 38.7 +/-11.9 mm Hg. The probability of a graft remaining clear was 79 percent at 1 year and 56 percent at 5 years.30 But in another study out of 25 patients with clear grafts before cyclophotocoagulation, 11 (44%) had graft decompensation.77 Trans-scleral Cyclophotocoagulation with Semiconductor Diode Laser The ergonomics of the semiconductor Diode laser have made it a better alternative to the Nd:YAG laser.34,37 Moreover, the Diode laser at 830 nm has a better absorption by the pigmented tissue of the ciliary body, requiring lesser energy per spot. Histopathologic studies have shown the diode laser to produce most of its coagulative effect on the ciliary body stroma. It requires less energy than Nd:YAG laser (4.0 Jvs. 1.2 J).38 The procedure is performed in the outpatient clinic. Contact method is superior as it has the advantages of reduced scattering and increased scleral transmission. The response of ciliary body destruction is thought to be gauged by the ‘pop’ sound. Although there have been few comparisons between the Diode and YAG laser, but postlaser pain and chances of persistent hypotony are greater with the Nd:YAG laser. Settings used for contact mode in one of the largest studies by Bloom et al on 210 eyes were 1.5 watts for 1.5 seconds using 40 spots over 360o (Figs 11.1 and 11.2). The probe is to be placed with its edge at the limbus, but is actually centred 1.2 mm posterior to the limbus in the region of the ciliary body (Fig. 11.3). Other authors prefer to keep the power just below the level

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Fig. 11.1: DLCP machine (Nidek)

Fig. 11.2: DLCP probe (Nidek)

at which ‘pop’ sound is heard (Table 11.3). The contact method uses a G probe (Figs 11.4 to 11.6) which is designed to deliver energy 1.2 mm from the limbus and has a small protusion that indents the conjunctiva and sclera to optimize delivery.

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Fig. 11.3: DLCP being done

Table 11.3: Treatnment parameters for diode laser cyclophotocoagulation

Non-contact Energy Duration Number Circumference

1.2 watts 990 msec 40 spots 360o

Contact 1.5 watts 1.5 seconds 25-30 spots 360o

Common complications following Diode laser cyclophotocoagulation are conjunctival burns, mild postoperative inflammation and atonic pupil. Uncommonly there may be severe uveitis, and loss of vision and rarely hyphema and vitreous hemorrhage. The success rate of Diode DLCP in various studies is listed in Table 11.4.

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Fig. 11.4: IRIS G-probe (side view)

Fig. 11.5: IRIS G-probe (end on view)

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Fig. 11.6: DLCP being done with G-probe Table 11.4: Success rates in various studies using diode laser cyclophotocoagulation

Authors

No. Follow- Success of up definition eyes (months)

Kosoko et al49 Bloom et al50 Spencer et al51

27 12 210 10 58 19

Werner et al52

106 24

Pucci et al53 Noureddin et al54 Ocakoglu et al55 Agarwal et al56 Levinger E et al57 Lai JS et al40 Schlote T et al43 Mistlberger A et al58 Gupta V et al59

120 36 32 52 33 14 100 206 52

26 12 11.4 12 12 12 12 9 12

Success Retreatrate ments (eyes)

<23 mm Hg 72% <22 mm Hg 66% <22 mm Hg 81% <17mm Hg 59% <22 mm Hg/ 85% pain relief <22 mm Hg 54% <21 mm Hg 72% <22 mm Hg 56% <22 mm Hg 92% 22 mm Hg 73% 21 mm Hg 85.7% 5-21 mm Hg 74.2% 22 mm Hg 72.7% 22 mm Hg 92%

— 102 26 23 55 9 14 22 — 2 33 22

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Results of Clinical Trials Agarwal HC et al39 evaluated contact and non-contact methods of diode laser delivery and found using an energy setting of 3 J per spot, both were equally effective in lowering IOP in eyes with refractory glaucoma. Lai JS et al40 evaluated the efficacy and safety of diode laser trans-scleral cyclophotocoagulation in the treatment of 14 patients of chronic angle-closure glaucoma. The total success rate defined as IOP < 21 mm Hg with or without medication(s) was 85.7 percent at 1 year of follow-up review. Two eyes required repeat treatment. Seven eyes (50%) had atonic pupil following the laser treatment. A retrospective analysis by Murphy CC et al41 of 263 eyes of 238 patients of refractory glaucoma who underwent trans-scleral diode laser cyclophotocoagulation at two centers showed 89 percent of patients achieved an IOP of less than 22 mm Hg or a greater than 30 percent drop in IOP after cyclodiode therapy. Hypotony occurred in 9.5 percent of patients, 76 percent of whom had neovascular glaucoma. Kramp K et al42 evaluated trans-scleral diode laser contact cyclophotocoagulation in the treatment of different glaucomas, also as primary surgery in 193 eyes. The IOP was successfully controlled (final IOP 10-22 mm Hg) in 76.4 percent of cases after a single or multiple TSCPC treatments. The best results were obtained among the patients with POAG, in the oldest age group and in those patients without any previous or subsequent glaucoma operations. The proportion of eyes requiring multiple treatments was 21.2 percent. There was a complication rate of 14.4 percent, mostly mild uveitis. Phthisis bulbi occurred in three eyes (1.6%).

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In Schlote’s43 series of 100 eyes overall success rate was 74.2 percent. A high success rate was achieved in inflammatory glaucoma (75%), primary open-angle glaucoma (89.5%), and neovascular glaucoma (86.7%) whereas the results were relatively poor in traumatic glaucoma (57.1%), aphakic glaucoma (57.1%), and congenital or juvenile glaucoma (62.5%). Role of diode laser cyclophotocoagulation in the management of refractory pediatric glaucomas is also good. With repeated treatment, cyclodiode can provide effective control of IOP pediatric glaucomas though the success rate is lower than with adults. Younger eyes may recover from treatment more rapidly but it has a lower rate of severe adverse effects than surgical modalities and has roles as a temporizing measure, as an adjunct to surgery, or in managing selected patients in whom surgery is undesirable because of a high risk of surgical complications.44 Inflammatory glaucoma is still a diagnostic and therapeutic dilemma and surgical intervention is always associated with a high risk of failure. Schlote T et al45 showed a success rate of 77.3 percent (72.2% of those with uveitic glaucoma). DLCP may become the surgical procedure of choice in treating secondary glaucoma caused by chemical injury and also in scleritis associated glaucoma, using reduced parameters for application. Semchyshyn TM et al 46 assessed the outcome of supplemental trans-scleral diode laser cyclophotocoagulation in twenty-one eyes with uncontrolled IOP despite the presence of an aqueous tube shunt and maximally tolerated glaucoma medications and found that adjunctive trans-scleral diode cyclophotocoagulation treatment(s) is a viable option to lower IOP in these cases.

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Patients with medically uncontrolled glaucoma persisting after intravitreal silicone oil removal can be treated with TSCP; however, the reduction of IOP is variable. The IOP usually falls after a mean of 2-3 sittings of DLCP.47 Patients with medically uncontrolled glaucoma secondary to intravitreal silicone oil injection can also be treated with TSCPC in spite of the retained intravitreal silicone oil.48 Krypton Laser Cyclophotocoagulation The layer absorbing greatest amount of energy is the pigmented epithelium of the ciliary body analogous to the role of retinal pigment epithelium, presumably, although there has been no experimental study on absorption of laser energy by the ciliary body. A large proportion of krypton laser energy is absorbed by the pigmented epithelium and then radiate to the non-pigmented epithelium of ciliary body. Though it has a poor scleral transmission its good absorption by the pigmented epithelium makes it a potentially useful method for cyclophotocoagulation. Settings used for 300 to 500 W energy for 10 seconds using 10 spots over 90o-360o (Table 11.5). Krypton produces comparable lesions at the ciliary body in an experimental study in rabbits with half the energy required by the Nd: Table 11.5: Treatment parameters for krypton laser cyclophotocoagulation

Trans-scleral Energy Duration Number Circumference

300 to 500 W 10 seconds 10 per quadrant 90-360o

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YAG laser.60 An advantage of the method is that standard retinal krypton photocoagulators can be used for the procedure. Results of Clinical Trials Raivio VE et al61 evaluated krypton laser for trans-scleral contact cyclophotocoagulation (CPC) in the treatment of glaucoma in young patients. The treatment was delivered by means of a fiberoptic probe with compression of the sclera by the probe and followed up for 2 years. After one or more krypton CPCs, but no other glaucoma procedures, an IOP level of 8 to 21 mm Hg or a decrease in IOP of more than 30 percent was obtained in 14 of 22 (64%) eyes at the last follow-up. No permanent hypotonia, phthisis bulbi, or devastating CPC-related complications were noted. Raivio VE et al62 also evaluated the krypton laser for trans-scleral contact cyclophotocoagulation in the treatment of post-traumatic glaucoma. With one or more cyclophotocoagulation treatments, the IOP decreased from the baseline mean (+/- standard deviation) of 32.6 +/- 12.8 mm Hg to 21.8 +/- 7.5 mm Hg (n = 13) at 3 months, and to 19.6 +/- 10.5 mm Hg (n = 18) at the last control visit (mean, 19.4 months; range, 3 weeks to 73 months) after cyclophotocoagulation but no other glaucoma procedure. One (6%) case of phthisis occurred. Because of the refractory nature of the disease, repeated treatments may be needed. Di Staso S et al 63 studied the role of trans-scleral cyclophotocoagulation in neovascular glaucoma (NVG) treatment with krypton laser on 12 eyes of 12 patients. Six months after treatment, intraocular pressure was down enough for the pain to disappear.

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Endoscopic Cyclophotocoagulation (ECP) ECP is a new technique to directly photocoagulate the ciliary body under endoscopic guidance. The ciliary body can be treated directly within the eye using argon laser light delivered through a 20-gauge fiberoptic probe placed through a pars plana port. A cotton-tipped applicator is used to indent the sclera and bring the ciliary processes into view through a dilated pupil.64-67 The end of the probe is placed about 3 mm from the ciliary body. This procedure is not commonly used because it is invasive. It may have some advantages in the management of post-penetrating keratoplasty glaucoma.67-69 Newer endoscopic systems that incorporate a viewing fiberoptic as well as a laser fiberoptic are available, which permits the ciliary body to be visualized on a television screen. Endoscopic laser endocyclophotocoagulation can be performed at the time of cataract extraction. The iris is lifted with a viscoelastic material, and the anterior portions of ciliary processes are treated. It can also be done at the time of vitrectomy, for example, in a diabetic patient with neovascular glaucoma and a vitreous hemorrhage. The two main approaches to reach the ciliary process are via a limbal or pars plana entry. In limbal approach cyclophotocoagulation is done through a temporal and nasal limbal entry for nasal 180 o and temporal 180o respectively. In pars plana approach after doing a limited three port anterior vitrectomy ECP probe is introduced through each superior port for opposite ciliary process treatment.67 It can be done with argon or diode laser (Table 11.6). The success rate of endoscopic cyclophotocoagulation in various studies is listed in Table 11.7.

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Table 11.6: Treatment parameters for argon laser cyclophotocoagulation

Energy Duration Number Circumference Spot Size

Endoscopic

Transpupillary

500-1000 mW 0.1-0.2 sec 3-5 per ciliary process 180-360o Fixed 20 gauge probe

500-1000 mW 0.1-0.2 sec 3-5 per ciliary process Limited by view 50-200 um

Table 11.7: Success rates in various studies using endolaser cyclophotocoagulation

Authors

No. Follow- Success of up definition eyes (months)

Chen J et al68 68 Uram et al69 10 Gayton JL et al71 58

12.9 8.8 24

Success Retreatrate ments (%) (eyes)

21 mm Hg 90 21 mm Hg 90 19 mm Hg 65

5 0 4

Results of Clinical Trials Chen J performed endoscopic cyclophotocoagulation which encompassed 180 to 360 degrees of the ciliary body circumference in 68 eyes through a limbal incision. Ninety percent of eyes achieved an intraocular pressure < or = 21 mm Hg from a mean preoperative value of 27.7 +/- 10.3 mm Hg. Best-corrected visual acuity was stable or improved in 64 eyes (94%), with four (6%) losing 2 or more lines of Snellen acuity. No case of hypotony (intraocular pressure < 5 mm Hg) or phthisis was observed.68 Uram et al 69 treated 10 patients with intractable neovascular glaucoma by pars plana ECP to coagulate between 90 and 180 degrees of ciliary processes. With a mean follow-up of 8.8 months, the IOP was reduced from a mean preoperative level of 43.6 mm Hg to a mean of

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15.3 mm Hg postoperatively. Nine of the 10 eyes (90%) were able to achieve an IOP < 21 mm Hg, with three of those eyes requiring glaucoma medication. The only major complication encountered was hypotony in two eyes, although both had chronic retinal detachments. Uram et al 70 also described 10 patients who had combined phacoemulsification, ECP, and intraocular lens (IOL) implantation. After phacoemulsification, 180 degrees of ciliary processes were treated before insertion of the posterior chamber IOL. After a mean follow-up of 19.2 months, the mean IOP was reduced to 13.5 mm Hg from a mean preoperative IOP of 31.4 mm Hg. There were no significant complications except a transient vitreous hemorrhage that was noted on the second postoperative day. Gayton JL et al71 conducted a randomized prospective study on 58 eyes of 58 patients comparing endoscopic laser cycloablation performed through a cataract incision at the time of cataract surgery with combined trabeculectomy and cataract surgery. At the final available visit of 2-year followup, 30 percent of endoscopic laser patients achieved intraocular pressure control (below 19 mm Hg) without medication and 65 percent with medication. Forty percent of trabeculectomy patients achieved control without medication and 52 percent with medication. Neely DE et al71 retrospectively review 51 endoscopic diode laser cyclophotocoagulation procedures performed on 36 eyes of 29 pediatric patients with glaucoma over a 6year period. Whereas baseline mean pretreatment IOP was 35.06 +/- 8.55 mm Hg final postoperative IOP was 23.63 +/- 11.07 mm Hg. Nine eyes (25%) were retreated at least once. Cumulative success rate after all procedures at last follow-up was 43 percent. Aphakic patients had an increased risk of postoperative complications including

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retinal detachment in 2 patients, hypotony in 1 patient, and progression of vision loss from hand motion to no light perception in 1 patient. In postpenetrating keratoplasty glaucoma, ECP has also been shown to be an effective treatment and may have advantages over trans-scleral cyclophotocoagulation. In study by Lin SC et al 10 patients who had penetrating keratoplasties (PKPs) were treated by ECP to control their IOP.33 The IOP control rate (IOP < 22 mm Hg) was 80 percent at last follow up consisting of 30 months from the time of PKP. There were no corneal graft failures. In comparison, several studies evaluating TCP treatment of keratoplasty associated glaucoma have demonstrated a high rate of graft failure after laser.72, 73 Lima FE et al 74 compare endoscopic cyclophotocoagulation (ECP) and the Ahmed drainage implant in the treatment of refractory glaucoma. Their success rate at 24 months was 70.59 and 73.53 percent for the Ahmed and ECP groups, respectively and difference is not significant. The eyes that underwent Ahmed tube shunt implantation had more complications than those treated with ECP. One advantage of ECP is surgeon can ablate ciliary process under direct visualization which is particularly helpful in cases of severe congenital glaucoma. In congenital glaucoma because of enlargement of eyeball ciliary processes may be displaced resulting in failure of trans-scleral cyclophotocoagulation.75 Barkana Y et al76 reported a case of congenital glaucoma where IOP was effectively lowered with ECP while repeated trans-scleral DLCP failed. They showed both misplaced laser burn as well as viable ciliary process over correctly placed laser burn. The main disadvantage of ECP is that it is an intraocular procedure with the probable risks of penetrating surgeries.

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Endophthalmitis, choroidal hemorrhage, and retinal detachment though rare, but remain potential complications.32 Hence, although ECP may be a preferable surgery in cases of refractory glaucoma with relatively intact vision, it is better to avoid in eyes with very poor vision, since it would unnecessarily expose them to such potential complications. It should be done in operation theater and not an office procedure. Transvitreal Cyclophotocoagulation This method of cyclophotocoagulation is performed in conjunction with vitrectomy. Procedure is performed after direct visualization through operating microscope of ciliary processes after scleral depression. It requires a clear media and aphakia or pseudophakia. After anterior vitrectomy, endolaser is inserted through same port used for vitrectomy. After doing limited pars plana anterior vitrectomy endolaser probe is inserted through same port for ciliary ablation while ciliary process is visualized through pupil by depressing sclera.67 Argon or diode laser can be used. 64,67,77 Patel A did vitrectomy and transvitreal endophotocoagulation of the ciliary processes to treat 18 eyes with severe glaucoma. Postoperative intraocular pressure was equal to or less than 20 mm Hg in 14 of 18 eyes, although nine of the 14 successful cases required postoperative medical therapy. Treatment of more than 180 degrees was necessary for sufficient lowering of the intraocular pressure. Complications included transient vitreous hemorrhage (2 eyes), transient choroidal detachment (2 eyes), and hypotony (1 eye).64 Zarbin MA et al67 in their study of 42 eyes with severe glaucoma that could not be managed successfully by

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medical therapy and conventional glaucoma surgery did endolaser photocoagulation and followed up till 36 months (mean, 13 months). After one or two (7 eyes) treatment sessions, 11 eyes (26%) had an IOP less than 21 mm Hg without medications; 21 eyes (50%) had an IOP less than 21 mm Hg with medications; 5 eyes (12%) had an IOP of 21 to 25 mm Hg with or without medications; and 5 eyes (12%) had an IOP greater than 25 mm Hg. Twenty-three (72%) of 32 patients were able to discontinue carbonic anhydrase inhibitors. Transpupillary Cyclophotocoagulation In patients who have visible ciliary processes, it is sometimes possible to deliver argon laser energy directly to the anterior surface of the ciliary processes. Transpupillary cyclophotocoagulation is performed with a slitlamp delivery system through a Goldmann three-mirror lens.66, 78 This technique is most useful in patients with traumatic aniridia or with very large sector iridectomies. In patients with advanced neovascular glaucoma, the iris is sometimes pulled anteriorly and peripherally, allowing a view of the ciliary processes. Trans-pupillary CPC through peripheral iridectomy or widely dilated pupil can be effective in treating ciliary block glaucoma.79 The long-term pressure control achieved by treating the anterior ciliary processes is rather short. The treatment is usually performed using an argon laser with duration of 0.1 to 0.2 seconds, a spot size of 50 to 200 μm, and a starting power of about 500 mW; which is increased until a visible burn is observed. It takes three to four applications to coagulate all visible portion of a ciliary process. Results of transpupillary cyclophotocoagulation are variable. Merritt JC80 treated 7 eyes of 6 patients with

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transpupillary photocoagulation. Only one patient showed a decrease in intraocular pressure to a normal level. This patient was the only one in this series in whom large numbers of ciliary processes could be coagulated. The limiting factor in effective transpupillary argon laser photocoagulation may, therefore, be the total number of ciliary processes visualized and treated. Results of Shields S et al81 is also not promising. Out of twenty-seven patients with glaucoma who underwent transpupillary argon laser cyclophotocoagulation only six patients (22.3%) had a successful outcome, and in many cases the postoperative course was complicated by an additional, sustained increase in intraocular pressure. Lee PF78,82 in their series did cyclophotocoagulation taking pit rather than whitening of the ciliary process as end point. Fifteen out of 22 patients showed 50 percent reduction in IOP. Kim DD et al 83 reported a patient with traumatic glaucoma who underwent transpupillary argon laser cyclophotocoagulation (TALC) for management of uncontrolled intraocular pressure (IOP) despite maximally tolerated medical therapy. Ten weeks after TALC, the patient’s IOP remained controlled with medications at 16 mmHg, and visual acuity had improved to 20/25 with an aphakic contact lens. So, in selected patients whose ciliary processes are visible with indirect gonioscopy due to the defect in the iris, TALC may be an effective alternative cyclodestructive procedure to lower IOP when conventional medical or laser treatments are not successful. Overall cyclophotocoagulation is a definitive advancement over previous modes of cilioablation. However, it is an unpredictable procedure with a narrow therapeutic window, and not reproducible. One should, thus, be careful while doing this procedure.

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POSTOPERATIVE MANAGEMENT These procedures unlike cyclocryotherapy are less painful. • At the end of the procedure, subconjunctival corticosteroids are usually administered and patching done for approximately 6 hours. • The patient should be placed on topical cycloplegics, antibiotics and corticosteroids, which are tapered as the inflammation subsides. • Preoperative antiglaucoma medications, glaucoma medications are continued until the effect of the procedure can be determined. The cholinergic drugs are avoided. • Sometimes very strong analgesic is required and at times one may have to use narcotic analgesics. • Follow up at 1 hr., 1 day, 1 week, 1 month and then according to the response. • Additional therapy should be considered if needed after one month.84 Interventions include drainage device, trabeculectomy, cyclocryotherapy and enucleation. COMPLICATIONS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Marked pain Mild to severe iritis, synechiae and pupillary block Transient rise of IOP Hypotony Phthisis bulbi Conjunctival surface burn Lens and zonular damage Reduced accommodation Posterior capsule fibrosis in pseudophakia Pupillary distortion Corneal graft failure Scleral thinning and staphyloma

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13. Malignant glaucoma 14. Macular edema 15. Retinal detachment 16. Serous and hemorrhagic choroidal detachment 17. Intraocular hemorrhage 18. Best corrected vision loss 19. Sympathetic ophthalmia 20. Endophthalmitis and panophthalmitis 21. Treatment failure Cyclodestructive procedures share similar risks, but they vary in degree of risk. The most troubling and common complication of these procedures is a decrease in visual acuity. This can result from a variety of causes, including hypotony, macular edema, and cataract. Due to risk of vision loss makes, cyclodesrtuctive procedures are a last resort in patients with good vision. Less intense laser therapy on a repeated basis rather than a single high dose treatment is suggested to minimize complications of treatment. Schuman et al3 in their study of 116 eyes treated by contact Nd:YAG TCP, had 19 eyes (16%) that progressed to NLP and 17 of 36 eyes (47%) having 20/200 or better vision lost 2 or more Snellen lines. In addition, nine out of 116 eyes (8%) developed hypotony (IOP of 3 mm Hg or less). Many of these hypotonous eyes were also considered to be phthisical. In Jennings’s85 series complications included anterior uveitis (42%), conjunctival injection (36%), pain (30%), and conjunctival hemorrhage (15%). Corneal edema, intraocular pressure spikes, and corneal epithelial defects were each noted in 9 percent of the eyes treated, whereas cataracts developed in 12 percent of the eyes. Two out of 33 eyes (6%) developed anterior segment ischemia with subsequent phthisis bulbi. Seven out of 33 eyes (21%) demonstrated no adverse reactions.

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Destroying the correct amount of the ciliary body is not a precise procedure. In eyes with minimal aqueous outflow, a small change in aqueous production can cause marked changes in lOP. If too much ciliary function is destroyed, the patient can develop hypotony (and perhaps phthisis). The risk of hypotony varies among studies, but it appears to be higher with cyclocryotherapy than with laser procedures. The risk of phthisis increases with each procedure performed. The cyclodestructive procedures lead to increase in inflammation especially with cyclocryotherapy. Laser procedures generally cause less inflammation. Eyes will often experience chronic aqueous flare after these procedures because of a breakdown in the blood-aqueous barrier. Pain is a significant feature of cyclocryotherapy. A decrease in pain is the single most obvious advantage of laser procedures over cyclocryotherapy. Hyphema is also a common side effect in patients with neovascular glaucoma. Pressure spikes during and after cyclocryotherapy are also common. The postoperative rise in lOP peaks at about 6 hours. Surface burns occur with non-contact laser procedures and they can occur with contact lasers if debris is present on the end of the fiberoptic because the debris can absorb the laser energy and heat up. There have been several published reports of sympathetic ophthalmia (SO) following TSCPC.86-88 Lam et al reported that the incidence of SO at their institution was 5.8 percent (four of 69) and 0.67 percent (one of 150) after non-contact and contact Nd:YAG cyclophotocoagulation, respectively.87 Bechrakis et al have reported a case of sympathetic ophthalmia after 20 months of treatment with 3 sessions of contact Nd:YAG laser. Cyclophotocoagulation and 1 session of cyclocryotherapy

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in a case of secondary glaucoma with Coat’s disease without any previous history of penetrating trauma or surgery, confirmed by classical histopathology of SO, thickening of choroid by lymphocytic infiltration with OKT3 positive mature T cells and Dalen-Fuchs nodules. Disintegration of uveal tissue seems to trigger a cellular immune response against uveal autoantigen possibly by release of high energy in a small spot, results in an explosion like reaction. Also postulated that these eyes being endstage glaucomatous may itself be a risk factor for developing SO.88 Malignant glaucoma has been reported both after diode laser TCP87,89 and after contact and noncontact Nd:YAG cyclophotocoagulation.90,91 A case of panophthalmitis has also been reported after contact diode laser cyclophotocoagulation in a patient with failed trabeculectomy and trabeculotomy for congenital glaucoma.92 About 3 to 5 percent of the power of laser reaches posterior pole as shown by a study by Jonathan et al. Noncontact Nd:YAG cyclophotocoagulation had significantly higher transmission compared to contact Nd:YAG and diode lasers. Exposure energies may approach or exceed ACGIH (American Conference of Governmental Industrial Hygienists) guidelines. Clinical significance of such exposure however is still not proven. It does not prove to be a source of visual loss in any patient. 93 Pupillary distortion has also been described after DLCP due to injury to peripheral iris caused by anterior displacement of laser spots. 94 Administration of 100 J with a Nd:YAG laser increases corneal touch threshold and causes a significant decrease in number, but not diameter, of major corneal nerve bundles. Nerve damage and corneal hypoesthesia are

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etiologic factors in ulcerative keratitis following Nd:YAG cyclophotocoagulation.95 Results of the preliminary study by Raivio VE et al96 suggest that cyclophotocoagulation with the 670-nm diode laser does not impair corneal innervation. CONCLUSIONS The concept of cycloablation has been present for several decades, but the inability to titrate a predictable and reproducible response has been its drawback. However, Cyclodestructive procedures still plays an important role in our paradigm of glaucoma therapy, since it is the last resort treatments for intractable glaucomas in eyes with poor or no visual potential. Cyclocryotherapy was the most commonly used method previously but it has now been replaced by laser cyclophotocoagulation, which causes less pain and is associated with less inflammation, hypotony, and phthisis. This is because of their frequent complications and unpredictable degree of pressure lowering. Experience with Nd:YAG or diode endolaser cyclophotocoagulation holds promise for these and other patients because it appears to provide good results and lesser side effects. Trans-scleral diode cyclophotocoagulation with G-probe is the procedure of choice and most generally used laser procedure because it is noninvasive and does not require a clear cornea or widely dilated pupil. Additional experience will better define the indications and scope of these newer modalities of cycloablation. REFERENCES 1. 2.

Bietti G. Surgical intervention on the ciliary body; new trends for the relief of glaucoma. JAMA 1950;142:889-97. Meyer SJ. Diathermy cauterization of ciliary body for glaucoma. Am J Ophthalmol 1948;31:1504-7.

188 3. 4.

5. 6. 7. 8. 9. 10. 11. 12.

13. 14. 15. 16.

Step by Step Minimally Invasive Glaucoma Surgery

Walton DS, Grant WM. Penetrating cyclodiathermy for filtration. Arch Ophthalmol. 1970;83:47-8. Haik GM, Breffeilh LA, Barbar A. Bete irradiation as a possible therapeutic agent in glaucoma : an experimental study with report of a clinical case. Am J Ophthalmol. 1948;31:945. Berens C, Sheppard LB, Duel AB Jr. Cycloelectrolysis for glaucoma. Trans Am Ophthalmol Soc. 1949;47:364. DeRoeth A Jr. Cryosugery for the treatment of advanced simple glaucoma. Am J Ophthalmol 1968;66: 1034-41. Bellows AR, Grant WM. Cryotherapy in advanced inadequately controlled glaucoma. Am J Ophthalmol 1973;75:679-84. Caprioli J, Strang SL, Spaeth GL, et al. Cyclocryotherapy in treatment of advanced glaucoma. Ophthalmology 1985;92:947-53. Bellows AR, Grant WM. Cyclocryotherapy of chronic openangle glaucoma in aphakic eyes. Am J Ophthalmol 1978;85:615-21. Polack PJ, et al. Histologic effects of contact ultrasound for the treatment of glaucoma. Invest Ophthalmol Vis Sci. 1991;32:2136-42. Finger PT, et al. Trans-scleral microwave cyclodestruction. Invest Ophthalmol Vis Sci. 1990;31:2151-55. Beckman H, Kinoshita A, Rata An, et al. Transscleral ruby laser irradiation of the ciliary body in the treatment of intractable glaucoma. Trans Am Acad Ophthalmol Otol 1972;76:423-36. Beckman H, Sugar HS. Neodymium laser cyclocoagulation. Arch Ophthalmol 1973;90:27-8. Shields MB. Cyclodestructive surgery for glaucoma: past, present, and future. Trans Am Acad Ophthalmol Otolaryngol 1985;83:285-303. Mastrobattista JM, Luntz M. Ciliary body ablation: where are we and how did we get here? Surv Ophthalmol 1996;41:193-213. Caprioli J, et al. Cyclocryotherapy in the treatment of advanced glaucoma, Ophthalmology 1985;92:947-54.

Cyclophotocoagulation

17. 18. 19.

20.

21.

22. 23.

24. 25. 26.

27.

189

van der Zypen E, et al. The effects of trans-scleral laser cyclophotocoagulation on rabbit ciliary body vascularization. Graefes Arch Clin Exp Ophthalmol 1989;227:172. Cantor LB, et al. Neodymium-YAG trans-scleral cyclophotocoagulation/ The role of pigment. Invest Ophthalmol Vis Sci. 1989;30:1834-37. Schubert HD, Federman JL. A comparison of CW Nd:YAG contact transscleral cyclophotocoagulation with cyclocryopexy. Invest Ophthalmol Vis Sci. 1989 Mar;30(3): 536-42. Schubert HD, Agarwala A, Arbizo V. Changes in aqueous outflow after in vitro neodymium: yttrium aluminum garnet laser cyclophotocoagulation. Invest Ophthalmol Vis Sci. 1990 Sep;31(9):1834-8. Liu GJ, Mizukawa A, Okisaka S. Mechanism of intraocular pressure decrease after contact transscleral continuouswave Nd:YAG laser cyclophotocoagulation. Ophthalmic Res. 1994;26(2):65-79. Stewart WC. Clinical practice of glaucoma.1990, Slack. Alward WLM. Laser cyclophotocoagulation. In Weingeist TA, Sneed SR (Eds): Laser Surgery in Ophthalmology: Practical Applications. East Norwalk, Conn., Appleton and Lange, 1992. Schuman JS, et al. Contact transscleral continuous wave Nd:YAG laser cyclophotocoaguIation, Ophthalmology 1990;97:571-80. Wilensky JT, Welch D, Mirolovich M. Transscleral cyclophotocoagulation using a Nd:YAG laser, Ophthalmic Surg 1985;16:95-98. Shields MB, Shields SE. Noncontact transscleral Nd:YAG cyclophotocoagulation: a long-term follow-up of 500 patients. Trans Am Ophthalmol Soc. 1994;92:271-83; discussion 283-7. Lin P, Wollstein G, Glavas IP, et al. Contact transscleral neodymium:yttrium-aluminum-garnet laser cyclophotocoagulation Long-term outcome. Ophthalmology 2004 Nov;111(11):2137-43.

190 28.

29.

30.

31. 32.

33. 34.

35.

36.

37.

