Modern Cataract Surgery
Developments in Ophthalmology Vol. 34
Series Editor
W. Behrens-Baumann
Magdeburg
Modern Cataract Surgery
Volume Editor
Thomas Kohnen
Frankfurt am Main
112 figures, 40 in color, and 40 tables, 2002
Basel ⭈ Freiburg ⭈ Paris ⭈ London ⭈ New York ⭈ New Delhi ⭈ Bangkok ⭈ Singapore ⭈ Tokyo ⭈ Sydney
Priv.-Doz. Dr. med.Thomas Kohnen Department of Ophthalmology Johann Wolfgang Goethe University Theodor-Stern-Kai 7 D–60590 Frankfurt am Main (Germany) Continuation of ‘Bibliotheca Ophthalmologica’, ‘Advances in Ophthalmology’, and ‘Modern Problems in Ophthalmology’ Founded 1926 as ‘Abhandlungen aus der Augenheilkunde und ihren Grenzgebieten’ by C. Behr, Hamburg and J. Meller, Wien Former Editors: A. Brückner, Basel (1938–1959); H.J.M. Wewe, Utrecht (1938–1962); H.M. Dekking, Groningen (1954–1966); E.R. Streiff, Lausanne (1954–1979); J. François, Gand (1959–1979); J. van Doesschate, Utrecht (1967–1971); M.J. Roper-Hall, Birmingham (1966–1980); H. Sautter, Hamburg (1966–1980); W. Straub, Marburg a.d. Lahn (1981–1993)
Bibliographic Indices. This publication is listed in bibliographic services, including Current Contents® and Index Medicus. Drug Dosage. The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any change in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. © Copyright 2002 by S. Karger AG, P.O. Box, CH–4009 Basel (Switzerland) www.karger.com Printed in Switzerland on acid-free paper by Reinhardt Druck, Basel ISBN 3–8055–7364–2
Contents
VII Preface 3 Topical Anaesthesia for Small Incision Cataract Surgery Bellucci, R. (Verona)
33 Why Viscoadaptives? Are They Really New? Arshinoff, S.A. (Toronto)
25 Comparison of Four Viscoelastic Substances for Cataract Surgery in Eyes with Cornea guttata Mester, U.; Hauck, C.; Anterist, N.; Löw, M. (Sulzbach)
32 The Staar Wave Fine, I.H.; Hoffman, R.S.; Packer, M. (Portland, Oreg./Eugene, Oreg.)
43 Phacotmesis Kammann, J.; Dornbach, G. (Dortmund)
44 Tilt and Tumble Phacoemulsification Davis, E.A.; Lindstrom, R.L. (Minneapolis, Minn.)
59 Phacoemulsification in the Anterior Chamber: Preliminary Results Alió, J.L.; Shalaby, A.M.M.; Attia, W.H. (Alicante)
74 Phaco Chop: Making the Transition Friedman, N.J. (Stanford, Calif.); Kohnen, T. (Frankfurt am Main/Houston, Tex.); Koch, D.D. (Houston, Tex.)
79 Ultrasound-Assisted Phaco Aspiration Olson, R.J. (Salt Lake City, Utah)
85 Management of the Mature Cataract Masket, S. (Los Angeles, Calif.)
97 Phacoemulsification in the Vitreous Cavity Ruiz-Moreno, J.M.; Alió, J.L. (Alicante)
306 Capsular Tension Ring as Adjuvant in Phacoemulsification Surgery Muñoz, G.; Alió, J.L. (Alicante)
339 Optical Coherence Biometry Haigis, W. (Würzburg)
333 Optical Biometry in Cataract Surgery Findl, O.; Drexler, W.; Menapace, R.; Kiss, B.; Hitzenberger, C.K.; Fercher, A.F. (Wien)
343 White-to-White Corneal Diameter Measurements Using the Eyemetrics Program of the Orbscan Topography System Wang, L. (Heidelberg/Houston, Tex.); Auffarth, G.U. (Heidelberg)
347 Injector Systems for Foldable Intraocular Lens Implantation Fabian, E. (Rosenheim)
355 Incisions for Implantation of Foldable Intraocular Lenses Development of a New Caliper, Measurement of Incision Sizes, and Wound Morphology of the Cornea Kohnen, T. (Frankfurt am Main)
387 Scheimpflug Imaging of Modern Foldable High-Refractive Silicone and Hydrophobic Acrylic Intraocular Lenses Baumeister, M.; Bühren, J.; Kohnen, T. (Frankfurt am Main)
395 Does the PCO Preventing Square Edge Concept Apply to Acrylic-Hydrophilic Intraocular Lenses? Jaullery, S.; Sourdille, P. (Nantes)
202 Posterior Capsule Opacification after Implantation of Polyfluorocarbon-Coated Intraocular Lenses: A Long-Term Follow-Up Auffarth, G.U.; Ries, M.; Tetz, M.R.; Faller, U.; Becker, K.A.; Limberger, I.-J.; Völcker, H.E. (Heidelberg)
209 Piggyback Intraocular Lens Implantation Gills, J.P.; Fenzl, R.E. (Tarpon Springs, Fla.)
237 Multifocal Intraocular Lenses Claoué, C.; Parmar, D. (London)
238 Author Index 239 Subject Index
Contents
VI
Preface
Although the first implantation of an intraocular lens (IOL) was undertaken just over 50 years ago (by Sir Harold Ridley, November 29, 1949 at St. Thomas’s Hospital, London, UK), removal of the natural lens with implantation of an IOL is the most commonly performed surgical intervention in humans. With small-incision surgery, using topical anesthesia, ultrasound or laser energy to remove the cataractous lens material and implantation of a foldable IOL, the patient can experience low invasiveness and fast rehabilitation of visual function. In this book, experts in the field of cataract surgery from all over the world have documented their clinical experience, research results and inventions to achieve the goal of successful modern cataract surgery. The present volume starts with a summary on topical anesthesia, followed by new research on ophthalmic viscoelastic substances (OVD), formerly called ‘viscoelastics’. Many of the articles report on new equipment and techniques for cataract removal, particularly in difficult surgical situations such as hard nucleus, mature cataracts and loss of lens material into the vitreous cavity as a complication of cataract surgery. Following removal of the lens, the now aphakic patient should be made pseudophakic to achieve acceptable vision. One important element of IOL implantation is to choose the correct lens power. The improvement of IOL power calculations is demonstrated by optical coherence biometry, a new measuring device to determine axial length. Two elements of sophisticated cataract surgery are to implant the IOL through an incision which is as small as possible but still large enough to reduce the risk of inflammation and induced astigmatism, and to choose the best IOL material and design for good long-term results. New methods to correct aphakia include the implantation of more than one IOL in high hyperopes and myopes (piggyback implantation) and multifocal IOLs (treatment of presbyopia after natural lens removal).
I wish to thank Prof. Behrens-Baumann for the invitation to edit this book in the series of Developments in Ophthalmology, Susanna Ludwig and Susanne Stolz of S. Karger Publishers for their editorial help, and all contributing authors for their effort to provide scientific information in this exciting subspecialty of ophthalmology. Thomas Kohnen, Frankfurt am Main
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VIII
Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 1–12
Topical Anaesthesia for Small Incision Cataract Surgery Roberto Bellucci Ophthalmic Unit, Hospital of Verona, Italy
Topical applications of anaesthetic agents have been employed in cataract surgery since the end of the 19th century, with cocaine 2 or 4% eyedrops as the most used drug [1]. About 30 years ago, retrobulbar anaesthesia with facial block was the standard method to relieve pain and to obtain akinesia during cataract surgery; cocaine eyedrops were sometimes used to obtain vasoconstriction of conjunctival vessels, and to increase mydriasis. Soon after the advent of posterior chamber intraocular lenses, surgeons began to look for different methods of anaesthesia. Peribulbar techniques were popularized by Davis and Mandel [2] in 1986; Smith [3] reported about a combination of topical and subconjunctival anaesthesia in 1990; Greenbaum [4] proposed his sub-Tenon approach in 1992. The current use of topical anaesthesia for small incision cataract surgery began in 1991, when Fichman [5] first decreased to 1 ml the volume of retrobulbar injection, and then performed a series of phacoemulsifications under topical anaesthesia using 0.5% tetracaine. This technique spread rapidly, and other drugs like lidocaine were tested. Intraocular irrigations of anaesthetic agents as an adjunct to topical applications were postulated in 1993 [6], giving rise to the current most popular approach to anaesthesia in phacoemulsification. Many anaesthetic techniques including topical application of an anaesthetic agent have been proposed. Variations include use of oral or intravenous sedation, administration of lid block, use of subconjunctival injections, intraocular anaesthetic irrigations and more. For the purpose of this chapter we will consider topical anaesthesia the only use of anaesthetic eyedrops without sedation, and topical/intraocular anaesthesia the use of anaesthetic eyedrops with intraocular anaesthetic irrigation.
Bases of Topical/Intraocular Anaesthesia in Small Incision Cataract Surgery
Small incision cataract surgery has anaesthesia requirements that are greatly different from the requirements of extracapsular cataract surgery. Instruments do not move within large wounds, but are moved as levers through small incisions thus preventing fluid leakage and hypotension. Usually two incisions are made, allowing the surgeon to stabilize and to direct the eye with two instruments. As a result, akinesia is no longer needed, yet the retained ocular motility can help the surgeon in some passages of surgery by simple instruction of the patient. In addition, phacoemulsification can be performed without painful manoeuvres typical of extracapsular surgery like muscle sutures, conjunctival incisions, iris manipulations, and also postoperative pain is very limited. Although this reduction in the need for analgesia promotes lighter anaesthesia techniques, still there are surgery procedures that usually cause pain: nucleus rotation stretches the zonula that elicits pain in the ciliary body, the increase in intraocular pressure with irrigation is also appreciated, iris touch can be painful especially at the end of the case. The patient’s safety lies in that cataract surgery with self-sealing small incisions can be interrupted at any time in case of pain sensations, for further anaesthesia delivery with no harm for the eyes under operation. Apart from these considerations about the feasibility of topical anaesthesia, there are many advantages over retro- or periocular injections. The risks of needle penetration within the eye or the optic nerve are obviously avoided, as orbital haemorrhages. During surgery, the level of analgesia obtained is more consistent and the intraocular pressure is lower than following periocular infiltrations. The limited amount of drug employed inhibits the general side effects commonly observed with local anaesthesia. After surgery, the prompt return of sensitivity allows ambulatory patients to realize immediately an unexpected ocular pain that could require treatment. Patients are delighted with topical anaesthesia, that suppresses all they remembered painful about surgery – periocular needle injections. With injections, sedation was needed more for anaesthesia delivery than for surgery itself. Topical anaesthesia brings a different concept than nerve block: receptor block. Nerve block involves the anaesthetic agent to come in touch with the sensory nerve, exerting its activity on non-myelinated fibres or on Ranvier nodes of myelinated fibres. Three to five nodes of Ranvier must be blocked to suppress impulse propagation, for a length of 3–7 mm. This relatively long portion could explain the variability we find in the level of anaesthesia after peribulbar injections. Receptor block involves the inhibition of sodium channels at nerve endings or receptors by the anaesthetic agents, thus blocking the production of nervous impulse. The exposed receptors could be reached more completely, being the drug in solution. As for drug concentration, A-delta and C fibres, carrying pain,
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Table 1. Anaesthetic agents most used for topical applications in ophthalmic surgery Agent
Linkage
Concentration (%)
pH
pKa
% base at pH 7.4
Duration min
Tetracaine Lidocaine
Ester Amide
0.5 4.0
4.5–6.5 6.0–6.5
8.5 7.9
艐10 艐25
10–15 15–20
The low pH of the solution is associated with subjective burning on application. If the pKa is high, the molecule is more dissociated at physiologic pH (low % base at pH 7.4) with higher surface activity but poorer corneal penetration.
temperature and touch, are blocked by lower concentrations of drugs than motor fibres. Usually thermal and tactile sensations are thought to be more resistant to anaesthetic agents, because of slight differences in conductivity among the various types of nerves.
Anaesthetic Agents for Topical Intraocular Anaesthesia
Topical anaesthetic agents are tertiary amines composed by an aromatic hydrophobic ring and an amidic hydrophilic group, with an ester (proparacaine, tetracaine, benoxinate) or an amidic (lidocaine, etidocaine) intermediate chain. The ester compounds are rapidly hydrolyzed by plasmatic esterasis, while the amide compounds are degraded more slowly. All the anaesthetic agents are stable in solution at relatively acid pH. They have to gain the non-dissociated form to cross the tear film and the cornea, and to return to the dissociated form at nerve endings or axons to exert their activity. The chemistry of body fluids favours these passages. The low pH of commercially available solutions is the main cause of the burning sensations perceived on the first eyedrop applications. The most used ester anaesthetic agent is tetracaine. The application of 0.5% solutions opened the way to topical anaesthesia for phacoemulsification [5], but at present it is less used because of the short duration of action and of the esterase deficiency that can be found in some patients. Currently the most employed drug is the amide lidocaine, available in many countries because it is widely used for cardiac diseases. It is available in concentrations from 1 to 4%, with or without preservatives. The unpreserved drug is selected for topical applications, because of the toxicity for the corneal epithelium exerted by chemical agents used for preservation. The unpreserved form is mandatory in case of intraocular irrigations. A comparison of tetracaine and lidocaine can be read in table 1.
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Table 2. Aqueous humor concentration of topical lidocaine Author
Year
Concentration (%)
pH
Drops
Instillation
Interval min
Level g/ml
Zehetmayer [11]
1997
4 4
5.2 7.2
3 3
3 3
3 3
4.75 ⫾ 3.5 15.06 ⫾ 8.2
Behndig [12]
1998
4 4
NR NR
1 1
3 3
1.5 1.5
1.4 ⫾ 0.5 4.2 ⫾ 1.5
Bellucci [13]
1999
4 4
5.97 5.97
1 1
3 6
10 10
8.7 ⫾ 2.4 23.2 ⫾ 8.9
Intracameral irrigation with anaesthetics was first proposed by Gills et al. [6], and then widely adopted to suppress pain coming from intraocular structures [7, 8]. The drug employed was lidocaine, at 1% concentration probably because of simplicity in preparation. We are not aware of pharmacological studies with different concentrations. Lidocaine 1% was mainly prepared from 4% solutions by diluting in BSS or BSS plus. Obtained solutions have a pH of 6.39 and 7.11 respectively [9]. Lidocaine is taken up quickly by the iris/ciliary body and cornea and rapidly removed from these tissues after BSS washout. Irrigation during phacoemulsification seems to limit lidocaine exposure to the ocular tissues, resulting in a short duration of anaesthesia. Lidocaine is not metabolized or broken down by the iris or cornea during this short period [10].
Intraocular and Systemic Levels of Topical and Intracameral Lidocaine
Studies about intraocular penetration of anaesthetic drugs have been carried out for lidocaine at 4% concentration (table 2). Zehetmayer et al. [11] found a huge dependence on the pH of the solution, as expected from chemical properties. Behndig and Linden [12] measured the lowest aqueous humor levels among published investigations. Higher levels were found in our study following instillations at 10-min intervals, probably because the damage of corneal surface favoured penetration: 8.7 ⫾ 2.4 g/ml after 3 instillations, and 23.2 ⫾ 8.9 g/ml after 6 instillations [13]. In this study, pain sensations during surgery were higher when the intraocular level of lidocaine was ⬍12 g/ml. With the commonly used irrigation of 1% unpreserved lidocaine, intraocular levels of the drug are a hundred times more elevated than after eyedrop applications: Behndig and Linden [12] found 341.8 ⫾ 151.6 g/ml in their study. The systemic absorption of topically applied lidocaine was studied by us [13]. Blood
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levels found after 1 h from the last instillation were 0.009 ⫾ 0.001 g/ml following 3 instillations, and 0.12 ⫾ 0.02 g/ml following 6 instillations. A study from Wirbelauer et al. [14] after intraocular irrigation gave the same results. These amounts are too low to cause systemic problems even in diseased patients, and are much lower than the 2.13 g/ml found by Salomon et al. [15] after periocular injections. In our studies no differences were found in pulse rate, blood pressure and oxygen saturation with peribulbar and with topical anaesthesia [9], with some variations within the peribulbar group that were confirmed in larger studies [16]. Local Side Effects and Toxicity
Although lacking in the potential risks of needle injections, topical/intraocular anaesthesia can have side effects that are mainly local. The application of an anaesthetic agent to the cornea impairs the tear film because of dilution and because of the pH of applied solutions. The inhibition of cellular sodium channels causes some swelling of the corneal epithelium, with the possibility of superficial punctate keratitis [17] that could be more important in older patients with low tear secretion. Epithelial toxicity is more pronounced when preservatives are added to the solution [18], and pushes to have patient’s eyes closed after instillation. A part of this toxicity can last a few days after surgery, slightly affecting vision, as we learn from the fellow non-operated eyes receiving some anaesthetic drops to prevent blinking during surgery. These epithelial side effects can impair visibility during surgery, and are an argument favouring the reduction of eyedrop instillation and the adjunct of intracameral anaesthetic irrigation. Intraocular lidocaine has been extensively tested for tolerance, starting from the amaurosis encountered in some patients after posterior capsule rupture [19]. Experimental studies on rabbits showed the lack of toxicity of common preparations both for corneal endothelium [20–23] and for the retina [24]. Reversible cellular swelling could be observed when the concentration is at least 1% [23], with permanent damage only at 2% [22]. Clinical and experimental studies on human corneas confirmed these results [23, 25–29], at least for lidocaine. Other compounds, like mepivacaine, seem more toxic [30]. Following the sensation of some amaurosis during uncomplicated surgery, Hoh et al. [31] investigated the speed of visual recovery after phacoemulsification with intracameral lidocaine: they found prompt return to normal vision after 4 h. Clinical Application of Topical/Intraocular Anaesthesia
The current application schedule of topical anaesthesia has some variations among surgeons, yet common features can be indicated.
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5
Patient Selection. At first, topical anaesthesia was not appreciated as a universal procedure, but it was felt that patient selection was mandatory. Grabow [32] was one of the first addressing difficulties in applying topical anaesthesia to some patients, like foreigners and those affected by deafness, dementia and uncontrolled eye movements. In addition, many surgeons avoided topical anaesthesia in patients unable to cooperate during tonometries or A-scan measurements [33], and in younger patients. At present some of these contraindications remain, but some have been overcome by the confidence both of surgeons and of patients in topical anaesthesia. Patient Instructions. As patients now expect to be operated under topical anaesthesia, few instructions have to be given before surgery. On the contrary, too many details could increase the patient’s anxiety. We only tell the patient that anaesthesia will be present, although with no needle injection; that anaesthesia can be increased at any time during surgery; that the lack of burning on eyedrop instillation is the proof of analgesia. Bilateral Instillation. Most surgeons apply the anaesthetic agent to both eyes, to prevent blinking and Bell’s phenomenon, elicited by the non-operated eye. This practice allows the patient to keep his eyes open without effort during surgery, but often causes some vision impairment in the postoperative, due to corneal epithelial toxicity of the drugs and lack of hydration. Instillation Schedule. Lidocaine 4% unpreserved eyedrops are instilled in the 10–60 min preceding surgery, according to the local protocol. We prefer 6 instillations at 10-min intervals, that assure steady analgesia for 10–15 min. The great variations in instillation schedule probably reflect more the characters of the local population than the precision of the surgical technique. Intraocular Irrigation. When intraocular irrigation of 1 or 0.5% unpreserved lidocaine is added to the anaesthesia schedule, it is usually performed immediately after the first corneal incision, or at hydrodissection. The first method requires fewer anaesthetic eyedrops, but adds one passage to surgery; the second method looks somewhat simpler, but capsulorhexis has to be performed under topical anaesthesia alone. The intraocular irrigation can be repeated in prolonged or complicated surgeries, because lidocaine is rapidly removed from ocular tissues by irrigating BSS [10]. Every surgeon should check the pH and the osmolarity of injected solutions. Preferred Surgery. There are some modifications to be made to our surgical technique to adjust for topical anaesthesia. The corneal surface rapidly dries during surgery, and must be frequently irrigated. The light of the microscope is frequently a cause of discomfort, especially in young patients, and microscopes with lights eccentric to the fovea should be preferred. We had to eliminate toothed forceps to grasp the conjunctiva, in favour of notched forceps. Conjunctival flap should be avoided, as diathermy of ocular surface. Should they be necessary,
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additional eyedrop instillation after conjunctival opening must be considered. The eye is better stabilized by a second instrument within a side port incision rather than grasping the sclera. Cataract extraction should be made with phacoemulsification, because the manoeuvres required for manual fragmentation could be more traumatizing for the eye. IOL implantation should not stretch the incision, as at that point analgesia is lower than at the beginning of the procedure. The lids must remain free from trauma because they are not anaesthetized, a condition evident on draping removal. Complications Management. Topical anaesthesia is not associated with a higher complication rate in published studies, still complications occur and have to be managed with safety and efficacy. Prolonged surgeries can be managed by repeating instillations or irrigations. Iris touch is painless if a sufficient amount of drug is present in the anterior chamber. Posterior capsule rupture and anterior vitrectomy cause no pain. Scleral fixation can be achieved with intraocular irrigation of unpreserved lidocaine [9]. Probably the only manoeuvre requiring additional peribulbar anaesthesia – to block the eye – is incision enlargement. Postoperative Instructions. One of the advantages of topical anaesthesia is the rapid recovery of sensation. Patients should be aware that ocular burning will be perceived by most of them, but ocular pain is not expected in uncomplicated cases. Burning sensation and vision impairment can also be observed in the fellow eye, if the anaesthetic agent was applied bilaterally. Following intraocular anaesthetic irrigation, vision in the operated eye is usually low at the end of surgery, with many patients speaking of ‘wonderful colours’ that probably reflect some retinal anaesthesia. When vitrectomy is added in aphakic eyes, a deep amaurosis lasting 4–6 h can be expected.