Step by Step Minimally Invasive Glaucoma Surgery

Phelan MJ, Higginbotham EJ. Contact transscleral Nd:YAG laser cyclophotocoagulation for the treatment of refractory pediatric glaucoma. Ophthalmic Surg Lasers 1995 SepOct;26(5):401-3. Delgado MF, Dickens CJ, Iwach AG, et al. Long-term results of noncontact neodymium:yttrium-aluminumgarnet cyclophotocoagulation in neovascular glaucoma. Ophthalmology 2003 May;110(5):895-9. Beiran I, Rootman DS, Trope GE, et al. Long-term results of transscleral Nd:YAG cyclophotocoagulation for refractory glaucoma postpenetrating keratoplasty. J Glaucoma. 2000 Jun;9(3):268-72. Schuman JS, Bellows AR, Shingleton BJ, et al. Contact transscleral Nd:YAG laser cyclophotocoagulation: midterm results. Ophthalmology 1992;99:1089–95. Schuman JS, Puliafito CA, Allingham RR, et al. Contact transscleral continuous wave neodymium:YAG laser cyclophotocoagulation. Ophthalmology 1990 May;97(5): 571-80. Miyazaki M, Hoya T. Effects of trans-scleral Nd:YAG laser cyclophotocoagulation: research for a new manner of treatment. Ophthalmologica 1994;208:122-30. Hampton C, Chields M B, Miller KN, et al. Evaluation of a protocol for trans-scleral neodymium :YAG cyclophotocoagulation in one hundred patients. Ophthalmology. 1990;97:910-17. Brancato R, Giovanni L, Trabucchi G, et al. Contact transscleral cyclophotocoagulation with Nd:YAG laser in uncontrolled glaucoma. Ophthalmic Surg 1989 Aug;20(8): 547-51. Klapper RM, Wandel T, Donnenfeld E, et al. Transscleral neodymium:YAG thermal cyclophotocoagulation in refractory glaucoma. A preliminary report. Ophthalmology 1988 Jun;95(6):719-22. Hennis HL, Stewart WC: Semiconductor diode laser transscleral cyclophotocoagulation in patients with glaucoma, Am J Ophthalmol 1992;13:81-85.

Cyclophotocoagulation

38. 39.

40.

41.

42.

43.

44. 45.

46.

47.

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Barasch K, Galin MA, Baras I. Postcyclodialysis hypotony. Am J Ophthalmol 1967;68:644-48. Agarwal HC, Gupta V, Sihota R. Evaluation of contact versus non-contact diode laser cyclophotocoagulation for refractory glaucomas using similar energy settings. Clin Experiment Ophthalmol 2004 Feb;32(1):33-8. Lai JS, Tham CC, Chan JC, et al. Diode laser trans-scleral cyclophotocoagulation in the treatment of chronic angleclosure glaucoma: a preliminary study. J Glaucoma. 2003 Aug;12(4):360-4. Murphy CC, Burnett CA, Spry PG, et al. A two centre study of the dose-response relation for trans-scleral diode laser cyclophotocoagulation in refractory glaucoma. Br J Ophthalmol 2003 Oct;87(10):1252-7. Kramp K, Vick HP, Guthoff R. Trans-scleral diode laser contact cyclophotocoagulation in the treatment of different glaucomas, also as primary surgery. Graefes Arch Clin Exp Ophthalmol 2002 Sep;240(9):698-703. Schlote T, Derse M, Rassmann K, et al. Efficacy and safety of contact transscleral diode laser cyclophotocoagulation for advanced glaucoma. J Glaucoma 2001 Aug;10(4):294301. Kirwan JF, Shah P, Khaw PT. Diode laser cyclophotocoagulation: role in the management of refractory pediatric glaucomas. Ophthalmology 2002 Feb;109(2):316-23. Schlote T, Derse M, Zierhut M. Transscleral diode laser cyclophotocoagulation for the treatment of refractory glaucoma secondary to inflammatory eye diseases. Br J Ophthalmol 2000 Sep;84(9):999-1003. Semchyshyn TM, Tsai JC, Joos KM. Supplemental transscleral diode laser cyclophotocoagulation after aqueous shunt placement in refractory glaucoma. Ophthalmology 2002 Jun;109(6):1078-84. Kumar A, Dada T, Singh RP, et al. Diode laser trans-scleral cyclophotocoagulation for glaucoma following silicone oil removal. Clin Experiment Ophthalmol 2001 Aug;29(4): 2204.

192 48.

49.

50.

51. 52. 53. 54.

55.

56.

57.

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Han SK, Park KH, Kim DM, et al. Effect of diode laser transscleral cyclophotocoagulation in the management of glaucoma after intravitreal silicone oil injection for complicated retinal detachments. Br J Ophthalmol 1999 Jun;83(6):713-7. Kosoko O, Gaasterland DE, Pollack IP, Enger CL. Longterm outcome of initial ciliary ablation with contact diode laser trans-scleral cyclophotocoagulation for severe glaucoma. The Diode Laser Ciliary Ablation Study Group. Ophthalmology 1996 Aug;103(8):1294-302. Bloom PA, Tsai JC, Sharma K, Miller MH, Rice NS, Hitchings RA, Khaw PT. “Cyclodiode”. Trans-scleral diode laser cyclophotocoagulation in the treatment of advanced refractory glaucoma. Ophthalmology 1997 Sep;104(9): 1508-19. Spencer AF, Vernon SA. “Cyclodiode”: results of a standard protocol. Br J Ophthalmol 1999 Mar;83(3):311-6. Werner A, Vick HP, Guthoff R. [Cyclophotocoagulation with the diode laser. Study of long-term results] Ophthalmologe 1998 Mar;95(3):176-80. Pucci V, Tappainer F, Borin S, et al. Long-term follow-up after transscleral diode laser photocoagulation in refractory glaucoma. Ophthalmologica 2003 Jul-Aug;217(4):279-83. Noureddin BN, Zein W, Haddad C, Ma’luf R, Bashshur Z. Diode laser transcleral cyclophotocoagulation for refractory glaucoma: a 1-year follow-up of patients treated using an aggressive protocol. Eye 2005 Apr 29. Ocakoglu O, Arslan OS, Kayiran A. Diode laser transscleral cyclophotocoagulation for the treatment of refractory glaucoma after penetrating keratoplasty. Curr Eye Res 2005 Jul;30(7):569-74. Gupta V, Agarwal HC. Contact trans-scleral diode laser cyclophotocoagulation treatment for refractory glaucomas in the Indian population. Indian J Ophthalmol 2000 Dec;48(4):295-300. Levinger E, Segev E, Geyer O. Diode laser cyclophotocoagulation in refractory glaucoma. Harefuah 2003 Jul;142(7):500-2, 568, 567.

Cyclophotocoagulation

58. 59.

60.

61.

62.

63.

64. 65. 66. 67. 68.

193

Mistlberger A, Liebmann JM, Tschiderer H, et al. Diode laser transscleral cyclophotocoagulation for refractory glaucoma. J Glaucoma 2001 Aug;10(4):288-93. Gupta V, Agarwal HC. Contact trans-scleral diode laser cyclophotocoagulation treatment for refractory glaucomas in the Indian population. Indian J Ophthalmol 2000 Dec;48(4):295-300. Kivela T, Puska P, Raitta C, et al. Clinically successful contact transscleral krypton laser cyclophotocoagulation. Long-term histopathologic and immunohistochemical autopsy findings. Arch Ophthalmol 1995 Nov;113(11): 1447-53. Raivio VE, Immonen IJ, Puska PM. Transscleral contact krypton laser cyclophotocoagulation for treatment of glaucoma in children and young adults. Ophthalmology 2001 Oct;108(10):1801-7. Raivio VE, Immonen IJ, Laatikainen LT, et al. Transscleral contact krypton laser cyclophotocoagulation for treatment of posttraumatic glaucoma. J Glaucoma 2001 Apr;10(2):7784. Di Staso S, Genitti G, Verolino M, et al. Trans-scleral krypton laser cyclophotocoagulation: our experience of its use on patients with neovascular glaucoma. Acta Ophthalmol Scand Suppl. 1997;(224):37-8. Patel A, Thompson JT, Michels RG, et al. Endolaser treatment of the ciliary body for uncontrolled glaucoma, Ophthalmology 1986;93:825-30. Lin S. Endoscopic cyclophotocoagulation. Br J Ophthalmol. 2002 Dec;86(12):1434-8. Review. Holz HA, Lim MC. Glaucoma lasers: a review of the newer techniques. Curr Opin Ophthalmol 2005 Apr;16(2):89-93. Review. Zarbin MA, Michels RG, de Bustros S, et al. Endolaser treatment of the ciliary body for severe glaucoma. Ophthalmology 1988 Dec;95(12):1639-48. Chen J, Cohn RA, Lin SC, et al. Endoscopic photocoagulation of the ciliary body for treatment of refractory glaucomas. Am J Ophthalmol 1997 Dec;124(6):787-96.

194 69. 70.

71. 72.

73.

74.

75. 76. 77.

78.

Step by Step Minimally Invasive Glaucoma Surgery

Uram M. Ophthalmic laser microendoscope ciliary process ablation in the management of neovascular glaucoma. Ophthalmology 1992;99:1823–8. Uram M. Combined phacoemulsification, endoscopic ciliary process photocoagulation, and intraocular lens implantation in glaucoma management. Ophthalmic Surg 1995;26:346–52. Neely DE, Plager DA. Endocyclophotocoagulation for management of difficult pediatric glaucomas. J AAPOS. 2001 Aug;5(4):221-9. Cohen EJ, Schwartz LW, Luskind RD, et al. Neodymium: YAG laser transscleral cyclophotocoagulation for glaucoma after penetrating keratoplasty. Ophthalmic Surg 1989;20: 713–16. Threlkeld AB, Shields MB. Noncontact transscleral Nd:YAG cyclophotocoagulation for glaucoma after penetrating keratoplasty. Am J Ophthalmol 1995;120:569– 76. Lima FE, Magacho L, Carvalho DM, et al. A prospective, comparative study between endoscopic cyclophotocoagulation and the Ahmed drainage implant in refractory glaucoma. J Glaucoma 2004 Jun;13(3):233-7. Bechrakis NE, Müller-Stolzenurg NW, Helbig, et al. Sympathetic ophthalmia following laser cyclophotocoagulation. Arch Ophthalmol 1994;112:80–4. Mora JS, Iwach AG, Gaffney MM, et al. Endoscopic diode laser cyclophotocoagulation with a limbal approach. Ophthalmic Surg Lasers 1997 Feb;28(2):118-23. Lim JI, Lynn M, Capone A Jr, et al. Ciliary body endophotocoagulation during pars plana vitrectomy in eyes with vitreoretinal disorders and concomitant uncontrolled glaucoma. Ophthalmology 1996 Jul; 103(7): 1041-6. Lee P-F. Argon laser photocoagulation of the ciliary processes in cases of aphakic glaucoma, Arch Ophthalmol 1979;97:21352138.

Cyclophotocoagulation

79. 80. 81. 82. 83. 84. 85. 86. 87.

88. 89. 90. 91.

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Herschler J. Laser shrinkage of the ciliary process. A treatment for malignant (ciliary block) glaucoma. Ophthalmology 1980;87:1155-9. Merritt JC. Transpupillary photocoagulation of the ciliary processes. Ann Ophthalmol 1976 Mar;8(3):325-8. Shields S, Stewart WC, Shields MB. Transpupillary argon laser cyclophotocoagulation in the treatment of glaucoma. Ophthalmic Surg 1988 Mar;19(3):171-5. Lee PF, Shihab Z, Eberle M. Partial ciliary process laser photocoagulation in the management of glaucoma. Lasers Surg Med 1980;1(1):85-92. Kim DD, Moster MR. Transpupillary argon laser cyclophotocoagulation in the treatment of traumatic glaucoma. J Glaucoma 1999 Oct;8(5):340-1. Schuman JS, Puliafito CA. Laser cyclophotocoagulation. Int Ophthalmol Clin 1990;30:111-9. Jennings BJ, Mathews DE. Complications of neodymium: YAG cyclophotocoagulation in the treatment of open-angle glaucoma. Optom Vis Sci. 1999 Oct;76(10):686-91. Edward DP, Brown SVL, Higginbothom E, et al. Sympathetic ophthalmia following neodymium:YAG cyclotherapy. Ophthalmic Surg 1989;20:544–6. Lam S. Tessler HH, Lam BL, et al. High incidence of sympathetic ophthalmia after contact and noncontact neodymium:YAG cyclotherapy. Ophthalmology 1992;99: 1818–22. Bechrakis NE, Müller-Stolzenurg NW, Helbig, et al. Sympathetic ophthalmia following laser cyclophotocoagulation. Arch Ophthalmol 1994;112:80–4. Azuara Blanco A, Dua HS. Malignant glaucoma after diode laser cyclophotocoagulation. Am J Ophthalmol 1999;127: 467-69. Harden DR, Brown JD. Malignant glaucoma after Nd:YAG cyclophotocoagulation. Am J Ophthalmol 1991;111:245-47. Wand M, Schuman JS, Pulinfito CA, et al. Malignant glaucoma after contact trans-scleral Nd:YAG laser cyclophotocoagulation. J Glaucoma 1993;2:110-111.

196 92.

93. 94. 95.

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Venkatesh P, Gogoi M, Sihota R, et al. Panophthalmitis following contact diode laser cyclophotocoagulation in a patient with failed trabeculectomy and trabeculotomy for congenital glaucoma. Br J Ophthalmol 2003;87(4):508. Jonathan S Myers, M G trevisani, N Imami, et al. Laser reaching posterior pole during Transscleral cyclophotocoagulation. Arch Ophthalmol 1998;116:488-91. Torsten schlote, M Derse, H J Thiel et al. Pupillary distortion after transscleral Diode laser cyclophotocoagulation. Br J Ophthalmol 2000;84:337-38. Weigt AK, Herring IP, Marfurt CF, et al. Effects of cyclophotocoagulation with a neodymium:yttriumaluminum-garnet laser on corneal sensitivity, intraocular pressure, aqueous tear production, and corneal nerve morphology in eyes of dogs. Am J Vet Res. 2002 Jun;63(6): 906-15. Raivio VE, Vesaluoma MH, Tervo TM, et al. Corneal innervation, corneal mechanical sensitivity, and tear fluid secretion after transscleral contact 670-nm diode laser cyclophotocoagulation. J Glaucoma 2002 Oct;11(5):446-53.

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INTRODUCTION Trabeculectomy has been the operation of choice for glaucoma since its introduction in 1961 and as a fullthickness operation it had its complications. Guarded filtration procedures were developed to reduce these risks such as hypotony, and infections. 1-3 In the standard trabeculectomy, as reported by Cairns, the trabecular block is excised anterior to the scleral spur or alternatively from the posterior side as proposed by Watson.2 The success rate of trabeculectomy is influenced by several factors including patient’s characteristics, type of glaucoma and wound healing processes. Other important factors that might reduce the success of this surgery include tissue scarring, anterior segment neovascularization, active uveitis, aphakia, previous ocular surgery and chronic conjunctival inflammation.1-5 Over the past 10 years new modalities in glaucoma surgery have been introduced as possible alternatives to trabeculectomy. Krasnov and Zimmerman have identified those procedures into deep scleretomy and viscocanalostomy. 3 The non-penetrating glaucoma surgeries aim to allow drainage of the aqueous humor by slow percolation through the inner trabecular meshwork and/or Descemet membrane (trabeculo-descemetic membrane) rather than through a patent scleral opening, as in standard trabeculectomy. This avoids sudden reductions in IOP, hypotony and flat chambers. Performing such a non-penetrating glaucoma surgeries has great advantages are the absence of anterior chamber opening and iridectomy, the facts that limit the risk of cataract and infection.6-9 In the past 10 years new non-penetrating modalities in glaucoma surgery were introduced as

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possible alternatives to Trabeculectomy. Krasnov and Zimmerman have proposed these procedures as deep sclerotomy and viscocanalostomy.3 The non-penetrating glaucoma surgeries aim to allow drainage of the aqueous humor by slow percolation through the inner trabecular meshwork and/or trabeculo-descemetic membrane rather than a patent trabeculoscleral opening, as in standard trabeculectomy. This avoids sudden reductions in IOP, hypotony and flat chambers. Non-penetrating glaucoma procedures have important potential advantages mainly the absence of anterior chamber opening and iridectomy, the fact that limits the risk of cataract and infection.6-9 One of the important targets while performing trabeculectomy or non-penetrating glaucoma surgeries is to minimize the stimulation of fibroblast proliferation that might reduce the success rate of the procedure. The cutting, spreading, and tearing of tissue should be kept to a minimum. In addition, the surgeon should strive to keep the incisions linear, rather than multilaminate, to maintain as small and localized incisional scars as possible.9-11 Milling trabeculoplasty is considered a variation of deep sclerectomy with more refining. The technique of milling trabeculoplasty provides the opportunity to perform a nonpenetrating glaucoma surgery with greater attention for the dissection of the deep scleral flap or the deroofing of the Schlemm´s canal with the addition advantage that is being much faster.12 INDICATIONS Eyes with primary open angle glaucoma are the best candidates for the milling surgery. However, all indications of deep sclerectomy are cases of milling procedure.

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PATIENT PREPARATION Preoperative Examination Before surgery, each patient had manifest refraction, slitlamp biomicroscopy with measurement of IOP by using Goldman tonometry, gonioscopy and computerized perimetry. Preoperative Medications Medications included Ciprofloxacin 0.3 percent eye drops 3 times/day for a week. The topical antiglaucoma therapy was stopped 3 days before the surgery. Anesthesia Peribulbar anesthesia in the form of combination of 8 ml of 0.75 percent Bupivacaine and 2 percent Lidocaine was injected. Intravenous sedation was used when necessary. A light compression with the Honnan balloon was applied 15 minutes prior to surgery for 5 minutes to insure diffusion of the anesthetic agent. MILLING SURGICAL PROCEDURE Instruments Milling drill (Katena Inc, Denville, NJ USA) is the main instrument necessary to perform this procedure. The mode of action of the drill is similar to that used to burr the nasal bone in dacryocystorhinostomy (DCR) surgery or that used to polish the bed after removing corneal foreign bodies. The drill used in our milling procedure is handheld 150 mg weight equipment and made of autoclaveble material (Fig. 12.1). Following the concept of refined tissue

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Fig. 12.1: Milling drill with the tips used in the surgery of milling

removal would decrease the rate of postoperative fibrosis, a high frequency and velocity motorized drill tip could be able to polish (no cutting method) the remaining scleral thickness with minimal tearing and smaller more localized scars at the end of the procedure. The high speed Milling drill (6000 RPM) allows easy (Fig. 12.2), quick and more controlled refining of the remaining scleral thickness by using sharp-metallic tip first to refine the sclera and later on as the tissue became thinner another notched hemispherical metallic tip was used to polish and not cut the remaining scleral thickness (Fig. 12.3). A new tip covered with diamond powder is also needed for more delicate maneuvers as removing debris making the technique ideal to have an extremely smooth bed (Fig. 12.4). In both groups, the procedure started as the initial steps of deep sclerotomy13 then the specific steps of milling surgery were continued. In Group II, the milling procedure is carried out until Schlemm’s canal is identified. Thereafter, phaco is performed (through a separate clear corneal incision) and after the IOL was implanted, the milling procedure was finished.

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Fig. 12.2: The drill held with the tip unassembled just before the surgery

Fig. 12.3: Milling set of metallic tips. The set includes tips for cutting, other for refining

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Fig. 12.4: The notched hemispherical metallic tips to polish but not cut the remaining scleral thickness

Surgical Steps 1. The eyelids are sterilized with ophthalmic Betadine solution (Purdue Frederick, Norwalk, CT), and after the sterile drape was placed, a lid speculum was inserted. 2. An 8-mm fornix-based conjunctival flap is prepared superiorly and Tenon’s capsule was retracted. Bipolar cautery is then applied sparingly to cauterize individual limbal vessels one by one to achieve homeostasis preserving as much as possible the episcleral vessel. 3. A superficial scleral flap of 4 × 4 mm hinged at the limbus was designed using ultra sharp mini blade such as the No. 7511 Beaver, extending 1 mm into the clear cornea (Fig. 12.5A). The thickness of the flap should be between 200 and 250 microns. The incision

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Fig. 12.5A: Fashioning of the scleral flap size and site

should be made definitively, without multiple tentative strokes (Fig. 12.5B). The edge of the scleral flap was then grasped with Hoskins forceps and gently retracted. The scleral dissection is carried out using a crescent-style blade extending the lamellar dissection anterior tell the blue limbal zone then more anteriorly until 1 or 2 mm of a clear cornea is reached and the iris details can be seen through the deep layers of corneal tissue (Figs 12.5C to E). 4. Under high magnification, a rectangular dry area of the scleral bed about 3 × 3 mm inside the superficially created flap is selected to start milling and the milling motorized drill was applied without pressure allowing to drill and refine the remaining scleral thickness in a linear pattern to leave a thin layer of sclera underneath (Fig. 12.6). The site of milling

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Fig. 12.5B: The scleral incision as being completed

Fig. 12.5C: Beginning of the lamellar dissection

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Fig. 12.5D: Lamellar dissection of the scleral flap

Fig. 12.5E: Completion of the lamellar dissection

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should be applied at the surgical limbus in order to expose the canal of Schlemm. The refining is carried anteriorly and downwards until the blue-gray color of the choroid should appear through the residual scleral fibers (Fig. 12.7). When reaching the appropriate depth, the canal openings are identified by passing a hook through them (Figs 12.8A and B). 5. The process of “Unroofing” of the canal is automatically done using the motorized milling drill but care should be taken not to apply any pressure (maintaining the high velocity) and leave the drill to refine the tissues. After being unroofed, the inner wall of Schlemm’s canal appears as a dark line, just anterior to the scleral spur. The milling is continued anteriorly towards the cornea to remove the sclero-

Fig. 12.6: The scleral bed refined and grazed using the milling motorized drill in dry field through the remaining scleral thickness in a linear pattern to leave a thin layer of sclera below and a width of 3.5 mm

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Fig. 12.7: The refining is carried anteriorly and down until the roof of Schlemm´s canal can barely be visible

corneal trabecular meshwork (TM), which typically exhibits a granular texture. If phacoemulsification is combined with the procedure, the superficial corneal flap is reposted and a clear-corneal incision is prepared then the phaco is performed. After the phaco has been completed the milling is carried out anteriorly and 1-2 mm of Descement´s membrane is exposed by milling anterior to the canal till clearcorneal tissue is reached and iris details could be identified though the remaining thin sheet of TM. Another alternative to create the descemtic window is using a mini-blade starting with down-up incision at one of the two opening of the canal then with a shaving movement a block of tissue is excised moving towards the other opening of the canal (Figs 12.9A to C).

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Figs 12.8A and B: A hook is passed through the opening of the canal to insure adequate level of dissection and milling

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Figs 12.9A and B

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Figs 12.9A to C: Deroofing of Schlemm’s canal is done: a. 2 incisions are created at both sides starting from the opened Schlemm canal and anteriorly tell reaching the clear corneal under the flap b. The site of incision is checked again and repeated on the other side c. The roof of the canal is removed using the surgical knife

6. At this stage of the procedure, aqueous humor should be seen percolating through the trabeculo-descemetic membrane. If still there is reduced outflow, stripping the inner wall of Schlemm´s canal was done (Fig. 12.10) to increase aqueous outflow and then further milling is carried out to smoothen the surface (Fig. 12.11). Ultimately, only the trabeculo-descemetic membrane remains intact. Visible filtration of aqueous through the thin trabeculo-descemetic membrane should be obtained. Dilatation of Schlemm´s canal could be also done by inserting a cannula into the canal for 0.5 or 1 mm.

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Fig. 12.10: Stripping of the floor of the canal is done if insufficient filtration is found

Fig. 12.11: Refining the descement window is done using the drill and the milling is done applying no pressure

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7. In case of glaucoma implant the implant should be inserted at this level of the surgery and sutures to sclera as in conventional deep sclerectomy.14 8. The flap is gently laid in its normal anatomic position (Fig. 12.12). Two 10-0 nylon stitches were placed at both edges of the superficial flap and tied fairly (not very tight and not very loose). The suture ends were cut and the knots were parried to prevent the suture tips from eroding the conjunctiva. After closing the scleral flap repositioning of the conjunctiva was then done with 2 lateral 10/0 nylon stitches (Figs 12.13 to 12.15).

Fig. 12.12: The scleral flap is reposted at the end of the surgery

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Fig. 12.13: Slit-lamp photo of the postoperative bleb obtained at 6-months in group I

Fig. 12.14: Slit-lamp photo of the postoperative bleb obtained at 6-months in group II (Phaco-milling)

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Fig. 12.15: The diffuse filtering bleb as appeared at the end of the 6th month in group II

POSTOPERATIVE FOLLOW-UP Treatment Antibiotic-steroidal combination; Tobradex® (Lab Alcon Cusi, Inc. Barcelona. Spain) eyedrops were instilled postoperatively 4 times daily for 1 week and slowly withdrawn over one month period. No viscoelastics was injected into the Schlemm canal, and the procedure was completed without the use of collagen device or mitomycin C at any stage of the surgery in our series. Follow-up Patients were scheduled for follow-up visits at 1 day, 1 week then 1, 3 and 6 months after surgery. The postoperative evaluation included the IOP, presence of

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functioning bleb, gonioscopy, visual acuity status and possible surgical and postoperative complications. RESULTS The study performed by the authors included 41 eyes (41 patients). The mean age of the patients was 67.9 ± 10.9 (range 50 to 80) years. The preoperative diagnoses had confirmed that all eyes have medically uncontrolled primary open-angle glaucoma. The mean preoperative cup/disk ratio was 0.7 ± 0.25. The mean angle grading as reported by gonioscopic findings was 3.6 ± 0.61 according to shaffer grading system. The eyes were divided into 2 groups: group I (20 eyes) underwent milling procedure and group II (21 eyes) underwent combined procedure, milling and phacoemulsification procedures. In both groups, the milling procedure was done without the use of collagen device or MMC. The other eye of each patient was operated by conventional deep sclerectomy and combined phaco and deep sclerectomy and their results are behind the scope of this chapter. The past medical history of the patients included hypertension in 36 percent patients, and one patient had history of diabetes mellitus. Among the eyes included in the study, 23.7 percent had history of cataract extraction and IOL implantation, 7.2 percent had history of previous glaucoma surgery (deep sclerectomy). Preoperative history of anti-glaucoma therapy is shown in Figures 12.16A and B. The study included 16 eyes (10 right and 6 left) of 13 patients. The mean age of the patients was 67.9 ± 10.9 (range 50 to 80) years. The patients included female, and 8 male. All eyes were diagnosed as having primary open angle glaucoma medically uncontrolled. Only one eye 1/16

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Fig. 12.16: Graph showing the percent of preoperative combination of antiglaucoma treatment in (A) Group I and (B) Group II

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(6.25%) had a previous unsuccessful glaucoma surgery (deep sclerectomy). The data of the 6th month postoperative visits are available for 100 percent of the eyes, and those for the 1st year follow up visits are available only for 37.5 percent of the eyes. Group I (Milling Procedure) Visual results and refractive results of this group: refer to Table 12.1. Intraocular pressure (IOP) and its results during the study are shown in Table 12.2. Figure 12.17 shows the IOP results of both groups during the follow-up period of the study. Table 12.1: Shows the results of group I, milling trabeculoplasty Group I: Milling trabeculoplasty

Range Standard Maxi- Minierror mum mum

N

Mean ± SD

20

0.828 ± 0.279 0.025 ± 0.648 -0.675 ± 1.067 -0.313 ± 0.512 0.725 ± 0.786

0.0624 0.145 0.239 0.115 0.176

1 1.5 0 0.5 2.500

0.05 -1.5 -4 -1.5 0.000

Post-op BCVA refraction Sphere at 1M Cylinder SE Defocus equivalent

20

0.792 ± 0.258 -0.025 ± 0.858 -0.0875 ± 2.507 -0.069 ± 1.302 0.713 ± 0.762

0.0578 0.192 0.561 0.291 0.170

1 1.25 10 4.5 2.500

0.05 -2 -3 -2.25 0.000

Post-op BCVA refraction Sphere at 6M Cylinder SE Defocus equivalent

20

0.835 ± 0.262 0.1 ± 0.357 -0.713 ± 0.964 -0.257 ± 0.336 0.625 ± 0.750

0.0587 0.0799 0.216 0.0752 0.168

1 1 0 0.13 3.000

0.05 -0.5 -4 -1 0.000

Pre-op refraction BCVA Sphere Cylinder SE Defocus equivalent

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Table 12.2: Shows the results of IOP in group I, milling trabeculoplasty Variable

N Mean ± SD

Initial IOP Basal IOP Objective IOP IOP at 1m Reduction IOP at 1m % Reduction IOP at 1m IOP at 1m Reduction IOP at 6m % Reduction IOP at 6m

20 20 20 20 20 20 20 20 20

Range Standard Maxi- Minierror mum mum

23.9 ± 7.166 32.640 ± 7.151 20.650 ± 3.99 12.65 ± 4.945 -7.994± 5.853 47.205 ± 15.039 14.45 ± 3.379 -6.200± 4.148 36.821 ± 17.252

1.602 1.599 0.894 1.106 1.309 3.282 0.756 0.928 3.765

50 50.0 26.60 22 6.50 88.89 24 1.5 64

Fig. 12.17: Graph showing the IOP changes during the follow-up period in both groups

16 22.0 14.4 2 -15.95 19.23 10 -14.6 -5.26

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Group II (Milling Procedure combined with Phaco) Visual results and refractive results of this group: refer to Table 12.3. Intraocular pressure (IOP) and its results during the study are shown in Table 12.4. Figure 12.17 shows the IOP results of both groups during the follow-up period of the study. DISCUSSION Non-penetrating glaucoma surgeries including viscocanalostomy and deep sclerectomy are difficult to perform, need a high learning curve and time consuming. In both non-penetrating glaucoma surgeries and milling Table 12.3: Shows the results of group II, milling trabeculoplasty plus phacoemulsification at the same session Group II: Milling+ Phaco

Range Standard Maxi- Minierror mum mum

N

Mean ± SD

Pre-op BCVA refraction Sphere Cylinder SE Defocus equivalent

21

0.298 ± 0.217 -2.821 ± 5.946 -1.012 ± 1.1 -3.328 ± 6.17 4.024 ± 6.339

0.0473 1.298 0.24 1.346 1.383

0.8 2.5 0.5 1.25 19.000

0.01 -16 -3.25 -17.5 0.000

Post-op BCVA refraction Sphere at 1m Cylinder SE Defocus equivalent

21

0.571 ± 0.313 -0.464 ± 1.004 -1.179 ± 1.151 -1.055 ± 1.247

0.0682 0.219 0.251 0.272

1 1.5 0 0.5

0.01 -2.5 -4.5 -4.75

1.714 ± 1.603

0.350

7.000

0.000

Post-op BCVA refraction Sphere at 6m Cylinder SE Defocus equivalent

21

0.636 ± 0.304 -0.238 ± 0.835 -1.19 ± 0.898 -0.835 ± 0.867 1.524 ± 1.006

0.0663 0.182 0.196 0.189 0.220

1 1.5 0 0.5 4.500

0.05 -1.5 -3 -3 0.000

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Table 12.4: Shows the results of IOP in group II, milling trabeculoplasty plus phacoemulsification at the same session Variable

N Mean ± SD

Initial IOP Basal IOP Objective IOP IOP at 1 m Reduction IOP at 1 m % Reduction IOP at 1 m IOP at 1 m Reduction IOP at 6 m % Reduction IOP at 6 m

21 21 21 21 21 21 21 21 21

Range Standard Maxi- Minierror mum mum

22.952 ± 7.619 33.310 ± 14.487 23.319± 10.154 15.762 ± 5.761 -7.546± 9.047 25.906 ± 28.22 15.19 ± 3.473 -8.11± 8.607 27.91 ± 26.897

1.663 3.161 2.216 1.257 1.974 6.017 0.758 1.878 5.734

42 65.1 25.2 38 6.9 56.67 23 6.9 56

10 13.0 6 10 -27.9 -60 10 -24.8 -60

surgery, both the postoperative recovery and follow-up are faster and the level of IOP reduction achieved is satisfactory when compared with the results of trabeculectomy. Milling trabeculoplasty in this prospective, pilot study on 41 eyes has shown good results as it led to a 30-40 percent reduction of IOP in both groups operated with the technique. The percent of success of surgery at the 6th month without the use of collagen device or MMC was 60 percent for group I and 80 percent for group II (Fig. 12.18). The rate of postoperative bleb fibrosis and the use of postoperative anti-glaucoma therapy was found to be similar to that found with deep sclerectomy. The followings are the potential advantages of the Milling trabecuoloplasty over the non-penetrating glaucoma surgeries: 1. Facilitate the surgical procedure of non- penetrating technique as the refining is carried anteriorly and down until the roof of Schlemm´s canal can barely be visible. Unlike deep non-penetrating sclerectomy,

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Fig. 12.18: Graph showing the percent of success of milling surgery and milling-phaco after 65 months, the percent of eyes that had to use topical treatment and eyes that had to go back to treatment as the target pressure was not reached

2.

3. 4. 5. 6.

this technique does not require any specific accuracy in the dissection of the deep sclera. To reduce the wound healing as a determinate factor for the IOP outcome as the diamond powder tip is available for more delicate maneuvers like removing debris, making the technique ideal and leaving an extremely smooth bed. Offers less complications than deep sclerectomy and it prevents the “double-cut” sclera and hazards. The economic coast of the drill. Saves time as this technique has an easier approach to the trabeculo-descemetic membrane. No need for the use of high expensive surgical set.

CONCLUSION Milling trabecuoloplasty is an evolving technique for easy scalpel-free non-penetrating glaucoma surgery. The milling

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surgery seems to be a promising technique for surgical management of POAG glaucoma. Milling trabeculoplasty is a fast, safe, effective technique to perform nonpenetrating glaucoma surgery low coast and simple instruments. Milling trabeculoplasty is a potential alternative to deep sclerectomy providing comparable results to conventional deep sclerectomy mainly the low level of IOP together with minimal intra- and postoperative complications. REFERENCES 1.

2.

3.

4. 5. 6. 7.

Carassa RG. Non-penetrating surgery. In: Weinreb RN, Kitazawa Y, Krieglstein GK (Eds): Glaucoma in the 21st Century. Philadelphia: Harcourt Health Communications, 2000;249-56. Watson PG, Grierson I. Early trabeculectomy in the treatment of chronic open-angle glaucoma in relation to histological changes. In Zimmerman TJ, Monica ML (Eds): Controversies in Glaucoma. Int Ophthalmol Clin 1984;24: 13-32. Zimmerman TJ, Kooner KS, Ford VJ, et al. Trabeculectomy vs. non- penetrating trabeculectomy: a retrospective study of two procedures in phakic patients with glaucoma. Ophthalmic Surg 1984;15:734-40. Mermoud A. La sclerectomie profonde. Technique chirurgicale. [Deep sclerectomy: surgical technique]. J-FrOphthalmol 1999;22:781-6. Bas JM, Goethals MJ. Non-penetrating deep sclerectomy preliminary results. Bull-Soc-Belge-Ophthalmol. 1999;272: 55-9. Carassa RG, Bettin-P, Fiori-M, Brancato-R. Viscocanalostomy: a pilot study. Eur J Ophthalmol 1998;8:57-61. Hara T; Hara T. Deep sclerectomy with trabeculotomy ab externo: one-stage procedure Ophthalmic Surg 1989;20: 406-9.

224 8.

9.

10.

11.

12. 13. 14.

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Demailly P, Lavat P, Kretz G, Jeanteur-Lunel-MN. Nonpenetrating deep sclerectomy (NPDS) with or without collagen device (CD) in primary open-angle glaucoma: middle-term retrospective study. Int-Ophthalmol 199697;20:131-40. Demailly P, Jeanteur-Lunel MN, Berkani M, Ecoffet-M, Kopel-J, Kretz-G, Lavat-P. La sclerectomie profonde nonperforante associee a la pose d’un implant de collagene dans le glaucome primitif a angle ouvert. Resultats retrospectifs a moyen terme. [(Non-penetrating deep sclerectomy combined with a collagen implant in primary open-angle glaucoma. Medium-term retrospective results). J.- Fr.- Ophtalmol 1996;19:659-66. Chiou AG, Mermoud A, Hediguer SE, Schnyder CC, Faggioni R. Ultrasound biomicroscopy of eyes undergoing deep sclerectomy with collagen implant. Br-J-Ophthalmol 1996;80:541-4. Tixier J, Dureau P, Becquet F, Dufier JL. Sclerectomie profonde dans le glaucome congenital. Resultats preliminaries. [Deep sclerectomy in congenital glaucoma. Preliminary results).]. J-Fr-Ophtalmol 1999;22:545-8. Rodriguez-Prats JL, Alio JL, Galal A. Milling trabeculoplasty for non-penetrating glaucoma surgery. J Cataract Refract Surg 2004;30:1507-16. Goldsmith JA, Ahmed IK, Crandall AS. Non-penetrating glaucoma surgery. Ophthalmol Clin North Am 2005;18: 443-60. Dahan E. Long-term results of deep sclerectomy with collagen implant. J Cataract Refract Surg. 2005;31:868-9.

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INTRODUCTION Surgery for primary open-angle glaucoma is usually a ‘last resort’ option. Today we exercise this option less frequently, thanks to better medications that have not only a pressure lowering effect but also neuro-protective properties. When there is a need for surgery, it implies that medical management alone is not sufficient in controlling the disease process. One would expect that the surgical procedure, therefore, would deliver the goods each time, every time, for keeps. Unfortunately, surgical outcomes do not always match the need of the hour. Glaucoma surgery is known to fail over a period and trabeculectomy, once the gold standard, is now known to stop draining as time progresses (Fig. 13.1). The chief culprit is fibrosis between the scleral bed and the flap that shuts down the drainage corridor.

Fig. 13.1: Trabeculectomy

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NATURE’S DRAINAGE CHANNELS Surgery for glaucoma is nothing but our attempt at duplicating nature’s process artificially. However, it does not always work out quite the way we intend it to. Let us, therefore, take a fresh look at nature’s drainage channels from the eye. Most of our focus these long years has been limited to structures within the anterior chamber, mainly the trabecular meshwork. We generally tend to ignore the fact that from the trabecular meshwork onward, fluid is gathered up by aqueous veins, which connect to the episcleral vasculature (Fig. 13.2). At no point is the aqueous allowed to flow naked and openly. However, during all our surgical procedures we do exactly that – let the aqueous drain out uncovered by a sheath. Have we, even for a moment, considered the deleterious effects of such an event? Do we pause to deliberate on a cause-and-effect relationship between a bare unsheathed drainage and fibrosis induced failure?

Fig. 13.2: Nature’s enclosed drainage channels

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ENSURE SURGICAL SUCCESS The only way to ensure continuous drainage is to mimic nature as closely as possible, i.e. by providing covered or sheathed outflow from the eye. An early attempt in this direction was made with the introduction of the Ahmed glaucoma valve (Fig. 13.3). It was, however, destined to fail, as it relied on the creation of an external drainage lake, which eventually filled up. Molteno designed an ‘extension’ lake by having two plates. This merely delayed the inevitable pressure equalization that resulted in ‘no-flow’. While the concept of sheathed outflow was brilliant, the setting up of an artificial lake was flawed. I attempted to rectify this flaw by directing the aqueous outflow into the potential supra-choroidal space. HISTORY OF THE PROCEDURE In 2001, I used a non-valvular silicon shunt to carry fluid directly from the anterior chamber to the supra-choroidal space (Fig. 13.4A). This drainage device, in its initial avatar, consisted of a simple small-bore silicon tube that had sharp tapered ends. After creating a scleral flap, an opening was made into the supra-choroid 3-4 mm from the limbus. The

Fig. 13.3: Ahmed glaucoma valve

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tube was anchored to the scleral bed by a 10-0 nylon suture and one end was introduced into the supra-choroid. It was then flushed with an insulin syringe containing Ringer’s, to open up the potential supra-choroidal space and ‘charge’ the device. This ‘charging’ served to remove any air pocket and permit a smooth capillary flow when this tube was made to puncture the anterior chamber next (Fig. 13.4B). Flap suture completed the procedure. The procedure worked well in terms of IOP control over time. The only disadvantage was that one had to open the anterior chamber. Then came along deep sclerectomy. DEEP SCLERECTOMY WITH T-FLUX IMPLANT As the procedure is well documented, I shall not attempt to reinvent the wheel. I shall reiterate, however, that this procedure offers several advantages over trabeculectomy. a. A proper and diligent technique ensures an adequate outflow. b. There is an inherent safety in not opening the anterior chamber. c. The T-flux implant, being a non-absorbable biocompatible acrylic polymer, helps to maintain a permanent intra-scleral space (Fig. 13.5A). This is achieved by anchoring it to the scleral bed with a single suture (Fig. 13.5B). d. It stabilizes the trabeculo-Descemet’s membrane and in case of micro punctures and prevents iris herniation. THE FLIP SIDE There is no denying the fact that deep sclerectomy is technically difficult. It has a steep learning curve. In the initial stages one often lands up converting to conventional trabeculectomy. It is no secret that this surgery places a

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Figs 13.4A and B: Non-valvular shunt

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Fig. 13.5A: T-flux

Fig. 13.5B: T-flux in scleral bed

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great demand on surgical skill, which can be mitigated to some extant only by expensive diamond blades! The data on long-term results is often conflicting, at best equivocal. Given these constraints, why would one want to take up this procedure, that to with modifications? DEEP SCLERECTOMY WITH T-FLUX IMPLANT WITH SUPRA-CHOROIDAL DRAINAGE The plain and simple answer is that DS with T-flux with supra-choroidal drainage is the surgery of the future. With the introduction of the T-flux implant one merely enhances the outcomes of a well done deep sclerectomy; however, with the added dimension of supra-choroidal drainage one virtually ensures perpetual outflow. The key step in this procedure is to make an aperture in the sclera, (Figs 13.6A to C) 2-3 mm from the limbus, up to the supra-choroid and insert the foot of the T-flux into this potential space. Being about 0.2 mm thick, it glides in easily (Figs 13.7A and B).

Fig. 13.6A: Deep sclerectomy

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Figs 13.6B and C: Supra-choroidal entry

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Figs 13.7A and B: Inserting foot of T-flux in supra-choroidal

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In one procedure it combines: a. Safety — One does not need to open the anterior chamber. b. Efficacy — Performed painstakingly, the procedure offers adequate drainage. c. Sheltered drainage — One can largely circumvent the deleterious effects of naked outflow by placing the Tflux upside down, thus providing a roof over outflow. There is also little chance of prolonged sclero-aqueous contact to induce any degree of significant fibrosis. d. Continuous drainage — By inserting the foot of the Tflux into the supra-choroid, one creates a channel along which fluid passively tracks down. Nature does the rest (Fig. 13.8). This is perhaps the only surgery that can ensure perpetual drainage, by utilizing the inherent vascularity of the choroid and its ability to absorb and return fluid to the general circulation. There is thus, no fear of closure of the ‘external lake’ as with the AGV and Molteno designs.

Fig. 13.8: T-flux with supra-choroidal lake

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During the period 2001-2002, I had an occasion to perform this procedure on five eyes in three patients. All patients also had significant cataract, necessitating combined surgery. All patients followed up regularly as advised, on weekly, monthly, quarterly and annual basis for three and a half years. Patient 1 (2 eyes) passed away 42 months after surgery, while patients 2 and 3 continue their annual follow-up. The mean preoperative IOP fell from a value of 28 to 13 mm at 1 month, stabilizing at 15 mm at end of 1 year, 17 mm at end of 2 years, and 18 mm at end of 3 years, 6 months (Fig. 13.9). During his period field remained stable without any topical therapy (Fig. 13.10).

Fig. 13.9: Postoperative IOP

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Fig. 13.10: Fields

My colleague, Dr Deepak Bhatt, performed ultrasound biomicroscopy (UBM) in late 2004, and documented patent passages from the intrascleral space up to the suprachoroid (Figs 13.11A and B). He was also able to trace the outline of the T-flux implant all the way down to the suprachoroid, thus providing anatomical corroboration to the clinico-physiological findings and lend credence to my theoretical musings (Fig. 13.13B) ( I am deeply grateful to him for the same). THE SURGICAL PROCEDURE There are essentially four parts to the surgical procedure: a. Deep sclerectomy; b. Placing and anchoring of the T-flux implant; c. Fashioning of the scleral aperture and

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Figs 13.11A and B: UBM at 1 year

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d. Inserting the foot of the implant in to the suprachoroidal space. 1. I generally prefer a peri-bulbar block. 2. A superior rectus bridle suture follows. 3. A standard fornix-based conjunctival flap is then dissected. 4. The scleral flap has to be a minimum of 5 × 5 mm (Figs 13.12A and B) with 1/3rd depth. 5. Within this flap, another 4 × 4 mm scleral pocket is dissected (Fig. 13.13). 6. Deep sclerectomy is then performed (Figs 13.14A and B). 7. Next, side pockets are made above the level of the deep sclerectomy in order to accommodate and embed the arms of the T-flux implant (Figs 13.15A and B).

Fig. 13.12A: Caliper

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Fig. 13.12B: Flap dissection

Fig. 13.13: Scleral pocket

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Figs 13.14A and B: Deep sclerectomy

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Figs 13.15A and B: Side pocket

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8. An opening is made into the sclera about 2 to 3 mm from the limbus. This is tunneled backwards, away from the limbus (Figs 13.16A and B).

Figs 13.16A and B: Supra-choroidal aperture

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9. The T-flux implant is sutured upside down onto the scleral bed (Fig. 13.17). 10. The arms embedded into the side pockets. 11. The next crucial step is to push the foot plate of the T-flux into the supra-choroidal space with the help of a spatula (Fig. 13.18). 12. All flaps are sutured. Postoperative regime consists of steroid antibiotic drops 3-4 times a day for 2 weeks. Follow-up visit protocol is as under: Next day, 1 week, 2 weeks, 1 month, 3 months (Repeat UBM), 6 months, 1 year, bi-annually thereafter.

Fig. 13.17: Suturing T-flux

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Fig. 13.18: Inserting foot of T-flux into supra-choroidal space

CONCLUSION The concept of supra-choroidal drainage is sound in theory. It also works in practice. In all the above cases, I have used an existing device (the T-flux implant, Figs 13.19A and B) to provide a roof over the filtering aqueous. It is very well suited for this surgery. However, cost is a major limiting factor, both for the patient and the surgeon. I am currently working on an indigenous design which will serve the same purpose at an affordable cost.

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Figs 13.19A and B: T-flux at 1 year

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INTRODUCTION In the last years non-penetrating glaucoma surgery achieved great interest as a possible alternative to trabeculectomy. This class of procedures are mainly represented by “deep sclerectomy” and by “viscocanalostomy” (which was introduced by R Stegmann in the early nineties), and are based on the original studies by Krasnov1 and by Zimmerman 2 on “non-penetrating trabeculectomy”. Similarly, both procedures are aimed at allowing drainage of the aqueous humor from the anterior chamber not through a patent scleral opening, but by slow percolation through the inner trabecular meshwork and/ or Descemet’s membrane (“sclerodescemetic membrane”). This avoids sudden IOP drops, hypotonies and flat chambers. The absence of anterior chamber opening and iridectomy limits the risk of cataract and infection. Compared to deep sclerectomy, viscocanalostomy is a step forward. In fact this procedure is aimed not only at taking the advantages of being non-penetrating, as deep sclerectomy, but, most important, in restoring the physiological outflow pathway, thus avoiding any external filtration. This would make the success of the procedure independent of conjunctival or episcleral scarring, leading cause of failure in trabeculectomy, with less indications for wound healing modulation. Moreover, the absence of the filtering bleb avoids related ocular discomfort, and the procedure can be carried out in any quadrant. MECHANISM OF ACTION Viscocanalostomy increases the aqueous outflow through different mechanism of action. It creates a by-pass by which aqueous humor can reach Schlemm’s canal skipping the

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trabecular meshwork, which is the site of the increased outflow resistance in open-angle glaucoma. This is obtained by producing a “chamber” inside the sclera which directly communicates both with Schlemm’s canal and with the anterior chamber through the “sclerodescemetic membrane”. The aqueous enters the “chamber” by percolating through the membrane, and leaves it via Schlemm’s canal. A recent experimental study on monkeys also showed the evidence of micro-openings throughout the wall of Schlemm’s canal over 360 degrees which may be invoved in the increased aqueous facility.3 Finally, as in deep-sclerectomy, aqueous humor can also leave the intrascleral chamber through the subconjunctival space and through the supra-coroidal space by uveoscleral absorption. SURGICAL TECHNIQUE In order to simplify the technique, a specific surgical set, composed by a 0.5 mm diamond knife, a 1 mm round steel bevel-up blade, and a 165 μm blunt needle to cannulate Schlemm’s canal (Grieshaber, Switzerland) should be used. Viscocanalostomy is performed under retrobulbar or peribulbar anesthesia and usually requires 25 to 40 minutes depending on bleeding control. In fact, in order to avoid damage to outflow channels (Schlemm’s canal, aqueous veins, collector channels, etc.), wetfield cautery is used as little as possible, and bleeding is reduced by frequent irrigation of the surgical area with vasoconstrictive solutions as ornipressin. To provide optimal visualization of the surgical site, a bridle suture should be passed either on the superior rectus or in clear cornea. The surgical technique can be divided in 9 steps:

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Conjunctival Flap Dissection Viscocanalostomy does not require any specific accuracy in the dissection of the conjunctival flap, and can be performed in any quadrant, although the upper and temporal ones are most commonly chosen. The surgical field is prepared by creating a fornix-based conjunctival flap, using as little wetfield cautery as possible. Outer Scleral Flap Dissection A 5 × 5 mm parabolic cut approximately 200 μm deep, is made using the diamond knife (the incision can be outlined using a calibrated diamond knife to assure a constant depth of cut). After reaching the correct plane of cut the flap is dissected anteriorly in clear cornea by advancing the incision with the bevel-up spatula which allows easier following of the plane. Inner Scleral Flap Dissection A 4 × 4 mm parabolic cut parallel to the outer incision is made beneath the outer flap. The choroidal plane must be almost reached, and this is revealed by the observation of a dark reflex at the bottom of the cut. Using the specific beaveled spatula a precise dissection is advanced until Schlemm’s canal is reached and deroofed leaving two patent openings on the lateral edges of the cut. In order to mantain the same plane of dissection and provide sharp lateral edges, progressive deepening of the lateral cuts is often needed (Fig. 14.1). Paracentesis A paracentesis should be always made in order to decrease intraocular pressure, to make incannulation of Schlemm’s

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Fig. 14.1: Dissection of the internal flap

canal easier and to reduce bulging of Descemet’s membrane during its cleavage from the corneal stroma, which is at high risk of tear formation. To avoid external pressure on the eye, the traction on the bridle suture should also be removed. Cannulation of Schlemm’s Canal (Figs 14.2 and 14.3) Using the specific 165 mm cannula, high molecular weight sodium hyaluronate is slowly injected into Schlemm’s canal by cannulating the two ostia at the lateral edges of the inner flap. To avoid damage to the canal endothelium, the insertion of the cannula should not exceed 1-1.5 mm from the ostia. The injection of viscoelastic substance allows progressive atraumatic dilatation of Schlemm’s canal up to 1-2 clock hours from the ostia. Moreover its hemostatic properties avoid bleeding and fibrin clot formation, thus limiting healing processes and scarring of Schlemm’s canal

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Fig. 14.2: Opening of Schlemm’s canal

Fig. 14.3: Injection of high molecular weight sodium hyaluronate into Schlemm’s canal

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openings. The slow injection should be repeated 6-7 times on each side (Fig. 14.4). Creation of Descemet’s Window The alternative route by which aqueous humor bypasses the trabecular meshwork and reaches Schlemm’s canal is a “window” created right anterior to the canal, and represented by the anterior portion of the trabecular meshwork and by the intact Descemet’s membrane. The window is realized by gently pulling the inner scleral flap upwards and delicately depressing the floor of the canal and Descemet’s membrane with the tip of a cotton swab. By delicately repeating the procedure, the membrane is progressively cleaved from the scleral flap. The flap itself

Fig. 14.4: Showing sclerodescemetic membrane and the two openings of Schlemm’s canal (Arrows)

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is then advanced in clear cornea for approximately 1 mm by a careful deepening of the lateral cuts with the round bevel-up spatula. Inner Scleral Flap Excision The inner scleral flap is then excided using very sharp Vannas’ scissors in order to avoid damage to Descemet’s membrane. Outer Scleral Flap Suture In order to seal the intrascleral “chamber”, the outer scleral flap should be tightly sutured by placing 6 or 7 10-0 nylon stitches. The step created by the different size of the two flaps allows a better and tight apposition of the external flap. Finally, in order to minimize bleeding and prevents collapsing and scarring of the intrascleral chamber, high molecular weight sodium hyaluronate is injected underneath the flap. Closure of the Conjunctiva The procedure ends by repositioning the conjunctiva with two lateral stitches, and by giving a subconjunctival injection of steroids-antibiotics. INDICATIONS Viscocanalostomy has specific indications and contraindications. It cannot be effective when the angle is closed or neovascularized, or when Schlemm’s canal is likely to be damaged. This is the case of previously operated eyes where an extensive cautery of the perilimbar area was made. Due to its final results the procedure is indicated in primary open-angle glaucoma when target IOP is not very

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low (as indicated by the Guidelines for Glaucoma of the European Glaucoma Society). The advantage of the absence (or very reduced) external filtration make the technique safe and particularly indicated in eyes with chronic blepharitis, in lens contact wearer, or when the surgery has to be perform in the lateral or inferior quadrants. Viscocanalostomy was shown effective also in uveitic glaucomas with well controlled inflammation.4,5 RESULTS Viscocanalostomy seems effective in lowering IOP with a good safety profile. It has low complications, an easy postoperative management and is inducing significant less eye discomfort than trabeculectomy, as could be expected considering the absence of the filtering bleb in the majority of the cases. When compared with trabeculectomy many of the studies lack to find significant differences between the procedures; nevertheless final IOPs seem higher after viscocanalostomy when compared with trabeculectomy. A direct comparison between different studies is difficult because criteria for success, length of follow-up and techniques are different. These can be grouped in retrospective, prospective and randomized controlled trials. Retrospective Studies Stegmann and co-workers 6 reported results of viscocanalostomy in 214 eyes of 157 African patients with open-angle glaucoma and a mean preoperative IOP of 47.4 ± 13.0 mmHg. After an average follow-up of 35 months, mean IOP was 16.9 ± 8.0 mmHg; 83 percent of eyes achieved an IOP less than 22 mmHg off all glaucoma medications.

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Two recent studies showed viscocanalostomy a successful procedure in glaucoma secondary to uveitis. Miserocchi et al4 found a complete and qualified success rate of 54.5 percent and 90.9 percent respectively, after 46 months of follow-up. Final IOP was 18.1+/-11.6 mmHg.(41) Auer et al5 after performed NPGDS (including viscocanalostomy) on 14 eyes: complete and qualified success rate were 45.4 and 90.4 percent at 12 months. Final IOP was 12.1+/-4.0.(42) Prospective Studies Carassa et al7 reported a series of 23 VCs performed in 23 patients. In four eyes, the procedure was converted to trabeculectomy. Of the 16 eyes with IOP less than 21 mmHg, mean IOP was 11.6 ± 4.4 mmHg. Sunaric-Mégevand et al8 evaluated the procedure in 67 eyes of 67 consecutive patients with chronic open-angle glaucoma. Complete success was an IOP =<20 mmHg with 30 percent or greater IOP reduction without ongoing medical or additional surgical treatment. Qualified success was an IOP =<20 mm Hg with further treatment or an IOP reduction less than 30 percent from preoperative level. The overall success rate was 88 percent at 1 year, 90 percent at 2 years and 88 percent at 3 years. The complete success rate was 68 percent at 1 year, 60 percent at 2 years and 59 percent at 3 years. No serious complications were reported in this series. Luke et al9 when comparing viscocanalostomy with and without a SKGel implant showed a success rate (IOP<22 mmHg without medications) of 40 percent in both groups at 12 months, with a very low complication rate. Shaarawy et al10 in a 5-year-follow-up study, showed a final IOP of 13.9 mmHg and a complete success rate with

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IOP <21mmHg in 60 percent of the eyes. Goniopuncture was performed in 37 percent of the cases. Randomized Controlled Studies Jonescu-Cuipers et al11 in 2001, showed at 6 months, a complete success rate (IOP <20 mmHg) of 0 percent after viscocanalostomy and 50 percent after trabeculectomy on 20 eyes. The same group in 2002,12 showed an IOP <22 mmHg without medications in 30 percent with VC and 56.7 after trabeculectomy group at 1 year on 60 patients. Viscocanalostomy showed significant less complications compared with trabeculectomy. O’Brart et al13 showed a 1 year success rate (IOP <21mmHg on no medications) of 60 percent after viscocanalostomy and of 91 percent after trabeculectomy. In a 24 months controlled randomized trial comparing viscocanalostomy with trabeculectomy, Carassa et al,14 reported similar final IOP levels of 14.1 ± 4.7 mm Hg after viscocanalostomy and 16.3 ± 5.1 mmHg after trabeculectomy. No significant difference was found between the 2 procedure as for IOP < 21 mmHg (76 versus 80%) or < 16 (56 versus 72%) on no medications. A recent study by Yalvac et al.15 on 50 eyes followed for 36 months found similar results. At 3 years, the mean IOP was 17.8 +/- 4.6 mmHg in the viscocanalostomy group and 16.0 mmHg +/- 7.07 in the trabeculectomy group (P=.694). Complete success (IOP 6 to 21 mm Hg without medication) was achieved in 35.3 percent after viscocanalostomy and 55.1 percent after trabeculectomy (P>.05). Postoperative hypotony and cataract formation occurred more frequently in the trabeculectomy than in the viscocanalostomy group (P=.002).

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O’Brart et al. 16 in a 20 months RCT comparing viscocanalostomy with trabeculectomy with adjunctive use of antimetabolites on 50 eyes, found a significantly lower complete success rate (IOP<21 mmHg) after viscocanalostomy (34%) than after trabeculectomy (68%). Early transient complications such as anterior chamber shallowing and encysted blebs were more common in the trabeculectomy group (p<0.05). Late postoperative cataract formation was similar between the two groups. CONCLUSIONS Viscocanalostomy seems a promising surgery for lowering IOP in glaucomatous eyes. It has several potential advantages over trabeculectomy, the major being the absence of external filtration and thus the independence of conjunctival and episcleral scarring. When considering final IOPs between 16 and 21 mmHg, the rate of failure over time is similar between the 2 procedures. The procedure is affected by few and minor complications, it requires an easy postoperative management and induces significant less eye discomfort than trabeculectomy. Viscocanalostomy is nevertheless technically demanding and requires a long learning curve. Results from basic researches aimed at defining the exact mechanism of action will certainly provide improvements in the surgical technique and more appropriate indications. REFERENCES 1. 2.

Krasnov MM. Sinusotomy: Foundations, results, prospects. Trans Am Ophthalmol Otolarygol 1972;76:369-74. Zimmerman TJ, Kooner KS, Ford VJ, Olander KW, Mandlekorn RM, Rawlings EF, Leader BJ, Koskan AJ.

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6. 7. 8. 9.

10. 11.

12.

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Trabeculectomy vs non-penetrating trabeculectomy: A retrospective study of two procedures in phakic patients with glaucoma. Ophthalmic Surg 1984;15:734-40. Tamm ER, Carassa RG, Albert DM, Gabelt BT, Patel S, Rasmussen CA, Kaufman PL. Viscocanalostomy in Rhesus Monkeys. Arch Ophthalmol 2004;122:1826-38. Miserocchi E, Carassa RG, Bettin P, Brancato R. Viscocanalostomy in patients with uveitis: A preliminary report. J Cataract and Refr Surg 2004;30:566-70. Auer C, Mermoud A, Herbort CP. Deep sclerectomy for the management of uncontrolled uveitic glaucoma: Preliminary data. Klin Monatsbl Augenheilkd 2004;221: 339-42. Stegmann R, Pienaar A, Miller D. Viscocanalostomy for open-angle glaucoma in black african patients. J Cataract Refract Surg 1999;25:316-22. Carassa R, Bettin P, Fiori M, Brancato R. Viscocanalostomy: a pilot study. Eur J Ophthalmol 1998;8:57-61. Sunaric-Mégevand G, Leuenberger P. Results of viscocanalostomy for primary open Angle glaucoma. Am J Ophthalmol 2001;132:221-28. Luke C, Dietlein TS, Jacobi PC, Konen W, Krieglstein GK. A prospective randomised trial of viscocanalostomy with and without implantation of a reticulated hyaluronic acid implant (SKGEL) in open-angle glaucoma. Br J Ophthalmol 2003;87:599-603. Shaarawy T, Nguyen C, Schnyder C, Mermoud A. Five year results of viscocanalostomy. Br J Ophthalmol 2003;87:441-45. Jonescu-Cuipers C, Jacobi P, Konen W, Krieglstein G. Primary viscocanalostomy versus trabeculectomy in white patients with open-angle glaucoma: A randomized clinical trial. Ophthalmology 2001;108:254-58. Luke C, Dietlein TS, Jacobi PC, Konen W, Krieglstein GK. A Prospective Randomized Trial of Viscocanalostomy versus Trabeculectomy in Open-angle Glaucoma: A 1 year Follow-up Study. J Glaucoma 2002;11:294-99.

260 13.

14.

15.

16.

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O’Brart DSP, Rowlands E, Islam N, Noury AMS. A randomised, prospective study comparing trabeculectomy augmented with antimetabolites with a viscocanalostomy technique for the management of open-angle glaucoma uncontrolled by medical therapy. Br J Ophthalmol 2002;86:748-54. Carassa RG, Bettin P, Fiori M, Brancato R. Viscocanalostomy versus trabeculectomy in white adults affected by open-angle glaucoma: A 2 years randomized, controlled trial. Ophthalmology 2003;110:882-87. Yalvac IS, Sahin M, Eksioglu U, Midillioglu IK, Aslan BS, Duman S. Primary viscocanalostomy versus trabeculectomy for primary open-angle glaucoma: Three-years prospective randomized clinical trial. J Cataract Refract Surg 2004;30:2050-57. O’Brart DP, Shiew M, Edmunds B. A randomised, prospective study comparing trabeculectomy with viscocanalostomy with adjunctive antimetabolite usage for the management of open-angle glaucoma uncontrolled by medical therapy. Br J Ophthalmol. 2004;88:1012-17.

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INTRODUCTION Currently, glaucoma is defined as a disturbance of the structural or functional integrity of the optic nerve that causes characteristic atrophic changes in the optic nerve, which may also lead to specific visual field defects over time. This disturbance usually can be arrested or diminished by adequate lowering of intraocular pressure (IOP). The generic term glaucoma should only be used in reference to the entire group of glaucomatous disorders as a whole, because multiple subsets of glaucomatous disease exist. People who maintain elevated pressures in the absence of nerve damage or visual field loss exist. They are considered at risk for glaucoma and have been termed glaucoma suspects or ocular hypertensives. POAG is a major worldwide health concern, because of its usually silent, progressive nature, and because it is one of the leading preventable causes of blindness in the world. With appropriate screening and treatment, glaucoma usually can be identified and its progress arrested before significant effects on vision occur. Following keratomileusis in situ and lamellar keratectomy in 1990, the author detected a decrease in the IOP of some patients. At first it was thought that this IOP dropping was due to modification of radial curvature or thickness of the cornea. Later it was supposed that suction was the lowering pressure mechanism, so in 1995 the application of the suction ring was started in a group of ocular hypertensive patients with no eye surgery antecedents. Intraocular pressure was measurably lower in a significant number of cases. This has also been seen in laser-assisted in situ keratomileusis (LASIK). It has been proposed that the decrease in IOP may be a real event.