Variations in Topical Drug Delivery
Although eyedrops and intraocular irrigation are the most popular methods of drug delivery, other procedures have been developed to prolong the contact between the applied agent and ocular surfaces. Lidocaine Gel. A single application of lidocaine 2% gel into the conjunctival sac has been found as effective as repeated eyedrop instillation in providing anaesthesia for cataract surgery [34–37], with the advantage of less burning on application and less corneal dehydration. The lidocaine gel seems to be an efficacious alternative to eyedrop instillation, with the advantage of simplicity. Anaesthetic Sponges. The use of sponges soaked with an anaesthetic agent in contact with ocular surfaces to obtain analgesia was advocated by Bloomberg and Pellican [38] and Rosenthal [39] in 1995. Bloomberg [38] proposed his
Topical Anaesthesia
7
anaesthetic ring, that was left in place for 10 min before surgery and during surgery itself, if no contraindication emerged. Since then, similar devices appeared sometimes in literature, but they were not widely used. Recently they were again proposed for Lasik and Intacs procedures, where deeper anaesthesia of the conjunctiva has to be obtained than in phacoemulsification.
Clinical Experience of Small Incision Cataract Surgery with Topical Anaesthesia
The first clinical reports about phacoemulsification with topical anaesthesia date back to 1993 [32, 40, 41]. Those early works had already recognized some of the main features of topical anaesthesia: the obvious lack of risks typical of needle injections, the efficacy of the obtained analgesia, the relative loss in corneal transparency during surgery, the steady rate of surgical complications as compared with peribulbar, the good acceptance from patients’ perspectives. As topical anaesthesia spread over the operating theatres, many variations were proposed for the treatment schedule. Most of surgeons incorporated some oral sedation in their protocol, especially during transition or when comparison studies were carried out [11, 42–44]. Using sedation in selected cases, Dinsmore [45] demonstrated the feasibility of topical anaesthesia in almost 100% of patients. Interestingly, some investigations demonstrated that in peribulbar cases sedation was necessary more for needle anaesthesia delivery than for surgery itself [42, 46], and at the same time Fichman [47] found that patients’ objective anxiety for the surgical procedure was very low. In other studies subconjunctival or periocular injections of anaesthetics were added [48, 49], all these adjuncts to topical anaesthesia reflecting in part the difficulties in changing the surgeon’s mentality and in establishing new relations with the patient in the operating room [50]. Not surprisingly, patients proved less attached to retrobulbar or peribulbar anaesthesia than surgeons. All the published studies report as anecdotal the preference for needle injections, the most feared part of cataract surgery itself, although discomfort is frequently greater during surgery with topical anaesthesia [51]. At present there is a push from patients towards topical anaesthesia, which is now regarded as the standard technique in many areas. This change in mentality will probably further increase success rates and will extend topical anaesthesia to other procedures on the anterior and posterior segment [52, 53]. The intracameral irrigation with unpreserved 1% lidocaine proposed by Gills et al. [7] was the event that helped change surgeons’ mentality [28]. Intraocular levels of drug are about 100 times the level after topical instillations [12], completely eliminating pain and discomfort coming from intraocular
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Table 3. Example of topical/intraocular anaesthesia for phacoemulsification 1. Topical
4% unpreserved lidocaine HCl single-dose unit (Lidocaine 4% monodose® Alfa-Intes, Casoria, Naples) 1 drop in both eyes every 5 min for 3 times
2. Intracameral
1% unpreserved lidocaine (4% solution diluted in BSS) (pH 6.4) 1 ml at hydrodissection
3. Topical repeated
In case of conjunctival manipulation
4. Intracameral repeated
In case of prolonged surgery/complications
structures. In his study on 1,000 subjects, Koch [8] had only 4 failures. In our study on 1,442 operations from 1996 to 1998, we had 14 partial failures (would prefer peribulbar injections because of discomfort) and 11 total failures (peribulbar injection selected before or during surgery): a percentage of 1.7% [9]. The current schedule of anaesthesia for phacoemulsification as preferred by us is reported in table 3. Intracameral irrigations with anaesthetic agents gained widespread popularity, and even allow to teach surgery without going back to heavier types of anaesthesia. Nevertheless, some concern rose about their necessity in topical anaesthesia, that seems sometimes questionable [54]. We believe that intraocular irrigation probably offers little advantage to uncomplicated cases performed by experienced surgeons, but also in these circumstances it adds to our surgery the confidence not to cause pain even with sudden or unwanted movements. Patient reaction to acetylcholine irrigation with and without intracameral irrigation does fully explain this concept. Conclusions
Small incision cataract surgery is a surgical procedure controlled step by step at the operating microscope. It looks quite obvious that the types of anaesthesia that were developed for other kinds of cataract extractions – intracapsular or extracapsular – have to be revised. Topical anaesthesia will rapidly become the preferred method in all countries for the reasons of simplicity, safety and cost. Although there are some drawbacks, the advantages by far exceed the disadvantages. Intraocular irrigation of unpreserved lidocaine induced many uncertain surgeons to abandon peribulbar injections, and helped in reducing the number and toxicity of instillations. It will probably last if signs of intraocular side effects do not emerge. The feasibility of intraocular irrigations of anaesthetics is a challenge for other types of ocular surgery. An increasing number of
Topical Anaesthesia
9
anterior and posterior segment procedures can now be performed with topical anaesthesia, in all or in selected cases. Again, cataract surgery is stimulating other types of ocular surgery to evolve.
References 1 2 3 4 5 6 7 8 9 10
11
12 13 14 15 16
17 18 19 20 21 22
Koller K: Über die Verwendung des Cocaïn zur Anästhesierung am Auge. Wien Med Wochenschr 1884;43:1309–1311. Davis DB, Mandel MR: Posterior peribulbar anesthesia: An alternative to retrobulbar anesthesia. J Cataract Refract Surg 1986;12:182–184. Smith R: Cataract extraction without retrobulbar injection. Br J Ophthalmol 1990;74:205–207. Greenbaum S: Parabulbar anaesthesia. Am J Ophthalmol 1992;114:776. Fichman RA: Topical anaesthesia; in Gills JP, Hustead RF, Sanders DR (eds): Ophthalmic Anesthesia. Thorofare, NJ, Slack Inc, 1993, pp 166–171. Gills JP, Hustead RF, Sanders DR: Editors’ comments; in Gills JP, Hustead RF, Sanders DR (eds): Ophthalmic Anesthesia. Thorofare, NJ, Slack Inc, 1993, p 183. Gills JP, Cherchio M, Raanan MG: Unpreserved lidocaine to control discomfort during cataract surgery using topical anesthesia. J Cataract Refract Surg 1997;23:545–550. Koch PS: Anterior chamber irrigation with unpreserved lidocaine 1% for anesthesia during cataract surgery. J Cataract Refract Surg 1997;23:551–554. Bellucci R, Morselli S: In defence of topical anaesthesia. XVIth Congress of the ESCRS, Nice, Sept 1998. Anderson NJ, Woods WD, Kim T, Rudnick DE, Edelhauser HF: Intracameral anesthesia: In vitro iris and corneal uptake and washout of 1% lidocaine hydrochloride. Arch Ophthalmol 1999; 117:225–232. Zehetmayer M, Rainer G, Turnheim K, Skorpik C, Menapace R: Topical anesthesia with pH-adjusted versus standard lidocaine 4% for clear cornea cataract surgery. J Cataract Refract Surg 1997;23:1390–1393. Behndig A, Linden C: Aqueous humor lidocaine concentrations in topical and intracameral anaesthesia. J Cataract Refract Surg 1998;24:1598–1601. Bellucci R, Morselli S, Pucci V, Zordan R, Magnolfi G: Intraocular penetration of topical lidocaine. J Cataract Refract Surg 1999;25:643–647. Wirbelauer C, Iven H, Bastian C, Laqua H: Systemic levels of lidocaine after intracameral injection during cataract surgery. J Cataract Refract Surg 1999;25:648–651. Salomon F, Körprich R, Biscoping J, Bitterich A, Hempelmann G: Plasmaspiegel von Lokalanesthetika nach örtlicher Betäubung am Auge. Fortschr Ophthalmol 1986;83:335–337. Suzuki R, Kuroki S, Fujiwara N: A comparison of blood pressure changes in phacoemulsification cataract surgery with topical and retrobulbar block local anesthesia. Graefes Arch Clin Exp Ophthalmol 1997;235:277–282. Sun R, Hamilton RC, Gimbel HV: Comparison of 4 topical anesthetic agents for effect and corneal toxicity in rabbits. J Cataract Refract Surg 1999;25:1232–1236. Marr MG, Wood R: Effect of topical anesthetics on regeneration of corneal epithelium. Am J Ophthalmol 1957;43:606 –610. Hoffman RS, Fine IH: Transient no light perception visual acuity after intracameral lidocaine injection. J Cataract Refract Surg 1997;23:957–958. Judge AJ, Najafi K, Lee DA, Miller KM: Corneal endothelial toxicity of topical anesthesia. Ophthalmology 1997;104:1373–1379. Werner LP, Legeais JM, Obsler C, Durand J, Renard G: Toxicity of Xylocaine to rabbit corneal endothelium. J Cataract Refract Surg 1998;24:1371–1376. Kadonosono K, Ito N, Yazama F, Nishide T, Sugita M, Sawada H, Ohno S: Effect of intracameral anesthesia on corneal endothelium. J Cataract Refract Surg 1998;24:1377–1381.
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Kim T, Holley GP, Lee JH, Broocker G, Edelhauser HF: The effects of intraocular lidocaine on the corneal endothelium. Ophthalmology 1998;105:125–130. Liang C, Peyman GA, Sun G: Toxicity of intraocular lidocaine and bupivacaine. Am J Ophthalmol 1998;125:191–196. Garcia A, Loureiro F, Limao A, Sampaio AM, Ilharco JF: Preservative-free lidocaine 1% anterior chamber irrigation as an adjunct to topical anesthesia. J Cataract Refract Surg 1998;24:403–406. Masket S, Gokmen F: Efficacy and safety of intracameral lidocaine as a supplement to topical anesthesia. J Cataract Refract Surg 1998;24:956–960. Martin RG, Miller JD, Cox CC, Ferrel SC, Raanan MG: Safety and efficacy of intracameral injections of unpreserved lidocaine to reduce intraocular sensation. J Cataract Refract Surg 1998;24:961–963. Kohnen T: Is intracameral anesthetic application the final solution to topical anesthesia for cataract surgery? (Editorial) J Cataract Refract Surg 1999;25:601–602. Elvira JC, Hueso JR, Martinez-Toldos J, Mengual E, Artola A: Induced endothelial cell loss in phacoemulsification using topical anesthesia plus intracameral lidocaine. J Cataract Refract Surg 1999;25:640–642. Anderson NJ, Nath R, Anderson CJ, Edelhauser HF: Comparison of preservative-free bupivacaine vs. lidocaine for intracameral anesthesia: A randomized clinical trial and in vitro analysis. Am J Ophthalmol 1999;127:393–402. Hoh HB, Bourne R, Baer R: Visual recovery after phacoemulsification using topical anesthesia. J Cataract Refract Surg 1998;24:1385–1389. Grabow HB: Topical anaesthesia for cataract surgery. Eur J Implant Refract Surg 1993;5:20–24. Fraser SG, Siriwadena D, Jamieson H, Girault J, Bryan SJ: Indicators of patient suitability for topical anesthesia. J Cataract Refract Surg 1997;23:781–783. Barequer IS, Soriano ES, Green WR, O’Brien TP: Provision of anesthesia with single application of lidocaine 2% gel. J Cataract Refract Surg 1999;25:626–631. Koch PS: Efficacy of lidocaine 2% jelly as a topical agent in cataract surgery. J Cataract Refract Surg 1999;25:632–634. Assia EI, Pras E, Yehezkel M, Rotenstreich Y, Jager-Roshu S: Topical anesthesia using lidocaine gel for cataract surgery. J Cataract Refract Surg 1999;25:635–639. Harman DR: Combined sedation and topical anesthesia for cataract surgery. J Cataract Refract Surg 2000;26:109–113. Bloomberg LB, Pellican KJ: Topical anesthesia using the Bloomberg SuperNumb anesthetic ring. J Cataract Refract Surg 1995;21:16–20. Rosenthal K: Deep, topical, nerve-block anesthesia. J Cataract Refract Surg 1995;21:499–503. Kershner RM: Topical anesthesia for small incision self-sealing surgery; a prospective evaluation of the first 100 patients. J Cataract Refract Surg 1993;19:290–292. Williamson CH: Clear corneal incision with topical anesthesia; in Gills JP, Hustead RF, Sanders DR (eds): Ophthalmic Anesthesia. Thorofare, NJ, Slack Inc, 1993, pp 176–186. Patel BCK, Burns TA, Crandall A, Shomaker ST, Pace NL, van Eerd A, Clinch T: A comparison of topical and retrobulbar anesthesia for cataract surgery. Ophthalmology 1996;103:1196–1203. Roman S, Auclin F, Ullern M: Topical versus peribulbar anaesthesia in cataract surgery. J Cataract Refract Surg 1996;22:1121–1124. Uusitalo RJ, Manuksela EL, Paloheimo M, Kallio H, Laatikainen L: Converting to topical anesthesia in cataract surgery. J Cataract Refract Surg 1999;25:432–440. Dinsmore SC: Approaching a 100% success rate using topical anesthesia with mild intravenous sedation in phacoemulsification procedures. Ophthalmic Surg Lasers 1996;27:935–938. Shammas HJ, Milkie M, Yeo R: Topical and subconjunctival anesthesia for phacoemulsification: Prospective study. J Cataract Refract Surg 1997;23:1577–1580. Fichman RA: Use of topical anesthesia alone in cataract surgery. J Cataract Refract Surg 1996; 22:612–614. Anderson CJ: Circumferential perilimbal anesthesia. J Cataract Refract Surg 1996;22:1009–1012. Maclean H, Burton T, Murray A: Patient comfort during cataract surgery with modified topical and peribulbar anesthesia. J Cataract Refract Surg 1997;23:277–283.
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Patel BCK, Clinch TE, Burns TA, Shomaker ST, Jessen R, Crandall AS: Prospective evaluation of topical versus retrobulbar anesthesia: A converting surgeon’s experience. J Cataract Refract Surg 1998;24:853–860. Nielsen PJ, Allerød CW: Evaluation of local anesthesia techniques for small incision cataract surgery. J Cataract Refract Surg 1998;24:1136–1144. Vicary D, McLennan S, Sun XY: Topical plus subconjunctival anaesthesia for phacotrabeculectomy: One year follow-up. J Cataract Refract Surg 1998;24:1247–1251. Yepez J, Cedeno de Yepez J, Arevalo JF: Topical anesthesia for phacoemulsification, intraocular lens implantation, and posterior vitrectomy. J Cataract Refract Surg 1999;25:1161–1164. Tan JHY, Burton RL: Does preservative-free lignocaine 1% for hydrodissection reduce pain during phacoemulsification? J Cataract Refract Surg 2000;26:733–735.
Roberto Bellucci, MD, Via Degli Abeti 17, I–25087 Salò/BS (Italy) Tel. ⫹39 036 543 678, Fax ⫹39 036 543 678, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 13–24
Why Viscoadaptives? Are They Really New? Steve A. Arshinoff York Finch Eye Associates, Toronto, Ont., Canada
In the past 2 years, ophthalmologists have been exposed to a lot of promotion about viscoadaptives. Most of us were not sure why we needed a new type of viscoelastic, or what is so new about the new ones to make us want to use them. Healon®5 is by now available in most parts of the world. MicroVisc® Phaco (iVisc® Phaco in Canada) has just been introduced in a number of ophthalmic markets. These two ophthalmic viscosurgical devices (OVDs – the new term recommended by the International Standards Association for viscoelastics, 2000) are referred to as ‘viscoadaptives’ (another new term), because their behavior in surgery is different from older OVDs. Ophthalmic surgeons are already presented with numerous OVD choices. Many of us have enough trouble deciphering the confusing and conflicting material that we receive from the manufacturers and distributors already, and often tend to just buy on price, assuming that they are all more or less the same anyway (which they definitely are not). Why then have viscoadaptives appeared and what is the difference between them and older OVDs? Can we really do anything new with viscoadaptives?
Materials and Methods Rheologic data was collected from all cooperative manufacturers of OVDs over 15 years to form a database of OVD rheology. New data was collected on the new viscoadaptives and compared to that of older OVDs. All data was verified from more than one source and converted into common comparable units. All OVDs reviewed were used in clinical surgery to ascertain that their behavior matched the manufacturers’ claims. New techniques were developed and tested as described below.
Results and Discussion
In order to understand why a new OVD is needed in modern cataract surgery, we must first understand the OVDs we had before viscoadaptives, and their limitations. Let us begin by looking at the classification of OVDs, and discuss the relative merits and drawbacks of each class, before viscoadaptives. In order to classify OVDs we must first decide which parameters to use as the basis of the classification. There are numerous chemical and physical properties that could be chosen, but the two that play the most important roles in determining utility in cataract surgery are zero shear viscosity (i.e. the viscosity of the material when it is at rest) and its relative cohesion or dispersion [1]. Table 1 illustrates the classification of OVDs based upon these two parameters, dividing OVDs into two broad groups: the higher viscosity cohesives and the lower viscosity dispersives. We can see that viscoadaptives fit into the higher viscosity cohesive group, but we will initially confine our discussion to the subgroups that existed prior to the advent of viscoadaptives. If we ignore the viscoadaptive subgroup and concentrate on the choices we had available before viscoadaptives, we see two groups, each divided into two subgroups. In each group, the subgroup on the top, with higher zero shear viscosity, performs better in cataract surgery than the lower viscosity subgroup below it. However, when looked at by major grouping, the higher viscosity cohesives and lower viscosity dispersives have opposite surgical benefits and drawbacks (table 2). We, as surgeons, therefore find ourselves in a difficult position without viscoadaptives. If we want to obtain maximum anterior chamber (AC) depth and stability in a shallow chambered hyperope, to allow easier insertion of the phaco tip, we must accept the fact that if we choose a higher viscosity cohesive OVD, and our surgery is prolonged or difficult, the OVD chosen may not be retained in the AC long enough to yield optimal protection for the corneal endothelial cells. On the other hand, if we choose a lower viscosity dispersive OVD, because the AC is shallow and we are concerned for the endothelial cells, we may not be able to deepen the AC sufficiently to allow safe insertion of the phaco at all. Furthermore, the irregular fracture boundaries seen with dispersives may obscure our view of the posterior capsule to the extent that in our zeal to overly protect the endothelium, we expose the posterior capsule to increased risk of rupture due to impaired visibility. It is precisely for these reasons that I devised the dispersive-cohesive viscoelastic soft shell technique a number of years ago. This method uses a dispersive and cohesive viscoelastic together, sequentially, in order to take advantage of the best characteristics of both types, and neutralize the drawbacks of each [2]. The viscoelastic soft shell technique gets around the problems
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Why Viscoadaptives?