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The mechanism may well involve stretching of the zonule which stretching produces some form of change in the trabecular meshwork either physiologically through chemical mediators, or through a mechanical opening of the trabecular pores. Pneumatic trabeculoplasty (PNT) is a noninvasive treatment, performed in an ophthalmologist office, which has been demonstrated to reduce the intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG), pigmentary glaucoma and ocular hypertension (OH). The ophthalmic international PNT device consists of a suction ring, a vacuum pump, and connecting tubing. The suction ring is made of disposable plastic. This ring is connected to a vacuum pump via three-way silicone tubing, which in turn connects to a single tube attached to the pump inlet (Figs 15.1 and 15.2). The pump is preset to deliver a maximum vacuum pressure corresponding to 65 mm Hg within the eye. The pump also provides a digital timer which counts down the treatment time selected by the user. The ring is supplied sterile, while the other components, which do not contact the patient, are supplied no sterile. To use the device to perform the PNT procedure, the physician first administers topical anesthesia to the patient. The patient is then placed in a supine position, and the eyelids are spread either manually (a speculum can be used but is not recommended). The ring must be positioned to clear the upper eyelid. The ring is then centered on the clear cornea and pressed downward slightly. In addition, to ensure proper suction, the surface of the eye should be wet when the ring is applied. Once the ring is properly positioned, the physician activates the pump which has been previously set to the

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Fig. 15.1

Fig. 15.2

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desired treatment time in seconds. Suction is applied for 60 seconds, followed by a 5 minute rest period, then repeated for an additional 60 seconds. Immediately prior to the end of each treatment period, the ring should be depressed slightly to minimize any discomfort to the patient when suction is released. Patches need not be applied following treatment, but one drop of antibiotic should be administered on completion of the PNT procedure. Tobradex or other steroid containing drops are to be avoided during this study. If steroid-containing drops and/or medications must be administered during the follow-up period, report(s) to that effect, identifying the patient, the eye(s) involved, dosage and duration of treatment must be remitted to the medical monitor. Patients should be examined at regular intervals (approximately every 3 to 4 months) to determine whether additional treatments are needed to maintain IOP control. Preliminary trials have shown that a repeat of the procedure at 1 week provides a more profound and lasting decrease in IOP The mechanism of action of PNT is unclear, but there is supporting evidence to show that it acts on the trabecular meshwork. This evidence comes in the form of measured increases in accommodative amplitude in early presbyopic patients undergoing PNT, albeit of a temporary nature. There is corroborating evidence from the studies of Schachar and Thornton in which expansion of the sclera over the cilliary body either by means of implanted plastic ring segments (Schachar) or radial incisions (Thornton) was accompanied by a measured decrease in post-surgical IOP. As we stated before the mechanism may well involve stretching of the zonule which stretching produces some form of change in the trabecular meshwork either physiologically through chemical mediators, or through a

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mechanical opening of the trabecular pores. Additional evidence that the mechanism of action involves improvement in outflow is that patients who respond well to latanoprost also seem to do well with PNT. There is no evidence that PNT causes any form of cyclodialysis and no cases of PNT have shown either flare or cells post-treatment. Clinical Trials Clinical trials have demonstrated that approximately 75 percent of POAG patients will demonstrate a PNT response. Of these patients, approximately 50 percent will eliminate their need for medication and the remainder will demonstrate a reduction in medication requirements. Pneumatic trabeculoplasty, when used in combination with antiglaucoma medication, was evaluated in two studies: a feasibility study involving 177 patients, and a separate efficacy study involving 317 eyes. Both studies were nonblinded, single-armed, and nonrandomized; the primary efficacy end point in each study was a decrease in intraocular pressure (IOP) compared with baseline. The first study reported a mean drop in IOP of 6.3 mmHg across the entire group. The second study showed a mean IOP after PNT treatment level at least 1 mmHg less than the pretreatment mean; except at 3, 6, 9, and 12 months, when it was at least 2 mmHg less than the initial mean IOP. The lesser reduction observed in the second study can be explained by the fact that a number of the patients were at least partially controlled by antiglaucoma medications at enrollment, and, as a result, the group had a lower starting IOP than those enrolled in the first study. In both studies, a clear trend to less medication was observed when PNT was added to a

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patient’s treatment regime. The ability of PNT to reduce IOP and medication requirements, along with its relatively benign safety profile, supports the use of PNT as part of a glaucoma patient’s treatment regimen. Adverse Events Adverse events reported following PNT are generally mild in nature and resolve within a few days. Patients receiving PNT typically experience transient ‘gray-out’ of vision sometimes associated with multicolored light patterns during the application of the vacuum ring. These phenomena typically vanish with 30-40 seconds upon release of the vacuum. Patients may experience some mild ocular discomfort (conjunctival hyperemia and conjunctival hemorrhage) following the PNT procedure. This discomfort will typically resolve, without treatment, within a few hours but may last as long as a day or two. Long-term side effects are absent following PNT. Considerations for Reduction in Anti-glaucoma Medication Generally speaking, reduction of anti-glaucoma medications can begin three weeks following the PNT repeat application. Given the numerous variations in antiglaucoma medication regimes, it is not possible to recommend a single specific medication reduction strategy. The Substantive Equivalence of PNT and ALT Argon laser trabeculoplasty is the procedure probably closest to being equivalent to pneumatic trabeculoplasty in its affect and possible mode of action. Clinical data shows that, overall, PNT produces the same or similar reduction

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in IOP with fewer serious side effects and has the advantage of being both totally noninvasive and repeatable with high success rates in repeated treatment. PNT lowers IOP in glaucoma patients at least as well, if not better than ALT and with much greater safety since no complications such as those reported to occur following ALT. CONCLUSION PNT can produce a significant reduction in IOP; reduction in IOP can be permanent; it is repeatable with similar or greater effect; can reduce or eliminate medication dependency; there is no damage to optic nerve fibers; does not accelerate/produce VF changes; may improve VA in some patients. BIBLIOGRAPHY 1.

Avalos-Urzua G, Bores LD, LiVecchi JT, Pneumatic Trabeculoplasty: A New Method to Treat Primary Openangle Glaucoma and Reduce the Number of Concomitant Medications, Ann Ophthalmol, 2005;37(1):37-46. 2. Bucci MG, Centofanti M, Oddone F, Parravano M, Balacco Gabrieli C, Pecori-Giraldi J, Librando A, Paone E, Bores ID. Pilot study to evaluate the efficacy and safety of pneumatic trabeculoplasty in glaucoma and ocular hypertension, Eur J Ophthal 2005;15 (3). 3. Wise JB, Witter SL. Argon laser therapy for open-angle glaucoma. A pilot study. Arch Ophthalmol 1979;97(2):31922. 4. Schwartz AL, Love DC, Schwartz MA. Long-term followup of argon laser trabeculoplasty for uncontrolled openangle glaucoma. Arch Ophthalmol 1985;103(10):1482-84. 5. Wilensky JT, Jampol LM. Laser therapy for open-angle glaucoma. Ophthalmology 1981;88(3):213-17.

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6. 7. 8. 9.

10.

11. 12.

13. 14. 15.

16.

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Wise JB. Long-term control of adult open-angle glaucoma by argon laser treatment. Ophthalmology 1981;88(3):197202. Thomas JV, RJ Simmons, Belcher CD. 3rd, Argon laser trabeculoplasty in the presurgical glaucoma patient. Ophthalmology 1982;89(3):187-97. Wilensky JT, Weinreb RN. Early and late failures of argon laser trabeculoplasty. Arch Ophthalmol 1983;101(6):89597. GLTRG. The Glaucoma Laser Trial (GLT). 1. Acute effects of argon laser trabeculoplasty on intraocular pressure. Glaucoma Laser Trial Research Group. Arch Ophthalmol 1989;107(8):1135-42. GLTRG. The Glaucoma Laser Trial (GLT). 2. Results of argon laser trabeculoplasty versus topical medicines. The Glaucoma Laser Trial Research Group [see comments]. Ophthalmology 1990;97(11):1403-13. GLTRG. The Glaucoma Laser Trial (GLT). 3. Design and methods. Glaucoma Laser Trial Research Group. Control Clin Trials 1991;12(4):504-24. GLTRG. The Glaucoma Laser Trial (GLT) 4. Contralateral effects of timolol on the intraocular pressure of eyes treated with ALT. GLT Research Group. Ophthalmic Surg 1991;22(6): 324-29. GLTRG. The Glaucoma Laser Trial (GLT). 5. Subgroup differences at enrollment. Glaucoma Laser Trial Research Group. Ophthalmic Surg 1993;24(4):232-40. GLTRG. The Glaucoma Laser Trial (GLT) and glaucoma laser trial follow-up study: 7. Results. Glaucoma Laser Trial Research Group. Am J Ophthalmol 1995;120(6):718-31. GLTRG. The Glaucoma Laser Trial (GLT). 6. Treatment group differences in visual field changes. Glaucoma Laser Trial Research Group. Am J Ophthalmol, 1995;120(1):1022. GLTRG. The Glaucoma Laser Trial (GLT) and glaucoma laser trial follow-up study: 7. Results. Glaucoma Laser Trial Research Group. Am J Ophthalmol 1995;120(6):718-31.

270 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.

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Coakes R. Laser trabeculoplasty. Br J Ophthalmol 1992;76(10):624-26. Finnstrom K. Laser treatment for open-angle glaucoma. A one year follow-up. Acta Ophthalmol (Copenh), 1985;63(1): 23-27. Hong C, Kitazawa Y, Tanishima T. Influence of argon laser treatment of glaucoma on corneal endothelium. Jpn J Ophthalmol 1983;27(4):567-74. Schachar RA, et al. In vivo increase of the human lens equatorial diameter during accommodation. Am J Physiol 1996;271(3 Pt 2):R670-76. Schachar RA. Zonular function: A new hypothesis with clinical implications. Ann Ophthalmol 1994;26(2):36-38. Schachar RA, et al. A physical model demonstrating Schachar’s hypothesis of accommodation. Ann Ophthalmol 1994;26(1):4-9. Schachar RA, T Huang, X Huang. Mathematic proof of Schachar’s hypothesis of accommodation. Ann Ophthalmol 1993;25(1):5-9. Lieberman MF, HD Hoskins Jr, J Hetherington Jr. Laser trabeculoplasty and the glaucomas. Ophthalmology 1983;90(7):790-95. Levene R. Major early complications of laser trabeculoplasty. Ophthalmic Surg, 1983;14(11):947-53. Brown SV, Thomas JV, Simmons RJ. Laser trabeculoplasty re-treatment. Am J Ophthalmol 1985;99(1):8-10.

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INTRODUCTION Since the introduction of the concept that laser treatment can be used in order to lower intraocular pressure (IOP) in open-angle glaucoma 1 by Krasnov in 1973, and the evolution into the currently used Argon laser trabeculoplasty (ALT), as described initially by Wise and Witter in 1979,2 Argon laser trabeculoplasty (ALT) has become a standard method of treatment for medically uncontrolled open angle glaucoma. However, the precise mechanism of this pressure reduction remains unclear. The efficacy of ALT in open angle glaucoma was demonstrated by the Glaucoma Laser Trial.3 The Glaucoma Laser Trial authors concluded that initial ALT is at least as effective as initial treatment with topical medication. Anderson and Parrish4 discovered that selectively absorbed laser by the Pigmented Trabecular Cells, can alter the structure of the Trabecular meshwork (TM), and gave the basis for the mechanical theory of action of ALT. Their findings revealed that precise focusing of the laser beam unnecessary because it is possible to use the tissue properties (absorbing only a specific wavelength), in order to provide target selectivity. Melamed et al suggested an important role for modified biological activity triggered by ALT,5 their studies of ALT in monkeys have shown increased phagocytic activity of Trabecular cells in the acute phase, followed by structural Trabecular alterations and accumulation of inflammatory cells in the long term. Regions adjacent to ‘lasered’ regions have shown more vacuolizations into the Schlemm’s canal and more permeability to flow, as detected by cationized ferritin perfusion. According to the mechanical theory, ALT causes coagulative damage to the TM, which results in collagen shrinkage and subsequent scarring of the TM. Tightening the meshwork in the area of each beam, thus

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and reopening the adjacent, untreated inter-trabecular spaces (Fig. 16.1).2,6,7 The cellular theory proposes that in response to coagulative necrosis induced by the laser, there is migration of macrophages, which phagocytose debris and thus clear the TM.8 Recently, an addition to the cellular theory has been suggested. This theory employs facts described by Wang et al9 who demonstrated that the TM endothelium shares similar response to oxidative insults as the systemic endothelial cells, and that inflammatory cytokines can play a role in glaucoma. Wang et al demonstrated that in response to a sublethal stress in glaucoma, specifically performed to the Trabecular meshwork, cytokines , such as endothelial leukocyte adhesion molecule-1, (ELAM-1), can be released into the aqueous and influence glaucomatous aqueous outflow

Fig. 16.1: Schematic view of ALT coagulation damage. Note the arrows indicating areas of No Flow, stretching and reopening the adjacent, untreated inter-trabecular spaces

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pathways. Signals, such as laser radiation, can promote oxidative stress. The gene for ELAM-1 has receptors in its promoter region that could respond to this kind of stress, and release and activate inflammatory cytokines, such as Interleukin-1 (IL-1), which could in turn increase the formation of ELAM-1. Bradley et al10,11 have demonstrated that IL-1 increases outflow facility and showed that IL-1α and tumor necrotizing factor-α, (TNFα), mediate ALTinduced MMP expression. For the first time it was shown that humoral pathway can be as important as the mechanical one. Although, the Glaucoma Laser Trial demonstrated the efficacy of ALT,3 in follow-up studies,12,13 it was shown that after a mean follow-up of 7-10 years, only 20-32 percent of the patients remained controlled. The need for repeat laser therapy was evident, but in fact that ALT creates a scar in the treated TM (Fig. 16.2), limited the possibility of repeated treatment. Selective laser trabeculoplasty (SLT) was developed in order to employ

Fig. 16.2: ALT Laser burn SEM

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the fact that cellular and humoral mechanisms, can effect the out-flow facility without creating a permanent scar in the TM.8-11 The energy delivered by the SLT is mostly absorbed by pigmented cells and is therefore spatially confined to the pigmented TM cells. SLT uses a Q-switched, frequency-doubled 532-nm Nd:YAG laser with a short pulse duration of 3 nano seconds. This modality limits the conversion of energy to heat, further minimizing the collateral tissue damage (Fig. 16.3).14 Histological studies,14 (Fig. 16.4) in human cadaver eyes after SLT reveal no evidence of coagulative damage or disruption of the corneoscleral or uveal Trabecular beam structure. Because of the minimal cytologic damage, SLT offers two theoretical advantages; one is that it may be repeatable and two, it may have a higher safety profile.15 Latina et al16 were the first to establish the efficacy and safety of SLT by demonstrating a 70 percent response rate and a 5.8 mm Hg (23.5%) IOP lowering effect of SLT, in addition, they demonstrated that SLT can be repeated after failed ALT without the risk of post-laser lOP spike. Other studies confirmed his findings.18-20 Melamed et al treated newly diagnosed glaucoma patients with SLT and demonstrated a mean lOP reduction of 7.7 mm Hg (30%). He also reported that the incidence of postoperative pressure spikes was very low.21 Chen E et al,22 reported that the IOP lowering effect of SLT was independent of previous ALT and that there is no difference between the effects of 25 spots on 90 degrees of TM vs. 50 spots on 180 degrees of TM. SLT was also reported to cause significantly less pain and flare than ALT. 23 To date, no remarkable postoperative complications have been reported with SLT. In conclusion, SLT is at least as good as ALT regarding lOP reduction. SLT may be safer than ALT because it delivers less energy to the TM, causing less post-therapy

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Fig. 16.3: Multi-layer optical model of Trabecular meshwork effect of ALT vs SLT (Modified from Manns et al.) Note the difference in the heatdiffusion zone, minimizing the collateral tissue damage

IOP spikes. The lack of structural damage to the TM offers re-treatment possibility following failed ALT. SLT should be considered as either a first or second- line treatment in open angle glaucoma patients with uncontrolled IOP.

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Fig. 16.4: SLT — No visible scar SEM

REFERENCES 1. 2. 3. 4. 5. 6.

Krasnov MM. Laser puncture of anterior chamber angle in glaucoma. Am J Ophthalmol 1973;75:674-8. Wise JB, Witter SL. Laser. Therapy for open-angle glaucoma: a pilot study. Arch Ophthalmol 1979:97:319-22. The Glaucoma Laser Trial Research Group. The Glaucoma Laser Trial (GLT), Results of laser trabeculoplasty vs. Topical medicines. Ophthalmology 1990;97:1403-13. Anderson RR, Parish HA. Selective photothermolysis: Precise microsurgery by selective absorption of pulsed radiation. Science 1983;220:524-47. Melamed S, Epstein DL. Alterations of aqueous humor outflow following argon laser trabeculoplasty in monkeys. Br J Ophthalmol 1987;71:776-81. Reiss GR, Wilensky IT, Higginbotham El. Laser trabeculoplasty. Surv Ophthalmol I991;35:407-28.

278 7.

8. 9.

10.

11.

12. 13. 14. 15. 16.

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Weinreb RN, Tsai CS. Laser trabeculoplasty. In: Ritch R, Shields MB, Krupin T (Eds): The glauomas: Glauoma Theropy. 2nd ed. Missouri: Mosby-Year Book, 1996;111: 1575-90. Damji KF, Shah KC Rock WJ, et al. Selective laser trabeculoplasty v argon laser trabeculoplasty:a prospective randomized clinical trial. Br J Ophthalmol 1999;83:718-22. Wang N, Chintala SK, Fini ME, Schuman JS. Activation of a tissue-specific stress response in the aqueous outflow pathway of the eye defines the glaucoma disease phenotype. Nat Med 2001 Mar;7(3):304-9. JM Bradley, J Vranka, CM Colvis, DM Conger, JP Alexander, AS Fisk, JR Samples, TS Acott. Effect of matrix metalloproteinases activity on outflow in perfused human organ culture. Inves Ophthalmol Vi Sci, Vol 39, 2649-2658, 1998. John MB Bradley, Ann Marie Anderssohn, Christine M. Colvis, Dorothy E. Parshley, XiangHong Zhu, Michael S. Ruddat, John R. Samples, Ted S. Acott. Mediation of Laser Trabeculoplasty–Induced Matrix Metalloproteinase Expression by IL-1β and TNF. Inves Ophthalmol Vis Sci 2000;41:422-430. The Glaucoma Laser Trial (GLTFS). AJO 1995;120:718. Bradford JS, Richter CU, Dharma SK, et al. Long-term efficacy of argon laser trabeculoplasty. Ophthalmol 1993;100;9:1324-29. Latina MA, Park C. Selective targeting of trabecular meshwork cells: In vitro studies of pulsed and CW laser interactions. Exp Eye Res 1995;60:359-72. Huck A. Holz and Michele C. Lirn. Glaucoma lasers: a review of the newer techniques Curr Opin Ophthalmol 2005;16:89-93. Latina MA, Sibayan SA, Shin DH, et al. Q switched 532nm Nd:YAG, Laser Trabeculoplasty (Selective Laser Trabeculoplasty) A multicenter Pilot cinical Study. Ophthalmol 1998;105;11:2082-88.

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17. 18.

19. 20. 21. 22. 23.

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Damji KF, Shah KC, Rock WJ, et al. Selective laser trabeculoplasty v argon laser trabeculoplasty: a prospective randomized clinical trial. Br J Ophthalmol 1999;83:718-22. Mermound A, Herbort CP, Schnyder CC, et al. Comparison of the effects of trabeculoplasty using the Nd:YAG laser and argon laser. Klin Monatsbl Augenheilkd 1992;200:4046. Tabak S, de Waard PWT, Lemij HG, et al. Selective laser ttabeculoplasty in glaucoma. Invst ophthalmol Vis Sci 1998;39:S472. Pirnazar JR, KoIker A, Wax M, et al. The efficacy of 532 nm laser trabeculoplasty. Invest Ophthalmol Vis Sci 1998;39:S5. Melamed S, Ben Simon GJ, Levkovitch-Verbin H. Selective laser trabeculoplasty as primary treatment for open-angle glaucoma. Arch Ophthalmol 2003;121:957-80. Chen E, Golchin S, Blomindahl S. Comparison between 90 degrees and 180 degrees selective laser trabeculoplasty. J Glaucoma 2004;13:62-65. Martinez-de-Ia-Gasa JM, Garcia-Feijoo J, Castillo A, et al. Selective vs argon laser trabeculoplasty: hypotensive efficacy, anterior chamber inflammation, and postoperative pain. Eye 2004; 18:498-502.

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INTRODUCTION The aim of surgical management of Open-angle glaucoma is to create an alternate channel for drainage of aqueous humor from the anterior chamber of the eye by surgical techniques collectively called “Filtration microsurgery”, or to open previously blocked trabecular meshwork with the help of lasers. Many surgical procedures have been devised for chronic open-angle glaucoma. These include: 1. Trabeculectomy (Fig. 17.1): This is the most commonly performed surgical technique and it involves making a surgical opening into the anterior chamber under a partial thickness scleral flap through which the excess fluid drains into the subconjunctival space. 2. Argon/Diode (Thermal) laser trabeculoplasty: 50 to 100 micron laser spots are aimed at the trabecular

Fig. 17.1: Aqueous drainage through sclerostomy and then via subconjunctival route in trabeculectomy

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meshwork. The laser application results in a biological and mechanical reaction in the trabecular meshwork to open the previously blocked meshwork and increases the flow of aqueous fluid from the eye. 3. Selective laser trabeculoplasty: Reduces intraocular pressure by enhancing drainage of excess aqueous fluid. The laser increases drainage by selectively treating certain cell tissue of the trabecular meshwork. 4. Non-penetrating deep sclerostomy (Viscocanalostomy): This is a modification of trabeculectomy, wherein a fullthickness hole in the eye is avoided. Instead, a very deep dissection is performed in the sclera and trabecular meshwork. 5. Tube-shunt: These are synthetic drainage devices particularly useful in neovascular glaucoma, aphakic glaucoma and advanced developmental glaucoma. In most cases the treatment is palliative. NPDS – AN EVOLUTIONARY TECHNIQUE The ideal glaucoma surgery is that which can create adequate drainage to enable a controlled reduction of IOP without the risk of over-filtration while ensuring long-term patency of the filtration channel. Hence, we believe that the model around which all glaucoma surgeries should be conceptualized is the non-penetrating deep sclerectomy (NPDS) or viscocanalostomy.1-4 In this procedure the intraocular pressure is lowered as fluid oozes through a permeable thin layer of tissue, the trabeculo-Descemet’s membrane. A bleb may be formed, but it is usually smaller than one that would be formed following trabeculectomy. The main advantage of this procedure is that it minimizes the chances of overfiltration. This avoids the complications of filtration blebs and the shallow anterior chamber seen

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after trabeculectomy.17 In Viscocanalostomy, the cut ends of the Schlemm’s canal are expanded with Sodium Hyaluronate. However, the IOP lowering capacity of this procedure is less than that of conventional trabeculectomy and the chances of closure are high. Some surgeons place a lake of viscoelastic such as sodium hyaluronate or a collagen implant5,6 under the scleral flap to reduce the chance of closure due to the natural process of healing. NPDS is fast gaining popularity among surgeons due to decreased incidence of postoperative complications when compared with conventional trabeculectomy. However, most surgeons find dissection of the trabecular meshwork and the scleral bed difficult to perform. The meticulous tissue excision is challenging even to the most skillful and experienced surgeon. Additionally, it is commonly reported by surgeons, that once aqueous percolation starts to occur during the course of tissue dissection, a significant amount of hypotony sets in, making the excision of tissue even more difficult. From the variable reports of clinical success, it is clear that this technique has a long learning curve. Nevertheless, the potential opportunity to create a filtration procedure which successfully controls intraocular pressure in the absence of a prominent bleb is prompting innovators to improve upon the technique of NPDS. Accelerated advancement in laser technology in the late 90s has been responsible for the widespread use of this hitech modality in ophthalmology and it is no surprise that investigators are aggressively exploring the potential of lasers to help evolve a more reliable version of NPDS. Technically, Lasers with predominant ablative properties have the advantage of helping the surgeon remove precise amount of tissue with relative ease. This appears to be the critical factor responsible for ensuring consistency in the surgical technique.

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LASER-ASSISTED TECHNIQUES FOR THE FUTURE Many investigators evaluated the use of of the Holmium laser,7 Nd: YAG,8,9 Erbium YAG laser10-12 and the Excimer laser13-15 in an attempt to create a minimally invasive controlled glaucoma procedure. The technique of nonpenetrating filtering procedure, called sinusotomy was first introduced by Krasnov in 1969. 1,2 Zimmerman et al investigated non-penetrating trabeculectomy in 1984 and demonstrated a success rate of 83.7 percent after 1 year.3,4 An increased success rate was demonstrated with collagen implants or sodium hyaluronate.1-4 Injection of sodium hyaluronate into the canal of Schlemm was recommended to make the procedure more effective and the procedure was called viscocanalostomy. 16,17 Non-penetrating techniques reported lower rate of complications1-4 as compared to conventional Trabeculectomy or Sclerostomies. However, it has been observed that most surgeons require extensive experience to master the technique of accurate dissection of the trabacular meshwork and the scleral bed. It is also difficult to control the amount of tissue to be excised even with the aid of specially designed surgical instruments. A pulsed laser, capable of ablating ocular tissue with high precision, is the obvious tool that can overcome this challenge. The laser should have cutting properties ideally suited for corneal and scleral tissues and should be preferably available to the surgeon at the tip of an ergonomically designed handpiece. Partial excimer laser sclerostomy and trabeculectomy has not gained wide acceptance due to inconsistent scleral ablative properties and lack of control arising from the nonavailability of a suitable delivery system through a surgical handpiece. Pulsed Erbium: YAG laser was used to ablate scleral and corneal tissue layer by layer to create filtration

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channels.18,19 Our own experience with the Er:YAG laser (unpublished studies) showed that the laser did produce significant colateral thermal damage. This would often lead to formation of coagulum at the tip of the fiber in the contact mode thus reducing the efficiency of subsequent ablation. CUSTOMIZED LASER ASSISTED FILTRATION SURGERY (CLAFS) WITH THE PR-270 The PR-270 Pulsed laser (Fig. 17.2) uses as its source, the Nd:YAG laser crystal and nonlinear crystals to generate the 4th harmonic at a UV wavelength of 266 nm. It is very efficient in ablating tissues with high water content such as cornea and sclera. The laser is delivered through a specifically designed articulated arm coupled to a handpiece which delivers the UV laser energy via a focusing lens (Fig. 17.3). The 5-nanosecond short pulsed laser is focused to a spot size of about 0.6 mm on the treated area with energy per pulse of 5 to 7 mJ and operates at 10 to 20 Hz. Both, the pulse energy and frequency, are adjustable. We note that this 5 ns frequency of the laser is much shorter than the typical excimer laser (about 10 to 20 ns), Ho:YAG laser (about 200 microsecond) or Er:YAG (about 500 microsecond). Therefore, it offers minimal thermal damage with effective tissue ablation. Furthermore, the focused UV laser spot may be as small as 0.3 mm if needed, an attribute which is not available with IR lasers. Being non-contact in its operation the laser overcomes two major disadvantages of the contact fiberbased lasers. Firstly, unlike contact ablative systems, one does not encounter progressive decrease in the efficiency of ablation due to accumulation of coagulum at the end of the fiber tip. Secondly, there is no apprehension about damage to the tips which, in the fiber-based system, adds significantly to running cost.

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Fig. 17.2: Picture of PR-270 UV laser with the “articulated arm” delivery system

Fig. 17.3: Schematics of the handpiece design for adjustable spot size on the treated surface by adjusting the distance of the attaching front end. “X” is the distance between the attached end piece and the position of the focal length

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Depending on the initial IOP and the target IOP we recommend different ab externo techniques of ablation: 1. Linear radial sclerostomy (Fig. 17.4A): After creating a conjunctival flap, preferably fornix based, a pair of linear ablative scleral grooves is created about 85 percent of scleral depth. The starting point of the groove is about 0.5 mm from the limbus and is about 4 mm in length. The limbal end of the groove is deepened in a controlled fashion until aqueous percolates. This provides an open non-penetrative aqueous drainage pathway via the subconjunctival space. The expected reduction in intraocular pressure is between 2 to 4 mmHg. 2. Extended linear radial sclerostomy: The opposite end of the groove is deepened until a small brownish dot, about 1 mm in size, appears indicating exposure of underlying choroidal tissue. This will provide additional suprachoroidal drainage for the aqueous. The IOP lowering effect of this modification is expected to be about 4 to 6 mm Hg. 3. Laser-assisted non-penetrating deep sclerostomy (Fig. 17.4B): The initial steps are same as that of the surgical NPDS procedure. After an initial 5 × 5 mm partial thickness scleral flap, the scleral bed overlying the canal of Schlemm is ablated in order to “De-roof” the canal. This ablative excision is carried on anteriorly as a partial trabeculectomy and further anteriorly to expose the Descemet’s membrane. The endpoint is the percolation of aqueous. This procedure may be combined with collagen implants sutured to the bed under the partial thickness scleral flap or a lake of Sodium Hyaluronate may be placed under the flap. Viscocanalostomy using Sodium Hyaluronate may also be carried out for additive effect. Judicious use of sponge soaked in 5-FU

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Figs 17.4A and B: CLAFS (A) Linear laser radial sclerostomy (B) Nonpenetrating deep laser sclerostomy providing multiple drainage channels

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or Mitomycin placed over the scleral bed is advocated in select cases or at the discretion of the operating surgeon. The expected IOP lowering capacity of this procedure is between 4 and 10 mm Hg and more. 4. Extended laser-assisted non-penetrating deep sclerostomy: An additional step of ablative dissection in the posterior part of the scleral bed in order to expose a small dot of brown choroidal tissue would be useful in providing additional suprachoroidal drainage for the percolating aqueous humor. The IOP lowering capacity of this modification in expected to be about the same as 3. However, the chances of short-term as well as longterm success are expected to be better. 5. Combination procedure: The procedure described above may be combined in a single operation or separately for additive effect. 6. Modified scleral bed ablation: In order to facilitate the drainage of the percolated aqueous under the flap, the surgeon can conveniently create ablative grooves connecting the trabeculectomized regions to the posterior parts. Creation of such multiple drainage channels will also decrease the chances of closure of the drainage channel and the grooves will facilitate fixation of the collagen implant. 7. Penetrating filtration procedure: Any of the above mentioned procedures can be converted to penetrating trabeculectomy combined with iridotomy if desired. From the above description it can be appreciated that the surgeon can customize the type of ablative excisions to suit the requirement of individual cases. Hence, we propose the name “Customized Laser Assisted Filtration Surgery” (CLAFS) to encompass all the variation of the procedures described. The multiple filtration channels are well illustrated in Figure 17.5. The procedure is preferably

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Fig. 17.5: CLAFS - Aqueous drainage through trabeculo-Descemet’s membrane and then via subconjunctival as well as through suprachoroidal spaces

carried out under peribulbar anesthesia, although, topical anesthesia with subconjunctival infiltration over the surgical site is also possible. As shown in Table 17.1, the PR-270 using a solid-state UV laser has the advantages of minimal thermal effects, small energy per pulse and intermediate range power required for efficient ablation. The unique feature of beam spot adjustable of 0.2 to 0.8 mm also offers better controllable precise ablation. One of the major innovations employed in the new laser unit is an optical delivery system through an articulated arm in place of a fiber-based system. Any fiber-based delivery system inherently demonstrates a fairly early and consistent deterioration of energy output due to progressive fiber damage during usage. Moreover, the beam spot size in such a system is limited by the size of

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Excimer

Laser Wavelength Pulse width Operation mode Energy/pulse Average power Ablation efficiency Thermal effects Beam delivery

CW gas 488/514 nm CW CW Varies Few W Low

Gas (XeCl) Solid-state 308 nm 2940 nm 200 ns 500 microsec Long-pulse Long-pulse 4-5 mJ 10-15 mJ 0.3 - 0.4 W 0.1 - 0.2 W Medium High

All thermal Partial Fiber/contact Same

Partial Same

Beam spot size Treating area

Fixed Trabeculum

Fixed Sclera

Fixed Trabeculum

IR (Er:YAG) UV-266 Solid state 266 nm 5 ns Q-switched 5-8 mJ 0.1 - 0.2 W High Minimal Noncontact Adjustable Sclera, cornea, Trabeculum [Customized]

the fixed fiber core. In contrast, the optic-based system gives a fairly steady output even during prolonged usage (Fig. 17.6). In Argon laser trabeculoplasty (LTP), focal burns with an argon laser beam of 50 micron spot size and 1000 mW power for 0.1 seconds causes contraction of the meshwork tissues. This causes separation of the adjacent trabecular sheets to increase the outflow of aqueous. Additionally the laser burns induce alteration in phagocytic activity of the trabecular cells.20 LTP does succeed in lowering the IOP in 70–75 percent of patients with open-angle glaucoma.21 Over time the effectiveness decreases so that 5 years after treatment only 30 to 60 percent of patients maintain good intraocular pressure control. 22 Basically, the type of filtration channel created by tissue ablation of UV or IR

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Fig. 17.6: Picture of linear radial laser sclerostomy

laser differs little from that created by surgical Trabeculectomy or NPDS. Preliminary studies indicate good initial IOP reduction. The main advantage of CLAFS is that the ablation pattern can be tailor-made to suit the target pressure. There appears to be adequate justification to expect that the long-term results of this minimallyinvasive procedure is likely to be the same or better than that of the more invasive, conventional filtration procedures.

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REFERENCES 1. 2. 3.

4. 5.

6. 7. 8. 9. 10. 11.

Krasnov M. Microsurgery of glaucoma: indications and choice of technique. Am J Ophthalmol 1969;67:857-64. Krasnov MM. Current technic of sinusotomy (externalization of Schlemm’s canal) without resection of the sclera. Vestn Oftalmol 1988;104:102-04. Zimmerman TJ, Kooner KS, Ford VJ, et al. Trabeculectomy vs nonpenetrating trabeculectomy: a retrospective study of two procedures in phakic patients with glaucoma. Ophthalmic Surg 1984;15:734-40. Zimmerman TJ, Kooner KS, Ford VJ, et al. Effectiveness of nonpenetrating trabeculectomy in aphakic patients with glaucoma. Ophthalmic Surg 1984;15:44-50. Delarive T, Mermoud A, Uffer S, Rossier A. Histological findings of deep sclerectomy with collagen implant in animal model. Proceedings of the First International Congress on Non-penetrating Glaucoma Surgery. Lausanne, February 2001. Sourdille P, Saniago PY, Ducourneau Y. Non-perforating surgery of the trabeculum with reticulated hyaluronicacid implant. J Fr Ophthalmol 1999; 22:794-97 Schuman JS, Stinson WG, Hutchinson BT, et al. Holmium laser sclerectomy. Success and complications. Ophthalmology 1993;100:1060-65. March WF, Gherezghiher T, Koss MC, Nordquist RE. Experimental Y AG laser sclerostomy. Arch Ophthalmol 1984;102:1834-36. March WF, Gherezghiher T, Koss MC, et al. Histologic study of a neodymium-YAG laser sclerostomy. Arch Ophthalmol 1985;103:860-63. Wetzel W, Haring G, Brinkmann R, Birngruber R. Laser sclerostomy ab externo using the Erbium:Y AG laser: first results of a clinical study. Ger J Ophthalmol 1994;3:112-25. Wetzel W, Otto R, Falkenstein W, et al. Development of a new Er:YAG laser conception for laser sclerostomy ab

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12. 13. 14. 15.

16. 17. 18. 19. 20.

21. 22.

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externo: experimental and first clinical results. Ger J Ophthalmol 1995;4:283-88. Wetzel W, Schmidt ED, Haring G, et al. Laser sclerostomy ab externo using two different infrared lasers: a clinical comparison. Ger J Ophthalmol 1995;4:1-6. Brooks AM, Samuel M, Carroll N, et al. Excimer laser filtration surgery. Am J OphthalmoI1995;119:40-47. Campos M, Lee PP, Trokel SL, et al. Transconjunctival sinusotomy using the 193-nm excimer laser. Acta Ophthalmol Copenh 1994;72:707-11. Traverso CE, Murialdo D, Di LG, et al. Photoablative filtration surgery with the excimer laser for primary openangle glaucoma: a pilot study. Int Ophthalmol 1992;16:36365. Stegmann RC. Viscocanalostomy: a new surgical technique for open-angle glaucoma. An Inst Barraquer Spain 1995;25:229-32. Stegmann R, Pienaar A, Miller D. Viscocanalostomy for open-angle glaucoma in black African patients. J Cataract Refract Surg 1999;25:316-22. Klink T, Lieb W, Grehn F. Erbium: YAG laser-assisted deep sclerectomy. Invest Ophthalmol Vis Sci 1999;40:272. Klink T, Lieb W, Grehn F. Erbium: YAG laser-assisted preparation of deep sclerectomy. Grafes Arch Clin Exp Ophthalmol 2000;238:792-96. Ticho U, Cadet JC, Mahler J, Sekelese, amd Bruchin A. Argon laser trabeculotimies in Primates: evaluation by histological and perfusion studies. Invest Ophthalmol Vis Sci 1978;17:667. Grinich NP, van Buskirk EM, Samples JR. Three-year efficacy of argon laser trabeculoplasty. Ophthalmology 1987;94:858. Shingleton BF, Richter CU, Bellows AR, Hutchinson BT, Glynn RJ. Long-term efficacy of argon laser trabeculoplasty. Ophthalmology 1987;94:1513.

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INTRODUCTION Increased intraocular pressure (IOP) accompanied by evidence of damage to the optic nerve requires a life-long treatment to maintain the pressure at acceptable levels. The new generations and combinations of medical therapy are indeed highly effective, however, they all require continuous instillation, at least once a day and often more, of eyedrops. Local side effects are significant and compliance is, therefore, a major problem in glaucoma medical therapy. Studies have shown that glaucoma surgery, namely trabeculectomy, is at least as effective as medications, and obviously does not require patients’ compliance. However, surgery may be associated with numerous complications such as hypotony, shallow anterior chamber, endophthalmitis, leaking blebs and many others. Successful procedures are associated with a 3-fold increase in cataract formation, as may occur in any penetrating ocular procedure. Non-penetrating filtration surgery (NPFS) is, therefore, a very appealing option. Since the anterior chamber is not penetrated, the procedure is actually an extraocular operation. A success rate similar to conventional trabeculectomy without the complications of intraocular surgery seems to offer as an ideal solution. However, dissection of the scleral wall to over 95 percent of its depth until fluids effectively percolates, without penetration into the eye, require very high skills and a long learning curve. Only a few highly experienced surgeons adopted this technique, which in spite of its obvious advantages did not gain a wide popularity. Also, several studies reported clinical results somewhat below the pressure reduction achieved by conventional trabeculectomy. Many modifications, such as placing spacers under the scleral flap, YAG laser goniopuncture and antimetabolites applications

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improved the efficacy of the procedure however not yet to the level of a wide acceptance. Attempts to apply laser technology to NPFS were previously reported, including excimer, holmium, and erbium:YAG lasers, however none was practically accepted. In the last years we looked for surgical techniques that would make NPFS both a simple procedure, suitable for any anterior segment surgeon, as well as clinically effective. Utilizing some of the unique features of the CO2 laser seemed theoretically optimal for this goal. The CO2 laser is very effective in ablating dry tissues, and is therefore widely used in general and plastic surgery. However, the far-infrared radiation of this laser is absorbed in water within a very short penetration depth and is thus ineffective when applied over wet tissues. We speculated that application of laser energy on the dried scleral tissue, over the trabecular meshwork, would cause a localized ablation of the sclera until fluid starts percolating through the thinned wall. When the aqueous wets the ablated area further laser applications would be ineffective, and would not cause any further tissue ablation (i.e. perforation). Thus, tissue ablation would cease “automatically” when the desired end-point of the procedure is achieved, i.e. aqueous percolation without perforation into the anterior chamber. The surgical procedure is quite simple and does not require any specific skills other than creation of a scleral flap. Use of a scanning device may further assist surgery by predetermining and accurately controlling the shape of the ablated tissue block and the energy distribution (Figs 18.1A to D). The CO2 laser that we used in our initial studies was the Kaplan PenduLaser 115® CO2 laser system (Optomedic Medical Technologies Ltd., Or Yehuda, Israel). This is the smallest and the most portable and compact CO2 laser in

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Figs 18.1A and B

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Figs 18.1A to D: Surgical procedure in a clinical case: (A) Before ablation– the red dots of the aiming beam indicate the scanned area (B) The area over the trabecular meshwork/Schlemm’s canal on the upper right corner is partially ablated; however no fluid percolation is yet evident. The wetted sponge (on the left) protects the remaining tissue from the laser energy. (C) Aqueous fluid is seen emerging from the ablated zone on the right and center. The left side is still untreated. (D) Effective aqueous percolation is seen over the entire treated area. No perforation into the anterior chamber

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the market and it transmits a beam of 5-15 W through an articulated arm. A scanner was attached to the CO2 laser to enable the surgeon to delimit the area to be treated and to provide even and regular distribution of the laser energy over this area. The laser probe was attached to the surgical microscope, thus maintaining the probe at a predetermined fixed distance from the ablated tissue when the microscope was in focus. In practice, tissue ablation is done while the surgeon is looking through the microscope, accurately targeting the scanner marks with the proper pattern and dimensions over the desired treatment location. PRECLINICAL STUDIES Initial studies were done on enucleated cow and sheep eyes at the Laboratory for Intraocular Microsurgery and Implants, Goldschleger Eye Research Institute, Sheba Medical Center, Israel, and at the Laboratory for Intraocular Microsurgery and Implants, Meir Medical Center, KfarSaba, Israel. The intraocular pressure was maintained at a constant predetermined pressure of 38 mm Hg by using anterior chamber maintainer (ACM) with the bottle placed at 50 cm above the tested eye. Following dissection of a scleral flap the tissue underneath was laser ablated until fluid was seen percolating in the treated area without evidence of penetration. These studies proved the validity and feasibility of the concept and help determine the laser parametes for clinical use. The second set of experiments was done on rabbit eyes. Rabbits are known to be very reactive to any surgical procedure and even full thickness trabeculectomy is often closed and ineffective within days after surgery. Nevertheless, in order to investigate the pure effect of the laser treatment we did not use any tissue spacers, viscoelastic substances or antimetabolites to enhance and

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prolong the surgical effect. The IOP was measured by pneumotonometry and compared to the fellow, untreated eye. In one case perforation into the anterior chamber was accompanied by iris prolapse. In the rest of the cases the IOP decreased immediately after the laser surgery (a mean of 10 mm Hg on day 1). The intraocular pressure was significantly lower than the fellow eye for the first 3 weeks. It should be emphasized that these rabbits did not have glaucoma and the pressure eventually stabilized at the preoperative normal levels. The third set of experiment was done on human cadaver eyes at the Center for Research on Ocular Therapeutics and Biodevices, Storm Eye Institute, Medical University of South Carolina, Charleston, SC, USA (Director: David J. Apple, MD). A 4 × 5 mm scleral flap was dissected and laser pulses of moderate power (10 W) were applied over the exposed scleral wall. Since it was evident from the rabbit study that tissue charring interferes with the laser effect, the charred tissue was removed after every 5-7 laser shots with a wetted sponge. Upon approaching the trabecular tissue, or when the first signs of fluid percolation were seen, the laser power was lowered to 5 W and the application rate was reduced. The treated zone was dried with a sponge, and the next shot was applied only after a delay of 2-3 seconds to allow localized wetting by the percolating fluid. This way only the dry area was further ablated, whereas over the wetted area, where more ablation was not required, the laser energy was absorbed by the percolating fluid. If the treated area seemed to be too small, laser dissection of the tissue was extended laterally to a desired width until satisfactory aqueous percolation was achieved. Histopathological studies confirmed the deep ablation down to the trabecular meshwork and Descemet’s membrane, leaving a micro-thin wall 30-50 m thick, with

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no perforation. The neighboring structures, including the sclera, cornea, iris base, and ciliary body, were not affected and remained undamaged (Fig. 18.2). CLINICAL STUDIES After completion of the preclinical studies that confirmed both the safety profile of the procedure and the potential efficacy for its clinical use, we proceeded to clinical controlled studies on patients with advanced glaucoma, uncontrolled with medications. Studies were done in 3 medical centers in Israel [Meir (Prof E. Assia), Carmenl (Prof O. Geyer) and Tel-Aviv Souraski (Dr S. Kurtz) Medical Centrs], 1 center in Johannesburg, South Africa (Dr E. Dahan) and at the L.V. Prasad Eye Institute in

Fig. 18.2: Histopathology of a human cadaver eye after CO2 laser ablation. The ablated area creates a “filtration pool”. The Trabecular-Descemet’s “membrane” is only a few microns thick, but it is still intact. Note that in spite of the extensive tissue ablation, no damage is evident in the adjacent corneo-scleral and uveal tissues

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Hydrabad, India (Prof R. Thomas). Twenty-three patients were treated using the protocol determined in the preclinical studies. We decided that on our initial cases we would study only the net effect of the laser treatment and would not use any adjunctive treatment. Even though we knew that we might reduce the chances of low pressure and filter survival we did not use spacers under the external flap, apply antimetabolic agents to reduce tissue scarring, inject viscoelastics into the Schlemm’s canal (viscocanalostomy) or perform YAG laser goniopuncture in failed cases. Surgical procedure succeeded in all cases and the pressure dropped dramatically on the first postoperative day from a mean of 27.4 to 5.2 mm Hg. There was no case of flat anterior chamber or any significant postoperative complication. In one eye prolapse of the iris base into the treated area was seen on gonioscopy and the iris was surgically repositioned. The mean pressure after the first week was 11.3 mmHg, however from the two-weeks visit on, two distinct groups were evident: those patients whose IOP was low at the two-weeks visit maintained a low pressure thereafter (half of the cases), whereas increased pressure at two weeks was usually associated with longterm elevated pressure that required additional medications, and in 3 cases re-operations (Fig. 18.3). The clinical studies confirmed that the CO2 laser can effectively ablate the dry tissue without tissue perforation by a relatively simple procedure. Satisfactory fluid percolation was achieved in all cases and no significant complications were seen in any of the eyes. The immediate postoperative results indicate that by applying the laser alone, long-term pressure drop without medications can be achieved in half of the cases. The late failure in the other cases is probably secondary to the localized tissue heating,

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Fig. 18.3: Ultrasonic biomicroscopy of a clinical case. The filtration “pool” is open, even though no spacers were used. A thin active sub-conjunctival bleb is seen above the scleral flap. Compare with the histology on Figure 18.2

which causes tissue irritation and inflammatory reaction. Anterior synechia and localized fibrosis were typically seen in the failed cases. The optimal laser parameters that would provide the desired tissue effect with minimal heating still need to be determined. We speculate that by using adjunctive therapy, such as placing spacers and applying Mitomycin C under the scleral flap, frequent application of local steroids and using external lasers for suturelysis and goniopuncture will increase the success rate of the procedure.

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SUMMARY In summary the CO2 laser assisted NPFS utilizes the unique qualities of this far-infrared laser, i.e. the ability to ablate dry tissue and the almost complete absorption by water. This promising procedure enables accurate dissection of the scleral wall and unroofing of the Schlemm’s canal without penetration into the anterior chamber. The technique is, therefore, practically extraocular, relatively simple and requires only a short learning curve. Further modifications of the surgical procedure, and more controlled clinical studies are still required. Video A clinical case of CO2 laser assisted non-penetrating filtration surgery. A large area under the scleral flap is first ablated in order to create a filtration “lake”. Then, the scanner pattern is narrowed to create a slit over the area above the trabecular meshwork. Treatment is applied until fluid easily exits through the thinned wall. Note that when the treated area is wet, repeated laser application are not effective and the remaining scleral “membrane” is not perforated. Two 10-0 nylon sutures are used to close the external flap and a single suture is sufficient to close the conjunctiva. Anterior chamber maintainer was used in this case to maintain constant intraocular pressure, however it is not necessary in a routine case.

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HISTORY The goal of all surgery for glaucoma is to lower the ocular pressure in order to reduce postoperative risk as much as possible. Surgical techniques using perforation have several postoperative disadvantages. A certain number produce complications such as hyphema, flat anterior chamber, choroid detachment, cataract, and endophthalmitis. Non-penetrative surgical techniques do not have the postoperative complications of the first, penetrative, surgery, but they are more difficult to carry out. An exact knowledge of the micro-anatomy of the region is important and a learning curve necessary. The main drawbacks with these new techniques are that they are less effective with weak hypertensions, and, importantly, they increase the number of times the operation needs to be performed due to poor healing and flap collapse. • 1909 Elliott’s trepanation • 1960 Burian’s trabeculectomy,7 Sugar 196126 • 1968 Cairn’s trabeculectomy for open angle glaucoma8 • 1962 Krasnov’s Sinusotomy: this technique aims to remove the external wall of the Schlemm canal15 • 1984 Zimmermann: Non-penetrating trabeculectomy28 • 1984 Fiodorov and Koslov suggest the term ‘nonpenetrating deep sclerectomy’ (NPDS)12 • 1990 Koslov improves his technique by adding a collagen implant into the base of the flap. At the same time, many others tried different types of implants to increase the duration of the drainage life of the aqueous humor14 • 1991 Arenas: Archila Trabeculotomy ab externo. Areans uses the same technique but employs the help of a trepan to open the Schlemm canal1

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• 1999 Stegman: Viscocanalostomy The author proposes a dissection and an injection of viscous fluid into the Schlemm canal.20 ANATOMOPHYSIOLOGY Goldman13 demonstrated by using manometric experiments, the main point of resistance to the drainage of the aqueous humor was situated between the anterior chamber and the Schlemm canal. 23 Nowadays, it is generally accepted that 75 percent of drainage resistance is situated at the level of the endothelium of the Schlemm’s canal and of the trabeculum network.21 New Techniques The new techniques of filtering non-perforating are all connected with dissection or injection of the Schlemm’s canal. Krasnov15 proposes the sinusotomy removing the endothelium of the Schlemm canal using microdissection. The principle of deep sclerectomy is to dissect the internal wall of the Schlemm canal where the greatest resistance to drainage of the aqueous humor is situated, thus allowing a physiological filtration, since the external wall is kept intact. The technique of using high viscosity to widen the Schlemm canal, allows better filtration of aqueous humor. The biggest drawback of these techniques, above all deep sclerectomy, is the formation of fibrous tissue on the sclerotic flap. Numerous authors have described a multitude of implants that would keep the space of the second flap free.10,11,14,16,18,19,24 We submit a new surgical technique which allows a synthesis of the three main surgical techniques for non-

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penetrative filter surgery. This reduces the risks of each, whilst increasing the long-term chances of success.4 SURGICAL TECHNIQUE IN OUTPATIENT SURGERY17 Local Anesthetic5 This anaesthetic technique has been described in the previous chapter. Let us remember that this local anesthetic allows — thanks to the patient’s ability to participate - exposure of the operative field for dissection and its best, and variable angles of work. Choices for Dissection The path of dissection and flap’s localization are chosen to spare the penetrating vessels and to search for the zone that is the most avascular. The draining vessels are on the surface, as shown by Stegmann.21 The choice of the best place for the flap to spare the penetrating vessels to find the most avascular zone, one must not forget that the draining vessels are on the surface, as shown by Stegmann in his film. CONJUNCTIVAL SHUTTER WITH LIMB Stages Stages are as follows: Dissection of the conjunctival shutter with limb, not less than 10 mm, with Vescoat scissors. Dissection in an L shape allowing the conjunctival flap to relax in the opening. Exposing the sclera by dissecting Tenon’s capsule with care (Figs 19.1A and B).

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Figs 19.1A and B: (A) Measure, the width being of less importance than the length (B) The path of dissection and flap’s localization are chosen to spare the penetrating vessels. Conjunctival flap at the limbus L shape

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Use the lightest possible electrocoagulation in order to spare the draining vessels as much as possible. 1st Scleral Flap Incision of the scleral flap (Figs 19.2A and B). • 6 mm × 4 mm, the width being of less importance than the length • depth of 300 microns, cut with a 30º diamond (Meyco, Switzerland) or with a diamond for KR (Meyco, Switzerland) up to the lames corneostromales. It is important to make a flap which is thick enough not to tear when one arrives in the corneal stroma6 (Fig. 19.3). It is important to dissect the lames corneennes, starting from the limb, the cut allowing more room when making the incision of the second flap. 2nd Scleral Flap 5 mm dissection, with a 30º diamond (Meyco, Switzerland), of the length of the second triangular flap of all the depth of the sclera leaving some lamelles sclerales in order to just reveal the choroidien tissue. This allows getting exactly at the scleral spur, at the beginning of Descemet’s membrane (Figs 19.4A and B). Dissection, holding on to the second flap, au tampon triangulaire pour repousser le stroma. Thus, we free Descemet’s membrane. Those who practice deep lamellar keratoplasty (“keratoplastie lamellaire”) operations will have no difficulty in finding the plane of dissection. Separation of the Descemet from the stromal tissue is quite easy, so long as one is in the right plane. The 1.5 mm incision in Descemet’s membrane is made in order that the Schlemm canal is not covered at the time of the cutting of the flap (Fig. 19.5).

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Figs 19.2A and B: (A) Dissecting the first flap (B) A. First scleral flap 6 × 4 mm × 300 micron B. Schlemm’s canal C. Scleral spur D. Sclera F. Descemet’s membrane

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Fig. 19.3: First flap’s dissection to the stromal lamellae

Fig. 19.4A

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Figs 19.4A and B: (A) Second flap’s dissection (B) Second triangular flap of all the depth of the sclera

Fig. 19.5: second flap as to be deep enough. This allows getting exactly at the scleral spur, at the beginning of Descemet’s membrane

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On this level, each side, in the scleral tissue, a slight bleeding can be seen at the cut in the drainage vein of the Schlemm canal (Fig. 19.6). Removal of the Second Flap Removal of the second flap with the diamond or the Vannas scissor (Fig. 19.7). This part of the operation is delicate and has to be done with great care. Because, on a number of occasions, when using Vannas or other scissors, Descemet’s membrane has been torn. Cut up the Scleral Flap in Half Cut up the scleral flap in half: one half is soaked for 5 minutes in 0.04 percent mytomicin, then rinsed. Schlemm canal dissection (Fig. 19.8). Using Bonn forceps with microteeth, a 5 mm dissection of the interior wall of the Schlemm canal is made, allowing us to see some seepage of the aqueous humor. Canalostomy The Schlemm canal vein gives the location of the Schlemm canal. Introduction of an extra fine Grieshaber cannula on both sides of the sclera of the Schlemm canal until some resistance is felt. Slow injection of high viscosity viscous fluid (Healon, G V AMO) whilst removing the microcatheter (Figs 19.9 and 19.10). Implant/Mitomycine C Put in place, in the bed of the second flap, the previously prepared implant, the implant having been, beforehand, soaked in mitomycine and rinsed before being used.

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Fig. 19.6: A slight bleeding can be seen at the cut in the drainage vein of the Schlemm canal

Fig. 19.7: Removal of the second flap with the diamond or the Vannas scissor

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Figs 19.8A and B: Schlemm canal dissection

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Fig. 19.9: Canalostomie

Fig. 19.10: Introduction of an extra fine Grieshaber cannula

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Close the first flap with inverted stitches using nylon 10.0, at each corner of the flap pulling the stitches tight (Fig. 19.11). Close the conjunctive with 3 inverted stitches using 9.0 reabsorbable thread. POSTOPERATIVE TREATMENT As this operation is extraocular, done with ambulatory surgery and local anesthetic, there is no need to cover the eye with a dressing. Patients are treated using eyedrops of cortisone and antibiotics. The dose is 1 drop 3 x a day for 3 weeks. POSTOPERATIVE CHECKUPS The postoperative follow-up must be rigorous. The patient is checked, one hour after the operation, before leaving the clinic, after 1 day, 1 week, and 1 month.

Fig. 19.11: Closing the flap

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Usually, all eye hypotensor treatments are stopped, even if it is necessary for them to be re-introduced at a later date. The filtration bubble that is found when trabectomy is used, does not exist using this technique. As a result, the patient has to be checked controlling the ocular tension in both the eyes. If possible, the measure has to be taken each time at the same hour, in order to avoid obtaining distorted results because of the curve of the nychthemeral ocular pressure. Patients who are cortisone respondant need particularly special attention. Continuous check-ups to control postoperative pressure are necessary in cases of glaucoma. It is extremely important to check the pre- and postoperative pressures in the two eyes at the same times. PEROPERATIVE COMPLICATIONS The most frequent complication is rupture of the Descemet’s membrane when dissecting the second scleral flap: the rupture happens after the scleral spur and, especially, after the removal ? with diamond or Vannas scissors. If this happens, it will be necessary to convert the deep sclerectomy into trabeculectomy without viscocanalostomy, whilst not forgetting to make an iridectomy. When the canalostomy is done, the viscous fluid can leak into the anterior chamber. In the hours following the operation, this will cause a rapid increase in the intraocular pressure. The operation will have to be reviewed, by carrying out a paracentesis, emptying the viscous fluid and rinsing the anterior chamber. The other possible complication is the perforation of the choroid, which has no postoperative importance.

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The most frequent complication from using this technique is increased postoperative pressure, more or less long-term, due to the collapse or closing up/healing of the scleral flap on the bed of the operation. This is the reason why many authors have proposed different types of implants which very in the rapidity of their re-absorbtion. Our technique uses an autograft from the sclera, soaked in mitomycin C2 which inhibits all fibrocyte proliferation. This produces the best results in the long term and the lowest costs. When, after this operation, pressure increases occur rarely, they can still happen after 3-4 years. If there is a recurrence, nowadays we favor repeating the procedure in a more favorable quadrant. We have never had to repeat this operation more than twice. We have stopped doing trabeculoplasty au yag for patients who have increased pressure after three weeks, this technique not having brought the expected results. We do no longer convert our deep sclerocanalostomy into a trabeculectomy, because the complications were too important. REFERENCES 1.

Arenas E. Trabeculectomy ab externo. Highlights of Ophthalmol. World Atlas Series Vol. 1. 1993;216-18. 2. Arenas E. The routine use of mytomycine in trabeculectomy ab externo using a modified drill technique Highlights of Ophthalmol. World Atlas Series Vol. 2 1993;236-37. 3. Baumgartner JM, Bovet J, Baumgartner A. Etude de la stabilisation de la plaie opératoire et de la rapidité de la récupération fonctionnelle dans la chirurgie de la cataracte: Comparaison des résultat entre quatre techniques chirurgicales différentes Ophtalmologie 1995;9:624-25. 4. Bovet J. Deep lamellar sclerectomy, what’s new Eye Advance Mumbay India (abstract) Chairmann Keiki Metha August 2004.

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5.

6.

7. 8. 9. 10.

11.

12. 13. 14. 15. 16.

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J Bovet, JM. Baumgartner, JC Bruckner, V Ilic, O Achard L’anesthésie topique en chirurgie oculaire et sa préparation In: Les Dimensions de la douleur en ophtalmologie A.B. Safran, T. Landis, P. Dayer eds Paris Masson, 1998;166173. J Bovet, I Molnar, JM Baumgartner, F Failla, C Tabatabay Combined Glaucoma and cataract surgery (phacotrabeculectomy) European Ophtalmic Society (abstract), SOE 1997, Budapest. Burian HM, Allen L. Trabeculotomy ab externo. A new glaucoma operation : technique and results of experimental surgery. Amer J Ophthalmol 1962;53:19-26. Cairns JE. Trabeculectomy; preliminary report of a new method. Amer J Ophthalmol 1968;66:673. Chiou AGY, de Courten C, Bovet J. Pseudophakic ametropia managed with a phakic posterior chamber intraocular lens. J Cataract Refract Surg 2001;27:1516-8. Chiou AGY, Mermoud A, Underahl PJ, Schnyder CC. An ultrasound biomicroscopic study of eyes after deep sclerectomy with collagen implant. Ophtalmology 1998;105,4:104-8. Demailly P, Jeanteur-Lunel MN, Berkani M, et al. Non penetrating deep slerectomy associated with collagen device in primary open angle glaucoma. Middle term retrospective study. J Fr Ophthalmol 1996; 19,11:659-66. Fyodorov SN, Ioffe DI, Ronkina TI. Deep sclerectomy: technique and mechanism of a new glaucomatous procedure. Glaucoma 1984;6:281-383. Goldmann H Drainage of aqueous in man. Ophthalmologica 1946;112:11-146. Koslov VI & all. Non penetrating. Deep sclerectomy with collagen. I IRTC Eye Microsurgery. RSFSR Ministry of Public Health, Moscow 1990;3:44-46. Krasnov MM. Externalization of Schlemm’s canal (sinusotomy) in glaucoma. Brit J Ophthalmol 52:157-161. Kershner RM. Nonpenetrating trabeculectomy with placement of collagen drainage device. J Cataract Refract Surg 1995;21:6:608-611.

326 17.

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Krasnov MM. Externalisation of Schlemm’s canal (sinusotomy) in glaucoma. Br J Ophthalmol 1968;52:15761. 18. Lebuisson DA, Bovet JJ. Le concept opératoire pour patients ophtalmologiques ambulants in Laroche L, Lebuisson DA, Montard M Chirurgie de la cataracte chap 6 pp 61-74ed Masson 1996. 19. Massy J, Gruber D, Muraine M, Brasseur G. Nonpenetrating Deep Sclerectomy: collagen implant and viscocanalostomy procedures. Bylsma S. Int Ophtalmol Clin 1999 Summer; 39(3):103-19. 20. Kozlov VI, Bagrow SN, Anisimova SY, et al. Deep sclerectomy with collagen. Eye microsurgery 1990;3:44-46. 21. Stegmann RC. Viscocanalostomy : a new surgical technique for open angle glaucoma. An Inst Barraque, Spain 1995;25:229-32. 22. Stegmann R, Piennaar A, Milller D. Viscocanalostomy for open-angle glaucoma in black African patients. J Cataract Refract Surg 1999;25:3,316-22. 23. Sampaolesi R. Glaucoma, 2nd edition, Editorial Médica Panamericana, Buenos Aires, 1991;525-26. 24. Perkins ES. Pressure in the canal of Schlemm. Brit J Ophthalmol 1955;39:215-19. 25. Sourdille P, Santiago PY, Villian F, et al. Reticulated hyaluronic acid implant in nonperforating trabecular surgery. J Cataract Refract Sur 1999;25:332-39. 26. Sugar HS. Experimental trabeculotomy in glaucoma. Am J Ophthalmol 1961;54:623-27. 27. Tanibara H, Negi A, Akimoto M, et al. Surgical effects of trabeculectomy ab externo on adults eyes with primary open angle glaucoma and pseudoexfoliation syndrome. Arch Ophthalmol 1993;111:1653-61. 28. Verges C, Llevat E. Non penetrating deep sclerectomy (NPDS) with an Er:YAG laser. Clinical results after 16 months follow-up ASCRS abstracts 2000;201. 29. Zimmerman ThJ, et al. Trabeculectomy vs. non penetrating trabeculectomy. A retrospective study of two procedures in phakic patients with glaucoma. Ophthalmic Surgery 1984;15:734-40.

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INTRODUCTION/INDICATIONS Cataracts and glaucoma have always been linked together. The crystalline lens is responsible for most of secondary glaucoma, these come from a pseudoexfoliation or a simple hypertrophy of the crystalline lens. The diagnostic problem we find in combined surgery is to know what is the part played by each of these pathologies in ocular hypertension.18 When should we feel the need to propose a combined operation when a simple cataract operation is enough.12 A study by Jean-Marc Baumgartner has shown a lowering of 3 mm Hg of ocular tension in normal patients after a simple cataract operation using phacoemulsification.3 In Europe, more and more patients suffer, because of their age, from pseudoexfoliation. The problem is important in cataract operations, because, in a certain number of cases, pseudoexfoliation leads to a zonulolysis that can develop into total lysis. The lens then falls into the vitreous fluid. On the other hand, pseudoexfoliation increases the pressure by deposit of hyaloids on the trabeculum level.21 The crystalline lens, whilst increasing in size, can diminish the flow of aqueous humor, especially in the hypermetropic eye with narrow anterior chamber. For all glaucoma and cataract surgery, the goal is to solve the two problems in one operation, without increasing postoperative risks and extending recovery time.6,20 Nowadays, the new operating techniques for cataract allow intervention by paracentheses of less than 1.2 mm and an implantation of the lens using an incision of 1.7 mm.5

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This removes all problems of astigmatism induced by the operation. This new technique allows less postoperatives checks and a faster visual recovery.3 Non-perforating surgery techniques for glaucoma, not only have a small number of postoperative complications, but also have the advantage of producing a very rapid recovery.9 We are going to describe our combined operation for cataracts/glaucoma using 2 new techniques.4,8 • one, Bimanual Microphaco technique for cataracts • the other, deep sclerocanalostomy In the combined operation, timing of the two operations is important. Several authors prefer to perform each of these operations separately at different sites. After having tried multiple combinations, either on one or two sites, it seemed to us that the best solution was to start on one side by dissecting the first flap up to the scleral blade, then to do a bimanual microphaco on a temporal site, at the end, finishing the second flap and the canalostomy under viscoelastic solution in the anterior chamber.11 This has several advantages: dissection of the first flap is done on an eye with healthy pressure, dissection is made easier, the cataract surgery is carried out without any risk of rupturing the Descemet and, in the end, the dissection of the second flap is carried out with weak intercamerular pressure, so diminishing risk of rupturing the Descemet. Non-penetrative surgical techniques do not have the postoperative complications of the first, penetrative, surgery, but they are more difficult to carry out. An exact knowledge of the micro-anatomy of the region is important and a learning curve necessary.