15
7.9 5.0 6.1 5.1 2.0 4.0 3.0 5.1 2.0 1.5
1.4% NaHa 1.4% NaHa 1.4% NaHa 1.0% NaHa 1.0% NaHa 1.0% NaHa 1.0% NaHa 1.2% NaHa 1.6% NaHa
4
2.3% NaHa
1.4% NaHa
7.9
2.5% NaHa
280 K 230 K 215 K 200 K 100 K 100 K
500 K
1.0 M
2.0 M
4.8 M
7M
24 M
3.0% Ha
Occucoat Hymecel Adatocel Visilon
Ocuvis
2.0% HPMC 2.0% HPMC 2.0% HPMC 2.0% HPMC
2.0% HPMC
Very low viscosity dispersives i-Cel 2.0% HPMC
Vitrax
Medium viscosity dispersives Viscoat 3.0% NaHa 4.0% CDS Cellugel 2.0% chemically modified HPMC
86 86 86 86
90
80
500
500 25 400
MW, D (K)
4 4 4 4
4.3
6.0
25
40
41
V0, mPa s (K)
MW, D Molecular weight (daltons); V0, mPa s shear zero viscosity (millipascal seconds); M million; K thousand; NaHa sodium hyaluronate; HPMC hydroxypropylmethylcellulose; CDS chondroitin sulfate.
Super Viscous Cohesive MicroVisc Plus (iVisc Plus, Hyvisc Plus) Healon GV Viscous-cohesive MicroVisc (iVisc, Hyvisc) Allervisc Plus (Viscorneal Plus) Provisc Healon Biolon Allervisc (Viscorneal) Amvisc Amvisc Plus
Viscoadaptive MicroVisc Phaco (iVisc Phaco) Healon5
content
OVD
V0, mPa s
OVD
MW, D (M)
Lower viscosity dispersive
Higher viscosity cohesive content
Table 1. Ophthalmic viscosurgical device classification, molecular weight and zero shear viscosity
Table 2. Best uses and drawbacks of OVD groups Higher viscosity cohesives Best uses Create and preserve spaces Displace and stabilize tissues Pressurize the AC Clear view of posterior capsule during phaco Disadvantages Leave AC too quickly during I/A or phaco Suboptimal endothelial protection Unable to partition spaces Lower viscosity dispersives Best uses Remain adjacent to corneal endothelium throughout phaco Selectively move and isolate Partition spaces Disadvantages Do not maintain spaces or stabilize as well Irregular fracture boundaries obscure view of posterior capsule More difficult to remove at the end of the procedure
encountered in selecting a single viscoelastic, as described above, in cataract surgery. But this technique demands that the surgeon bear the cost and inconvenience of two OVDs for each procedure, and further requires that the surgeon learn to use the two OVDs in the proper sequence and relative amounts in every possible circumstance. Unfortunately, this leaves the technique prone to improper use. This makes the soft shell technique, although excellent, less than ideal. In September of 1996, I was retained by Pharmacia & Upjohn to work with them to develop a new OVD that would possess all of the best properties of Healon®GV, and yet be retained in the AC, at least as well as the best dispersive OVDs throughout the phaco procedure, and permit partitioning of the AC into an OVD-protected space and a surgical zone, where phaco or I/A could be carried out. Healon®5 is the result of this effort, and the unique properties, which make it viscoadaptive, are best described by explaining the behavior of Healon®5 when compared to previous OVDs [3, 4]. MicroVisc® Phaco was recently introduced as the second viscoadaptive in the world. ‘Viscoadaptive’ means that somehow the rheologic molecule adapts its behavior to the intended surgical task, without the surgeon having to do anything,
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Property
Fracturable at high turbulence Healon5 Cohesive at low turbulence
Cohesive at all settings
Healon GV
Viscoat Dispersive at all settings
10 35 Flow rate (cm3/min)
Fig. 1. Viscoadaptive response to fluid turbulence. The rheologic behavior of ophthalmic viscosurgical devices is dependent upon the environmental stress that the molecule is exposed to. In phacoemulsification, the ultrasonic tip is too remote from most of the OVD to have any effect, but the fluid turbulence, which is a function of flow rate, induces stress upon the OVD, which may break it up. We can see from the illustration that under all commonly encountered flow rates in phacoemulsification, Viscoat, a typical dispersive OVD, behaves in a dispersive fashion, whereas Healon GV behaves in a cohesive fashion. Healon5, on the other hand, changes its behavior from cohesive to fracturable, or ‘pseudo-dispersive’ at flow rates around 25 cm3/min, enabling the surgeon to select the behavior wanted by altering the BSS flow rate.
except perform the task. Figure 1 explains how this is achieved. Viscoadaptivity was achieved by increasing the concentration of the rheologically effective polymer (sodium hyaluronate) to the point that the OVD solution became so viscous that its properties began to approach those of a solid, hence becoming fracturable. This is analogous to the behavior of chocolate pudding. When it is initially made, it is watery, and a child will spill most of it over their clothes when trying to eat it. But, after placing the pudding in the refrigerator for a while, it becomes sufficiently rigid for a piece to be fractured out of it with a spoon. Similarly, in a viscoadaptive, the interchain entanglement strength exceeds the intrachain carbon to carbon bond strength, to the point that imposed stress will cause the chains to fracture, disassembling the mass, instead of untangling to reshape the mass.
Why Viscoadaptives?
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During ophthalmic surgery, the behavior of the OVD depends upon its response to the fluid turbulence (the ‘stress’) in its environment. The ultrasonic energy of the phaco tip is felt only in the immediate vicinity of the needle tip, whereas the OVD in the entire AC is exposed to the fluid turbulence of irrigation, and it is this turbulence that affects its behavior. As we can see in figure 1, created to demonstrate the viscoadaptivity of Healon®5, Viscoat® demonstrates dispersive behavior over the entire range of fluid turbulence (proportional to flow rate) normally encountered in phaco surgery. Similarly, Healon®GV demonstrates cohesive behavior over this entire range of fluid flow rates. Healon®5, however, is different. When exposed to low flow rates, it behaves like a super viscous cohesive device, as if it were super Healon®GV, demonstrating zero shear viscosity three and a half times greater than Healon®GV. However, as flow rates increase above 25 cm3/min, Healon®5 begins to fracture into smaller pieces, making its behavior appear to mimic some of the properties of dispersive viscoelastics, behavior we have come to describe as pseudodispersive. It is this duality of function that allows viscoadaptives to be effective replacements for both cohesive and dispersive OVDs in cataract surgery. This is at first surprising when the pseudoplasticity curves of the two available viscoadaptives are reviewed (fig. 2). Figure 2 shows the pseudoplasticity curve of Healon®5 and iVisc® Phaco (MicroVisc® Phaco). Most of the work done quantifying the behavior of viscoadaptives has been done on Healon®5, and inferred to also apply to iVisc® Phaco. In the description below, I will therefore discuss the information that we already have on Healon®5, and generalize in the instances that the same has been shown to apply to iVisc® Phaco. Because of high pseudoplasticity, viscoadaptives are easily injected through small-bore cannulas, but one gauge size larger bore is usually preferred in comparison to super viscous cohesives like Healon®GV. They behave like super Healon®GV to yield excellent pressurization of the AC and stability for capsulorhexis. During the phaco part of the procedure, viscoadaptives can be fractured at the pupillary plane, because the turbulence behind the iris exceeds that in front of the iris, thus emptying the capsular bag of OVD, while the AC remains full of immobile viscoelastic, effectively preventing any irrigation of the corneal endothelial cells. For IOL implantation, viscoadaptives maintain the stability of the capsular bag and AC like super Healon®GV, while removal requires some special considerations (see below under removal). What ultimately determines the utility of a new OVD is not just that it can be used to perform familiar tasks as well as currently available OVDs, but rather that it enables ophthalmic surgeons to do things they could not do before. It was the ability to safely implant IOLs while protecting the endothelium that encouraged us to first use Healon®, despite worrisome reports of severe postoperative IOP spikes during the first few months after the release of Healon® in 1980.
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8
i Visc Phaco
7
6
Healon GV Healon
5
Viscoat 4
Occucoat
log viscosity (mPa s)
Healon5
3
2 3
2
1
0 log shear rate (s1)
1
2
3
Fig. 2. Pseudoplasticity curves of viscoadaptives. The pseudoplasticity curves of viscoadaptives are compared to other common ophthalmic viscosurgical devices. Both Healon5 and iVisc (MicroVisc) Phaco have higher zero shear viscosities than Healon GV, and are very pseudoplastic as demonstrated by their low viscosity at log shear rate 3 (shear rate 1,000). An examination of this curve makes it clear that there is more to the story of viscoadaptivity than is evident in pseudoplasticity curves. Indeed their behavior demonstrated in figure 1 must also be taken into account.
Similarly, it is the new things we can do with viscoadaptives that will encourage surgeons to change over from their current favorite OVD. To date, surgeons that have moved over to Healon®5 rarely go back. Enough experience with iVisc® Phaco has not yet been accumulated to draw conclusions, but it also seems very promising. To date, the following new things that can be done with viscoadaptives have been identified: (1) Dissect the anterior hyaloid face from the posterior capsule in pediatric cataract surgery. I first heard this described at conferences by Robert Stegmann of South Africa. He claims that the use of Healon®5 for this makes the performance of a posterior capsulorhexis in young children considerably easier. (2) Perform phaco tumble techniques better. David Brown of Florida has popularized phaco tumble techniques. Healon®5 greatly stabilizes the vertically tilted nucleus and preserves the depth of the AC, making this technique easier and safer.
Why Viscoadaptives?
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(3) The use of trypan blue (Vision blue®) in mature cataracts is much easier with Healon®5, making phacoemulsification of mature white cataracts a simple matter. See below (Ultimate Soft Shell Technique). (4) Do viscosurgery with only partial filling of chamber with OVD. With all OVDs prior to viscoadaptives, the OVD was ineffective, unless the entire target space (usually the AC) was filled with the OVD. This is because, in an incompletely filled space, the OVD will just float around with aqueous surrounding it, and therefore the AC would behave as if it was filled with aqueous (it is only the OVD effect that is present at boundaries with the surrounding or contained structures that has any rheologic effect), yielding no effect of the OVD. Viscoadaptives, for the first time, are so viscous and rigid that a column of OVD can be formed in the center of the AC, contacting the endothelium above and the capsule below, and yielding viscoadaptive properties in the intervening space, even if the viscoadapive column is surrounded by a ring of aqueous. This means that for the first time, we do not need to inject the OVD in the angle, making later removal easier. It also means that we will need less viscoadaptive to do a given case than conventional viscoelastic. (5) Viscomydriasis. Because of their increased zero shear viscosity, viscoadaptives allow the attainment of unparalleled viscomydriasis. (6) Central delling of capsule for capsulorhexis. Capsulorhexis is performed on an anteriorly convex surface with posterior pressure behind it from the tension in the extraocular muscles. This posterior pressure causes the tendency for the capsulorhexis to go errantly toward the periphery. If the AC pressure can be made to equal or exceed this posterior pressure, a pressure equalized capsulorhexis can be done, which makes the whole thing much easier. Viscoadaptives are so viscous that not only can the anterior capsule be flattened, but it can be indented forming a central dell, thus making the creation of a small round capsulorhexis very easy. The first users of Healon®5 actually repeatedly described the tendency of the capsulorhexis to be too small, rather than too large. In other words the increased AC pressure tended to make the capsulorhexes run inward rather than outward, the opposite of the experience with other OVDs. (7) Prevention of leakage of cortex out of capsular bag during capsulorhexis. The extremely high zero shear viscosity of viscoadaptives prevents the leakage of cortex out of mature cataracts during capsulorhexis, when the AC is adequately pressurized, thus improving visibility. (8) Greater stability for trauma cases, corneal transplants. The high zero shear viscosity of viscoadaptives makes them ideal for repair of lacerated eyes, and for preservation of the AC during corneal transplantation. (9) Facilitate AC IOL implantation. Again, because of increased zero shear viscosity, the AC stability during AC IOL implantation is enhanced with viscoadaptives.
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(10) Enhanced corneal contact lens stability for vitrectomy. Retinal surgeons have commented that the corneal contact lens remains much more stable when placed in position with Healon®5. (11) Wound blockade. It is important to observe whether or not wound blockade is achieved with a viscoadaptive, and to do it only intentionally. When lower viscosity dispersive OVDs are used, irrigation of BSS in the OVD-filled AC dilutes the dispersive OVD and it exits the eye gradually diluted with the irrigant. When a higher viscosity cohesive OVD, like Healon®GV is used, the irrigating BSS does not dilute the cohesive OVD mass, but instead may get behind it and cause wound blockade. This blockade results in elevation of the intraocular pressure as the irrigation of BSS continues, and eventually with the burping out of the mass of Healon®GV. The zero shear viscosity of viscoadaptives is so high that they may not burp out, but instead may permit the IOP to increase to a level high enough to dislocate the cataract posteriorly. It is therefore important to create an exit path for BSS when injecting it into an AC full of viscoadaptive in order to prevent causing viscoadaptive wound blockade unintentionally. However, wound blockade can be used to tremendous advantage, if done intentionally under appropriate conditions (see Ultimate Soft Shell Technique below).
The Ultimate Soft Shell Technique [5]
The idea of adapting the soft shell technique to Healon®5 came to me while performing a capsulorhexis with Healon®5, and noticing the increased resistance, and then again when using Vision Blue® with Healon®5 in a mature cataract case. The ultimate soft shell technique works equally well with Healon®5 and iVisc® Phaco. In the soft shell technique, the idea is to use two OVDs with very disparate properties [2]. When I began to use Healon®5, it came to me that the ultimate disparate combination would be to use a viscoadaptive and BSS. So I tried that combination, and the BSS leaked out of the AC. But there is always a way with small modifications. In the ‘ultimate soft shell technique’ the viscoadaptive is used with BSS as illustrated in figure 3. The AC is filled about 60–80% full of OVD. Then the remainder of the AC is filled with BSS by advancing the injection cannula to the angle opposite the incision before commencing injection. Injection of BSS is then done slowly. A curious thing happens. Since the AC was not completely filled with OVD, the viscoadaptive mass is reasonably free to move around in the remaining space in the AC as the BSS is injected. If the BSS is injected just over the lens surface into the angle remote from the incision, the viscoadaptive
Why Viscoadaptives?
21
Viscoadaptive filled space Incision BSS or trypan blue filled space
Fig. 3. The ultimate soft shell technique. The ultimate soft shell technique is performed by first filling the anterior chamber 60–80% with a viscoadaptive. BSS or trypan blue is then injected along the surface of the lens capsule beginning as remote as possible from the incision. This has the effect of causing the viscoadaptive to rotate backward along the corneal internal surface to blockade the incision, preventing BSS escape. As a consequence, the eye is pressurized as if the viscoadaptive alone was used, and the capsulorhexis can be done in a low viscosity aqueous environment, as if BSS alone was used.
mass will rotate upwards along the corneal concavity away from the BSS injection site, and tamponade the incision, causing a high degree of incisional blockade due to the extremely high viscosity of the viscoadaptive. If the BSS injection is continued until the eye just begins to become firm, the result is a layer of viscoadaptive extending along the internal corneal surface from the incision around to, but not including the distal angle. Underneath the OVD layer, a thin layer of BSS has been fashioned along the surface of the lens, but unable to exit the incision, due to the intentional OVD incisional blockade that has been created. When the capsulorhexis is begun, to the terrific surprise of the surgeon, the capsule surface remains well tamponaded, as if a viscoadaptive alone had been used (due to AC pressurization), but the resistance to movement of the needle or forceps with the capsular flap is minimal, as if we were just using BSS alone (because it is surrounded by BSS), making the performance of the capsulorhexis extremely easy. Furthermore, since the viscoadaptive wound blockade exists, the eye remains pressurized, so that as the capsulorhexis proceeds, the BSS overlying the lens surface spontaneously begins to hydrodissect the lens, without the surgeon doing anything. After capsulorhexis, hydrodissection is completed, but is easier than usual and the procedure is continued using your favorite phaco technique. When confronted with a white, hypermature cataract, Vision Blue® (trypan blue) is substituted for the BSS in the ultimate soft shell technique, yielding
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Table 3. Parameters for OVD removal Vacuum Flow rate Bottle height I/A tip size
350–500 mmHg 25–30 ml/min 60–70 cm 0.3
fantastic visibility of the capsule. When the Vision Blue is injected below the viscoadaptive, it is merely painted along the capsular surface in a very thin layer, sufficient to dye the capsule. Since only a very thin layer of the Vision Blue® is injected with the ultimate soft shell technique, there is no need to wash it out before performing the capsulorhexis, and the procedure is very easy.
Removal
Viscoadaptives are indeed different, and they are designed to fracture. Therefore, if insufficient care is taken, it is easy to leave OVD behind at the end of the case, which may result in a postoperative spike in intraocular pressure. Pharmacia has sponsored a lot of work to determine optimal removal techniques. As often turns out, our understanding of removal of all OVDs has improved. The first point to make is that in order to remove any OVD, turbulence must be created in the AC to fracture the molecular mass. Only once the mass is fractured are pieces of the OVD free to move around and be aspirated by the irrigation/aspiration device. Therefore a high flow rate and high vacuum are necessary. The desirable parameters of I/A were worked on by the initial Healon®5 investigators, and the consensus is shown in table 3. High flow rates (25–30 cm3min) and vacuum (350–500 mm Hg) require an adequate bottle height (60–70 cm above the patient’s eye) to prevent AC collapse. The 0.3-mm aspiration port size was found experimentally to be most effective [K. Solomon, MD, pers. commun.]. The ‘rock ‘n’ roll’ method of OVD removal has hitherto been demonstrated to be the most efficient and effective technique for OVD removal (before the advent of viscoadaptives) [6 – 8]. This has been challenged by Tetz et al. [9], specifically with respect to viscoadaptive removal. Tetz et al. have found their two-compartment technique to be quicker and more effective in removing Healon®5. The studies performed for the US FDA Healon®5 submission showed that both of these techniques are superior to attempts to remove Healon®5 without using any formalized technique.
Why Viscoadaptives?
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In summary, viscoadaptives are new fracturable higher viscosity cohesive OVDs that can behave in a pseudodispersive fashion in an environment of high shear stress. This allows them to emulate the behavior of either cohesive or dispersive OVDs when the BSS flow rate is altered in phacoemulsification, considerably enhancing the viscoelastic maneuvers that can be performed by the surgeon, and enabling new surgical techniques. Because of their unique behavior, specific attention must be paid to removal techniques when viscoadaptives are used.
References 1 2 3
4 5 6 7 8
9
Arshinoff SA: Dispersive and cohesive viscoelastic materials in phacoemulsification revisited 1998. Ophthalmic Pract 1998;16:24 –32. Arshinoff SA: Dispersive-cohesive viscoelastic soft shell technique. J Cataract Refract Surg 1999; 25:167–173. Arshinoff SA: The unusual rheology of viscoadaptives, and why it matters (video). American Society of Cataract and Refractive Surgery Film Festival, Seattle, Wash. April 1999 (video available from Pharmacia & Upjohn AB). Arshinoff SA: Why Healon5. The meaning of viscoadaptive. Ophthalmic Pract 1999;17:332–334. Arshinoff SA: The ultimate soft shell technique. Ophthalmic Pract 2000;18:289–290. Arshinoff SA: Rock ‘n’ roll removal of Healon GV; in Arshinoff SA (ed): Proceedings of the 7th Annual National Ophthalmic Speakers Program, Ottawa, June 1996. Medicopea 1997. Arshinoff SA: Rock ‘n’ roll removal of Healon GV (video). American Society of Cataract and Refractive Surgery Film Festival, Seattle, Wash. June 1996. Auffarth GU, Wesendahl TA, Solomon KD et al: Evaluation of different removal techniques of a high-viscosity viscoelastic. Best papers of sessions 1994 Symposium on Cataract, IOL and Refractive Surgery. J Cataract Refract Surg 1994(suppl):30–32. Tetz MR, Holzer MP: Two-compartment technique to remove ophthalmic viscosurgical devices. J Cataract Refract Surg 2000;26:641– 643.