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We submit to you two new surgical techniques with specific timings, allowing glaucoma and cataract operations to be done with the minimum of risk. The operation reduces the risks inherent in each technique, whilst increasing the long-term chances of success. SURGICAL TECHNIQUE 1st Stage: Glaucoma 1st Scleral Flap Sclera flap under local anesthetic and subconjunctival bubble in outpatient surgery (Figs 20.1A and B).15 This anesthetic technique has been described in the previous chapter. Let us remember that this local anesthetic allows thanks to the patient’s ability to participate - exposure of the operative field for dissection and its best, and variable angles of work.7,10 Choices for dissection: The path of dissection and flap’s localization are chosen to spare the penetrating vessels and to search for the zone that is the most avascular. The draining vessels are on the surface, as shown by Stegmann. The choice of the best place for the flap to spare the penetrating vessels to find the most avascular zone, one must not forget that the draining vessels are on the surface, as shown by Stegmann in his film.19 Conjunctival shutter with limb Stages are as follows: • Dissection of the conjunctival shutter with limb, not less than 10 mm, with Vescoat scissors. Dissection in an L

Bimanual Microphaco and Deep Sclerocanalostomy

Figs 20.1A and B

331

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shape allowing the conjunctival flap to relax in the opening. • Exposing the sclera by dissecting Tenon’s capsule with care. • Use the lightest possible electrocoagulation in order to spare the draining vessels as much as possible. Incision of the scleral flap • 6 × 4 mm, the width being of less importance than the length • depth of 300 microns, cut with a 30º diamond (Meyco, Switzerland) or with a diamond for KR (Meyco, Switzerland) up to the lames corneostromales. It is important to make a flap which is thick enough not to tear when one arrives in the corneal stroma (Fig. 20.2). It is important to dissect the lames corneennes, starting from the limb, the cut allowing more room when making the incision of the second flap.

Fig. 20.2

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2nd Stage: Cataract Bimanual Microphaco 19G Two paracenteses are made at temporal level, with a 20 gauge diamond knife. Then we make an intracameral injection of a solution of lidocaine diluted 0.2 percent without preservative. This allows the iris to be anesthetized in case of mobilization. Enlargement of the 2 paracenteses to exactly 1.2 mm 19G (Fig. 20.3) and filling the anterior chamber with viscous. Capsulorhexis Capsulorhexis with a special capsulorhexis cannula (Fig. 20.4).

Fig. 20.3

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Fig. 20.4

Hydrodissection and hydrodelineation of the nucleus and the epinucleus. Penetration in the anterior chamber, first with a Nagahara irrigation cannula of 19G, then introduction of our phacotip of 0.9 mm diameter, without sock. The difference between 19G (1,2 mm) and 0.9 mm allows complete cooling of the cannula (Fig. 20.5). Any type of phaco-emulsification machine can be used for this new procedure, but the most appropriate are the machines that allow a strong aspiration mixing the peristaltic rotative force with the force of the Venturi pump. Parameters The parameters are the following:• Irrigation 65 cc/min • Aspiration strength minimal 150 mm Hg • Power 40 percent

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Fig. 20.5

Flip and Chop Phacoemulsification Flip and chop phacoemulsification technique, after having aspirated the viscous and the superior cortex: We first make a groove using maximum aspiration, then we lift the nucleus slightly in order to pass the irrigation cannula behind it and break it into 1/8 slices that are each sucked up as we go along. We repeat this procedure until we have emulsified the nucleus in its entirety.17 In order to avoid the collapse of the chamber, first, we remove the phacotip and only after that, do we remove the Nagahara irrigation chopper. Then, we introduce the irrigation-aspiration cannula (de Duet 19G) to aspirate the cortex and occasionally the rest of the nucleus. Once this procedure is done, we fill up the anterior chamber with viscous (Fig. 20.6).

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Fig. 20.6

Lens Implantation We enlarge the paracentisis from 1.2 to 1.7 mm and an acrylic hydrophobe and hydrophile Acri Smart 36a implant is injected (Acritec Germany, inserted in a silicone special capsule), This enables us to avoid introducing the capsule into the anterior chamber and to inject solely the implant (Fig. 20.7). The implant is very easily positioned in the anterior chamber. Once the implant is in situ, we leave in the viscous and proceed to the second stage of the glaucoma operation. 3rd Stage Glaucoma 2nd Scleral Flap 5 mm dissection, with a 30º diamond knife (Meyco, Switzerland), of the length of the second triangular flap of

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Fig. 20.7

all the depth of the sclera leaving some scleral plates in order to just reveal the choroidien tissue. This allows getting exactly at the scleral spur, at the beginning of Descemet’s membrane (Fig. 20.8). Dissection, holding on to the second flap, with a triangular swab in order to push back the stroma. In this way, we free Descemet’s membrane. Those who practice deep lamellar keratoplasty (“keratoplastie lamellaire”) operations will have no difficulty in finding the plane of dissection. Separation of the Descemet from the stromal tissue is quite easy, so long as one is in the right plane. The 1.5 mm incision in Descemet’s membrane is made in order that the Schlemm canal is not covered at the time of the cutting of the flap.

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Fig. 20.8

On this level, each side, in the scleral tissue, a slight bleeding can be seen at the cut in the drainage vein of the Schlemm canal. Removal of the second flap with the diamond. This part of the operation is delicate and has to be done with great care. Because, on a number of occasions, when using Vannas or other scissors, Descemet’s membrane has been torn (Fig. 20.9). Cut up the scleral flap in half: one half is soaked for 5 minutes in 0.04 percent mytomicin, then rinsed. Schlemm canal dissection: Using Bonn forceps with micro teeth, a 5 mm dissection of the interior wall of the Schlemm canal is made, allowing us to see some seepage of the aqueous humor. Canalostomy: The Schlemm canal vein gives the location of the Schlemm canal. Introduction of an extra fine

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339

Fig. 20.9

Grieshaber cannula on both sides of the sclera of the Schlemm canal until some resistance is felt. Slow injection of high viscosity viscous (Healon, G V AMO) whilst removing the microcatheter (Fig. 20.10).16,14 Implant/Mitomycine C: Put in place, in the bed of the second flap, the previously prepared implant, the implant having been, beforehand, soaked in Mitomycine and rinsed before being used.1,13 Close the first flap with inverted stitches using nylon 10.0, at each corner of the flap pulling the stitches tight. Close the conjunctive with 3 inverted stitches using 9.0 re-absorbable thread (Fig. 20.11). Remove the viscous from the anterior chamber, and also from behind the lens, in order to avoid any of the viscous remaining. Any left remaining could cause postoperative hypertension.

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Fig. 20.10

POSTOPERATIVE TREATMENT This combined operation, is carried out as ambulatory surgery and with local anesthetic, there is no need to cover the eye with a dressing. Patients are treated with cortisone and antibiotic drops. Dosage is 1 drop 3 x a day for 3 weeks. POSTOPERATIVE CHECK-UPS The postoperative follow-up must be rigorous. The patient is checked, one hour after the operation, before leaving the clinic, after 1 day, 1 week, and 1 month.

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341

Fig. 20.11

Usually, all eye hypotensor treatments are stopped, even if it is necessary for them to be re-introduced at a later date. The filtration bubble that is found when trabectomy is used, does not exist using this technique. As a result, the patient has to be checked controlling the ocular tension in both the eyes. If possible, the measure has to be taken each time at the same hour, in order to avoid obtaining distorted results because of the curve of the nychthemeral ocular pressure. Patients who are cortisone respondent need particularly special attention. Continuous check-ups to control postoperative pressure are necessary in cases of glaucoma.

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It is extremely important to check the pre- and postoperative pressures in the two eyes at the same times. COMPLICATIONS Complications During the Operation Complications specifically connected with this combined operation consist in the rupture of the Descemet’s membrane. This happens if the timing already described is not respected and if the second flap is done before operating on the cataract. Postoperative Complications The most frequent postoperative complication with this technique is an increase of pressure, more or less long-term, with the collapse or closing up/healing on the site of the operation. Our technique uses an autograft of the sclera, soaked in Mitomycin C which inhibits all fibrocyte proliferation. This produces the best results and the lowest costs in the long term REFERENCES 1.

Arenas E. The routine use of mytomycine in trabeculectomy ab externo using a modified drill technique. Highlights of Ophthamol.World Atlas Series Vol. 2 1993;236-37. 2. Baumgartner JM, Bovet J, Baumgartner A. Etude de la stabilisation de la plaie opératoire et de la rapidité de la récupération fonctionnelle dans la chirurgie de la cataracte:Comparaison des résultat entre quatre techniques chirurgicales différentes. Ophtalmologie 1995;9:624–25. 3. JM Baumgartner, J Bovet, A Baumgartner. Deep Sclerectomy or trabeculectomy in outpatient eye surgery. SOE Budapest (abstract) June 97.

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4.

5. 6.

7. 8. 9. 10. 11.

12. 13.

14.

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J Bovet. Catarefractive Surgery: A next Step to Phakonit. In: A. Garg (Ed): Mastering the Art of Bimanual Microincision Phaco. Jaypee Brothers Medical Publishers, New Dehli 2005. J Bovet, et al. Combined Glaucoma and cataract surgery (phacotrabeculectomy). Instruction course ( abstract) SOE, Budapest, European Ophthalmic Society, 1997. J Bovet, et al. L’anesthésie topique en chirurgie oculaire et sa préparation In: A.B. Safran, T. Landis, P. Dayer (Eds): Les Dimensions de la douleur en ophtalmologie. Paris Masson 1998;166-73. J Bovet, et al. Deep Phaco Glaucoma tunnel. ESCRS, video Nice 1998. J Bovet. Deep lamellar sclerectomy, what’s new Eye Advance Mumbay India (abstract) Chairman Keiki Mehta, August 2004. J. Bovet. Combined Sclerectomy and Phaco in Topical and conjunctival Bubble Anaesthesia. Island Ophthalmology, Puerto Rico (abstract) 1999. Chiou AGY, et al. An ultrasound biomicroscopic study of eyes after deep sclerectomy with collagen implant. Ophthalmology 1998;105,4:104-08. Gianoli F, et al. Combined surgery for cataract and glaucoma: phacoemulsification and deep slcerectomy compared with phacoemulsification. J Cataract and Refractive Surgery 1999;25:340-46. Krasnov MM. Externalisation of Schlemm’s canal (sinusotomy) in glaucoma. Br J Ophthalmol 1968;52:15761. Lebuisson DA, Bovet JJ. Le concept opératoire pour patients ophtalmologiques ambulants in Laroche L, Lebuisson DA, Montard M Chirurgie de la cataracte chap 6 pp61-74ed Masson 1996. Massy J, Gruber D, Muraine M, Brasseur G. Nonpenetrating Deep Sclerectomy: collagen implant and viscocanalostomy procedures. Bylsma S. Int Ophthalmol Clin. 1999 Summer; 39(3):103-19.

344 15. 16.

17. 18. 19.

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Metha KR. The new phaco cleaves techniques for hard cataracts. J intraocular Implant and Refractive Society India 1996;1:74-75. Molnar L, Beuchat J, Bovet M, Bumbacher JF. Chanson, JC Corne, C de Courten, F Failla, A Merz, F Paccolat, P Rabineau, F Rossi, F Simona, C Tabatabay, E Thorthon (Switzerland). Swiss multicentre study group for phacotrabeculectomy: current state ESRC Gothenburg, Sweden, (abstract) 10-13 October 1996. Stegmann RC. Viscocanalostomy : a new surgical technique for open angle glaucoma. An Inst Barraque, Spain 1995;25:229-32. Sampaolesi R. Glaucoma, Editorial Médica Panamericana, Buenos Aires, 1991; 2nd edition, pp. 525-26. Tanibara H, Negi A, Akimoto M, et al. Surgical effects of trabeculectomy ab externo on adults eyes with primary open angle glaucoma and pseudoexfoliation syndrome. Arch Ophthalmol 1993;111:1653-61.

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INTRODUCTION Standard nonpenetrating glaucoma surgery (NPGS) currently consists of different methods, the most popular of which are deep sclerectomy and viscocanalostomy.1,2 The goal of NPGS is to create a surgical procedure as efficient as trabeculectomy but with less complications.3-6 The main idea of NPGS is to target the portion of the aqueous outflow pathway responsible for the main resistance to outflow, and to create filtration through the thin trabeculo-Descemet’s membrane. The uveoscleral pathway was described more than 30 years ago.7 It was also termed unconventional outflow route (as opposed to the conventional or trabecular meshwork outflow) and showed to be responsible for up to 50 percent of aqueous humour drainage in monkey eyes.7 The aqueous percolates through the tissue spaces of the ciliary muscle into the supraciliary and suprachoroidal spaces. We have observed that by tightly suturing the scleral flap, bigger amounts of the percolating aqueous could be forced through the remaining sclera into the uveoscleral outflow.8 Deep sclerectomy with collagen implant (VDSCI) is a modification of deep sclerectomy that was devised with the goal of increasing aqueous outflow via the uveoscleral pathway. By dissecting part of the deep sclera, the drainage of aqueous humour into the suprachoroidal space should be enhanced. Aqueous in the supra-choroidal space may hypothetically reach the uveoscleral outflow, and it could also induce a chronic ciliary body detachment thus reducing aqueous production. At the same time, we aimed to reduce dependency on subconjunctival outflow to minimize the size of the filtering bleb and bleb-related discomfort and complications.

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We furthermore aimed to gain further knowledge in the mechanisms of function of NPGS that are not yet properly understood. GENERALITIES Indications for NPGS include primary or secondary openangle glaucoma, and exclude neovascular and closed-angle glaucoma. The procedure is particularly well adapted for patients with myopia due to the slow and gradual postoperative pressure reduction and the smaller subconjunctival filtering bleb size which enhances the comfort of wearing a contact lens. SURGICAL TECHNIQUE Retrobulbar, peribulbar or topical anesthesia can be used at the discretion of the surgeon. With peribulbar or retrobulbar block, the smallest amount of anesthetic should be used to allow rotation of the globe and thus give good exposure for the deep sclerectomy dissection. The initial steps for VDSCI are identical to those for standard DSCI, for which we give a short description here. Conjunctiva and Tenon’s capsule are opened on 8-10 mm either at the limbus or at the fornix. Some light wetfield cauterization should be performed on the sclera as necessary at this stage. A superficial scleral flap measuring 5 × 5 mm and including 1/3 of the scleral thickness (about 300 μm) is first delineated using a metal blade and then dissected with a crescent ruby blade (Huco vision SA, St-Blaise, Switzerland). In order to be able to later dissect the corneal stroma down to Descemet’s membrane, the scleral flap is dissected 1 to 1.5 mm into clear cornea. A sponge soaked in mitomycin-C, 0.02 percent, is used at this stage in

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patients at high-risk of scarring (i.e. age below 60; melanoderma patients; previous history of conjunctival surgery; long standing history of glaucoma treatment; previous uveitis; or trauma). Deep sclero-keratectomy is done by performing a second deep scleral flap (4 × 4 mm). The two lateral and the posterior deep scleral incisions are made using a 15-degree diamond blade. The deep flap is smaller than the superficial one leaving a margin of sclera on the three sides. This will allow a tighter closure of the superficial flap in cases of a preoperative perforation of the TDM. The deep scleral flap is then dissected horizontally. The remaining scleral layer should be as thin as possible (50 to 100 μm). Reaching the anterior part of the dissection, Schlemm’s canal is unroofed and the sclero-corneal dissection is prolonged anteriorly into clear cornea for 1 to 1.5 mm in order to remove the sclero-corneal tissue behind the anterior trabeculum and the Descemet’s membrane. When the anterior dissection between the corneal stroma and Descemet’s membrane is completed, the deep scleral flap is cut anteriorly using the diamond knife. At this stage of surgery, the very deep scleral dissection is performed. In the posterior quadrant of the sclera, two very deep flaps (each 1.5 × 1.5 mm) of the remaining 5-10 percent of sclera are excised and the choroid is exposed. A thin bridge of deep scleral tissue is left between the two flaps in order to prevent a possible choroidal prolapse (Figs 21.1 and 21.2). At that last stage of the procedure, there should be a diffuse percolation of aqueous through the remaining trabeculo-Descemet’s membrane. The juxtacanalicular trabeculum and Schlemm’s endothelium are then removed. To avoid a secondary collapse of the superficial flap over the TDM and the remaining scleral layer, a collagen implant

Very Deep Sclerectomy

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Fig. 21.1: Standard deep sclerectomy after dissection of the deep scleral flap

Fig. 21.2: Very deep sclerectomy after dissection of two 1.5 x 1.5 mm very deep scleral flaps. A scleral bridge is left to prevent choroidal prolapse, and the collagen implant is placed to re-inforce it for the early postoperative period

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is placed in the center of the scleral bed over the remaining bridge of deep sclera and secured inside the scleral bed with a single 10/0 nylon suture. The superficial scleral flap is then repositioned into place, and closed with two loose 10/0 nylon sutures. Conjunctiva and Tenon’s capsule are closed in two layers with a running 8/0 Vicryl suture. PRELIMINARY RESULTS In a prospective randomized trial that involved 50 patients we looked at the intraocular pressure lowering effect and safety of the new method of very deep sclerectomy with collagen implant (VDSCI, 25 patients) and compared it to standard deep sclerectomy with collagen implant (DSCI, 25 patients). The two groups were well matched with respect to gender, age, race, and glaucoma type. Mean preoperative IOP was 21.5 mmHg (±7.4) in the VDSCI and 22.7 mmHg (±4.4) in the DSCI group. After a mean followup of 6 months, the two procedures produced similar outcomes with respect to IOP (Fig. 21.3), success rates, reduction of medication use, and safety. On the first postoperative day IOP fell to 4.4 in the VDSCI and 5.6 mmHg in the DSCI group, a positive prognostic sign for IOP control as shown by Shaarawy and co-workers.9 Mean IOP at six months’ follow-up was 12.0 mmHg in the VDSCI and 12.5 in the DSCI eyes. The safety profile of the new procedure has also been favorable with significantly fewer patients requiring postoperative MMC (3 VDSCI vs. 10 DSCI eyes) and only two eyes in the VDSCI group developing a choroidal detachment versus none in the DSCI group. There were no significant postoperative complications in this series. No shallow or flat anterior chamber, no-bleb-related endophthalmitis, and no surgery-induced cataract was observed in either group. There was one case of a malignant

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Fig. 21.3: IOP over time for VDSCI and DSCI groups. There was no significant difference at any point at time. Mean follow-up period was 6.5 months (maximum 12 months)

glaucoma in a patient of African origin in the DSCI group. Goniopuncture with the Nd:YAG laser was performed on 3 VDSCI-treated eyes and 5 DSCI-treated eyes. High frequency ultrasound biomicroscopy (UBM), as developed by Pavlin and Foster,10 provides in vivo detailed anatomic evaluation of the anterior segment of the eye. Using ultrasound biomicroscopy, it was possible to observe greater uveoscleral outflow in VDSCI eyes as measured by suprachoroidal effusion in 80 percent of VDSCI vs. 20 percent of DSCI patients (Figs 21.4 to 21.7). Mean subconjunctival bleb size was smaller in VDSCI eyes compared to DSCI eyes (9.1 vs. 29.6 mm3). POSTOPERATIVE MANAGEMENT As in standard NPGS, the first postoperative weeks are crucial for the success of the new procedure. Experience has shown that the appropriate postoperative management can have the same magnitude of influence on the surgical outcome as surgery itself. The following regimen for postoperative check-up is recommended as a guideline:

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Fig. 21.4: UBM of a nice subconjunctival filtering bleb after DSCI

Fig. 21.5: UBM after VDSCI. Hypoechoic areas in the suprachoroidal space indicative of uveoscleral outflow can be seen

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Fig. 21.6: UBM after VDSCI. Hypoechoic areas in the suprachoroidal space indicative of uveoscleral outflow can be seen

the patient is seen on the first postoperative day, where a complete ophthalmic examination is performed, with particular attention given to the appearance of the bleb and the depth of anterior chamber. After that, the patient is seen weekly for the first month, and then at month 2 , 3, 6, and, finally every 6 months with visual field examinations every year. We use a topical regimen of corticosteroids and antibiotics in the immediate postoperative period. Tobradex© (Tobramycin and Dexamethasone) is

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Fig. 21.7: UBM after VDSCI. The suture securing the collagen implant can be seen

administered beginning on the first postoperative day. Drops are given every 6 hours during waking hours for at least four weeks. In the next stage, patients are treated with a non-steroidal anti-inflammatory drug for two months. CONCLUSION In our first study with up to12 months of follow-up, there is no statistically significant difference between very deep sclerectomy with a collagen implant and standard deep sclerectomy in terms of intraocular pressure, complete and

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qualified success rates, and reduction of number of medications. In VDSCI, UBM showed a statistically significant increase in amount of suprachoroidal effusion associated with a tendency towards smaller size of the subconjunctival bleb compared to DSCI. We therefore conclude that VDSCI might be a good alternative to standard penetrating surgery by decreasing the complications and discomfort related to the subconjunctival bleb. However, at this stage, longer follow-up is needed to assess the safety and efficacy of this new procedure. REFERENCES 1.

Stegmann RC. Visco-canalostomy: a new surgical technique for open angle glaucoma. An Inst Barraquer Spain 1995;25:229-32. 2. Kozlov VI, Bagrov SN, Anisimova SY, et al. Nonpenetrating deep sclerectomy with collagen. Eye Microsurg (Russian) 1995;3:44-46. 3. Watson PG, Jakeman C, Ozturk M, et al. The complications of trabeculectomy: a 20-year follow-up. Eye 1990;4:425-38. 4. Jonescu-Cuypers C, Jacobi P, Konen W, Krieglstein G. Primary viscocanalostomy versus trabeculectomy in white patients with open-angle glaucoma: A randomized clinical trial. Ophthalmology 2001 Feb;108(2):254-58. 5. Shaarawy T, Mansouri K, Schnyder C, Ravinet E, Achache F, Mermoud A. Long-term results of deep sclerectomy with collagen implant. J Cataract Refract Surg 2004 Jun; 30(6):1225-31. 6. Mermoud A, Schnyder CC, Sickenberg M, Chiou AG, Hediguer SE, Faggioni R. Comparison of deep sclerectomy with collagen implant and trabeculectomy in open-angle glaucoma. J Cataract Refract Surg 1999 Mar;25(3):323-31. 7. Bill A. The aqueous humor drainage mechanism in the cynomolgus monkey (Macaca irus) with evidence for unconventional routes. Invest Ophthalmol 1965 Oct; 4(5):911-19.

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Chiou AG, Mermoud A, Hédiguer SE, et al. Ultrasound biomicroscopy of eyes undergoing deep sclerectomy with collagen implant. Br J Ophthalmol 1996;80:541-44. 9. Shaarawy T, Flammer J, Smits G, Mermoud A. Low first postoperative day intraocular pressure as a positive prognostic indicator in deep sclerectomy. Br J Ophthalmol 2004 May;88(5):658-61. 10. Pavlin CJ, Sherar MD, Foster FS. Subsurface ultrasound microscopic imaging of the intact eye. Ophthalmology 1990 Feb;97(2):244-50.

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INTRODUCTION Here we introduce a new concept in the primary therapy of glaucoma where a G-Probe of an Iris Medical Diode laser is used to treat glaucoma along with phacoemulsification on a primary basis, i.e. a first glaucoma procedure of choice! MATERIALS AND METHODS During the course of a year at the Mehta International Eye Institute Mumbai, 50 patients had combined phacoemulsification and G-probe performed in the same sitting for coexisting cataract and glaucoma. Only those patients with IOP>21 on maximum tolerated medication were chosen. A peribulbar block was given and the G –probe was applied for 24 applications circumferentially (1 for each clock hr) over the ciliary body at 2W for 2 seconds. Then clear corneal phaco was performed and an injectable intraocular lens implanted in all cases. The IOP was measured on day 1 week 1 and months 1, 3 and 6. All surgery was carried out by the same surgeon (CM) using the Alcon Infinity unit, Iris Medical Diode laser and G-Probe. Pressures were measured with Topcon-CT80 air puff tonometer (Figs 22.1 to 22.4). CLASSIFICATION Glaucoma surgery can be broadly classified into: 1. Cyclodestructive (reducing inflow). or 2. Filtering (increasing outflow): Filtration surgery, typically trabeculectomy and more recently, nonpenetrating techniques have usually been the procedure of choice as an initial intervention because of their efficacy and relative safety and predictability. Ciliary

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Fig. 22.1: The iris medical 810 nm laser

Fig. 22.2: The G-probe

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Fig. 22.3: Iris medical base unit with the probe attached

Fig. 22.4: Note the spade shaped footplate

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destruction has been reserved for more refractory cases of glaucoma and in eyes which have little or no visual potential. Refractory or relatively “untreatable” glaucomas include neovascular glaucoma, posttraumatic angle recession glaucoma, aphakic glaucoma severe congenital/developmental glaucoma, postretinal surgery glaucoma especially with the use of silicon oil and glaucoma associated with penetrating keratoplasties. In the past, cyclodestructive glaucoma procedures have been carried out by either surgical excision, diathermy, cryotherapy, or by laser. Laser cyclophotocoagulation has now become the principal method for what has been termed as “turning down the tap.” Beckman and Sugar pioneered the use of trans-scleral cyclophotocoagulation (TCP) thirty odd years ago. In the beginning they tried the procedure with a Ruby laser but they found that the (Nd:YAG) laser was more effective in penetrating the sclera and optimizing energy absorption by the ciliary epithelium. The delivery of laser energy through the sclera may be performed by either the non-contact or contact method. In the non-contact approach, a slit lamp is employed to apply laser energy through the conjunctival/scleral eyewall. The focus of energy delivery is 1–1.5 mm behind the limbus, through a contact lens so that maximal effect is at the level of the ciliary body. The total number of laser applications are usually about 32 (eight per quadrant), avoiding the 3 and 9 o’clock positions in order to preserve the long posterior ciliary arteries. More recently, contact cyclophotocoagulation has gained favor as a preferred modality. Using the Nd:YAG laser (Surgical Laser Technologies (SLT), a hand-held sapphire tipped probe is placed on the conjunctiva and

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sclera, 1–2 mm behind the limbus. Depending on the requirement, 28 spots are applied, also avoiding the 3 and 9 o’clock positions. Energy levels are titrated to avoid an audible “pop” which signifies an overtreatment and explosion of the ciliary body tissue. The semiconductor diode laser (Iris Oculight SLx, Iris Medical Inc, Mountain View, CA, USA) emits at 810 nm wavelength and is better absorbed by melanin than the Nd:YAG. The spade shaped tip of the handpiece (known as the “G-Probe”) protrudes 0.7 mm deeper than the contact surface. There is better absorption of this wavelength by the pigmented tissues of the ciliary body than the 1064 nm Nd:YAG laser. Also a lower incidence of the complications seen with other cyclodestructive techniques namely, phthisis, hypotony, uveitis, pain, and loss of visual acuity are reported in the literature. The most widely adopted treatment strategy is the treatment protocol recommended by Spencer and Vernon. Here the laser energy was delivered through the 600 μm diameter quartz fiber oriented within the G-probe handpiece to center treatment 1.2 mm behind the limbus. Transillumination is recommended to identify the ciliary body position in eyes with congenital glaucoma or where the limbal anatomy was distorted by previous surgery. The fibreoptic tip protrudes 0.7 mm from the G-probe contact surface in order to indent the conjunctiva and sclera thereby improving the laser transmission to the ciliary body. The posterior angulation of the fiber is ensured by simply placing the spade shaped tip flush with the limbus in the manner shown in the figure was correctly oriented to protect the lens of phakic eyes from laser damage. Their standard treatment protocol was used at each “session” to treat three quarters (270 degrees) of the circumference of the ciliary body. This usually resulted in 14. An energy of 2.0 W was used for 2.0 seconds,

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resulting in a power delivery of 4.0 J per application (56 J per session for 14 applications). This was not altered even if “pops” were heard during treatment. In the first treatment session the temporal 90 degrees was left untreated. A different 90 degrees was left untreated if further treatment sessions proved necessary. On subsequent treatments the 90 degrees untreated varied depending on the appearance of the sclera and conjunctiva at the limbus—that is, if an area of scleromalacia from previous surgery was present this area could be avoided. In Spencer and Vernons (S&V) study, the mean IOP before treatment was 33.0 mm Hg (10.7) and by the last visit this had fallen to 16.7 mm Hg at 6 months. It is apparent that the cyclodiode gives a mean reduction of at least 33 percent in IOP. The visual acuity fell in half the patients by 1 line when utilising the Iris diode laser with the G-probe. In their experience, when “pops” were heard continually with a consistent energy level they did not have any eyes with marked inflammation post-laser. They did not find a particular association between race and hearing “pops”. Different protocols and treatment strategies are found in the literature. Kosoko et al delivered between 17 and 19 applications to 270 degrees of the ciliary body for a 2.0 second period and commencing at 1.75 W increasing to 2.0 W if no “pops” or “snaps” were heard. The theory behind reducing the energy so as not to hear “pops” at each application is that these are indicative of tissue disruption, thus leading to unwanted extra inflammation. No eyes in Kosoko and others’ multicenter study of 27 eyes had had a previous cyclodestructive procedure and only two eyes had repeat treatment (after 9 and 13 months). About 60 percent of eyes were controlled (IOP < 22 mm Hg) which is less than the figure of 81 percent from the S & V study.

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In a study carried out by Philip Bloom, they allowed more than one treatment session but 18 percent of their eyes had had cyclodestructive procedures before cyclodiode and the mean follow-up was only 10 months. In addition, the treatment protocol varied considerably between eyes, from 20 to 40 applications of 1.5 W and 1.5 seconds “titrated against risk of phthisis”. Brancato et al 20 had a higher retreatment rate of 65 percent than Spencer and Vernons, 45 percent. This is probably due to patient group differences as 10/48 patients in Brancato’s series had “pediatric glaucoma”. Different types of glaucoma behaved differently. The rubeotic eyes, those with silicone oil glaucoma, those with glaucoma related to corneal disease (including postkeratoplasty glaucoma), and those with chronic posttraumatic glaucoma had the greatest percentage drop in IOP (56.7 to 65.6%) in the S & V study. These groups, however, had the highest pretreatment pressures and therefore would have required a larger drop to achieve the target pressure. In our practice the following procedure is followed (Figs 22.5 to 22.11). The eye to be operated, undergoes G-probe applications, over 360 degrees with the probe in the proper orientation, we use 2 watt power and 2 second exposure time. We aim for a “pop-less” endpoint. To simplify,I put 2 or 3 applications. If popping occurs, the energy is decreased in 0.5 watt increments till popping subsides,usually at 1.5 watts or sometimes even at 1 watt. Twenty-two applications are administered with care taken to avoid pigmented lesions on the conjunctiva, common pigmented Indian eyes. Also 3 and 9 o’clock meridians are best avoided to avoid pain, uveitis and ischemia which

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Fig. 22.5: Cross-sectional view of the laser delivery to the ciliary body

Fig. 22.6: Note the presence of a mature traumatic cataract

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Fig. 22.7: Proper placement of the spots

Fig. 22.8: Apple Miyake view of spots applied on the ciliary processes

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Fig. 22.9: 22 applications for 22 clock hours avoiding 3 and 9 o’clock

Fig. 22.10: Aiming beam of the G-probe tip

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Fig. 22.11: Applying the G-probe laser energy

occurs with damage to the long ciliary nerves and vessels. The applications are put with firm indentation so as to maximize transmission of energy through the sclera and also as indentation leaves a mark which helps to position and space the next application. Once the applications are over, the eye is washed with betadine solution and cataract surgery is carried out ether with a standard 2.8 mm clear corneal phaco technique involving drect backcracking after tipping the nucleus up in hydrodissection in a procedure called lens salute phaco, or by employing a Microphaco technique and the same chopping maneuver with a Cyres Scythe chopping tip on the MST Duet inflow system. In my (CM) experience, of combining phacoemulsification wth G-probe as a primary procedure for coexisting cataract and primary open angle glaucoma the dreaded complication, phthisis has never occurred, probably as

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these were “virgin” eyes and had not undergone any surgical intervention for glaucoma previously. Phthisi bulbi in the literature review occurs in less than 1 percent of cases. Typically these patients have had 2 or three trabeculectomies and a healthy dose of cryotherapy as well. The G-probe application adds the final straw on the camels back so to speak! Phthisis has never been reported in a case where no previous intervention (surgery or cryo) has been attempted in “virgin” eyes. No patient had significant pain apart from a feeling of heaviness of the head. Postoperatively the patient is typically on topical dexa or beta methasone eyedrops and Moxifloxacin eyedrops. Oral diclofenac sodium tablets 50 mg twice a day is all that is needed for any pain control for three to four days. Oral steroid is administered in a dosage of 16 mg triamcinolone tablets for 4 days. There was no extra uveitis seen in these patients and no appreciable cells or flare, apart from that expected in a simple clear corneal phacoemulsification with a good quality viscoelastic. This procedure in our hands has proved its safety and efficacy and deserves a try. When you consider, bleb failures, bleb leaks, bleb related endophthamlitis, overhanging blebs, bleb failure, persistent hypotony, maculopathy, etc. simply turning down the tap, may prove to be a more attractive alternative. RESULTS At the end of one day all patients had pressure less than 10 mm Hg. At week one, 3 patients had pressures greater than 21. At month 1 the number of patients (IOP > 21) had increased to 6.