Steve A. Arshinoff, MD, York Finch Eye Associates, 2115 Finch Ave. W. #316, Toronto, Ont M3N 2V6 (Canada) Tel. 1 416 745 6969, Fax 1 416 745 6724, E-Mail
[email protected]
Arshinoff
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 25–31
Comparison of Four Viscoelastic Substances for Cataract Surgery in Eyes with Cornea guttata U. Mester, C. Hauck, N. Anterist, M. Löw Department of Ophthalmology, Bundesknappschaft’s Hospital Sulzbach, Germany
One major improvement in modern cataract surgery was the introduction of viscoelastics: They protect the corneal endothelium from surgical trauma, and have the ability to open and preserve intraocular spaces. Several viscoelastic agents with different chemical and physical properties are available and can be classified in two major groups: Sodium hyaluronate of different molecular weight and viscosity and hydroxypropylmethylcellulose (HPMC) products. Another viscoelastic substance is Viscoat® (Alcon), combining 3% sodium hyaluronate with 4% chondroitin sulfate. Investigations of chemical and rheological characteristics of sodium hyaluronate and HPMC products demonstrated remarkable differences between the substances tested [1], which may influence the protective properties of the viscoelastic. Clinical comparative investigations of several viscoelastics showed some controversial results or did not detect significant differences in corneal endothelium protection. All these studies are characterized by an interindividually comparing study protocol without selection according to the preoperative endothelial status [2– 4]. We looked for the corneal protective effect of four different viscoelastics during phacoemulsification. To improve the sensitivity we chose an intraindividually comparative study design in patients with bilateral cornea guttata, a condition prone to endothelial decompensation, thus expecting to more easily detect differences with regard to endothelial protection.
Table 1. Physical and chemical properties of the investigated viscoelastics Provisc® (Alcon) Sodium hyaluronate Molecular weight Production pH Viscosity
1.0% 1.1 million daltons Microbial fermentation 7.25 207.3 Pas
Ocucoat® (Storz) Hydroxypropylmethylcellulose Molecular weight Production pH Viscosity
2.0% 80,000 daltons Plant material 7.18 5.9 Pas
Healon®GV (Pharmacia & Upjohn) Sodium hyaluronate Molecular weight Production pH Viscosity
1.4% 5 million daltons Rooster comb 7.5 2,451.4 Pas
Healon®5 (Pharmacia & Upjohn) Sodium hyaluronate Molecular weight Production pH Viscosity
2.3% 4 million daltons Rooster comb 7.31 5,524.6 Pas
Patients and Methods We performed a prospective, randomized and intraindividually comparing trial in patients with bilateral preexisting compromised endothelium (cornea guttata) in 90 patients (180 eyes). Thirty patients each were randomly assigned to Provisc®, Ocucoat®, and Healon®5. The reference viscoelastic applicated in the fellow eye was Healon®GV in all patients. The main physical and chemical properties of the four viscoelastics are summarized in table 1. Patients included in this study had to fulfill the following criteria: (1) Comparable cataract formation in both eyes. Exclusion of advanced nuclear sclerosis. (2) Bilateral cornea guttata with 10% difference of corneal endothelial cell density. (3) Intraoperative ultrasonic time 1 min, use of 150 ml BSS irrigating fluid. (4) Bilateral surgery within 4 weeks, performed by the same surgeon. (5) In the bag phacoemulsification after capsulorhexis with IOL implantation into the capsular bag without complication (e.g. damage of the posterior capsule, vitreous loss, zonulolysis). (6) No postoperative raise of intraocular pressure beyond 24 mmHg. (7) Control examinations preoperatively, at day 1, and 1–2 weeks postoperatively including assessment of best corrected visual acuity, intraocular pressure, biomicroscopy of
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Table 2. Central endothelial cell density (cells/mm2) (30 eyes, mean values of three measurements, significance level: p 0.01) Preop.
1 day
1–2 weeks
Preop., 1 day postop., 1–2 weeks postop.: Wilcoxon test Healon®GV 1,880.0 539.6 1,786.4 533.6 Provisc® 1,893.4 541.6 1,755.1 606.7 p 0.60 0.97
1,749.1 522.2 1,790.0 677.4 0.42
Preop. and 1–2 weeks postop.: t test, 1 day postop.: Wilcoxon test 2,040.4 468.0 1,943.8 475.2 Healon®GV Ocucoat® 2,069.8 337.0 1,890.3 377.5 p 0.57 0.67
2,002.7 413.6 2,003.7 427.9 0.98
Preop. and 1 day postop.: t test, 1–2 weeks postop.: Wilcoxon test Healon®GV 2,185.0 252.6 2,106.6 212.0 Healon®5 2,211.9 236.9 2,108.6 207.2 p 0.47 0.95
2,099.6 212.5 2,105.1 188.9 0.71
the anterior and posterior segment, mean endothelial cell density (Endothelial specular microscope EM-1100, Tomey), anterior chamber flare (Laser flare meter, KOWA FM-500), and central corneal thickness (Teknar pachymeter). Mean values based on 3 (endothelial cell density), 5 (flare) and 10 (pachymetry) measurements. The statistical evaluation was performed using the Wilcoxon and t tests with a level of significance of 0.01. Out of the 30 patients of the Healon®GV vs. Healon®5 group, 21 were re-examined after 5 months.
Results
The results of central endothelial cell density assessment in the three groups (Healon®GV vs. Provisc®; Healon®GV vs. Ocucoat®; Healon®GV vs. Healon®5) are shown in table 2. Table 3 demonstrates the pachymetric data of central corneal thickness in the three groups. The results did not show a statistically significant difference between both eyes concerning improvement of visual acuity, intraocular pressure, and anterior chamber flare. Corneal endothelial cell density revealed a postoperative reduction compared to the preoperative findings, but without statistically significant difference between both eyes for all viscoelastics investigated. The only highly significant difference was found concerning the pachymetric values: The eyes which had received Provisc® demonstrated a marked increase of central corneal thickness compared to the fellow eyes with Healon®GV at day 1 postoperatively (p 0.0002) and 1–2 weeks after surgery (p 0.007).
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Table 3. Central corneal thickness (m) (30 eyes, mean values of ten measurements, significance level p 0.01) Preop.
1 day
1–2 weeks
Preop., 1 day postop. and 1–2 weeks postop.: Wilcoxon test Healon®GV 539.1 51.9 601.2 60.5 Provisc® 543.1 57.3 673.4 88.8 p 0.61 0.0002
567.6 47.0 605.5 69.2 0.007
Preop. and 1–2 weeks postop.: t test, 1 day postop.: Wilcoxon test Healon®GV 544.0 74.7 631.9 65.1 Ocucoat® 543.9 79.3 604.4 65.9 p 0.99 0.18
572.6 71.1 564.6 74.7 0.38
Preop.: t test, 1 day postop. and 1–2 weeks postop.: Wilcoxon test Healon®GV 531.0 77.0 612.9 67.5 Healon®5 528.8 77.8 595.7 66.6 p 0.60 0.11
560.4 69.2 558.8 72.1 0.84
Additionally, two eyes with transient corneal decompensation belonged to the Provisc® group.
Discussion
Viscoelastics have been proved to protect the corneal endothelium from surgical trauma: Fry et al. [5] compared Healon®GV with Healon® in extracapsular cataract surgery, Arshinoff et al. [6] performed a randomized study using Microvisc® and Healon®. Alpar et al. [7] compared Viscoat® and Healon®. Further comparative studies investigated the corneal protection of Ocucoat®, Viscoat®, and Healon® [2] and the effect of Provisc® compared to Healon® [3]. More recent studies investigated the application of Healon®5 [8–10]. While Viscoat® proved to be superior to Healon® [11, 13], most of the studies were unable to demonstrate a statistically significant difference in postoperative endothelial cell loss or corneal thickness. Furthermore, some clinical studies showed inconsistent results: Lane et al. [2] did not find a difference in endothelial protection between an HPMC product (Ocucoat®) and a hyaluronate (Healon®). In contrast, the assessment of postoperative corneal thickness by Pederson [12] revealed a superior corneal protection by Healon® compared to a HPMC product. Ravalico et al. [13] found less increased corneal thickness and endothelial permeability when using Healon®GV or Viscoat® compared to Healon® and Hymecel®.
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The influence of the surgical technique on endothelial impairment during cataract surgery was shown in a clinical investigation comparing Healon® vs. Viscoat® by Koch et al. [11]: In eyes receiving Viscoat®, iris-plane phacoemulsification resulted in significantly less corneal endothelial damage compared to the eyes which received Healon®. Eyes with posterior-chamber phacoemulsification, conceivably with less surgical trauma, did not reveal different results, regardless the viscoelastic used. Ravalico et al. [13] investigated four viscoelastics (Healon®, Healon®GV, Viscoat®, Hymecel®) in a prospective, randomized study. One major result was that, despite the lack of postoperative differences in endothelial cell density, significant differences in functional endothelial impairment could be detected by the assessment of central corneal thickness and the endothelial permeability coefficient. These findings indicate that comparative clinical investigations of viscoelastics should be addressed more to the functional impairment of the corneal endothelium than to postoperative endothelial cell loss. To improve the sensitivity of a clinical study investigating the endothelial protection of different viscoelastics during cataract surgery, we chose an intraindividual comparative study design in patients with bilateral cornea guttata, that means eyes prone to endothelial decompensation. Additionally, strong entrance criteria and comparable surgical procedures should minimize the risk of bias. Despite the very sensitive study design most of the parameters investigated did not reveal statistically significant differences between the four viscoelastics tested, though the hyaluronates (Provisc®, Healon®GV, Healon®5) have markedly different molecular weights and viscosity, and Ocucoat® as an HPCM product has completely different chemical and physical properties. The only statistically highly significant difference in our study was found comparing Provisc® with Healon®GV: The central corneal thickness in eyes which received Provisc® was increased not only at day 1 (p 0.0002) but also 1–2 weeks after surgery (p 0.007). Two transient clinical corneal decompensations also occurred in the Provisc® group only. Our results confirm the observation of Ravalico et al. [13] that a transient functional impairment of the corneal endothelium may be present without a corresponding reduction of endothelial cell density. Arshinoff and Hoffman [6] demonstrated that the corneal thickness reached the preoperative values at about 1 week after surgery. In our patients the corneal thickness was still increased in all patients 1–2 weeks after surgery. Out of the 30 patients in the Healon®GV vs. Healon®5 group, 21 were re-examined after 5 months. The central corneal thickness had reached the preoperative value. The endothelial cell density showed a reduction of 2% (Healon®) and 4% (Healon®GV). Similar results were reported by Schwenn et al. [10] comparing
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Healon®5 with Viscoat®. Our results are not easy to explain: There is a general assumption that viscoelastics with high molecular weight and great viscosity (cohesive) have better space-maintaining properties than substances with low molecular weight and viscosity (dispersive). Conversely, low molecular viscoelastics are more likely to protect the corneal endothelium due to a better surface retention on the intraocular structures [7]. The identical endothelial protection by Ocucoat® and Healon®GV may be the result of the specific binding affinity of the hyaluronic acid to the endothelial cells [14] and its superior protection against compressive and drag forces on the corneal endothelium [13, 15], respectively the better surface retention on intraocular structures by the HPMC product Ocucoat®. If the superior space-maintaining properties of the hyaluronates are causative for the endothelial protection during surgery, one should expect different results using hyaluronates of different viscosity and molecular weight. Our results demonstrate this effect comparing Healon®GV with Provisc® only, not in the comparison between Healon®GV and Healon®5 despite the much higher viscosity of Healon®5. That may be due to several factors: Provisc® and Healon®GV as well as Healon®5 are manufactured by different companies using different techniques, which may lead to different chemical and physical properties (e.g. osmolality, galenic composition, pH value) [14]. Furthermore, compromised eyes with cornea guttata are particularly susceptible to pH value change. Dick and Schwenn [16] measured pH values of 7.11 0.09 for Provisc® and 7.5 0.07 for Healon®GV. The identical findings in endothelial protection of Healon®GV and Healon®5 despite the markedly higher viscosity of the latter may also be caused by the somewhat more complicated removal maneuver for Healon® 5 [9].
Conclusions
The results of our study may permit the following conclusions: (1) The intraindividually comparative study design, phacoemulsification in eyes with compromised corneal endothelium, strong entrance criteria, and identical surgical procedures are able to reveal differences between viscoelastics which are not detected using less sensitive study designs. (2) Corneal protection may also be influenced by other factors than the basic chemical structure, viscosity and molecular weight of the viscoelastic. Therefore, each viscoelastic substance has to be investigated before clinical application. (3) The surgeon’s choice of agents must balance several factors: The endothelial protection of HPMC products is basically not worse than by
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hyaluronates. Higher viscosity of hyaluronates does not inevitably lead to better corneal protection. On the other hand stand the superior space-maintaining properties of hyaluronate products, depending on molecular weight and viscosity [4]. References 1
2
3 4 5 6 7 8 9
10
11 12
13 14 15 16
Dick B, Pakula T, Hirschmann T, Pfeiffer N: Viskoelastica: Ein aktueller Vergleich und praktische Konsequenzen; in Dunker G, Ohrloff C, Wilhelm F (eds): 12. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie. Berlin, Springer, 1999, pp 267–277. Lane S, Naylor D, Kullerstand L, Knauth K, Lindstrom R: Prospective comparison of the effects of Ocucoat, Viscoat and Healon on intraocular pressure and endothelial cell loss. J Cataract Refract Surg 1991;17:21–26. Lehmann R, Brint S, Stewart R, White G, McCarty G, Taylor R, Disbrow D, Defaller J: Clinical comparison of Provisc and Healon in cataract surgery. J Cataract Refract Surg 1995;21:543–547. Hütz W, Eckhardt B, Kohnen T: Comparison of viscoelastic substances used in phacoemulsification. J Cataract Refract Surg 1996;22:955–959. Fry L, Yee R: Healon GV in extracapsular cataract extraction with intraocular lens implantation. J Cataract Refract Surg 1993;19:409– 412. Arshinoff S, Hofmann I: Prospective, randomized trial of Microvisc and Healon in routine phacoemulsification. J Cataract Refract Surg 1997;23:761–765. Alpar J, Alpar A, Baca J, Chapman D: Comparison of Healon and Viscoat in cataract extraction and intraocular lens implantation. Ophthalmic Surg 1988;9:636–642. Rainer G, Menapace R, Findl O, Georgopoulos M, Kiss B, Petternel V: Intraocular pressure after small incision cataract surgery with Healon 5 and Viscoat. J Cataract Refract Surg 2000;26:271–276. Auffarth G, Dick B, Vissesook N, Völcker H: Entfernungstechniken eines neuen viskoadaptiven Viskoelastikums (Healon®5); in Dunker G, Ohrloff C, Wilhelm F (eds): 12. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie. Berlin, Springer, 1999, pp 478– 481. Schwenn O, Dick B, Krummenauer F, Christmann S, Vogel A, Pfeiffer N: Healon 5 versus Viscoat during cataract surgery: Intraocular pressure, laser flare and corneal changes. Graefes Arch Clin Exp Ophthalmol 2000;238:861–867. Koch D, Liu J, Glasser D, Merlin L, Haft E: A comparison of corneal endothelial changes after use of Healon or Viscoat during phacoemulsification. Am J Ophthalmol 1993;115:188–201. Pederson O: Comparsion of the protective effects of methylcellulose and sodium hyaluronate on corneal swelling following phacoemulsification of senile cataracts. J Cataract Refract Surg 1990; 16:594–596. Ravalico G, Tognetto D, Baccara F, Lovisato A: Corneal endothelial protection by different viscoelastics during phacoemulsification. J Cataract Refract Surg 1997;23:433– 439. Hessemer V, Dick B: Viskoelastische Substanzen in der Kataraktchirurgie, Grundlagen und aktuelle Übersicht. Klin Monatsbl Augenheilkd 1996;209:55– 61. Stenevi U, Gwin T, Härfstrand A, Apple D: Demonstration of hyaluronic acid binding to corneal endothelial cells in human eye-bank eyes. Eur J Implant Refract Surg 1993;5:228–232. Dick B, Schwenn O: Viskoelastika: Eine Übersicht. Berlin, Springer, 1998.
Prof. Dr. Ulrich Mester, Department of Ophthalmology, Bundesknappschaft’s Hospital Sulzbach, D– 66280 Sulzbach (Germany) E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 32–40
The Staar Wave I. Howard Fine, Richard S. Hoffman, Mark Packer Casey Eye Institute, Oregon Health and Science University, Portland, Oreg., and Oregon Eye Institute, Eugene, Oreg., USA
The last decade has given rise to some of the most profound advances in both phacoemulsification technique and technology. Techniques for cataract removal have moved from those that use mainly ultrasound energy to emulsify nuclear material for aspiration to those that utilize greater levels of vacuum and small quantities of energy for lens disassembly and removal. Advances in phacoemulsification technology have allowed for this ongoing change in technique by allowing for greater amounts of vacuum to be utilized in addition to power modulations that have allowed for more efficient utilization of ultrasound energy with greater safety for the delicate intraocular environment [1, 2]. One of the most recent new machines for cataract extraction is the Staar Wave™ (fig. 1). The Wave was designed as an instrument that combines phacoemulsification technology with new features and a new user interface. Innovations in energy delivery, high vacuum tubing, and digitally recordable procedures with video overlays make this one of the most technologically advanced and theoretically safest machines available. Conventional Surgical Features
The Wave contains all of the customary surgical modes routinely used to perform cataract surgery including ultrasound, irrigation/aspiration, vitrectomy, and diathermy. The ultrasound handpiece is a lightweight (2.25 oz) 2-crystal, 40-kHz piezoelectric autotuning handpiece that utilizes a load compensating ultrasonic driver. The driver senses tip loading 1,000 times a second allowing for more efficient and precise power adjustments at the tip during phacoemulsification. One of the unique features of the Wave is its ability to adjust vacuum as a function of ultrasound power. This feature is termed ‘A/C’ (autocorrelation)
Fig. 1. The Staar Wave phacoemulsification console.
mode. It enables lens fragments to be engaged at low vacuum levels in foot position 2. Vacuum levels are proportionally increased with increases in ultrasound power in foot position 3. Proportional increases in vacuum allow for faster aspiration of lens fragments by overcoming the repulsive forces generated by ultrasound energy at the tip. Another unique feature of the Wave is the Random Pulse Mode which randomly changes the pulse rate. This increases followability by preventing the formation of standing waves in front of the tip.
New Surgical Features
Although ultrasonic phacoemulsification allows for relatively safe removal of cataractous lenses through astigmatically neutral small incisions, current technology still has its drawbacks. Ultrasonic tips create both heat and cavitational energy. Heating of the tip can create corneal incision burns [3, 4]. When incisional burns develop in clear corneal incisions, there may be a loss of selfsealability, corneal edema, and severe induced astigmatism [5]. Cavitational energy results from pressure waves emanating from the tip in all directions. Although increased cavitational energy can allow for phacoemulsification of dense nuclei, it can also damage the corneal endothelium and produce irreversible corneal edema in compromised corneas with pre-existing endothelial dystrophies. Another aspect of current phacoemulsification technology that has received extensive attention for improvement has been the attempt to maximize
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Rest
Compression
Expansion
Fig. 2. Regular ultrasonic tip motion: the tip undergoes compression and expansion continuously changing its dimensional length. Heat is generated due to intermolecular friction.
anterior chamber stability while concurrently yielding larger amounts of vacuum for lens removal. The Wave addresses these concerns of heat generation and chamber stability with the advent of its revolutionary ‘Sonic’ technology and high resistance ‘SuperVac’ coiled tubing. Sonic technology offers an innovative means of removing cataractous material without the generation of heat or cavitational energy by means of sonic rather than ultrasonic technology. A conventional phaco tip moves at ultrasonic frequencies of between 25 and 62 kHz. The 40-kHz tip expands and contracts 40,000 times per second generating heat due to intermolecular frictional forces at the tip that can be conducted to the surrounding tissues (fig. 2). The amount of heat is directly proportional to the operating frequency. In addition, cavitational effects from the high-frequency ultrasonic waves generate even more heat. Sonic technology operates at a frequency much lower than ultrasonic frequencies. Its operating frequency is in the sonic rather than the ultrasonic range between 40 and 400 Hz. This frequency is 1–0.1% lower than ultrasound resulting in frictional forces and related temperatures that are proportionally reduced. In contrast to ultrasonic tip motion, the sonic tip moves back and forth without changing its dimensional length (fig. 3). The tip of an ultrasonic handpiece can easily exceed 500°C in a few seconds while the tip of the Wave handpiece in Sonic mode barely generates any frictional heat since intermolecular friction is eliminated (fig. 4). In addition, the Sonic tip does not generate cavitational effects and thus true fragmentation, rather than emulsification or vaporization, of the lens material takes place. This adds more precision and predictability in grooving or chopping and less likelihood for corneal endothelial compromise or incisional burns.
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Rest
Forward
Backwards
Fig. 3. Sonic tip motion: the tip moves back and forth without changing its dimensional length. Heat due to intermolecular friction is eliminated.
Fig. 4. Phacoemulsification tip in Sonic mode being grasped with an ungloved hand demonstrating lack of heat generation.
The most amazing aspect of the Sonic technology is that the same handpiece and tip can be utilized for both Sonic and Ultrasonic modes. The surgeon can easily alternate between the two modes using a toggle switch on the foot pedal when more or less energy is required. The modes can also be used simultaneously
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Fig. 5. Phacoemulsification handpiece attached to SuperVac coiled tubing.
Fig. 6. High magnification view of SuperVac coiled tubing.
with varying percentages of both sonic and ultrasonic energy. We have found that we can use our same chopping cataract extraction technique [4] in sonic mode as we utilized in ultrasonic mode with no discernable difference in efficiency. The ideal phacoemulsification machine should offer the highest levels of vacuum possible with total anterior chamber stability. The Staar Wave moves one step closer to this ideal with the advent of their SuperVac tubing (fig. 5, 6). SuperVac tubing increases vacuum capability up to 650 mm Hg while significantly increasing chamber stability. The key to chamber maintainance is to achieve a positive fluid balance which is the difference between infusion flow and aspiration flow. When occlusion is broken, vacuum previously built in the
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Surge flow (cm3/min)
250 200 150 100 50
100
200 300 400 Vacuum (mm Hg)
500
Fig. 7. When braking occlusions, regular phaco systems generate a flow surge in linear relation with the vacuum.
Surge flow (cm3/min)
250 200 150 100 50
100
200 300 400 Vacuum (mm Hg)
500
Fig. 8. The SuperVac tubing dynamically limits the flow surge. As shown, the surge at 500 mm Hg or higher is the same as for a regular phaco system operating at 200 mm Hg.
aspiration line generates a high aspiration flow that can be higher than the infusion flow. This results in anterior chamber instability. The coiled SuperVac tubing limits surge flow resulting from occlusion breakage in a dynamic way. The continuous change in direction of flow through the coiled tubing increases resistance through the tubing at high flow rates such as upon clearance of occlusion of the tip (fig. 7, 8). This effect only takes place at high flow rates (⬎50 cm3/min). The fluid resistance of the SuperVac tubing increases as a function of flow and unoccluded flow is not restricted.
New User Interface
Perhaps the most advanced feature on the Wave is its new user interface. The Wave Powertouch™ computer interface mounts onto the Staar cart above
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Fig. 9. The Wave Powertouch™ computer interface mounts onto the Staar cart above the phacoemulsification console.
the phacoemulsification console (fig. 9). The touchscreen technology allows the user to control the surgical settings by touching parameter controls on the screen. The interface utilizes Windows® software and is capable of capturing digitally compressed video displaying the image live on the monitor screen. A 6-GB hard disk can store up to 8 h of video without the need for VHS tapes. The most useful and educational aspect of the Wave interface is the Event List that displays multiple data graphs to the right of the surgical video (fig. 10). The event list displays recorded power, vacuum, flow, theoretical tip temperature, and risk factor for incisional burns on a constantly updated timeline. The vertical line in each graph represents the actual time event occurring on the video image. Surgical events to the left of the line represent past events while data to the right of the line represent future events ready to occur. A CD-ROM recorder can be used to transfer surgical video and data graphs from the hard drive to a writable CD. This allows the surgeon to view each case on any Windows® home
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Fig. 10. Wave video overlay demonstrating multiple data graphs to the right with power, vacuum, flow, and theoretical tip temperature parameters. Note the vacuum is 500 mm Hg and the aspiration flow rate is 40 cm3/min.
or office computer or use the images for presentations. The ability to review surgical parameters on a timeline as the video image is being displayed can allow surgeons the capability of analyzing unexpected surgical events as they are about to occur in a recorded surgical case. This information can then be used to adjust parameters or surgical technique to avoid these pitfalls in future cases. Staar eventually plans to transmit live surgical cases over the Internet so that surgeons anywhere in the world can log on and watch a selected surgeon demonstrate his or her technique with real-time surgical parameter display.
Conclusion
The Staar Wave is one of the most advanced phacoemulsification systems available today. The use of sonic rather than ultrasonic energy for the extraction of cataracts represents a major advancement for increasing the safety of cataract surgery. Sonic mode can be used by itself or in combination with ultrasonic energy allowing for the removal of all lens densities with the least amount of energy delivered into the eye. SuperVac tubing allows for the use of higher levels of vacuum to be used for extraction with increased chamber stability
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by nature of the resistance of this tubing to high flow rates when occlusion is broken. Finally, the addition of advanced video and computer technology for recording and reviewing surgical images and parameters will allow surgeons to further improve their techniques and the techniques of their colleagues through better communication and teaching.
References 1 2
3 4 5
Fine IH: The choo-choo chop and flip phacoemulsification technique. Operative Tech Cataract Refract Surg 1998;1:61– 65. Fine IH, Packer M, Hoffman RS: The use of power modulations in phacoemulsification of cataracts: The choo-choo chop and flip phacoemulsification technique. J Cataract Refract Surg 2001;27:188–197. Fine IH: Special Report to ASCRS Members: Phacoemulsification Incision Burns. Letter to American Society of Cataract and Refractive Surgery Members, 1997. Majid MA, Sharma MK, Harding SP: Corneoscleral burn during phacoemulsification surgery. J Cataract Refract Surg 1998;24:1413–1415. Sugar A, Schertzer RM: Clinical course of phacoemulsification wound burns. J Cataract Refract Surg 1999;25:688– 692.
Dr. I. Howard Fine, 1550 Oak Street, Suite 5, Eugene, OR 97401 (USA) Tel. ⫹1 541 687 2110, Fax ⫹1 541 484 3883, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 41– 43
Phacotmesis Jochen Kammann, Gabriele Dornbach Augenklinik des St. Johannes-Hospitals, Dortmund, Germany
Phacoemulsification by ultrasound within the scope of cataract surgery has been successfully performed for more than 30 years. In order to disassemble the nucleus faster and more efficiently, Anis [1] developed phacotmesis in the 1990s. This procedure combines longitudinally operating ultrasound oscillation with cutting high-speed rotation. The rotation frequency can be varied linearly up to a maximum of 10,000/min with eligible constant ultrasound performance and eligible constant suction pressure. The phaco tips are constructed in such a way that the lumen is reduced at the back stepwise to transfer the demolition of the nucleus as far inside as possible and therefore reduce the risk of endothelial damage.
Material and Method Phacotmesis was evaluated concerning intra- and postoperative complications in 1994 within the scope of small-incision surgery during 30 successive cataract operations. All operations were performed by the same surgeon. The Frown incision, preparation of the scleral tunnel, capsulorhexis, hydrodissection and hydrodelineation is followed by the crosswise division of the nucleus by using the divide-and-conquer technique applying phacotmesis [2]. The ultrasound performance was constantly tuned to 40% but could at anytime be varied as well as the suction pressure on the apparatus itself. The rotation was controlled linearly by means of a foot pedal and adjusted regarding the density of the nucleus. The medium frequency used was between 2,000 and 4,000/min. The rotation was switched off after fragmentation of the nucleus and the four fragments were then emulsificated by ultrasound adjusted by the foot pedal. In 15 cases the phacotmesis tip had a diameter of 2.5 mm and a teflon sleeve. In the 15 other cases it had a diameter of 1.8 mm and a silicone sleeve due to our animation.
Results
The group with the larger phacotmesis tip showed an obvious vibration of the eye that was transferred to the eyelid retractor. A positive side effect was that the parts of nucleus were loosened and therefore sucked off more easily. The flow of irrigation fluid was high (350–450 ml). Pressure changes were observed with collapse of the anterior chamber and forward movement of the posterior lens capsule. In 2 cases it came to a rupture of the posterior capsule. Three eyes showed a corneal decompensation on the first postoperative day that recoiled under adequate therapy rapidly. The intraocular pressure in this group decreased on an average from preoperative 15.7 ⫾ 3.1 mm Hg down to 13.6 ⫾ 3.1 mm Hg on the first postoperative day. The visual acuity on an average increased from 0.23 ⫾ 0.16 to 0.31 ⫾ 0.2 on the first postoperative day. The group with the smaller phacotmesis tip showed a significantly lower degree of vibration. The flow of irrigation fluid was less, the anterior chamber stable and the incision closed. No capsular ruptures were reported nor corneal decompensation. The preoperative intraocular pressure was on an average 15.8 ⫾ 2.4 mm Hg and on the first postoperative day 15.2 ⫾ 4.1 mm Hg. The visual acuity on average increased from 0.23 ⫾ 0.16 to 0.31 ⫾ 0.2 on the first postoperative day. During phacotmesis, small fragments of the nucleus were aspirated quite frequently by the tip resulting in a propeller like rotation.
Discussion
The principle of phacotmesis is well combinable with the classical phacoemulsification technique. Using the divide-and-conquer technique it supports splitting also denser nuclei with its cutting rotation and disassembling the nucleus after hydrodissection. The capsular ruptures in our series are not due to the principle rather due to intraocular pressure deviation due to inadequate incision closure. The relatively thick 2.5-mm tip strains the wound region and the teflon sleeve cannot seal it. The corneal decompensation we also rather put down to the high flow of irrigation fluid. After reducing the tip diameter to 1.8 mm and changing the sleeve material to silicone, these complications did not occur any longer. A disadvantage was the obvious vibration of the bulbi because of rotation, particularly when using the thicker tip. They were decreased by reducing the lumen but still definitely there. Furthermore, small fragments of the nucleus were frequently aspirated by the tip causing propeller-like rotations. Summing up, it may be said that phacotmesis seems to be suitable for denser nuclei from grade 3 onwards. The cutting rotation saves ultrasound energy
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when dividing the nucleus. The rotation mechanism is adaptable to numerous phaco machines so it is not necessary to abandon one’s customary apparatus. The rotation though should give way to an oscillating movement similar to a vitrectomy cutter to reduce turbulence of nucleic fragment as well as bigger iris and sphincter damages through possible aspiration. Furthermore, other efficient and easier methods of dividing nuclei have been developed in the last few years [3–5] making an acquisition of a additional phaco tip superfluous.
References 1
2 3 4 5
Anis AY: Phacotmesis: A new technique for automated small-incision cataract extraction utilizing a new surface discriminating instrument. Proceedings of the ASCRS Symposium on Cataract, IOL and Refractive Surgery, Seattle, May 1993. Gimbel HV: Divide-and-conquer nucleofractis phacoemulsification: Development and variations. J Cataract Refract Surg 1991;17:281–291. Nagahara K: Phaco-chop technique eliminates central sculpting and allows faster, safer phaco. Ocul Surg News Int Ed 1993;4:12–13. Kammann J: Reversed tip and snip – A new phaco technique. Ocul Surg News Int Ed 1997;8: 18–19. Kammann J, Dornbach G: Rotbrauner Linsenkern? – 4-before-Phaco! Klin Monatsbl Augenheilkd 1997;210(suppl):13.
Prof. Dr. J. Kammann, Chefarzt der Augenklinik des St. Johannes-Hospitals, Johannesstrasse 9 –17, D– 44137 Dortmund (Germany) Tel. ⫹49 231 1843 2241, Fax ⫹49 231 1843 2508, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 44–58
Tilt and Tumble Phacoemulsification Elizabeth A. Davis, Richard L. Lindstrom Minnesota Eye Consultants PA, Minneapolis, Minn., USA
The technique of tilt and tumble, which is a modified form of supracapsular phacoemulsification, was developed by Dr. Richard Lindstrom. Dr. Lindstrom learned phacoemulsification in 1977 during a fellowship with William S. Harris, MD, in Dallas, Texas. At that time, phacoemulsification techniques were generally divided into anterior chamber phaco as championed by Charles Kelman, MD, iris plane phaco as championed by Richard Kratz, MD, and posterior chamber phaco as championed by John Sheets, MD, and Robert Sinskey, MD. Under the tutelage of Dr. Harris, Dr. Lindstrom performed all of these techniques, and over a period of time selected the iris plane phacoemulsification technique as his procedure of choice. What follows is a description of the evolution of the tilt and tumble procedure as Dr. Lindstrom developed it. Prior to the introduction of capsulorhexis and hydrodissection, a relatively large can opener anterior capsulectomy was performed just inside the zonules. Following this, a portion of the central core nucleus was emulsified leaving an inferior shelf of tissue. Using a bimanual technique, the superior pole of the nucleus was tilted above the capsule and engaged by a beveled phacoemulsification tip. The nucleus was then supported in the iris plane with a nucleus rotator and emulsified. The nucleus could be subluxated into the anterior chamber, particularly if there was concern about a capsular tear. However, there were instances where posterior chamber phacoemulsification was the preferred technique, such as in very soft nuclei in younger patients. After the technique of continuous tear anterior capsulectomy (capsulorhexis) had been developed it was incorporated into the procedure. Initially a relatively small diameter capsulorhexis in the range of 4.0–5.0 mm was constructed, especially when utilizing 5.5-mm round optic polymethylmethacrylate intraocular lenses. This small continuous tear anterior capsulectomy made it
impossible to subluxate the nucleus safely into the iris plane or anterior chamber and thus it was necessary to employ posterior chamber, endocapsular phaco techniques. With most nuclei a nuclear cracking technique was used where the core nucleus was emulsified and the peripheral bowl of retained nuclear material and nuclear plate was infractured in a so-called ‘one-handed technique’ useful for soft nuclei in younger patients. Soon thereafter, hydrodissection and hydrodelineation became a standard part of the technique in order to loosen the nucleus and allow it to be rotated easier. With a small continuous tear anterior capsulectomy, the nucleus always remained localized in the posterior chamber. While there are many positive features to the endocapsular cracking techniques, they were more difficult to teach with a steeper learning curve. In addition, procedure times were somewhat longer than they had been with the iris plane technique. Furthermore, Dr. Lindstrom found a mild increase in the capsular tear rate from approximately 1 to 1.8%. On the positive side, visual recovery was very rapid, especially when foldable intraocular lenses were used, and most patients had a clear cornea on the first postoperative day. With time, the capsular tear rate was reduced to 1.3%, but the procedure required 10–15 min to complete. In addition in some instances, such as patients with loose zonules from pseudoexfoliation, the capsulorhexis was somewhat smaller, in the 4-mm range. In these cases other undesirable side effects were possible, such as the capsular-contraction syndrome. Several Japanese investigators at the time suggested that retained subcapsular epithelium might play a role in postoperative inflammation and capsular opacity. Thus, the procedure was modified to incorporate larger diameter continuous tear anterior capsulectomies. With a continuous tear anterior capsulectomy of 5.0–6.0 mm the nucleus would often inadvertently partially or totally subluxate anterior to the capsular rim. The nucleus could simply be pushed back into the capsular bag and the procedure completed utilizing a nuclear fracture technique. It soon became obvious that subluxating the nucleus into the anterior chamber was advantageous, particularly in high-risk cases. When there was a large anterior segment, as in a myopic patient, a healthy cornea and a relatively soft nucleus, the nucleus could be subluxated to a position anterior to the capsular bag and then a deep anterior chamber phacoemulsification performed while supporting the nucleus with a nucleus rotator. The larger anterior capsulectomy allowed an easier phacoemulsification with no apparent adverse effect in regard to intraocular lens centration. Fundus visibility was good and the occasional case of capsular contraction syndrome disappeared. Capsular opacity rates appeared low and a small randomized study suggested that they were somewhat lower than with the smaller anterior capsulectomy utilized in the past. The impact of capsulorhexis size on capsular opacity rate and postoperative inflammation remains controversial with studies favoring both arguments.
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The next influence came from David Brown, MD, and Bill Maloney, MD, who have championed the concept of supracapsular phacoemulsification where the nucleus is hydrodissected and tumbled prior to phacoemulsification. Although the technique was very efficient, it was not always easy to tumble the nucleus safely in every eye. Also, there was more postoperative corneal edema in these eyes compared to those treated with an endocapsular approach. However, use of this technique spurred the discovery that the nucleus could simply be supported in the plane of the iris and anterior capsular leaflet, rather than completely tumbling of the entire nucleus. Half of it could then be emulsified. Then, with a much smaller nuclear remnant, the remaining one half could be tumbled upside down and emulsified as in the classical supracapsular approach. The surgical technique was fast, simple and safe. The following day the corneas of these patients were similarly clear compared to those treated with an endocapsular nuclear fracture approach. The author chose to call the technique ‘tilt and tumble’ and refined it so that it could be taught effectively to residents, fellows and other ophthalmologists with confidence. It is basically ‘back to Kratz’ with help from Brown and Maloney, in the capsulorhexis, hydrodissection, viscoelastic and modern phaco machine era. In the following paragraphs we will describe and illustrate this technique in enough detail to allow an ophthalmologist to evaluate it for his or her own patients.
Indications
The indications for the tilt and tumble phacoemulsification technique are quite broad. It can be utilized in either a large or small pupil situation. Some surgeons favor with small pupils where the nucleus can be tilted up such that the equator is resting in the center of the pupil and is then carefully emulsified. It does require a larger continuous tear anterior capsulectomy of at least 5.0 mm. If a small anterior capsulectomy is achieved, the hydrodissection step of tilting the nucleus can be dangerous, and it is possible to rupture the posterior capsule during the hydrodissection step. If, inadvertently, a small anterior capsulectomy is created, it is probably safest to convert to an endocapsular phacoemulsification technique or enlarge the capsulorhexis. If it is not possible to tilt the nucleus with either hydrodissection or a manual technique, the surgeon should convert to an endocapsular approach. Occasionally the entire nucleus will subluxate into the anterior chamber. In this setting if the cornea is healthy, the anterior chamber deep, and the nucleus soft, then the phacoemulsification can be completed in the anterior chamber supporting the nucleus away from the corneal endothelium. The nucleus can also be pushed back inferiorly over the capsular bag to allow the iris plane tilt and tumble technique to be completed.
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In patients with severely compromised endothelium, such as Fuchs’ dystrophy or previous keratoplasty patients with a low endothelial cell count, endocapsular phacoemulsification is preferred to reduce endothelial. In a normal eye, corneal clarity on the first day postoperatively is excellent. Nevertheless, the tilting and tumbling maneuvers do increase the chance of endothelial cell contact of lens material compared to an endocapsular phacoemulsification. Therefore, the endocapsular technique should be employed in eyes with borderline corneas. The technique is a very good transition technique for teaching residents, fellows and surgeons who are transitioning to phacoemulsification, because it is easy to convert to a planned extracapsular cataract extraction with the nucleus partially subluxated above the anterior capsular flap at the iris plane.