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At month one these 6 underwent the same procedure again (G-probe). At month 6 all patients except one has pressures less than 21 mm Hg on no additional medication. CONCLUSION Combined G-Probe Phaco with IOL implantation has proved to be safe consistent and reproducibly easy to perform. It is a very effective way to control glaucoma without any incisional surgery! BIBLIOGRAPHY 1. 2. 3.

4. 5. 6. 7. 8.

Abadie C. Section de la zone ciliare ou ciliairatomie. Arch Ophthalmal 1910;30:262-8. Albaugh CH, Dunphy EB. Cyclodiathermy: an operation for the treatment of glaucoma. Arch Ophthalmol 1942;27: 543-57. Beckman H, Kinoshita A, Rota AN, et al. Transscleral ruby laser irradiation of the ciliary body in the treatment of intractable glaucoma. Trans Am Acad Ophthalmol Otol 1972;76:423-36. Beckman H, Sugar HS. Neodymium laser cyclocoagulation. Arch Ophthalmol 1973;90:27-8. Bellows AR, Grant WM. Cyclocryotherapy in advanced inadequately controlled glaucoma. Am J Ophthalmol 1973;75:679-84. Bellows AR, Grant WM. Cyclocryotherapy of chronic openangle glaucoma in aphakic eyes. Am J Ophthalmol 1978; 85:615-21. Bietti G. Surgical intervention on the ciliary body: new trends for the relief of glaucoma. JAMA 1950;142:889-97. Bloom PA, Tsai JC, Sharma K, et al. “Cyclodiode”: transscleral diode laser cyclophotocoagulation in the treatment of advanced refractory glaucoma. Ophthalmology 1997;104:1508-20.

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9. 10. 11. 12. 13. 14.

15.

16. 17. 18. 19. 20.

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Brancato R, Giovanni L, Trabucchi G, et al. Contact transscleral cyclophotocoagulation with Nd:YAG laser in uncontrolled glaucoma. Ophthalmic Surg 1989;20:547-51. Caprioli J, Strang SL, Spaeth GL, et al. Cyclocryotherapy in the treatment of advanced glaucoma. Ophthalmology 1985;92:947-53. DeRoeth A Jr. Cryosurgery for the treatment of advanced simple glaucoma. Am J Ophthalmol 1968;66:1034-41. Dickens CJ, Nguyen N, Mora JS, et al. Long-term results of noncontact transsceral neodymium:YAG cyclophotocoagulation. Ophthalmology 1995;102:1777-81. Feibel RM, Bigger JF. Rubeosis iridis and neovascular glaucoma: evaluation of cyclocryotherapy. Am J Ophthalmol 1972;74:862-7. Hampton C, Shields MB, Miller KN, et al. Evaluation of a protocol for transscleral neodymium: YAG cyclophotocoagulation in one hundred patients. Ophthalmology 1990;97:910-17. Kosoko O, Gaasterland DE, Pollack IP, et al. Long-term outcome of initial ciliary ablation with contact diode laser transscleral cyclophotocoagulation for severe glaucoma. Ophthalmology 1996;103:1294-1302. Meyer SJ. Diathermy cauterization of ciliary body for glaucoma. Am J Ophthalmol 1948;31:1504-7. Noureddin BN, Wilson-Holt N, Lavin M, et al. Advanced uncontrolled glaucoma: Nd:YAG cyclophotocoagulation or tube surgery. Ophthalmology 1992;99:430-7. Schuman JS, Bellows AR, Shingleton BJ, et al. Contact transscleral Nd:YAG laser cyclophotocoagulation: midterm results. Ophthalmology 1992;99:1089-95. Schuman JS, Puliafito CA, Allingham RR, et al. Contact transscleral continuous wave neodymium:YAG laser cyclophotocoagulation. Ophthalmology 1990;97:571-80. Shields MB, Shields SE. Noncontact transscleral Nd:YAG cyclophotocoagulation: A long-term follow-up of 500 patients. Trans Am Ophthalmol Soc 1994;92:271-87.

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Simmons RB, Shields MB, Blasini M, et al. Transscleral Nd:YAG laser cyclophotocoagulation with a contact lens. Am J Ophthalmol 1991;112:671-7. 22. Spencer AF, Vernon SA. “Cyclodiode”: results of a standard protocol. Br J Ophthalmol 1999;83:311-16. 23. Walton DS, Grant WM. Penetrating cyclodiathermy for filtration. Arch Ophthalmol 1970;83:47-8. 24. Weekers L, Weekers R. Nonperforating thermometric cyclodiathermy in treatment of hypertensive uveitis. Arch Ophthalmol 1948;40:509-17. 25. Wright MM, Grajewski AI, Feuer WJ. YAG cyclophotocoagulation: outcome of treatment for uncontrolled glaucoma. Ophthalmic Surg 1991;22:279-83.

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INTRODUCTION The association of a primary open-angle glaucoma (POAG) and a cataract has led many ophthalmic surgeons to perform combined procedures, to treat the two diseases at the same time, in spite of the well-known hypotensive effect of catatact extraction alone, which seems to be limited in duration, rarely exceeding one year in actual glaucoma patients. Intraocular pressure (IOP) results were improved when going from extracapsular extraction to phacoemulsification, probably because of the reduction of the size of the incision, leading to less postoperative inflammation, but significant complications from hypotony were sometimes encountered after trabeculectomy associated to phacoemulsification. The combined procedure with deep sclerectomy and placement of a non-absorbable, hydrophilic acrylic drain (T-Flux®, IolTech Laboratories) is a safe procedure which can provide a sustained IOP reduction in glaucomatous eyes requiring cataract extraction. SURGICAL TECHNIQUE The combined surgery begins with cataract removal using phacoemulsification through a 2.8 mm clear-corneal incision followed by implantation of a foldable intraocular lens (IOL). Then the anterior chamber is refilled with the rest of the ophthalmic viscoelastic device (OVD) used for phacoemulsification (Fig. 23.1), in order to begin sclerectomy on a firm eye. The conjunctiva is opened at the limbus using Vannas scissors (Fig. 23.2); a superficial (one-third of the sclera) 4.5 × 4.5 mm scleral flap is dissected quite anteriorly using a disposable Crescent knife (Fig. 23.3). Then a trapezoidal profound flap is pre-cut (Fig. 23.4) with a disposable 15° blade and dissected with the Crescent knife. At this step, it is particularly important to enter

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Fig. 23.1

Fig. 23.2

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Fig. 23.3

Fig. 23.4

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directly into the Schlemm’canal at the end of the dissection (Fig. 23.5). Next, Mitomycin-C at concentration 0.2 mg/ml is applied for one to two minute (Fig. 23.6), this time being used: first, to check the permeability of the two openings of the Schlemm’s canal with a trabeculotome (Fig. 23.7), or a Rycroft cannula, and secondly to remove the trabeculum of the inner wall of the Schlemm’s canal using the disposable capsulorhexis forceps (Fig. 23.8). This step is facilitated by the absence of aqueous outflow through the surgical wound from the trabecular area, as the anterior chamber is filled with the OVD (“dry technique”). After having carefully rinsed the Mitomycin-C, the nonabsorbable, hydrophilic acrylic drain is placed beneath the superficial scleral flap and embedded into the deep sclerectomy to create a permanent drainage space. No suture fixation is required, as the two lateral tips of the device enter the Schlemm’s canal (Fig. 23.9), preventing

Fig. 23.5

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Fig. 23.6

Fig. 23.7

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Fig. 23.8

Fig. 23.9

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any migration. There is also no need for suturing of the superficial flap; only two 10/0 Vicryl sutures are placed to close the conjunctiva at the limbus (Fig. 23.10). Finally, the OVD is completely aspirated beneath and below the IOL with the I/A cannula (Fig. 23.11). PERSONAL STUDY Here is presented a retrospective study of 200 consecutive eyes of 158 patients aged 72 ± 11 were operated on between September 2001, and November 2003. Follow-up for the group averaged 26 ± 8 months and ranged from 16 to 41 months. Prior to surgery, mean IOP was 19.2 ± 4.4 mm Hg and patients were using an average of 1.4 ± 0.9 glaucoma medications, with at least one medication being used in about 80 percent of eyes. The preoperative best distance corrected visual acuity (BCDVA) was 0.37 ± 0.24; the

Fig. 23.10

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Fig. 23.11

spherical equivalent was - 3.5 diopters ± 6.4 (-26 to +6 D) with 95 myopes > -1D (47.5%) and 34 hyperopes >+1D (17%). About one half of the eyes had POAG (Fig. 23.12). The surgery was initially successful in all but one eye, which went on to trabeculectomy after six months. For the entire group, mean IOP was reduced to 13.1 + 6 mm Hg on the first postoperative day, remained at 13.6 mm Hg at 12 months, and was only slightly higher at 24 and 36 months (15.2 ± 3.3 mm Hg and 15.1 ± 3.3 mm Hg, respectively) (Fig. 23.13). IOP control has been maintained without the need for goniopuncture in any eye and with minimal use of topical hypotensive medication. At the last available visit, medical therapy was being used in only 36 (21%) of 171 eyes. That treatment consisted of a single agent in 19 eyes, a betablocker plus a prostaglandin in 16 eyes, and 3 medications in a single eye. The postoperative BCDVA was

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Fig. 23.12

Fig. 23.13

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0.67 ± 0.30, with a mean postoperative equivalent of -0.74 diopters ± 1.38. Seventy-one percent of the eyes gained at least 2 lines of visual acuity; 4.5 percent lost least 2 lines of visual acuity. The only complications encountered were: a malignant glaucoma treated by posterior vitrectomy; a retinal detachment in 12 diopters myopic patient, which required two procedures to flatten the retina. There was no case of migration or displacement of the drain, neither under the conjunctiva nor inside the anterior chamber. CONCLUSIONS Since its first description in 1989,1 deep sclerectomy (DS) has regularly evolved to attain a reproducible surgical method, which is not yet stereotyped, as every ophthalmic surgeon propose his own technique. The IOP results are fairly good,2 even though long-term results are sometimes deceiving.3 The main advantage of DS is the absence of postoperative hypotony with its well-known complications; it also gives less astigmatic change than trabeculectomy.4 From the beginning, many authors have proposed the adjunction of resorbable drainage devices, such as collagen, 1 as Aquaflow® processed from lyophilized porcine scleral collagen 2 or reticulated hyaluronic acid (SK-Gel®). Histopathological evaluation confirmed that the presence of a drain could form a smooth and regular intrascleral space to prevent collapse of the scleral flap over the site of the DS.5 More recently, a nonresorbable drain made of hydrophilic acrylic material and designed by E. Dahan has been commercialized (Fig. 23.14) to maintain more durably an wide opened intrascleral space. With this drain, Ates et al6 showed IOP success rates comparable to viscocanalostomy, with few complications. As it has been recently proved that the adjunction of

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Fig. 23.14

Mitomycin-C could give better IOP results without increasing the complication rate,7 it appears logical to use this drug to reduce a possible postoperative fibrosis around this foreign body represented by the acrylic drain. REFERENCES 1. 2. 3.

Kozlov, et al. Non-penetrating deep sclerectomy with collagen IRTC Eye Microsurgery, Moscow, RSFSR Ministry of Public Health, 1989;44-46. Shaarawy T, et al. Long-term results of deep sclerectomy with collagen implant. J Cataract Refract Surg 2004;30:122531. Lachkar Y, et al. Non-penetrating deep sclerectomy: a 6year retrospective study European Journal of Ophthalmol 2004;14;1:26-36.

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4.

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Egrilmez S, et al. Surgically induced corneal refractive change following glaucoma surgery: non-penetrating trabecular surgeries versus trabeculectomy J Cataract Refract Surg 2004;30:1232-39. 5. Erbiliç K, et al. Deep sclerectomy with various implants : an experimental and histopathological study in a rabbit model. Ophthalmologica 2004;218:264-69. 6. Ates H, et al. Deep sclerectomy with a non-absorbable implant (T-Flux): preliminary results Can J Ophthalmol 2003;38:482-88. 7. Neudorfer M, et al. Non-penetrating deep sclerectomy with the use of adjunctive Mitomycin-C. Ophthalmic Surg Lasers and Imaging 2004;35;1:6-12.

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INTRODUCTION The glaucoma filtration surgery technique has remained nearly static during the past century, mainly for the reason that the surgical tools have remained more or less the same.1 The instruments have become smaller and finer, as well as the operating microscope has become a standard aid for improved magnification. Nonetheless, the only palpable ‘revolution’ has been the making of a scleral flap. The introduction of mitomycin has improved certain case results, but it has also added many new serious complications. In spite of the availability of antibiotics, steroids, and non-steroidal anti-inflammatory medication, there has been no real breakthrough. Results remain unpredictable and there are too many serious side effects, often related to immediate collapse of the anterior chamber. For these reasons, most anterior segment surgeons avoid glaucoma filtration surgery.2 In this scenario, the arrival of a new ablative surgical tool in the form of the Fugo Plasma Blade has brought about a fundamental change in the approach to filtration surgery. This new approach could only happen thanks to the unique ability of Fugo Plasma Blade to ablate the surface of the sclera with a hair thin plasma cloud. The Fugo Blade can ablate permanent tracks through tissues such as cornea, sclera and ciliary body in a resistance free fashion. And, the plasma ablation of tissue occurs without any clinically significant collateral damage or postoperative reaction to the incision wall. FUGO BLADE® The Fugo Blade® is a unique cutting instrument, which employs plasma, the 4th state of matter, for ablating incision paths in tissue in a manner similar to the eximer laser and is the only electrosurgical device approved for

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intraocular use by the Food and Drug Administration (FDA) in the USA.3 The Fugo Blade is also known as the Plasma Blade in many other parts of the world, since it ablates with plasma energy.4 It consists of a console, a hand-piece with a disposable tip and an activation footswitch (Fig. 24.1). Four rechargeable “C” cell flashlight size batteries provide the energy. The power generated is about 1watt for little energy is needed to energize the cutting tip, thereby, one charge of the batteries lasts for about an hour of cutting time. The plasma is visible under high magnification, looking like bees on a honey cone or a miniature fluorescent light bulb. This plasma ablates in such a fashion that it creates a smooth wall along the ablation/incision path. The secret is that the electromagnetic waves are brought to a sharp

Fig. 24.1: The Fugo Blade® console and the hand-piece with attached disposable tip. There is an outlet for the hand-piece and one for the footswitch. There are controls to regulate the cutting power of the tip

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focus by the electronics in the console and in the handle, onto the tip of the blunt incising filament which has the thickness of a human hair.5 The electromagnetic oscillations knock electrons from their orbits in the atoms of the tissue. Thus plasma, the fourth state of matter, consisting of charged atoms and electrons is produced. This plasma cloud at the activated tip-tissue junction becomes visible to the naked eye. Surgeons such as Prof Randal Olson (Utah, USA), Prof Ike Ahmed (Toronto, Canada) and Dr I Howard Fine (Washington State, USA) have all emphatically stated that this device has nothing to do with classic electrosurgery or diathermy. Under a high power microscope, the plasma cloud is visible as a 25-50 micron wide pulsating yellow cloud on the hair thin, blunt activated tip (Fig. 24.2).6 Around the

Fig. 24.2: The cutting power resides in the thin, inner yellow looking plasma cloud surrounding the activated filament of Fugo Blade® tip. The much wider, outer non-cutting photon cloud looks orange

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plasma cloud, there is reddish much wider photon cloud. The cutting power resides in the inner thin plasma cloud. The plasma sustains itself as long as the electromagnetic oscillations from the activated tip keep interacting with the tissue, which is ablated in the truest sense.7 The plasma cloud oscillations instantly shatter the macromolecules of the tissue into small fragments. The micro-molecular fragments thus produced mix with water vapor and are discharged at great speed as a plume; just as is seen with the eximer laser.8 During extra-ocular procedures such as touching a bleeding area, the molecular oscillation throws the particles millimeters away. This produces a process called “Autostasis” wherein these small particles plug the top of small vessels thereby producing a non-cauterizing hemostasis. Histologic sections show that cautery produces charred, blistered wound margins whereas the Fugo Blade wound margins have been shown to be pristine clean, thereby reducing swelling, redness, pain and scarring.9 The plasma energy at the tip is at a very high energy density, while possessing very low total energy since the plasma cloud has a very small volume. However, the energy field does not extend beyond 25 microns from the plasma, meaning that little or no heat is generated in tissue outside of the incision. Therefore, the Fugo Blade does not burn or cauterize. This has been demonstrated by ablating through visible conjunctival or muscle vessels, as well as the creation of bloodless pupiloplasties in seconds.10 The Fugo Blade® possesses this important function of non-cauterizing during incision of cut tissue. It does this in two ways- firstly by the ablation of the vessels in the cutting path and secondly by the particle oscillation, which tends to plug the small bleeding vessels. Finally, it should be made clear that the Fugo Blade® is completely different from a diathermy unit. The Fugo Blade® uses minute amounts of energy yet cuts

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sharper than a diamond blade whereas diathermy uses large amounts of energy but cuts poorly and damages the wall of the incision path, as seen on histologic sections.11 THE IMPORTANCE OF CONJUNCTIVAL LYMPHATICS IN GLAUCOMA SURGERY Conjunctival lymphatics are generally ignored in discussions of ocular fluid dynamics.12 However, if we visualize the extremely well knit lymphatic network under the conjunctiva, we soon realize that it has a role in fluid drainage in normal and operated eyes. Normally, over 30 percent of the aqueous humor filters out of the eye through uveoscleral outflow. There is an additional leakage from the anterior chamber through the aqueous veins. All this interstitial fluid has a substantial chance of being trapped by the lymphatics and then drained away from the eye. Post-surgical drainage is nothing short of managing a flood of aqueous – the lymphatics act as flood drains.13 The lymphatics and the Pallisades of Vogt are frequently visible under slit-lamp microscope as transparent channels and columns running parallel to the limbus (Fig. 24.3).14 However, the most spectacular view is seen in some patients who have pigmentation around the limbus. The pigment outlines the finest lymphatic channels at the limbus as well as the Pallisades of Vogt, (Fig. 24.4).15 Once it is realized that the lymphatics have a role in the drainage of the aqueous, the surgeons will then begin to understand the importance of doing minimal dissection, minimal cautery and minimal use of mitomycin C. The greater the trauma and destruction to the lymphatics, the greater the chance of scar and Tenon’s cyst formation with subsequent decrease of aqueous flow from the subconjunctival space and back into the vascular tree.16

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Fig. 24.3: It shows beautifully outlined small and large lymphatic vessels as well as the Pallisades of Vogt. The channels on the limbus are vertically placed. Beyond the limbus they form a dense network with the larger vessels having a general direction parallel to the limbus

Fig. 24.4: This shows beautifully outlined lymphatics at the limbus. There is pigment around the lymphatics and the Pallisades of Vogt

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GLAUCOMA SURGERY TECHNIQUES WITH THE FUGO BLADE® Four different techniques of glaucoma surgery have been developed and practiced. They are as follows: 1. Transciliary filtration (TCF). 2. Transconjunctival transciliary filtration (TC-TCF). 3. Microtrack filtration (MTF). 4. Non-perforating filtration (NPF). Transciliary Filtration (Singh Filtration)17 The technique of surgery is as follows: 1. The conjunctiva is detached from the limbus for about 6-7 mm and it is retracted away from the limbus. 2. The Tenon’s capsule from the exposed sclera is excised with scissors. 3. The bleeding spots on the sclera are closed with the lowest energy of the Fugo Blade. A 600 microns tip is used for this purpose. 4. A scleral ablation point behind the surgical limbus is chosen for TCF. There is a variation dependent upon ocular type from high myopia to high hyperopia. The experienced TCF surgeon can easily identify the correct spot for scleral ablation, whereas the novice TCF surgeon can quickly and easily identify the location of the iris root employing anterior chamber transillumination. Instructional tapes on this are available from Medisurg, Ltd, USA (Tel 610-277-3937).18 5. The 600 microns tip is chosen to ablate the sclera at the chosen point. A scleral pit is formed (Fig. 24.5). The energy at medium settings is applied in small steps, until the ciliary body is visible. The edges of the pit are beveled especially at the proximal edge (Fig. 24.6).

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Fig. 24.5: The conjunctiva has been detached from the limbus.A pit is getting formed on the sclera, about 1 mm behind the surgical limbus, with the help of activated 600 microns tip of Fugo Blade

Fig. 24.6: The scleral pit has reached to the depth of the anterior part of the ciliary body. The edge of the scleral pit has been beveled with Fugo Blade. Any part of the sclera that is merely touched by activated Fugo Blade, it just disappears

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6. There is a choice of a 100 microns or a 300 microns tip for the next step, which is the next step of the creation of a track through the ciliary body into the posterior chamber (Fig. 24.7). The tip is directed behind the iris root, through the anterior part of the pars plicata. The tissue is touched a couple of times with the activated Fugo Blade tip until suddenly there is a rush of posterior chamber fluid along with small particles of ciliary body epithelium. The track formation is over in several seconds. 7. For demonstration purpose, air may be injected through the track with a 22 gauge cannula. The air appears in the anterior chamber from under the iris (Fig. 24.8). The posterior chamber may be irrigated in a similar fashion to wash out any pigment or blood. A drop of trypan blue placed on the track is washed away by outflow of aqueous. 8. Finally, the conjunctiva is lifted back to the limbus and sutured with one or more sutures (Fig. 24.9).19 TCF is done without a scleral flap or under a scleral flap. Atwal has modified the technique such that he makes two tracks- one transciliary and another one is made into the anterior chamber from under the base of the scleral flap. He terms the procedure the “Atwal Balanced Approach” or “ABA”.20 As of this writing, Dr Atwal has performed over 100 ABA procedures with a maximum follow-up time of slightly more than 4 months and with only 3 failed filters but with not a single collaped anterior chamber. Mitomycin is normally not used in the TCF operation. However, it can be judiciously used in high risk cases before making the scleral pit, or inside the pit before making the track through the ciliary body. Recall that this must only be performed with minimal exposure of the tissue to the mitomycin.

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Fig. 24.7: A 300 microns activated Fugo Blade tip is in the process of going through the most anterior part of the ciliary body.The plasma energy is visible to the naked eye

Fig. 24.8: Injection of air in the filtering track shows the air bubble is appearing in the papillary area, from under the iris, confirming that the track is through the ciliary body

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Fig. 24.9: The conjunctiva has been sutured back to the limbus with 30 microns stainless steel suture

TCF is suitable for phakic eyes and pseudophakic eyes with an intact posterior capsule. Surgical errors are possible and manageable. A posteriorly directed perforating tip can disturb vitreous, which then may plug the TCF pore and therefore does not allow the aqueous to flow out. Repeating the ablation in an in and out movement of the activated Fugo Blade ablation probe into the area of vitreous causes plasma ablation of vitreous strands and thereby may open up ablation pits clogged with errant vitreous strands. If the surgeon wishes to reverse the TCF, the sclera may be closed at the site of the error with a suture. Then another site may be selected for a TCF track. The scleral pit may bleed excessively if the patient has a coagulation deficiency. This can occur with standard anticoagulation medication or with natural herbs or food such as high intake of fish, flax seed, ginsing balboa, vitamin E, etc. Make sure that there is no bleeding before proceeding to the next step of

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making a track through the ciliary body. In case there is any doubt, this site is abandoned and another close by site is chosen for restarting the procedure. Recall that the scleral pit takes seconds to create. Sometimes misdirection of the operating tip opens the track into the anterior chamber. Agitation of aqueous in the anterior chamber or formation of air bubbles in the anterior chamber is a diagnostic sign. In such a case, the anterior chamber is filled with air and another track is made somewhat posteriorly through the ciliary body into the posterior chamber. It becomes the Atwal procedure in reverse. It is imperative to make the posterior chamber ablation pit since this decompression of the posterior chamber all but eliminates flat anterior chambers postoperative, even with an eye pressure of 2-3 mm Hg.21 Postoperative management of the Fugo Blade procedures is much easier and more pleasant for both patient and physician than it is with trabeculectomy. There is practically never a flattening of the anterior chamber. Any bleeding into the anterior chamber is either from the angle or from the posterior chamber. It is uncommon. The blood is absorbed very slowly, since the greater fluid flow is through the posterior chamber. Choroidal detachment is comparable to that of trabeculectomy and is usually self absorbing. Failure of the procedure is possible. In the first few days, the filtration track or the scleral pit may be closed by a blood clot. Another cause could be ‘posterior iris bombe’ which closes the internal opening. The track may be reopened after waiting for 2-3 days. The conjunctiva is detached from the limbus and then sutured back after the corrective procedure. Late failure can occur due to the formation of scar tissue or the formation of Tenon’s cyst. These are relatively easy to diagnose. The condition is

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treated by reopening the operation site and removing the scar tissue. The filtration track is usually found functional underneath the scar or the cyst. Mitomycin may be used with discretion and pinpoint application. A primary success rate of over 80 percent is expected in cases of primary glaucoma. Furthermore, TCF is a filtering procedure that most anterior surgeons can perform rapidly and with a small amount of tissue manipulation. Importantly, postoperative chair time is minimized because flat anterior chambers are rarely seen, even with eye pressures of 2-3 mmHg.22 Cases of angle-closure glaucoma achieve chamber deepening with the procedure. The use of mitomycin increases the success rate in these cases, but it also seems to increase the rate of avascular bleb formation. The procedure of TCF reduces surgery time, decreases tissue trauma and decreases the number and severity of early and late postoperative complications. Re-operation at the old site or an adjoining site is easy and without excessive trauma to tissues.23 The learning curve is low but there are techniques which must be mastered.24 There is significant surgeon variation in preference to surgical approach, e.g. ABA versus pure TCF. For example Dr Myron Wilson (Georgia, USA) and his associate Dr Johnny Gayton have performed over 30 pure TCF procedures (personal correspondence). They no longer employ anterior chamber transillumination and are now performing 3 TCF patients in a 15 minutes surgical block. They have had 2 failures in their group but note that re-ops are simple to perform. Most notably, they have stated that a large percentage of their TCF patients have the “most horrible pathology in our practice with no good option to treat” their glaucoma. Dr Herbert Kaufmann, Director of the LSU Eye Center, (USA) relayed a similar

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sentiment regarding his “worse eyes” glaucoma patients to one of the authors (RJF). Transconjunctival Transciliary Filtration (Singh TC-TCF)25 In this technique, the posterior chamber is connected to the subconjunctival space without any dissection. This technique comes in handy in a number of situations like malignant glaucoma, painful neovascular glaucoma, pseudophakic glaucoma with iris bombe, and phakomorphic glaucoma preliminary to cataract surgery with or without IOL implantation. It is also helpful in such glaucomatous eyes that have extensive scarring, so that it is difficult to dissect close to the limbus. The operation is done under full local or a short general anesthesia. The steps are as follows: 1. The most important landmark is the point of reflection of the conjunctiva from the cornea. The second landmark is the posterior edge of the bluish looking surgical limbus (Fig. 24.10). The relationship between the first and the second landmarks should be clearly visualized. The scleral entry has to be about a mm. posterior to the surgical limbus. Keep that point in sight. It should be away from any big vessel on the sclera. Nonetheless, anterior chamber transillumination is simple to perform and gives the new TCF surgeon a definite location for a scleral ablation pit. 2. Gentian violet is applied on the conjunctiva over the limbus (Fig. 24.11). The conjunctiva is gripped with a forceps about 7-8 mm away from and parallel to the limbus. The conjunctiva is pulled down over the cornea. The attachment of the conjunctiva to the cornea becomes sharply visible as a blue line (Fig. 24.12). At

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Fig. 24.10: A case of malignant glaucoma, of three weeks duration, causing very severe constant pain and loss of eyesight. Notice the posterior edge of the surgical limbus visible under the conjunctiva. This edge is about 1 mm from the attachment of the conjunctiva to the cornea

Fig. 24.11: The conjunctiva in the region of the limbus is stained with gentian violet

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Fig. 24.12: A conjunctival fold is pulled down with forceps, revealing the sharp edge of the conjunctival limbus.A blade holder with a blade fragment is ready to be placed at the sharp line

this point, we press down on the conjunctiva with the dull edge of a razor blade fragment, held in a blade holder, so that the conjunctiva shall not slide back. 3. A Fugo Blade tip of 100 microns or 300 microns is chosen according to the surgeon’s choice. The tip is placed at the chosen pre-selected point and directed towards the plane just posterior to and parallel with the iris (Fig. 24.13).26 The tip is activated and made to ablate a track between the posterior chamber and the subconjunctival space (Fig. 24.14). The system energy is turned off and the tip is withdrawn. The completion of the track is signaled by the flow of fluid and sometimes uveal pigment.

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Fig. 24.13: The conjunctiva is being restrained with the dull side of the razor fragment. The Fugo Blade tip 100 micron size is brought close to the conjunctiva, about 2 mm behind and aimed behind the iris, towards the posterior chamber

Fig. 24.14: The activated 100 microns filament passes through the conjunctiva, sclera and ciliary body in a fraction of a second. The escaping fluid inactivates the filament. The filament is withdrawn immediately

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Fig. 24.15: A filtering bleb starts getting raised, as the conjunctiva is allowed to fall back to its normal place

4. The conjunctiva is allowed to fall back (Fig. 24.15). The filtering fluid begins elevating the conjunctiva. The hole in the conjunctiva may be closed with a suture. Microtrack Filtration (Singh MTF)27 This technique employs a transconjunctival approach using a 100 microns Fugo Blade filament to create a filtering track between the anterior chamber and the subconjunctival space. The objective is to have a minimally invasive procedure for a variety of glaucoma cases having normal or deep anterior chambers. It can deal with emergency situations such as traumatic and inflammatory glaucomas if the intraocular pressure is uncontrolled by medical means. Sometimes there is a case with extensive scarring with a small area of virgin conjunctiva remaining, therein only a technique such as this shall work. The track is made

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right under the attachment of the conjunctiva to the cornea. The width of the track created with the Fugo Blade is 200 microns. A very small 1-2 mm fold of conjunctiva is pulled down over the cornea before making the track. There is no involvement of the uveal tissues in the surgery. There is minimal disturbance of the reactive Tenon’s tissue. The fine microtrack is created with the hope that the iris shall not block the internal pore opening and scarring shall not occur over the external pore opening. The procedure is as follows: The pupil is constricted prior to the operation. The operation may be performed under topical anesthesia, subconjunctival anesthesia or general anaesthesia. The important point is that the eye should not move during the fraction of a second that it takes to perform the actual operation. 1. Make a note of the attachment of the conjunctiva to the cornea. The track has to be made right under it without creating a buttonhole. 2. The conjunctiva has to be brought down not with a forceps but with a dull sapphire or ruby knife (Fig. 24.16). The dull knife should be able to hold the conjunctiva down but not cut it. One can use a diamond knife with 0.6 mm or 1 mm tip. Even a sharp knife shall not cut the conjunctiva if it is not moved side to side and is not pressed to firmly. Why use such a sharp tool for bringing down the conjunctiva ? Because we need a moderately sharp but poor electrical conductor to hold down the conjunctiva. The inactivated Fugo Blade Plasma tip has to touch this instrument before it is activated and pushed into the anterior chamber (Fig. 24.17). A plastic tool may perform the same function but is not yet available. A metallic tool possesses a high electrical conductivity.