Preoperative Preparation
The patient enters the anesthesia induction or preoperative area and tetracaine drops are placed in both eyes. The placement of these drops increases the patient comfort during the placement of the multiple dilating and preoperative medications, decreases blepharospasm and also increases the corneal penetration of the drops to follow. The eye is dilated with 2.5% neosynephrine and 1% cyclopentolate every 5 min for three doses. Additionally, preoperative topical antibiotic and antiinflammatory drops are administered at the same time as the dilating drops. We favor the combination of a preoperative topical antibiotic, topical steroid and topical nonsteroidal. The rationale for this is to preload the eye with antibiotic and nonsteroidal prior to surgery. The pharmacology of these drugs and the pathophysiology of postoperative infection and inflammation support this approach. An eye that is preloaded with anti-inflammatories prior to the surgical insult is likely to have a much reduced postoperative inflammatory response. Both topical steroids and nonsteroidals have been found to be synergistic in the reduction of postoperative inflammation. In addition, the use of perioperative antibiotics is supported in the literature as reducing the small chance of postoperative endophthalmitis. Since the patient will be sent home on the same drops utilized preoperatively, there is no additional cost. Our usual anesthesia is topical tetracaine reinforced with intraoperative intracameral 1% nonpreserved (methylparaben-free) xylocaine. For patients with blepharospasm a ‘miniblock’ O’Brien facial nerve anesthesia, utilizing 2% xylocaine with 150 units of hyaluronidase per 5 cm3 of xylocaine, can be quite helpful in reducing squeezing. This block lasts 30–45 min and makes surgery easier for the patient and the surgeon. Patients are sedated prior to the block to eliminate any memory of discomfort. One way to determine when this facial
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nerve block might be useful is to ask the technicians to make a note in the chart when they have difficulty performing applanation pressures or A-scan because of blepharospasm. In these patients a mini facial nerve block can be quite helpful. In younger anxious patients and in those with difficulty cooperating, we perform a peribulbar block. Naturally, general anesthesia is used for very uncooperative patients and children. While this is controversial, in some patients where general anesthesia is chosen and a significant bilateral cataract is present, we will perform consecutive bilateral surgery completely re-prepping and starting with fresh instruments for the second eye. Again, this is a clinical decision weighing the risk to benefit ratio of operating both eyes on the same day versus the risk of two general anesthetics. Upon entering the surgical suite the patient table is centered on preplaced marks so that it is appropriately placed for microscope, surgeon, scrub nurse and anesthetist access. We favor a wrist rest, and the patient’s head is adjusted such that a ruler placed on the forehead and cheek will be parallel to the floor. The patient’s head is stabilized with tape to the head board to reduce unexpected movements, particularly if the patient falls asleep during the procedure and suddenly awakens. A second drop of tetracaine is placed in each eye. If the tetracaine is placed in each eye, blepharospasm is reduced. A periocular prep with 5% povidone-iodine solution is completed. We do not irrigate the ocular surface and fornices with povidoneiodine. Under topical anesthesia we have found that the patients note a significant burning. If a few drops leak into the eye this is certainly acceptable. An aperture drape is helpful for topical anesthesia to increase comfort. We have noted that when the drape is tucked under the lids this often irritates the patient’s eye and also reduces the malleability of the lids, decreasing exposure. Since it is important to isolate the meibomian glands and lashes a reversible solid bladed speculum (Lindstrom/Chu Speculum – Rhein Medical) may be used. With temporal and nasal approaches to the eye, the solid blades of the speculum are not in the way. In those cases where a superior approach is planned, a Tegaderm drape is used, tucking it under the lids. In these cases, a Kratz-modified Barraquer wire is useful, as this enhances access to the globe. Nevertheless, we have been using a superior approach incision less and less. Balanced salt solution (BSS) is used in all cases. For the short duration of a phacoemulsification case, BSS plus does not provide any clinically meaningful benefit. We place 0.5 cm3 of the intracardiac nonpreserved (sodium bisulfatefree) epinephrine in the bottle for assistance in dilation and perhaps hemostasis. We also add 1 ml (1,000 units) of heparin sulfate to reduce the possibility of postoperative fibrin. This is also a good anti-inflammatory and coating agent. At this dose there is no risk of enhancing bleeding or reducing hemostasis. The lids are separated with a solid blade speculum. A solid blade Barraquer speculum or the Lindstrom/Chu aspirating speculum (Rhein Medical) which
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Fig. 1. Paracentesis incision. Fig. 2. Injection of nonpreserved xylocaine.
can be placed temporally or nasally, isolates the lashes. A final drop of tetracaine is placed in the operative eye or the surface is irrigated with the nonpreserved xylocaine. We do not like to utilize more than three drops of tetracaine or other topical anesthetic as excess softening of the epithelium can occur, resulting in punctate epithelial keratitis, corneal erosion and delayed postoperative rehabilitation. Operative Procedure
The patient is asked to look down. The globe is supported with a dry Merocel sponge, and a counter puncture is performed superiorly at 12 o’clock with a diamond stab knife (Osher/Storz). The incision is about 1 mm in length (fig. 1). Approximately 0.25 ml of 1% nonpreserved methylparaben-free xylocaine is injected into the eye (fig. 2). We advise the patient that they will feel a ‘tingling’ or ‘burning’ for a second, and then ‘the eye will go numb’. This provides a psychological support for the patient that they will now have a totally anesthetized eye and should not anticipate any discomfort. We tell them that while they will feel some touch and fluid on the eye, they will not feel anything sharp, and if they do, we can supplement the anesthesia. This injection also firms up the eye for the clear corneal incision. We do not find it necessary to inject viscoelastic prior to constructing the corneal wound. We perform a temporal or nasal anterior limbal or posterior clear corneal incision. We perform a modified Langerman incision. A groove is made
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Fig. 3. Clear corneal incision.
400–500 m deep into the perilimbal capillary plexus just anterior to the insertion of the conjunctiva. Care is taken not to incise the conjunctiva as this can result in ballooning during phacoemulsification and irrigation aspiration. Some surgeons define this as being a posterior clear corneal incision and others as an anterior limbal incision. The anatomical landmark is the perilimbal capillary plexus and the insertion of the conjunctiva. When the groove is made there will be a small amount of capillary bleeding. Since the incision is into a vascular area, long-term wound healing can be expected to be stronger than it is with a true clear corneal incision. True clear corneal incisions, such as performed in radial keratotomy, clearly do not have the wound-healing capabilities that a limbal incision demonstrates where there are functioning blood vessels present. The anterior chamber is then entered parallel to the iris at a depth of approximately 300 m or above the deepest portion of the groove. This creates a hinge type or Langerman type of incision (fig. 3). We prefer the width of the incision to be 1.75–2.00 mm and Dr. Lindstrom has designed a keratome with Storz with two small black lines which can serve as a guide to the surgeon in creating an appropriate width incision (Lindstrom Keratome/Storz). In right eyes the incision is temporal, and in left eyes, nasal. This allows the surgeon to sit in the same position for right and left eyes. The nasal cornea is thicker, has a higher endothelial cell count and allows very good access for phacoemulsification. The nasal limbus is approximately 0.3 mm closer to the center of the cornea than the temporal limbus, and this can, in some cases where there is excess edema, reduce first day postoperative vision more than one might anticipate with a temporal incision. There also can, in some patients, be pooling of irrigating fluid. For this reason, an aspirating speculum is useful. It is also helpful to tip the head slightly to the left side. Nonetheless, in left eyes a nasal
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clear corneal approach is an excellent option, particularly for surgeons who find the left temporal position uncomfortable. The groove may be constructed by simply taking the keratome and tipping it up and utilizing the tip of the keratome. Some surgeons utilize a guarded knife to create a consistently deep incision. An astigmatic keratotomy blade can be quite useful in this regard. This blade can also be helpful when patients present with high astigmatism and an intraoperative astigmatic keratotomy is felt to be appropriate. In some patients it may be safest to create a corneal scleral incision. Examples of these include patients who have had a previous radial keratotomy or demonstrate findings of peripheral corneal ulcerative keratitis, in some patients with very low endothelial cell counts, and any case where there is any significant peripheral pathology or thinning. The anterior limbal or posterior corneal incision described above can be made temporally, nasally, in the oblique meridian or even superiorly without induction of significant corneal edema or endothelial cell loss. With a corneal scleral incision we will raise a small conjunctival flap with Westcott scissors. Prior to this, anesthesia can be provided by holding a Merocel sponge soaked in tetracaine or nonpreserved xylocaine in the area of the limbus where the conjunctival flap will be raised for 30–60 s. Mild cautery can be applied or one can utilize a Merocel soaked in thrombin 1/1,000 in BSS to effect hemostasis. If there is minimal capillary oozing the mild bleeding can also simply be ignored. Thrombin solution is also very useful in anterior segment reconstruction cases where excess bleeding is noted and may be safely injected into the anterior chamber if diluted in BSS. We prefer to close all clear corneal incisions ⬎4 mm with a horizontal mattress, X or single radial suture. The least early astigmatism is induced with the horizontal mattress suture. A corneal scleral incision ⬎5.5 mm is also closed with one horizontal mattress suture. The incision, if 3 mm in length, tends to cause an induction of 0.25 ⫾ 0.25 dpt of astigmatism. If it is placed on the steeper meridian, it can therefore be expected to reduce the astigmatism somewhere between 0 and 0.50 dpt. If the incision is 4 mm in length, there usually is a reduction in astigmatism of 0.50 ⫾ 0.50 or 0–1.00 dpt if the incision is placed on the steeper meridian. In routine cataract surgery we do not utilize incisions ⬎4 mm. An incision in the 3-mm range will almost always be self-sealing. With modern injector systems most foldable intraocular lenses can be implanted through a 3-mm anterior limbal incision. In select patients an intraoperative astigmatic keratotomy can be performed at the 7–8 mm optical zone. This can be done at the beginning of the operation. The patient’s astigmatism axis is marked carefully using an intraoperative surgical keratometer which allows one to delineate the steeper and flatter meridian and not be concerned about globe rotation. One 2-mm incision at a 7–8 mm
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Fig. 4. Start of large diameter anterior capsulectomy. Fig. 5. Completion of anterior capsulectomy.
optical zone will correct 1 dpt of astigmatism and two 2-mm incisions will correct 2 dpt of astigmatism in a cataract age patient. One 3-mm incision will correct 2 dpt, and two 3-mm incision 4 dpt. One can combine a 3-mm and 2-mm correcting 3 dpt. Larger amounts of astigmatism can also be corrected utilizing the Arc-T nomogram. Depending on the age of the patient, one can correct up to 8 dpt of astigmatism with two 90° arcs. Many surgeons have moved to a more peripheral corneal limbal arcuate incision, but Dr. Lindstrom favors the 7–8 mm optical zone because of his years of experience with this approach. There certainly is a variation in response, but there have not been any significant induced complications with this approach. The outcome goal is 1 dpt or less of astigmatism in the preoperative axis. It is preferable to undercorrect rather than overcorrect. The key in astigmatism surgery is ‘axis, axis, axis’. If one is not careful in preoperative planning and the incision is placed more than 15° off axis, one is better avoiding this approach. The anterior chamber is constituted with a viscoelastic. Our studies have not found any significant difference between one viscoelastic or another in regard to postoperative endothelial cell counts. Occucoat has proved be an excellent viscoelastic which can also be utilized to coat the epithelial surface during surgery. This eliminates the need for continuous irrigation with BSS. It gives a very clear view. It is also economically a good choice in most settings. Amvisc Plus also works well and we can obtain 0.8 cm3 of it at a very fair price. Next a relatively large diameter continuous tear anterior capsulectomy is fashioned (fig. 4, 5). This can be made with a cystotome or forceps. The optimal size is 5.0–6.0 mm in diameter and inside the insertion of the zonules (usually at
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Fig. 6. Hydrodissecting the nucleus out of the capsular bag (tilt). Fig. 7. Rotation of the nucleus toward the incision.
7 mm). Larger is better than smaller, as there is less subcapsular epithelium and thus lower risk of capsular opacification. Additionally, a larger capsulorhexis makes for an easier cataract operation. With this technique there has not been any change in the incidence of intraocular lens decentration. With some intraocular lenses the capsule will seal down to the posterior capsule around the loops rather than be symmetrically placed over the anterior surface of the intraocular lens. These eyes do extremely well and this might be preferable to having the capsule anterior to the optic. This is also certainly a controversial position. Hydrodissection is then performed utilizing a Pearce hydrodissection cannula on a 3-cm3 syringe filled with BSS. Slow continuous hydrodissection is performed gently lifting the anterior capsular rim until a fluid wave is seen. At this point irrigation is continued until the nucleus tilts on one side, up and out of the capsular bag (fig. 6). If one retracts the capsule at approximately the 7:30 o’clock position with the hydrodissection cannula, usually the nucleus will tilt superiorly. If it tilts in another position, it is simply rotated until it is facing the incision (fig. 7). Once the nucleus is tilted some additional viscoelastic can be injected under the nucleus pushing the iris and capsule back. Also, additional viscoelastic can be placed over the nuclear edge to protect the endothelium. The nucleus is emulsified from outside-in while supporting the nucleus in the iris plane with a second instrument, such as a Rhein Medical or Storz Lindstrom Star or Lindstrom Trident nucleus rotator (fig. 8). Once half the nucleus is removed, the remaining one half is tumbled upside-down and approached from the opposite pole (fig. 9). Again, it is supported in the iris plane until the emulsification is
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Fig. 8. Phacoemulsification in the iris plane. Fig. 9. Tumbling and phacoemulsification of remaining half nucleus.
completed (fig. 10). Alternatively the nucleus can be rotated and emulsified from the outside edge in, in a carousel or cartwheel type of technique. Finally, in some cases, the nucleus can be continuously emulsified in the iris plane if there is good followability until the entire nucleus is gone. This a very fast and very safe technique, and as mentioned before, it is a modification of the iris plane technique taught by Richard Kratz, MD, in the late 1970s and 1980s. It is basically ‘back to Kratz’ with help from Brown and Maloney in the modern phacoemulsification, capsulorhexis, hydrodissection and viscoelastic era. Surgery times now range between 5 and 10 min with this approach rather than 10–15 min for endocapsular phacoemulsification. In addition, our capsular tear rate has now gone under 1%. Therefore, we find this technique which to be easier, faster and safer. It is true that in this technique the phacoemulsification tip is closer to the iris margin and also somewhat closer to the corneal endothelium. There is, however, a significantly greater margin of error in regard to the posterior capsule. Care needs to be taken to position the nucleus away from the corneal endothelium and away from the iris margin when utilizing this approach. If the nucleus does not tilt with simple hydrodissection, it can be tilted with viscoelastic or a second instrument such as a nuclear rotator, Graether collar button or hydrodissection cannula. When utilizing this approach of phacoemulsification with the Storz Premier instrument, we utilize a vacuum of 60 mm Hg and an anterior chamber maintainer pressure of 60 mm Hg. We favor the Storz microflow plus needle with a 30° bevel.
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Fig. 10. Completion of phacoemulsification. Fig. 11. Irrigation and aspiration of subincisional cortex with right-angled tip.
When utilizing a peristaltic machine, a slightly higher vacuum in the range of 80–100 mm Hg is used. It is best to maintain a relatively high bottle with some overflow of fluid. Again a 30° bevel needle is appropriate for this approach. When utilizing tilt and tumble, very high vacuum settings are not necessary and may be inappropriate. The reason for this is that the iris margin is in the vicinity of the phacoemulsification tip, and it is possible to core through the nucleus and aspirate the iris margin if very high vacuums are utilized. The dual function Storz Millennium™ is also excellent for all cataract techniques including ‘tilt and tumble’. The vacuum is set with a range of 60–100 mm Hg and the ultrasound power from 10 to 50% with the Storz Millennium™. The foot pedal is arranged such that there is surgeon control over ultrasound on the vertical or pitch motion of the foot pedal, and then on the yaw or right motion foot pedal, there will be vacuum control. This allows very efficient emulsification, and the Millennium™ is currently our preferred machine. The microflow plus needle with a 30° angle tip works well with the Millennium™. Following completion of nuclear removal, the cortex is removed with the irrigation aspiration hand piece. We prefer a 0.3-mm tip and utilize the universal hand piece with interchangeable tips. A curvilinear tip is used for most cortex removal. Subincisional cortex can be aspirated with a Lindstrom right-angle sand-blasted tip currently manufactured by Rhein and Storz (fig. 11). If there is significant debris or plaque on the posterior capsule, one can attempt some polishing and vacuum cleaning but not so aggressively as to risk capsular tears. Many times there is an unexpected small burr or sharp defect on the I&A tip which results in a capsular tear after a case that was otherwise well done.
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Fig. 12. Injection of intraocular lens into capsular bag. Fig. 13. Posterior chamber lens seated in capsular bag.
The anterior chamber is reconstituted with viscoelastic and the intraocular lens is inserted utilizing an injector system (fig. 12, 13). We prefer the 3-piece silicone lenses which are injectable through a 3-mm incision. In select cases an acrylic implant is chosen, although with a cross-action folder this requires enlargement of the incision. One can inject the acrylic lens with care through a Bartelt injector, but proper technique is necessary or the loops can be damaged. Excess viscoelastic is removed with irrigation aspiration. Pushing back on the intraocular lens and slowly turn the irrigation aspiration to the right and left two or three times allows a fairly complete removal of viscoelastic under the intraocular lens. We favor injection of a miotic and tend to prefer carbachol over miochol at this time, as it is more effective in reducing postoperative intraocular tension spikes and has a longer duration of action. It is best to dilute the carbachol 5:1, or one can obtain an excessively small pupil which results in dark vision for the patient at night for 1–2 days. The anterior chamber is then refilled through the counter-puncture and the incision is inspected. If the chamber remains well constituted and there is no spontaneous leak from the incision, wound hydration is not necessary. If there is some shallowing in the anterior chamber and a spontaneous leak, wound hydration is performed by injecting BSS peripherally into the incision and hydrating it to push the edges together. We suspect that within a few minutes these clear corneal or posterior limbal incisions seal, much as a LASIK flap will stick down, through the negative swelling pressure of the cornea and capillary action. It is important to leave the eye slightly firm at 20 mm Hg or so to reduce the side effects of hypotony and also help the internal valve incision appropriately seal.
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At completion of the procedure another drop of antibiotic, steroid and nonsteroidal, is placed on the eye. Additionally, one drop of an antihypertensive such as Betagan or Alphagan is applied to reduce postoperative intraocular tension spikes. Postoperative Care
No patch is routinely utilized for the topical and intracameral approach. If a miniblock of the lids has been performed, this will wear off in 30–45 min, and there is usually adequate lid function for a normal blink at the completion of the procedure. Patients are advised that they will have some erythropsia, meaning they will see a pink after image for the rest of the day, but usually this will resolve by the next morning. They are also told that their vision may be a little dark at night from the miotic, and not to be concerned if they wake up at night and their vision seems dimmer. The patient is seen on the first day postoperative and then at approximately 2–3 weeks postoperative. At this time a refraction, slit lamp, and funduscopic examination is performed. If there is no inflammation, patients are seen again 1 year postoperative. If at 3 weeks there is still persistent inflammation, additional postoperative anti-inflammatory medications are recommended, and the patient is asked to return again at 2–3 months postoperative. Topical antibiotic, steroid and nonsteroidal, are utilized twice a day, usually requiring a 5-cm3 bottle and 3–4 weeks of therapy. Occasionally a second bottle of steroid and nonsteroidal is necessary if flare and cell persist at the 3-week examination. There are minimal restrictions, including a request that there be no swimming and no very heavy lifting for 2 weeks. Many patients are given halfglasses the first postoperative day allowing functional vision at distance and near. We consider the ideal postoperative refractive spherical equivalent for a monofocal lens to be ⫺0.62 dpt with ⬍0.50 dpt of astigmatism in the same axis as existed preoperatively. Most patients can see 20/30⫹ and J3⫹ with this type of correction. Monovision can be utilized in the appropriate settings. Good results can also be obtained with the Allergan ARRAY multifocal intraocular lens. In this setting we target plano to ⫺0.25 dpt with minimal astigmatism. The second eye is done at 1 month or greater postoperatively except in rare situations. Any YAG lasers are deferred for 90 days in order to allow the blood aqueous barrier to become intact and capsular fixation to be firm. Conclusion
We hope other surgeons will find this approach to cataract surgery useful. These techniques must be personalized, and every surgeon will find that slight
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variations in technique are required to achieve optimum results for their own individual patients in their own individual environment. Continuous efforts at incremental improvement result in meaningful advances in our ability to help the cataract patient obtain rapid, safe, visual recovery following surgery. Dr. Richard L. Lindstrom, Minnesota Eye Consultants PA, 710 East 24th Street, Suite 106, Minneapolis, MN 55404 (USA) Tel. ⫹1 612 813 3633, Fax ⫹1 612 813 3601, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 59–73
Phacoemulsification in the Anterior Chamber: Preliminary Results Jorge L. Alió , Ahmad M.M. Shalaby, Walid H. Attia Alicante Institute of Ophthalmology, Alicante, and Department of Ophthalmology, Miguel Hernández University, Medical School, Alicante, Spain
The term extracapsular cataract extraction (ECCE) refers to an operation in which the lens nucleus is delivered intact through a limbal incision of about 10 mm, as opposed to phacoemulsification, in which the nucleus is ultrasonically fragmented and aspirated through a 3-mm incision [1, 2]. Phacoemulsification was slowly adopted by a wider group of surgeons and its popularity increased, becoming the procedure of choice for about 50% of surgeons by 1990, 79% of surgeons by 1992 [3] and is almost universal nowadays [4]. However, the extracapsular cataract operation is still used and, in some cases, it may be safer than phacoemulsification. In cases in which operative exposure is difficult, the pupil dilates poorly, posterior synechiae, subluxation, hypermature cataract, deep anterior chamber and posterior capsular tear, endocapsular phacoemulsification carries the risk of serious intraoperative complications [5] and the surgeon will eventually need to abort phacoemulsification and change into ECCE [4]. Phacoemulsification after delivering the nucleus into the anterior chamber is another option in managing these problematic cases. This will maintain the advantages of small incision surgery and meanwhile decrease the incidence of possible complications. Our main concern should be directed towards protecting the corneal endothelium intraoperatively and managing the possible postoperative intraocular inflammation. Nagahara, at the ASCRS in Seattle in 1993, then in Milan at the Videocataract in 1994, presented the phaco chop technique, which is an effective technique especially in hard nuclei [6]. The main problem with this technique is that after splitting a hard nucleus into four quadrants, the four nuclear fragments are difficult to remove from the capsular bag, as there is not enough room for such
a manipulation. For this reason, Koch [7] suggested a variation of the technique called stop and chop. Both Nagahara’s technique and Koch’s modified technique carry the advantage of tackling hard nuclei without having to resort to very high-power levels and long ultrasound time. In this work, we present the anterior chamber phacoemulsification technique (phaco-out) as an option for managing such problematic cases, and compare its safety and effectiveness to that of endocapsular phacoemulsification using the stop and chop technique.