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Fig. 24.16: The conjunctiva is being pushed down to show the ‘root’ of the conjunctiva, where it is attached to the cornea.The micro-track in to the anterior chamber has to be made close the ‘root’

Fig. 24.17: The conjunctival fold is held at the ‘root’ with the edge of a diamond knife, while the Fugo Blade is touch it in an inactivated state, poised and ready to move. The tip should be kept at the desired angle, before it is activated

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The knife edge is placed lightly about 1 to 1.5 mm from the conjunctival limbus. It is used to press and push the conjunctival towards the cornea, until its further progress is stopped by the root of the conjunctiva. In other words, the conjunctival flap cannot be pulled further because of traction from its attachment at the lumbus. 3. The inactivated Fugo Blade tip is pressed against the conjunctiva retracting knife, then it is activated with the foot switch. With a smart jab, the activated Fugo Blade tip is pushed in then out of the anterior chamber (Fig. 24.18). A track is instantly created in a resistance free fashion. A small air bubble may be injected if desired. 4. The conjunctival fold steadying knife is lifted and the conjunctiva is allowed to retract back to normal. The aqueous seepage through the track starts raising a bleb (Fig. 24.19). 5. A bandage contact lens is put in place, to prevent excessive leakage (Fig. 24.20). It is removed after 2 weeks. Following creation of the MTF, the lymphatics are seen to fill at the limbus (Fig. 24.21). The bandage contact lens slows down the movement of aqueous in order to inhibit excessive anterior chamber decompression with subsequent collapse of the anterior chamber. Soon the lymphatics become invisible due to bleb formation. Postoperative management requires close attention. The pupil is kept constricted for at least one month when the fluid movement through the track becomes stabile, and there is no further tendency of the iris to block the internal opening. If the track becomes blocked with iris, the intraocular pressure will rapidly rise. On gonioscopy, the blocked internal opening of the Micro Transciliary

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Fig. 24.18: The moment the tip is activated, it enters the anterior chamber in a minute fraction of a second. It is withdrawn immediately. It is just an ‘in and out’ operation

Fig. 24.19: The conjunctival hole is held with a plane forceps for a few seconds

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Fig. 24.20: A bandage contact lens is placed to cover the filtration track

Fig. 24.21: It shows MTF opening and filled up lymphatics at the limbus, 4 hours after operation. There is a bandage contact lens in place, which slows down the movement of aqueous and sometimes fills up the lymphatics. The presence of pigmentation at the limbus helps in the visualization of the lyphatics

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Filtration track shall be seen to be plugged with a fine wick of iris (Fig. 24.22). This wick can be blown away with a single shot of YAG laser and the filtration will be restored (Fig. 24.23). The idea of making the track under the most distal part of the conjunctiva is to minimize the chance of iris blockage as well as to minimize Tenon’s scarring. In case of failure, the procedure can be easily and quickly redone in an adjoining area. The procedure is not suitable as such for angle closure cases. An additional manual iridectomy is needed. Since the procedure is minimally traumatic and completed in a minute or two, it has the possibility of becoming a frontline field tool to fight worldwide glaucoma. It is particularly suitable for very sick and uncooperative patients. A primary success rate of over 80 percent is achievable. MTF fills a void in the vast world, where millions go blind for lack of costly glaucoma medication and for lack of costly surgical care. Like all other filtration procedures, there is need for regular follow-up. Since we are decompressing the anterior chamber of the eye, the possibility of postoperative collapsed anterior chamber is a consideration. Non-perforating Filtration (NPF) Non-perforating filtration has been around for some years in the form of viscocanalostomy and deep sclerectomy with or without a collagen implant. The objective is to tap Schlemm’s canal and not to open the anterior chamber. Both of these techniques require meticulous dissection under high magnification of the microscope. The techniques have not attracted many converts, mainly because they are considered more difficult to perform and the reported results have shown uneven success, compared

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Fig. 24.22: It shows the blockage of the internal opening of MTF with a small nipple of iris tissue, two days after the operation

Fig. 24.23: Same patient as above. The iris tissue blocking the internal opening has been blown away, which restored the filtration. Notice that the intrnal MTF opening is anterior to the corneascleral trabeculae. The more anterior the better

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to the “gold standard” trabeculectomy. The basic problem has been that surgeons must first perform a standard trabeculectomy type scleral flap, then proceed to perform a second scleral flap under the first flap. This second flap requires the surgeon to use a blade to bisect the thin scleral layer under the first scleral flap – truly a daunting surgical feat. This maneuver cannot be repeatedly performed by most surgeons. Dr Ike Ahmed is performing a series of non-perforating glaucoma filtration procedures at the University of Toronto with the Fugo Blade. Dr Ahmed and his fellows now use the Fugo Blade to perform what they have coined “erasing tissue” from the scleral flap bed. They erase the scleral tissue until aqueous percolates through the thinned scleral window. This procedure requires less than a minute to perform and according to Dr Ahmed eliminates the last remaining hurdle for all ophthalmologists to perform the non-perforating glaucoma procedure (personal communication). There are many ways to perform NPF with the Fugo Blade. They are as follows: a. Open non-perforating filtration. b. NPF under a limbus based sclero-corneal flap. c. NPF under a fornix based corneo-scleral flap. Open Non-perforating Filtration (Singh NPF) The surgery is done under local anesthesia as described previously. 1. The conjunctiva is detached from the limbus for about 5 mm. 2. Any blood ooze is hemostased with a minimum energy setting of the Fugo Blade 600 microns tip (Fig. 24.24). 3. Any Tenon’s capsule in the exposed area is cut with forceps and scissors.

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Fig. 24.24: The conjunctiva has been detached from the limbus. The blood vessels in the area of surgery are being ablated with 600 microns tip of Fugo Blade

4. Fugo Blade Ablation of the limbal area to expose the canal of Schlemm’s. A 600 microns Fugo Blade tip is used to ablate the limbal area by moving the tip from the corneal to the scleral side. With every passage, the limbal pit becomes deeper (Fig. 24.25). The pit is also widened in a sloping fashion to facilitate deeper ablation in the center. The ablation involves the tissues on either side of the surgical limbus. The surgical limbus overlies the anterior corneoscleral trabeculae. Thus, we would expect to find the canal of Schlemm just posterior to it. Thinning of the cornea anterior to the surgical limbus may help later on in producing a filtration pore with the YAG laser, in cases where enhancement of filtration is needed. The thinning of the limbal tissues by Fugo Blade ablation is continued at the lowest energy

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Fig. 24.25: The scleral pit over the Schlemm’s canal is being deepened and widened with 600 microns tip of Fugo Blade

settings, until an aqueous ooze is observed. Once the ooze starts (Fig. 24.26), the Fugo Blade tip becomes less effective at erasing tissue because the fluid causes a decrease in resonance of the ablation energy at the Fugo Blade tip and thereby damps the energy transfer into the scleral tissue.28 Observe the oozing area for a minimum of one minute. The ooze may be highlighted by putting a drop of trypan blue (Fig. 24.27), which is then washed away. 5. The conjunctiva is sutured back to the limbus (Fig. 24.28). We use 30 microns steel suture or other minimally reactive suture. There is scope for innovation in this technique. The filtration can be done with a 200 microns tip and without a wider limbal pit.

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Fig. 24.26: The ooze is evident in the scleral pit over Schlemm’s canal

Fig. 24.27: The oozing aqueous is washing away the trypan blue that was dropped on the scleral pit

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Fig. 24.28: The conjunctiva has been sutured back to the limbus with multiple sutures

NPF Under a Limbus Based Sclerocorneal Flap The steps of operation are as follows: 1. The limbus is detached as usual and the scleral surface is cleared of Tenon’s capsule and bleeding points. 2. A triangular scleral flap about 1/3 mm thick and 2 mm wide is made with its base towards the limbus. 3. The flap is held with a forceps, while ablation of the limbal tissues is performed as before until aqueous begins to percolate though the thinned window. 4. The conjunctiva is sutured back to the limbus. Note that the scleral flap is not sutured, since it is not required. Mitomycin may be applied under the flap before the exteriorization of the Schlemm’s canal, in selected cases. In case a collagen implant is desired, a rectangular scleral flap is fashioned, which is sutured back at the end of

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surgery. Collagen implants create a space under the flap and are absorbed in about 6 months. NPF Under a Fornix Based Corneoscleral Flap (Singh) The steps of operation are as follows: 1. The conjunctiva is detached for 6-7 mm. 2. A 0.3 mm thick and 2.5 mm wide flap of corneosclera is raised anterio-posteriorly. 3. The exposed base is ablation-thinned. The edges of the base are also ablated. 4. The tissue ablation is done as before to start seepage of fluid from the area of Schlemm’s canal. 5. The corneoscleral flap is sutured back with two 30 micron sutures. 6. The conjunctiva is sutured back at the limbus. The point to note is that there is no trauma to the Tenon’s capsule and the episcleral blood vessels. The filtering aqueous escapes from the ablated edges of the base under the corneoscleral flap. FOLLOW-UP A careful follow-up of non-perforating filtration cases is required. In the first few days, the filtration may become blocked by a blood clot. A pressure bandage may relieve the block. Sluggish aqueous flow may raise the intraocular pressure beyond normal. In such a case, the fluid flow can be augmented by making a YAG laser pore in the thinned limbal area. The surgery of non-perforating filtration has a learning curve. The filtration area may not be found as desired. It may open into the anterior chamber, in which case a peripheral iridectomy is done with the Fugo Blade and the case finished like any anterior chamber filtration. In this

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case, placement of a TCF pore may serve to protect against anterior chamber collapse. On the other hand, the ciliary body area may be exposed without finding Schlemm’s canal. In this case, the operation is finished with a transciliary filtration (TCF) procedure. A case may be finished as double filtration track-one in the anterior chamber and the other transciliary (Atwal procedure). With a little experience, Fugo Blade filtration procedures may be performed with 6 X or 8 X head worn loop magnification, which underscores the value for Third World glaucoma, especially since the procedures require minutes to perform. Besides the techniques described above, the Fugo Blade is helpful in the placement of valves and setons.29 It can make a gutter on the sclera that accommodates and holds the silicone tubing of the valve. It can be used to remove tenon cyst formation around the valve and tubing to restart the function of the valve. The Fugo Blade is an excellent tool to cut and destroy Tenon’s cysts without extensive dissection. The conjunctiva is ballooned around the cyst. A special 300 or 600 microns Fugo Blade tip is introduced from one side to ablate the walls of the tenon cyst from edge to edge, at the same time removing much of the scar tissue. A suture is applied to the entry point of the tip. CONCLUSION The Fugo Blade is an important surgical tool that is fundamentally different from all the previous devices that have been employed in surgery.30 It does not cut, but it ablates much like excimer laser, with clinically insignificant collateral damage.31 This has been confirmed by such leaders in our field such as Dr I Howard Fine, Dr Ike Ahmed, Dr Herbert Kaufman and Dr F Hampton Roy. Rather, the Fugo Blade creates tracks even through vascular

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tissues such as the ciliary body. It closes the blood vessels as it makes an ablation path in the tissues by autostasis. It is not a cautery, and causes no charring. A note of extreme caution is warranted wherein no surgeon should attempt the herein presented procedures with any other electrosurgical device besides the Fugo Blade.32 The Fugo Blade uses a small amount of energy in the form of plasma to ablate, remove, or “erase” tissue. It has the potential for application in every field of ophthalmology, general surgery, even dentistry.33 Glaucoma surgery shall never be the same with the introduction of Fugo Blade. Transciliary filtration and nonperforating techniques substantially remove all worries connected with anterior chamber integrity. Microtrack filtration needs further development and refinement for an application on a mass scale to fight the worldwide menace of glaucoma. The future surgical techniques shall take into account the importance of preserving a healthy lymphatic network under the conjunctiva and strive for minimally traumatic operations. During the time of Galen circa 150AD, Roman physicians possessed over 150 distinct operations in their surgical repertoire in areas such as abdominal surgery, brain surgery and eye surgery. The surgical trays from the era of Galen had impressive, refined surgical equipment which if examined carefully were not much different from present day equipment except for the material used in their production. Over the last century, we have added standard electrosurgery, fiberoptics and laser. Now, ophthalmology has introduced a technology which shall provide a quantum leap in surgical capability. This technology is known as the Fugo Blade wherein tissue is “erased” by thin layers of plasma. This requires minimal energy, cuts resistance free and leaves incision walls pristine clean. This

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work represents an intense collaboration between the two authors. With a solid background in biophysics, Dr. Fugo has concentrated on the equipment while Dr Singh has focused on truly remarkable clinical applications which require a combination of imagination and the skill of a master surgeon. This work has been accomplished at much personal sacrifice. Nonetheless, it is an honor to be a part of a project that has the potential to elevate the quality of healthcare worldwide….for the industrialized world but also for the poorest of the poor. One of the authors (DS) refers to this new technology as “the great equalizer”. This new solid state technology will allow the poorest clinic in a remote part of the world to have access to the most advanced medical technology in the world. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8.

Sabbagh LB. The never-ending quest: Creating a better way to remove the lens. Eyeworld 1998;3,4:50-53. Kent C. Transciliary Filtration – Without Bleeding. Ophthalmology Management 2002;6,11:84-87. Sabbagh LB. The leading edge: Harnessing electrons for a faster, smarter incision. Eyeworld 1998,3,4:88. Kronemyer B. Fugo Blade uses low-level energy to create anterior capsulotomy. Ocular Surgery News 2000;18,21:4546. Kellan R, Fugo RJ. Device increases safety, efficiency of cataract surgery. Ophthalmology Times 2000;25,22:7-9. Fugo RJ, DelCampo DM. The Fugo Blade™: The next step after capsulorhexis. Annals of Ophthalmology 2001;33,1: 12-20. Kent C. Plasma Capsulotomy. Ophthalmology Management 2001;5,8:72-73. Fine IH, Hoffman RS, Packer M. Highlights of the 2002 ASCRS Symposium, Part I. Eyeworld 2002;7,7:38.

422 9. 10. 11.

12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

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Hidalgo-Simon, A. Plasma Knife Provides Clean and Accurate Cut for Capsulorhexis. Eurotimes 2002; 7,11:27. Singh D, et al. Plasma Powered Squint Surgery with the Fugo Blade. Annals of Ophthalmology 2003;35,1:12-14. Izak, Andrea M, et al. Analysis of the capsule edge after Fugo plasma blade capsulotomy, continuous curvilinear capsulorhexis, and can-opener capsulotomy. Journal of Cataract and Refractive Surgery 2004;30,12:2606-11. Kent C. Revealed: The Eye’s Lymphatic System. Ophthalmology Management 2002;6,5:114. Singh D. Letters: Conjunctival Lymphatic System. Journal of Cataract and Refractive Surgery 2003;29,4:632-33. Singh D, et al. The Conjunctival Lymphatic System. Annals of Ophthalmology 2003;35,2;99-104. Singh D. Transciliary Filtration and Lymphatics of Conjunctiva- A Tale of Discovery. Tropical Ophthalmology 2002;2,1:9-13. Bethke WC. A New Clue to Lymphatic Drainage? Review of Ophthalmology 2002;9,3:12. Singh D, Singh K. Transciliary Filtration Using the Fugo Blade. Annals of Ophthalmology 2002;34,3:183-87. Roy FH. Course for Fugo Blade is enlightening, surgeon says. Ocular Surgery News 2001;19,17:35-38. Scimeca G. Phaco with Transciliary Filtration an Alternative to Triple Procedure. Ocular Surgery News 2005; 23,11:58. Atwal A. ‘Atwal’s Balanced Approach’ for Glaucoma Filtration Surgery Presented. Ocular Surgery News. 9/15/ 2005. Fugo R. A New Way to Perform Trabeculectomy. Ophthalmology Management March 2005. Fugo R. Transciliary Filtration Procedure Offers New Approach to Glaucoma. Ocular Surgery News 2005;23,5:426. Fugo R. Transciliary Filtration Procedure Offers New Approach to Glaucoma. Ocular Surgery News 2005;16,6: 18-19.

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24. 25. 26. 27. 28. 29. 30.

31. 32. 33.

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Wolf K. Surgeon Describes Learning Curve with Fugo Blade. Ocular Surgery News 2004;22,10:10. Guttman C. Transciliary filtration provides improved safety and simplicity. Ophthalmology Times. 2005;30,3:28. Fugo R. Regarding Transciliary Filtration. Tropical Ophthalmology 2002;2,1:7-8. Singh D. Singh Micro-filtration for Glaucoma; A New Technique. Tropical Ophthalmology 2001;1,6:7-11. Singh SK. Fugo Blade Capsulotomy: A New High Tech Cutting Technology. Tropical Ophthalmology 2001;1,1:1416. Fugo R. The Fugo Blade Allows New Surgical Maneuvers. Ocular Surgery News 2003;21,22;5-7. Singh D, Singh RSJ. Applications of the Fugo Blade. In: Wilson ME, Triverdi RH, Pandey SK (Eds): Pediatric Cataract Surgery: Techniques, Complications, and Management. 1st Edition. Lippincott Williams and Wilkins, 2005;97-100. Peponis E, Rosenberg P, Reddy SV, Herz JB, Kaufman HE. The Use of the Fugo Blade in Cornea Surgery: A Preliminary Animal Report. Cornea (In Press). Video Journal of Cataract and Refractive Surgery. New Developments: New Devices- Fugo Blade. Vol. XVIII, Issue 1, 2002. Kent C. Corneal Pits May Relieve Edema. Review of Ophthalmology 12,9. September 2005.

INDEX A Ab externo techniques of ablation 288 Ab-externo sclerostomy 68 Ab-interno sclerostomy 67 Abraham type of iridotomy lens 11, 83 Acetyline chloride 104 Ahmed glaucoma valve 228 AIDA excimer laser 102 Alcon infinity unit 358 ALT coagulation damage 273 ALT laser burn SEM 274 Ambulatory surgery, topical anesthesia in 148 Angle recession glaucoma 38 Angle-closure glaucomas 47 Anterior chamber maintainer 307 Anterior hyaloidotomy 92 Anterior synechia 37,47,54,56,85 Apraclonidine 35,37,55,58 Argon and YAG laser combined, iridotomy 15 Argon blue-green laser 53 Argon fluoride excimer laser 136 Argon laser 36,46,88,90 Argon laser cyclophotocoagulation 177 Argon laser peripheral iridoplasty 57 Argon laser photomydriasis 82 Argon laser trabeculoplasty (ALT) 34,36,53, 99,267,272

complications 37 indications 34 repeat trabeculoplasty 39 technique 35 Argon/Diode (thermal) laser trabeculoplasty 282 Astigmatism 329 Atropine 83

B Benzodiazepines 154 Best distance corrected visual acuity (BCDVA) 380 Betoptic solution 143 Bimanual microphaco 19 G 333 Bimanual Microphaco and deep sclerocanalostomy 327 1st stage: glaucoma 330 2nd stage: cataract 333 3rd stage glaucoma 335 Bimanual microphaco technique 329 Bimanual phacoemulsification 148 Blepharitis 255 Brimonidine 55 Bupivacaine 200

C Caliper 239 Canalostomy 338 Capsulorhexis 333 Cataract formation 17,328

426

Step by Step Minimally Invasive Glaucoma Surgery

Chronic granulomatous uveitis 84 Ciliary body 141, 174, 176, 304, 346, 362, 363, 365 Ciliary process treatment 176 Ciliary processes 366 Ciprofloxacin 200 CO2 laser 136,299,305 CO2 laser assisted nonpenetrating filtration surgery 307 Coagulation necrosis 60 Congenital or juvenile glaucoma 38 Conjunctival bleb 68 Conjunctival shutter with limb 312 1st scleral flap 314 2nd scleral flap 314 cut up the scleral flap in half 318 canalostomy 318 implant/mitomycine C 318 removal of the second flap 318 stages 312 Cornea guttata 55 Corneal edema 51, 54 Corneal endothelium lesions 54 Corneal innervation, anatomical review of 149 Corneal tunnel incision 104 Crescent knife 374 Cup/disc ratio 128 Customized laser assisted filtration surgery (CLAFS) 281 Customized laser assisted filtration surgery with PR-270 286, 290

Cyclocoagulation 58 Cyclodestructive procedures, indications of 162 Cyclophotocoagulation 161, 164, 169, 175 complications 183 endoscopic cyclophotocoagulation (ECP) 176 krypton laser cyclophotocoagulation 174 postoperative managements 183 trans-scleral cyclophotocoagulation with the Nd: YAG laser 164 trans-scleral cyclophotocoagulation with semiconductor diode laser 167 transvitreal cyclophotocoagulation 180 transpupillary cyclophotocoagulation 181 Cyclophotocoagulation 182,361 Cyclophotocoagulation noncontact and contact ND: YAG 185 Cyres scythe chopping tip 368

D Dacryocystorhinostomy 200 Deep lamellar keratoplasty 337 Deep scleectomy 136,232,237, 241,383

Index

427

Deep sclerectomy with collagen implant (VDSCI) 346 Deep sclerectomy with T-flux implant 225,229,232 Deep sclerocanalostomy 309,329 Deep sclero-keratectomy 348 Descemet’s membrane 52,116, 140,141,208,251, 253,303,337,342 Descemeto-goniopuncture (DGP) 142 Dexamethasone 120,127,353,369 Diclofenac sodium 369 Diode cyclophotocoagulation probe 60 Diode endolaser cyclophotocoagulation 187 Diode laser 46,58-60, 167 Diode laser cyclophotocoagulation 60,62,169, 171 Diode laser trans-scleral cyclophotocoagulation 172 Diode laser treatment, parameters for 169 Dormicum 154

Endoscopic cyclophotocoagulation 62 Endoscopic diode laser cyclophotocoagulation 61, 178 Endoscopic laser endocyclophoto-coagulation 176 Endothelial cell loss 18 Endothelial leukocyte adhesion molecule-1 273 Er:YAG laser 91,92,136,285,286 Erbium-YAG goniotomy 100 Erbium-YAG laser-assisted deep sclerectomy 91 Excimer laser 99, 139, 136, 140 Excimer laser surgery 139 Excimer laser treatment 142 Excimer-laser-trabeculotomy 102, 110 Exfoliation syndrome 38 External trabeculectomy, sclerostomy 136

E

Filtering sclerostomy 136 Filtration microsurgery 282 Fistulation surgery 102 Flap collapse 310 Flap dissection 240 Flip and chop phacoemulsification 335 Fluoromethalone 37 Foldable intraocular lens (IOL) 374 Fuch’s endothelial dystrophy 55 Fugo blade® 388

ELT: Kaplan-Meier-survival curve 108 ELT+Phako:Kaplan-Meiersurvival curve 109 Endolaser cyclophotocoagulation 177 Endophthamlitis 369 Endoscopic cyclophotocoagulation 179

F

428

Step by Step Minimally Invasive Glaucoma Surgery

G Glaucoma 2,262,328,358 Glaucoma filtration surgery 388 Glaucoma laser surgery 47 Glaucoma surgery 358 Glaucoma surgery, anesthesia in 148 Glaucoma surgery techniques with the fugo blade® 387 microtrack filtration 405 non-perforating filtration (NPF) 411 NPF under a fornix based corneoscleral flap 418 NPF under a limbus based sclerocorneal flap 417 open non-perforating filtration 413 transciliary filtration 394 transconjunctival transciliary filtration 401 Glaucoma surgery, importance of conjunctival lymphatics in 392 Glaucoma treatment, comparison of laser candidates for 292 Glaucomatous optic neuropathy 98 Goldman manometric experiments 311 Gonio lens 35 Goniopuncture 351 Gonioscope 88 Gonioscopy 51 G-Probe iris medical diode laser 187,358,362 G-probe laser energy 368 Grieshaber cannula 339 Group I (milling procedure) 218

Group II (milling procedure combined with phaco) 220

H Healon GV 119,122 High frequency ultrasound biomicroscopy (UBM) 351 High speed milling drill 201 High-frequency diathermic probe 118,119,131 Holmium laser 136 Holmium: YAG laser 68 Homatropine 83 Honnan balloon 200 Hoskins lens 64, 88 Human cadaver eye after CO2 laser ablation, histopathology of 304 Hyphema 16 Hypotony 362

I Interleukin-1 274 Intraocular contact lenses 48 Intraocular lens 178 Intraocular pressure 16,37,47,58,123,219,262, 263,266,272,298,350,374 Intrastromal excimer laser ablation 136, 139 Intravenous injection, complementary sedation 152 Intravitreal silicone oil 174 Iridocorneal endothelial syndrome 49 Iridocyclitis 16 Iridolenticular adhesions 85

Index Iridotomy 10,12,17,58 closure of 17 failure of 18 indications for 10 site, selection of 12 IRIS G-probe 170 Iris medical diode laser 358 Iris synechia 91 Ischemia 364

J Juvenile glaucoma 117

K Keratomileusis in situ 262 Keratoplasty glaucoma 176,179, 364 Krasnov sinusotomy 311 Krypton laser for trans-scleral contact 175 Krypton lasers 46 Krypton red laser 89

L Lamellar keratectomy 262 Laser assisted techniques for the future 285 Laser cyclophotocoagulation 162 Laser iridotomy 10,47,48,57,138 Laser peripheral iridoplasty 56 Laser principle 44 Laser sclerotomy with ND: YAG instrumentation 25 clear corneal incision 26 closure of incision 31 laser sclerotomy 26 laser phakonit and IOL implantation 31

429

laser sclerotomy in pseudophakia and aphakia 32 paracentesis 25 peripheral iridectomy 29 phakic laser sclerotomy 31 Laser suturolysis 88 Laser therapy 84 Laser trabeculoplasty 52 Laser treatments after filtering surgery 63 Laser-assisted bleb remodeling 89 Laser-assisted in situ keratomileusis (LASIK) 262 Latanoprost 266 Lidocaine 150, 154, 155, 200 Linear radial laser sclerostomy 293 Lysis of vitreous strand, cataract wound 93

M Macular edema 64 Malignant glaucoma 18,58,186 Methylene blue 90 Milling drill 201 Milling surgical procedure 200 Milling trabeculoplasty 199,221 Milling trabecuoloplasty, advantages of 221 Minimally invasive glaucoma surgery (MIGS) 2 laser-based MIGS 5 excimer laser trabeculotomy 5 non-penetrating glaucoma surgery with the CO2 laser 6

430

Step by Step Minimally Invasive Glaucoma Surgery

selective laser trabeculoplasty 6 titanium sapphire laser trabeculoplasty 5 scleral expansion bridge (SEB) 6 surgical based MIGS 3 deep sclerectomy 3 deep sclerocanalostomy (DSC) 4 milling trabeculoplasty 4 sclerothalamotomy (STT) 4 viscocanalostomy 3 Mitomycin C 89,131,215,306,342, 377, 384,339 Moxifloxacin 369 MST duet inflow system 368

N Nature’s drainage channels 227 Nd: YAG cyclophotocoagulation 165, 186 Nd: YAG goniopuncture 90 Nd: YAG iridolenticular synechiolysis 86-88 Nd: YAG laser 10, 24, 39, 46, 59, 82,88,90,92,167,186, 275,285,351,361 Nd: YAG laser iridotomy 14 Nd: YAG laser membranectomy 65 Nd: YAG laser, modified technique for 86 Nd:YAG laser trabeculoplasty (YLT) 53 Neodymium YAG laser iridolenticular synechiolysis 82 Neovascular glaucoma 166,175, 177

Non-penetrating deep sclerectomy (NPDS) 90,115,283 Non-penetrating filtration surgery (NPFS) 298 Non-penetrating filtration surgery with CO2 laser 297 Non-penetrating glaucoma surgery 137,139,346 Non-penetrative surgical techniques 310,329 Notched hemispherical metallic tips 203

O Ocular hypertension 263 Open angle filter surgery for glaucoma 309 Open angle glaucoma 38, 55, 56, 98, 132,276,282 Ophthalmic viscoelastic device 374

P Partial excimer laser sclerostomy 285 Pediatric glaucoma 166, 173 Peribulbar anesthesia 200 Phacoemulsification 101,358,374 Phacoemulsification and deep sclerectomy with T-flux 373 Phenylepherine 83,88 Photomontage of the fiberoptic system 103 Phthisis 362,369 Pigment dispersion syndrome 48 Pigmentary glaucoma 38,47,263 Pilocarpine 53,57,104,120

Index Pneumatic trabeculoplasty (PNT) 261,263 Posterior synechiae 18,52 Post-laser treatment 15 Postpenetrating keratoplasty refractory glaucoma 167 PR-270 Pulsed laser 286 Prednisolone 37 Primary open-angle glaucoma (POAG) 263,374 Proparacaine 88,90 Pseudoexfoliation 328 Pseudoexfoliation glaucoma 55,56 Pulsed erbium:YAG laser 285

431

Refractory glaucoma 61 Retinal burns 18 Ring synechiae 82 Ritch lens 64 Rose bengal 90 Rycroft cannula 377

Sclero-corneal trabecular meshwork 208 Scleromalacia 363 Sclerostomies 285 Sclerostomy 66, 67 Sclerothalamectomy 115 Sclerothalamotomy ab interno surgery 113,116,128 Selective laser trabeculoplasty 39,271,274,283 Selective laser trabeculoplasty and ALT, comparison of 39 Semiconductor diode laser 362 Slit-lamp 88,214 Sodium hyaluronate 251 Standard deep sclerectomy 349 STT glaucoma tip 118 Sturge-Weber syndrome 91 Subconjunctival bubble in glaucoma 147 Subconjunctival bubble of anesthesia lidocaine 153 Supra-choroidal aperture 243 Supra-choroidal entry 233 Surgical laser tecnologies (SLT) 361 Suturing T-flux 231, 244-246 Suturolysis 89 Synechiolysis 85, 86

S

T

Schlemm’s canal 65, 103, 115, 120, 141, 143, 199, 207, 211,215,248,251, 254,311,337,338, 348,377 Scleral flap sutures 63 Scleral pocket 240

Tetracaine 150 T-flux in scleral bed 231 T-flux in supra-choroidal 234 T-flux with supra-choroidal lake 235 Timolol maleate 83 Tobradex 265

Q Q-switched Nd: YAG laser 90, 91 Q-switched Nd: YAG laser machine 83

R

432

Step by Step Minimally Invasive Glaucoma Surgery

Tobramycin 120,353 Topical anesthesia techniques 151 cataract 151 combined cataract/ glaucoma 152 glaucoma 151 Topical anesthetics 150 Trabecular meshwork 103,115, 120,263,272,303 Trabecular meshwork ablation 97 Trabecular meshwork outflow 346 Trabeculectomy 101,114,198,226, 282,285,383 Trabeculectomy technique 63 Trabeculo-descemet’s membrane 65,90,139,211,229, 291,346 Trabeculum network 311 Transient mild iritis 37 Transpupillary argon laser cyclophotocoagulation 182 Trans-scleral cyclophotocoagulation 61,179,361 Trans-scleral diode laser contact cyclophotocoagulation 172 Trans-scleral sinusotomy 136 Traumatic cataract 365 Triamcinolone 369 Tropicamide 83 Tube-shunt 283 Tumour necrotizing factor 274

U Ulcerative keratitis 187 Ultrasonic biomicroscopy 237, 306 Ultrasonic emulsification 46 Uveitis 85,86,166,362,364

V Vannas scissors 374 Very deep sclerectomy 345,349 Viscocanalostomy 65,198,220, 248,285,383 cannulation of schlemm’s canal 251 closure of the conjunctiva 254 conjunctival flap dissection 250 creation of descemet’s window 253 inner scleral flap dissection 250 inner scleral flap excision 254 outer scleral flap dissection 250 outer scleral flap suture 254 paracentesis 250

X Xenon arc photocoagulator 10 Xylocaine 88

Y YAG laser goniopuncture 305