Patients and Methods We performed this prospective pilot study on 30 eyes of 15 patients with bilateral cataract (8 females and 7 males), with an average age of 68 5.38 (range 62–79) years. Patients were selected from our outpatient clinic. The inclusion criteria of the selected patients were: older than 60 years with senile cataract, round regular dilatable pupil (up to at least 6.00 mm), and a visual acuity of 0.32 (20/63) or more. We excluded patients who were younger than 60 years, had complicated cataract, pseudoexfoliation syndrome, other ocular pathology, diabetes mellitus, an endothelial cell count 1,800, and their pupil not being able to reach 6.00 mm of dilatation. Also we excluded patients with the following intraoperative complications: rupture of the posterior capsule, pseudoexfoliation syndrome, and subluxated lens. Each patient was preoperatively evaluated, and the ocular examination included: gonioscopy, B-scan biometry, and anterior chamber depth estimation by an Ophthasonic Ultrasonic Biometer (Tecknar Inc., St. Louis, Mo., USA), applanation Goldmann tonometry (Haag-Streit, Bern, Switzerland) and keratometry. The spectacle best-corrected visual acuity was estimated in all patients as well as PAM. A corneal endothelial study of the central cornea was performed by the same physician using a Konan SP5500 contact endothelial cell meter, and cell density, hexagonality, and the coefficient of variation were all documented. At each examination, 2–3 specular microscopic images (an area of 500–1,000 m2) of the central portion of each cornea were taken using video specular endothelioscopy. The images were analyzed after digitization by a Konan KC-87 A image analysis system. For each cornea, 100–150 cells were digitized and analyzed using the morphometry program of the software. Cell density (cells/mm2) was calculated automatically by the computer Cell Analyzer VER 4.00 (Konan Camera Research Institute, Inc., Hyogo, Japan). Ocular inflammation was assessed using a Kowa laser flare meter (LFCM-1000; Kowa Co. Ltd, Tokyo, Japan) to evaluate the amount of postoperative subclinical inflammation. Surgical Procedure Bilateral simultaneous phacoemulsification was performed in the 30 eyes of the 15 patients included in this study using the Legacy 2000 phaco machine (Alcon, Forth Worth, Tex., USA) by the same surgeon. For each patient one eye was operated upon using the phaco-out technique, and the other eye underwent phaco stop and chop technique. The mean nuclear hardness in the phaco stop and chop group was 2.8 0.68 (range 1.5–4.0) and in the phaco-out group was 2.63 0.67 (range 1.5– 4.0), with no statistically significant difference between the two groups (p 0.502, independent sample t-test).
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The procedure was performed under topical anesthesia using lidocaine 2% (Braun, Barcelona, Spain). A corneal incision was made at 12 o’clock using a 3.2-mm phaco-slit blade (Sharpoint, Surgical Specialities Corp., Reading, Pa., USA). Viscoelastic materials, HPMC and Viscoat (Alcon) were injected in the anterior chamber followed by performing a paracentesis using a 1-mm MVR blade (Sharpoint). Capsulorhexis (about 6 mm in diameter) was then performed using a capsulorhexis forceps (Katena, Denville, N.J., USA). Hydrodissection of the nucleus using a J-hooked and a straight 25-gauge cannula (Sincoe, ASICO, Westmont, Ill., USA) is then performed. Phaco Stop and Chop Technique. This begins with a groove, as though the surgeon was preparing for Sheperd’s cross nucleofracture. This produces a space for U/S tip and the hook, which will be able to fracture the nucleus into two parts, using a phaco power of 100%, and a vacuum of 60 mm Hg. At this point, the surgeon stops, rotates the nucleus 90°, and changes the machine parameters; the vacuum is increased to 400 mm Hg and the phaco power is changed to 60% in a pulse mode. The surgeon fixes the lower half of the nucleus with the U/S tip, and a crack is created with a chopper instrument (Katena). A number of fragments result, which can be easily mobilized from the capsular bag to be emulsified. Phaco-Out Technique. Excess hydrodissection is performed. The corneal endothelium is protected using abundant viscoelastic material, HPMC and Viscoat (Alcon). A Sinisky hook (Katena) and a fine blunt-ended spatula are used to deliver the nucleus into the anterior chamber. With the vacuum set at 400 mm Hg and the ultrasound power at 60%, the nucleus is then approached, with a 30° phaco tip, at the equator of one sector removing first the superficial layer, then the intermediate part, and eventually the deep portion. Using the Sinisky hook, the nucleus is rotated 90–180° in order to fragment another sector, and rotated again to remove further sectors, thus reducing progressively the nuclear volume. This technique will prevent early fragmentation of the nucleus, which might wander around the anterior chamber with possible contact with the endothelium. Throughout the procedure, the second instrument is always pushing the nucleus backwards preventing any possible contact with the back of the cornea. The Acrysoft MA30 intraocular lens (Alcon) was implanted in 11 patients (22 eyes) and the AMO Sensar AR40 (Allergan, Irvine, Calif., USA) was implanted in 4 patients (8 eyes). A single 10/0 Nylon suture (Alcon) is used to close the corneal incision followed by intracameral injection of Curoxima 2% antibiotic (Glaxo-Wellcome, Burgos, Spain). Postoperative Treatment All the patients followed a regimen of topical antibiotic trimethoprim-sulfamethoxazole (Oftalmotrim, Alcon) 4 times a day for 2 weeks, and 2 times a day for another 2 weeks, diclofenac sodium (Voltaren; Ciba Vision, Barcelona, Spain) 4 times a day for 2 weeks, and 2 times a day for another 2 weeks and dexamethasone 2% (Maxitrol, Alcon) 4 times a day for 1 week, 3 times a day for 1 week, 2 times a day for another week, and 1 time a day for 2 more weeks. Postoperative Follow-Up All the patients fulfilled a follow-up period of 3 months. The first visit was 3 days postoperatively, then at 2 weeks, 1 month and 3 months postoperatively. Every postoperative examination included slit lamp biomicroscopy, uncorrected and best-corrected visual acuity, corneal pachymetry and laser flare cell meter (LFCM-1000; Kowa Co. Ltd). Endothelial
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microscopy (Konan Camera Research Institute, Inc.) was performed only once on the third postoperative visit (1 month after surgery). Statistical analysis was performed with the SPSS statistics software package SPSS/Pc 4.0 for Windows® (SPSS Inc., Madrid, Spain). Normality of the data in each group was confirmed by normal probability plots. Statistically significant differences between data samples means that they were determined by the t-test; p values 0.05 were considered significant. Correlation between different parameters was studied using the Pearson correlation test.
Results
The mean ultrasound time was less in the phaco-out group (1.12 0.69 min, range 0.1–2.3) using a mean ultrasound power of 20.5 6.7% (range 6–32%) compared the phaco stop and chop (1.3 0.74 min, range 0.28–2.7) using a mean power of 25.3 7.9% (range 11– 42%), but this was not statistically significant (p 0.515 and p 0.089 respectively, independent samples t-test) (fig. 1). The mean preoperative best-corrected visual acuity (BCVA) was 20/63 20/125 (range 20/400–20/32) in the phaco-out group, and 20/63 20/100 (range 20/400–20/25) in the phaco stop and chop group. In the first postoperative visit, the mean BCVA was 20/32 20/80 (range 20/400–20/20) in the phaco-out group and 20/32 20/63 (range 20/400–20/20) in the phaco stop and chop group. At the last visit (3 months after surgery) the mean BCVA was 20/25 20/100 (range 20/100–20/20) in the phaco-out group and 20/25 20/80 (range 20/200–20/20) in the phaco stop and chop group. The differences were not statistically significant (table 1, fig. 2). Corneal edema (table 2, fig. 3) was observed clinically by the slit lamp biomicroscopy during the first postoperative visit in 5 eyes (33.3%) of the phaco-out group, 2 eyes (13.3%) edema grade ‘’ and 3 eyes (20%) edema grade ‘’. In the phaco stop and chop group, edema was present in 5 eyes (33.3%), all edema grade. Two weeks after surgery, edema was still present in 2 eyes (13.3%) of the phaco-out group, all grade ‘’. Edema grade ‘’ was also present in 1 eye (6.7%) of the phaco stop and chop group. One month after surgery there was still no clinically significant edema present in either group. Again these differences were not statistically significant (table 1). The mean preoperative intraocular pressure (IOP) (measured by the applanation Goldmann tonometry; Haag-Streit) in the phaco-out group was 15.6 2.9 mm Hg (range 10–22). In the phaco stop and chop technique the mean preoperative IOP was 15.67 3.66 mm Hg (range 8–23). In the first postoperative visit the mean IOP was 19.67 4.01 mm Hg (range 12–30) in the phaco-out group, and 19.73 4.63 mm Hg (range 10–30) in the phaco stop and chop
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1.8
95% confidence interval
1.6
1.4
1.2
1.0
0.8
0.6 Out (n 15)
a
Chop (n15)
Phaco time (min) 32
95% confidence interval
30 28 26 24 22 20 18 16 Out (n 15)
b
Chop (n15)
Phaco power (%)
Fig. 1. a Phaco time (min). b Phaco power (%).
technique. Three months after surgery the mean IOP was 15.53 2.97 mm Hg (range 8–18) in the phaco-out group, and 14.87 2.53 mm Hg (range 10–18) in the phaco stop and chop group. The increase in IOP during the first visit was statistically significant compared to the preoperative value in both groups (p 0.001 and p 0.01 in the phaco-out and phaco stop and chop respectively, Student’s t-test), but there was no difference between the two groups throughout the follow-up (table 1).
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Table 1. Comparison of the different evaluation parameters between both groups
Phaco time Phaco power Preoperative endothelial cell count Postoperative endothelial cell count Percentage endothelial loss Preoperative laser flare cell count Postoperative laser flare cell count (visit 1) Postoperative laser flare cell count (visit 2) Postoperative laser flare cell count (visit 3) Postoperative laser flare cell count (visit 4) Preoperative pachymetry Postoperative pachymetry (visit 1) Postoperative pachymetry (visit 2) Postoperative pachymetry (visit 3) Postoperative pachymetry (visit 4) Preoperative BCVA Preoperative BCVA Postoperative BCVA (visit 1) Postoperative BCVA (visit 4) Corneal edema (3 days postoperatively) Corneal edema (2 weeks postoperatively) Corneal edema (1 month postoperatively) Preoperative IOP Postoperative IOP (first visit)
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Type
Number
Mean
SD
p value (independent sample t-test)
Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop Out Chop
15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15
1.12 1.3 20.5 25.27 2,809 2,620 2,523 2,318 10.65 11.85 6.73 7.07 23.8 23.6 18 16.13 8.93 8.13 7.53 7.47 529 525 559 556 543 542 532 532 523 528 20/63 20/63 20/63 20/63 20/32 20/32 20/25 20/25 0.53 0.33 0.13 0.067 0 0 15.6 15.67 19.67 19.73
0.69 0.74 6.7 7.9 575 473 602 491 5.4 5.14 2.15 1.98 3.65 4.05 3.21 2.95 2.66 2.13 1.88 1.55 46.02 44.94 54.8 49.73 43.4 41.69 44.82 41.03 47.60 41.46 20/125 20/100 20/125 20/100 20/63 20/80 20/100 20/80 0.83 0.49 0.35 0.26 0 0 2.9 3.66 4.01 4.64
0.515 0.089 0.333 0.316 0.536 0.662 0.888 0.108 0.371 0.917 0.799 0.876 0.936 0.987 0.771 0.346 0.346 0.608 1.000 0.429 0.559 –a 0.956 0.967
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Table 1. (continued)
Postoperative IOP (last visit) Nuclear hardness
Type
Number
Mean
SD
p value (independent sample t-test)
Out Chop Out Chop
15 15 15 15
14.53 14.87 2.63 2.8
2.97 2.53 .67 .68
0.743 0.502
p 0.05 is considered not statistically significant. a Cannot be computed because the standard deviations of both groups are 0.
1.0
95% confidence interval
0.8
0.6
C
C B
B
0.4
A
0.2 A
0.0 15
15 Out (n)
15
15
15 Chop (n)
15
Evolution of BCVA
Fig. 2. Evolution of BCVA. A Preoperatively; B postoperatively, visit 1; C postoperatively, visit 4.
The mean preoperative laser flare cell meter count was 6.73 2.15 (range 4–11) in the phaco-out group, and 7.07 1.98 (range 5–12) in the phaco stop and chop group. In the first postoperative visit, the mean laser flare cell meter count increased significantly in both groups compared to the preoperative values (p 0.0001, Student’s t-test). The count started to decrease 2 weeks after surgery in both groups reaching its preoperative values 3 months after surgery (table 3, fig. 4). There were no significant differences between the two groups in all visits (table 1).
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Table 2. Postoperative corneal edema No edema
Mild edema ()
Moderate edema (++)
Chop (15 eyes) 1–3 days 15 days
10 eyes (66.7%) 14 eyes (93.3%)
5 eyes (33.3%) 1 eye (6.7%)
0 0
Out (15 eyes) 1–3 days 15 days
10 eyes (66.7%) 13 eyes (86.7%)
2 eyes (13.3%) 2 eyes (13.3%)
3 eyes (20%) 0
No eye had corneal edema at the first month follow-up visit.
100 3 days phaco out 3 days phaco chop 80
2 weeks phaco out 2 weeks phaco chop
Patient percentage
1 month phaco out 60
1 month phaco chop
40
20
0 None
Postoperative corneal edema
Fig. 3. Postoperative corneal edema.
The mean preoperative endothelial cell count (table 4, fig. 5) was 2,620 473 cells/mm2 (range 1,992– 4,010) in the phaco stop and chop group, and 2,809 575 cells/mm2 (range 1,897– 4,069) in the phaco-out group. Three months after surgery the mean endothelial cell count was 2,318 491 cells/mm2
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Table 3. Laser flare cell meter readings Preoperative
1–3 days postoperatively
15 days postoperatively
1 month postoperatively
3 months postoperatively
Phaco chop (15 eyes)
7.07 1.98 (5–12)
23.6 4.05 (16 –33)
15.13 2.95 (12–23)
8.13 2.13 (6–14)
7.47 1.55 (6–11)
Phaco out (15 eyes)
6.73 2.15 (4–11)
23.8 3.65 (18–31)
18 3.21 (14 –25)
8.93 2.66 (5–14)
7.53 1.88 (4–11)
95% confidence interval
30
B
20
B
C C 10 D A
E
A
15
15
D
E
15
15
0 15
15
15
15
Phaco out (n)
15
15
Phaco chop (n)
Laser flare cell meter counts
Fig. 4. Laser flare cell meter counts. A Preoperatively; B postoperatively, visit 1; C postoperatively, visit 2; D postoperatively, visit 3; E postoperatively, visit 4.
(range 1,607–3,745) in the phaco stop and chop group, and 2,523 602 cells/ mm2 (range 1,615–3,861) in the phaco-out group. The cell loss was statistically significant in both groups (p 0.0001, Student’s t-test), but the difference between groups was not statistically significant. The mean percentage cell loss was 11.85 5.14% (range 6.61–26.39%) after the phaco stop and chop technique and 10.65 5.4% (range 4.55–24.25%) after the phaco-out technique. Again this was not statistically significant (table 1).
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Table 4. Endothelial cell changes Preoperative
3 months postoperatively
Percentage endothelial loss
Phaco chop (15 eyes)
2,620 473 cells/mm2 (1,992– 4,010)
2,318 491 cells/mm2 (1,607–3,745)
11.85 5.14 % (6.61–26.39 %)
Phaco out (15 eyes)
2,809 575 cells/mm2 (1,897– 4,069)
2,523 602 cells/mm2 (1,615–3,861)
10.65 5.4 % (4.55–24.25 %)
Regarding the corneal thickness, measured by Ophthasonic Ultrasonic Biometer (Tecknar Inc.), both groups showed a significant increase in corneal thickness. A maximum corneal thickness was reached at the first postoperative visit (p 0.0002 and p 0.001 in the phaco stop and chop, and the phaco-out groups respectively, Student’s t-test), and decreased gradually to reach the preoperative values by the third month (table 5). However, the difference between the two groups was not statistically significant (table 1).
Discussion
Removal of the nucleus by ultrasound can be performed using a number of techniques. Originally, Kelman [8] developed phacoemulsification in the anterior chamber in 1967, seeking for a procedure that reduces astigmatism and provides early rehabilitation. Many surgeons, seeking the same objective, performed thousands of Kelman phacoemulsification cases, and their results were reported [9, 10]. However, the corneal endothelium damage (many cases being impossible to accomplish with the instruments available by that time), the realization that very dense nucleus resisted ultrasonic fragmentation, and the need of an incision 3 mm to implant the intraocular implants available at that time limited the universal application of Kelman’s procedure. Corneal problems have been significantly minimized by the advent of in situ, or what has become known as posterior chamber, phacoemulsification and the protective properties of viscoelastic substances [11, 12]. Phacoemulsification as the surgical procedure of choice increased from 12% in 1985 to 79% in 1992 [3]. The tremendous 7-year growth can be directly correlated with the introduction of continuous curvilinear capsulorhexis (CCC) in 1985 [13, 14]. Following the introduction of CCC, various endocapsular phacoemulsification techniques developed, from which surgeons can choose depending on their own skill, machine available and more important the type of cataract
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3,200
95% confidence interval
3,000
2,800
2,600 A 2,400 A 2,200 B B
2,000
1,800 15
15 Out (n)
a
15
15 Chop (n)
Endothelial cell count (cell/mm2) 16
95% confidence interval
14
12
10
8
6 Out (n15)
b
Chop (n15)
Percentage endothelial cell loss (%)
Fig. 5 a Endothelial cell count (cell/mm2). b Percentage endothelial cell loss (%).
they are dealing with. The various endocapsular techniques include [7, 15–17]: technique of cut and suck for nuclei of moderate-low hardness, technique of cleavage for nuclei of moderate hardness (chip and flip), and techniques of nucleofracture for nuclei of moderate-high hardness, Sheperd’s cross technique,
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Table 5. Corneal pachymetry Preoperative
1–3 days postoperatively
15 days postoperatively
1 month postoperatively
3 months postoperatively
Phaco chop (15 eyes)
525 44.94 m (430–589)
556 49.73 m (478 – 644)
542 41.69 m (470–604)
532 41.03 m (450–592)
528 41.46 m (455–590)
Phaco out (15 eyes)
529 46.02 m (450–589)
569 54.8 m (464 –652)
543 43.4 m (460–604)
532 44.82 m (455–595)
523 47.6 m (439–585)
divide and conquer by Gimbel, crack and flip by Fine, phaco chop by Nagahara, and stop and chop by Koch. Owing to the great development of phacoemulsification techniques and machines, as well as the availability of various forms of foldable intraocular lenses, phacoemulsification is the technique of choice by most surgeons nowadays. However, we should not ignore the fact that in certain situations the surgeon will find himself obliged either to perform an ECCE procedure from the very beginning or to switch from phacoemulsification to ECCE during the procedure. These difficult situations include very deep anterior chamber, where the surgeon will need to keep the tip in an almost vertical position, limiting the depth of field of the microscope and the surgeon will have less control and all of the intraoperative maneuvers will be more difficult. Another factor is difficult visual control of the peripheral lens structure due to miosis, as in cases of dystrophic iris; doubts regarding the strength of the zonules or the integrity of the posterior capsule. Performing phacoemulsification in these cases carries the risk of further intraoperative complications, and switching to ECCE is a viable alternative to decrease the incidence of complications. In this study we are making use of the great improvement in the phacoemulsification techniques, machines as well as the viscoelastic materials to compare the results of performing phacoemulsification in the anterior chamber (phaco-out), against phacoemulsification using the phaco stop and chop technique and study the effect of both procedures on corneal endothelial cells, and the intraocular postoperative inflammatory reactions. Several studies have evaluated the functional behavior of the corneal endothelium, IOP, and intraocular inflammatory response after cataract surgery. Carlson and Bourne [18] observed that the barrier function of the endothelium was transiently decreased following cataract surgery but appeared to recover by the third month. Sawa et al. [19] also reported a recovery of the barrier function 3 months after cataract surgery. Comparative studies evaluating the percentage of cell loss with ECCE and phacoemulsification have been reported. Davidson [20]
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reported a mean endothelial cell loss of 10.7 11% after ECCE and 10.0 12.9% after phacoemulsification and posterior chamber IOL implantation. Ravalico et al. [21] reported endothelial cell loss of 8% after phacoemulsification. In our current study both the phaco-out technique and phaco stop and chop technique resulted in endothelial cell loss in the same range that was reported by these authors, the mean endothelial cell loss was 10.65% after phaco-out, and 11.85% after phaco stop and chop technique. Thus both techniques affected corneal endothelial cells to the same extent with no significant difference (p 0.536, independent sample t-test), a point favoring the safety of the phaco-out technique described. We attribute this to the proper use of viscoelastics throughout the procedure, to fill the anterior chamber and protect the endothelium during the delivery of the nucleus to the anterior chamber and performing the phacoemulsification [22]. On clinical examination, corneal edema was more evident with the phacoout technique during the first 2 weeks after surgery after which there was no clinically detected corneal edema in both groups (table 2). Thus in our study, corneal edema, although it was present more with the phaco-out technique, its effect did not interfere with the visual outcome of both procedures. This finding could be related to the short distance between the cornea and ultrasound probe in the phaco-out technique in comparison to the phaco stop and chop technique. Corneal thickness, measured by the ultrasonic pachymetry, correlated well with the postoperative clinical corneal edema. There was a significant increase in the corneal thickness in both groups during the first 2 weeks after surgery; corneal thickness was more evident in the phaco-out group. However, this did not affect the final outcome in both groups. There was no significant difference between the mean preoperative value and 3 months after surgery. Even when considering the postoperative inflammation measured by the laser flare cell meter, in both groups there was a significant difference between the preoperative and the first postoperative visit means, that decreased with time to return to the preoperative values at 3 months. This agrees with the fact that intraocular inflammation usually responds well to the postoperative steroidal and nonsteroidal anti-inflammatory agent [23]. However, the difference between the two groups was not statistically significant throughout the follow-up. This further supports the safety of the phaco-out technique. The final visual outcome in both groups was satisfactory. The mean BCVA improved from a mean value of 20/63 20/125 (range 20/400–20/32) in the phaco-out group, and 20/63 20/100 (range 20/400–20/25) in the phaco stop and chop group to 20/25 20/100 (range 20/100–20/20) in the phaco-out group and 20/32 20/80 (range 20/200–20/20) in the phaco stop and chop group 3 months after surgery.
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Conclusion
With the significant improvement in phacoemulsification techniques, machines and viscoelastic materials, performing phacoemulsification in the anterior chamber (phaco-out technique) proved to be comparably safe to endocapsular phacoemulsification using the stop and chop technique. In addition, it is easier to learn. Thus in cases where endocapsular phacoemulsification carries a higher risk of intraoperative complications (deep anterior chamber, miosis, weakness of the capsular zonules, and rupture of the posterior capsule), the phaco-out technique could be used. This will help the surgeon avoid the problems that can occur in such conditions, while maintaining the benefits of the small incision surgery to the patient. According to our results, we recommend the use of this technique for the previously mentioned cases after applying it to a larger group of patients.
References 1 2
3 4 5 6 7 8 9 10 11 12
13 14 15
Kraff MC, Sanders DR: Planned extracapsular extraction versus phacoemulsification with IOL implantation: A comparison of current series. J Am Intraocul Implant Soc 1982;8:38–41. Watson A, Sunderraj P: Comparison of small incision phacoemulsification with standard extracapsular cataract surgery: Post-operative astigmatism and visual recovery. Eye 1992;6: 626–629. Leaming DV: Practice styles and preferences of ASCRS members 1992 survey. J Cataract Refract Surg 1993;19:600 – 606. Chakrabarti A, Singh S: Phacoemulsification in eyes with white cataract. J Cataract Refract Surg 2000;26:1041–1047. Metani S, Kishi H, Nakai Y: Usefulness of risk score in evaluating the safety of phacoemulsificationaspiration cataract surgery. Jpn J Clin Ophthalmol 1998;52:643–646. Burrato L: Techniques of phacoemulsification; in Burrato L (ed): Phacoemulsification, Principles and Technique. Thorofare, Slack Inc, 1998, chapt 6, pp 150–156. Koch PS, Katzen LE: Stop and chop phacoemulsification. J Cataract Refract Surg 1994; 20:566 –570. Kelman CD: Phacoemulsification and aspiration – A new technique of cataract removal. A preliminary report. Am J Ophthalmol 1967;64:23–35. Emery JM, Wilhelmus KA, Rosenburg S: Complications of phacoemulsification. Ophthalmology 1978;85:141–150. Kraff MC, Sanders DR, Lieberman HL: Total cataract extraction through a 3-mm incision. A report of 650 cases. Ophthalmic Surg 1979;10:46–540. Glasser DB, Kratz HR, Boyd JE: Protective effects of viscous solutions in phacoemulsification and intraocular lens implantation. Arch Ophthalmol 1989;107:1047–1051. Glasser DB, Osborn DC, Nordeen JF, Min YI: Endothelial protection and viscoelastic retention during phacoemulsification and intraocular lens implantation. Arch Ophthalmol 1991;109: 1438–1440. Gimbel HV, Neuhann T: Development advantages and methods of the continuous circular capsulorhexis technique. J Cataract Refract Surg 1990;16:31–37. Gimbel HV, Neuhann T: Continuous curvilinear capsulorhexis (letter). J Cataract Refract Surg 1991;17:1–10. Fine H: Chip and flip phacoemulsification technique. J Cataract Refract Surg 1991;17:366–371.
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16 17 18 19
20 21 22 23
Gimbel HV: Divide and conquer nucleofractis phacoemulsification: Development and variations. J Cataract Refract Surg 1991;17:281–291. Allen ED: Understanding phacoemulsification. III. Principles of nucleofractis techniques. Eur J Implant Refract Surg 1995;7:347–353. Carlson KH, Bourne WM: The clinical measurement of endothelial permeability. Cornea 1988;7:183–189. Sawa M, Sakanishi Y, Shimizu H: Fluorophotometric study of anterior segment barrier functions after extracapsular cataract extraction and posterior chamber intraocular lens implantation. Am J Ophthalmol 1984;97:197–204. Davidson JA: Endothelial cell loss during the transition from nucleus expression to posterior chamber-iris plane phacoemulsification. J Am Intraocul Implant Soc 1984;10:40–43. Ravalico G, Tongnetto D, Baccara F, Lovisato A: Corneal endothelial protection by different viscoelastics during phacoemulsification. J Cataract Refract Surg 1997;23:433–439. Burrato L: Viscoelastic substances and cataract surgery; in Burrato L (ed): Phacoemulsification, Principles and Technique. Thorofare, Slack Inc, 1998, chapt 12. Sanders DR, Kraff M: Steroidal and non-steroidal anti-inflammatory agents. Effects on postsurgical inflammation and blood aqueous barrier breakdown. Arch Ophthalmol 1984;102:1453–1456.
Prof. Dr. Jorge L. Alió, Instituto Oftalmológico de Alicante, Universidad Miguel Hernández, Avenida de Denia 111, E–03015 Alicante (Spain) Tel. 34 965 150 025, Fax 34 965 151 501, E-Mail
[email protected]
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Phaco Chop: Making the Transition Neil J. Friedman a, Thomas Kohnen b, c, Douglas D. Koch c a
Stanford University Hospital, Stanford, Calif., USA; Department of Ophthalmology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany; c Cullen Eye Institute, Baylor College of Medicine, Houston, Tex., USA b
Remarkable innovations in cataract surgery have made phacoemulsification an extremely sophisticated procedure. Since Kelman [1, 2] first introduced phacoemulsification in 1967, advances have been made in every step of the surgery from incisional architecture to lens design. Numerous methods of dismantling the nucleus have been described. Initially, one-handed anterior chamber techniques were used, and subsequently, two-handed posterior chamber methods were developed [3–9]. Alternative approaches [10–13] continue to emerge for handling the lens nucleus, and among these, various nuclear chopping techniques have become popular. Commonly referred to as ‘phaco chop’, these methods of disassembling the nucleus are faster, more efficient, and possibly safer than traditional sculpting and cracking techniques [14–16]. However, learning any new procedure and making the transition can be difficult. From studies of residents performing different types of cataract surgery, it is evident that with proper instruction, excellent results can be achieved [17–22]. In this chapter, we share some concepts and techniques that we have found helpful in our own surgery and in assisting others with the transition to phaco chop.
Methods and Materials Phaco chop was first described by Nagahara [10]. His method consists of impaling the lens nucleus with a 0 or 15° beveled phaco tip, holding it with high vacuum, and using a second instrument (chopper) to chop it. Koch [11] modified this technique in order to facilitate quadrant removal. He found that, after cracking the nucleus by Nagahara’s method, the quadrants were held tightly together within the capsular bag and could not be easily extracted. Thus, he
Fig. 1. In the stop and chop technique, after the central groove is created, the phaco tip and chopper are used to crack the nucleus into two halves.
developed the technique of stop and chop (fig. 1), in which a central groove is created, the nucleus is cracked in half, and then each half is chopped into smaller, more manageable pieces. The initial groove removes enough of the central nuclear mass so that subsequently chopped fragments can be mobilized from within the capsular bag. Additional variations and chopping maneuvers have been developed [12, 13]. Patient selection is an essential factor with any surgical procedure, especially when learning a new phacoemulsification technique. Therefore, it is advisable to choose routine cases, specifically eyes that have a widely dilatable pupil, a bright red reflex, and a normal axial length. Exposure is also important, so we suggest avoiding patients with narrow palpebral fissures and deep set orbits during the transition period. Lens density affects the ease of chopping, and a cataract with 3⫹ nuclear sclerosis, not too soft and not too hard, is ideal. Helpful intraoperative elements include: (1) a large capsulorhexis (⬎5 mm), which facilitates placement of the chopper and minimizes the risk of inadvertently catching the edge of the anterior capsule; (2) a complete hydrodissection, so that the nucleus rotates freely, and (3) a good hydrodelineation, to create whenever possible a golden ring, which demarcates the inner nucleus from the outer epinuclear shell, and thus identifies the peripheral landmark at which the blade of the chopper is to be positioned. Elaborate, high-tech, new instruments are not required for phaco chop, but having the appropriate tools is necessary. A Sinskey hook is excellent to use as the initial chopping instrument for transitioning surgeons to practice chopping smaller nuclear pieces. Many different styles of choppers exist, varying in shape, size, and cutting surface. They can be curved or straight, pointed or flat, and angled or universal; it is largely a matter of personal preference. Any phaco tip may be used, however, one should remember that the flatter the bevel, the better the occlusion. Also, enough of the tip must be exposed to permit it to be buried in the nucleus, thereby enhancing nuclear purchase. As for phaco settings, these of course will vary by machine, but a good starting point is to use typical quadrant removal parameters (i.e., high aspiration flow rate and vacuum), which can be adjusted as necessary.
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Fig. 2. The chopper is placed around the nucleus at the golden ring.
Fig. 3. The chopper and phaco tip are separated creating a successful chop.
The actual steps involved in chopping can be summarized as follows: (1) the nucleus is impaled with the phaco needle by burying the tip into lens material (foot-pedal position 3); (2) while holding the nucleus with the phaco probe (foot-pedal position 2), it is gently displaced towards the surgeon as the chopper is placed under the capsulorhexis rim around the outer edge of the nucleus at the golden ring (fig. 2); (3) the chopper is then pulled towards the phaco tip, and, just prior to contact, the two instruments are sufficiently separated to create the fracture (fig. 3).
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Results
Transitioning to phaco chop can be challenging, and therefore learning a progression of skills is helpful. A logical way to practice chopping is to first perform a divide and conquer technique and then chop each quadrant (either with a Sinskey hook or chopper). Once comfortable with the chopping maneuver, stop and chop can be quickly mastered. The advantage of this method is that, if chopping becomes difficult, the surgeon can readily convert to a standard cracking technique, since the nucleus has already been grooved and split into two halves. Finally, other methods of chopping can be attempted; however, if problems are encountered, it may be more difficult to revert to divide and conquer phaco, especially if too much of the central nuclear mass has been removed, and a bowling technique may be needed to complete nuclear removal. We have found this stepwise method of learning to chop to be an invaluable tool in teaching surgeons to make the transition to phaco chop. A number of potential pitfalls exist for phaco chop. The most feared complication is damaging the capsule during the chop. This usually involves the anterior capsule by improper placement of the chopper above or peripheral to rather than under the anterior capsule. The posterior capsule can also be torn, perhaps most commonly during removal of the last quadrant when a change in fluid dynamics may suddenly bring an unprotected posterior capsule in contact with the chopper. A less worrisome occurrence is dislodging the nucleus from the phaco tip when placing the chopper, a problem that is easily solved by increasing the vacuum setting. Finally, very hard and very soft nuclei are difficult to chop and pose unique challenges. With the hard nucleus, after propagation of the crack, the posterior nucleus often contains bridging bands that prevent complete separation. The soft nucleus typically cannot withstand the requisite high vacuum levels, and therefore it fragments and emulsifies before the phaco needle can attain an adequate purchase to initiate the chop.
Comment
Learning new techniques is always challenging, but with careful attention to case selection and practicing a straightforward progression of skills, phaco chop can become a valuable tool for nucleus removal during cataract surgery. Although this method is technically more difficult than many others, it is within the grasp of any two-handed phaco surgeon. Phaco chop is fast, dramatically reducing phaco time and potentially minimizing corneal endothelial damage from ultrasound energy [14–16]. It also causes less zonular stress than standard cracking methods and can be performed without an intact capsulorhexis. Once mastered, phaco chop can be an invaluable addition to the phaco surgeon’s armamentarium.
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References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
17 18 19 20 21 22
Kelman CD: Phaco-emulsification and aspiration: A new technique of cataract extraction: a preliminary report. Am J Ophthalmol 1967;64:23–35. Kelman CD: Phaco-emulsification and aspiration: A progress report. Am J Ophthalmol 1969;67: 464–477. Kelman CD: Phacoemulsification in the anterior chamber. Ophthalmology 1979;86:1980–1982. Emery JM, Little JH: Phacoemulsification and aspiration of cataracts. St Louis, Mosby, 1979, p 201. Little JH: Outline of Phacoemulsification for the Ophthalmic Surgeon, ed 2. Oklahoma City, Samco Color Press, 1975. Shepherd JR: In situ fracture. J Cataract Refract Surg 1990;16:436– 440. Gimbel HV: Divide and conquer – Nucleofractis phacoemulsification development and variations. J Cataract Refract Surg 1991;17:281–291. Fine IH: The chip and flip phacoemulsification technique. J Cataract Refract Surg 1991;17: 366–367. Fine IH, Maloney WF, Dillman DM: Crack and flip phacoemulsification. J Cataract Refract Surg 1993;19:797– 802. Nagahara K: Video of phacochop. Presented at the American Society of Cataract and Refractive Surgery, Seattle, May 1993. Koch PS, Katzen LE: Stop and chop phacoemulsification. J Cataract Refract Surg 1994; 20:566–570. Vasavada AR, Desai JP: Stop, chop, chop, and stuff. J Cataract Refract Surg 1996;22:526–529. Zirm ME, Salchow DJ: Double phaco chop. J Cataract Refract Surg 1999;25:732–735. Ram J, Wesendahl TA, Auffarth GU, Apple DJ: Evaluation of in situ fracture versus phaco chop techniques. J Cataract Refract Surg 1998;24:1464–1468. DeBry P, Olson RJ, Crandall AS: Comparison of energy required for phaco-chop and divide and conquer phacoemulsification. J Cataract Refract Surg 1998;24:689–692. Pirazzoli G, D’Eliseo D, Ziosi M, Acciarri R: Effects of phacoemulsification time on the corneal endothelium using phacofracture and phaco chop techniques. J Cataract Refract Surg 1996;22: 967–969. Badoza DA, Jure T, Zunino LA, Argento CJ: State-of-the-art phacoemulsification performed by residents in Buenos Aires, Argentina. J Cataract Refract Surg 1999;25:1651–1655. Noecker RJ, Allinson RW, Snyder RW: Resident phacoemulsification experience using the in situ nuclear fracture technique. Ophthalmic Surg 1994;25:216–221. Tarbet KJ, Mamalis N, Theurer J, Jones BD, Olson RJ: Complications and results of phacoemulsification performed by residents. J Cataract Refract Surg 1995;21:661–665. Corey RP, Olson RJ: Surgical outcomes of cataract extractions performed by residents using phacoemulsification. J Cataract Refract Surg 1998;24:66–72. Albanis CV, Dwyer MA, Ernest JT: Outcomes of extracapsular cataract extraction and phacoemulsification performed in a university training program. Ophthalmic Surg Lasers 1998;29:643–648. Pingree MF, Crandall AS, Olson RJ: Cataract surgery complications in 1 year at an academic institution. J Cataract Refract Surg 1999;25:705–708.
Priv.-Doz. Dr. med. Thomas Kohnen, Department of Ophthalmology, Johann Wolfgang Goethe University, Theodor-Stern-Kai 7, D–60590 Frankfurt am Main (Germany) Tel. ⫹49 69 6301 6739, Fax ⫹49 69 6301 3893, E-Mail
[email protected]
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Ultrasound-Assisted Phaco Aspiration Randall J. Olson University of Utah Health Sciences Center, Salt Lake City, Utah, USA
When I first had teenage children and our car insurance went up dramatically, I realized that the car insurance industry is interested in how many miles are driven and what the risk is per mile. This analogy holds for cataract surgery in that the most dangerous thing we do is the use of ultrasound with phacoemulsification. We can aspirate the iris, the capsule or be near the cornea with no or minimal damage; however, if we perform exactly the same maneuver and ultrasound is used, damage is usually immediate and significant. It would seem logical, therefore, that all maneuvers we use that decrease our ultrasound reliance will decrease our complication risk during cataract surgery. It is often stated that we usually break the capsule during the irrigation and aspiration phase of cataract surgery. In order to verify whether or not that was our experience, we reviewed all complications at the John Moran Eye Center for one academic year both to determine the incidence of complications and to better understand when these complications occurred [1]. What we found is that over 70% of the capsular breaks occurred during the use of ultrasound energy. This confirms our concern that it is during the use of ultrasound that we are at our greatest risk as surgeons. Dr. Bill Fishkind [pers. commun.] has also reviewed his complication rate and has come to a similar conclusion. So what alternatives do we have? Laser has been proposed as a safer modality as has phacoptemesis. While both may be a safer energy modality than ultrasound, they have had difficulty with very hard nuclei. In fact, it is our thesis that neither have much to add to the use of mechanical forces which change the nature of the disassembly of the nucleus from an ultrasound-based procedure to a mechanical-based one. Mechanical forces are something we have used for a long time and, therefore, greater utilization of these should be no surprise. Irrigation as a force maintains our anterior chamber and moves things freely around. It has been well
known that increasing the irrigation flow will make things happen much faster. Aspiration is another important mechanical force, which in the past when it was increased above very low levels would result in a surge or flattening of the anterior chamber as the pent up energy in the system resulted in a rapid efflux of fluid from the anterior chamber. The latest in phacoemulsification platforms, however, have powerful fluidic capabilities that monitor the aspiration levels and occlusion as well as decrease the kinetic energy of the system such that surge is tamed at levels of aspiration previously unheard of. Chunks of nucleus that would require significant ultrasound energy can often be aspirated without any ultrasound use. Certainly this is an important mechanical modality to help the efficiency of our surgery. Beyond irrigation and aspiration, for a long time we have used second instruments to crack the nucleus into multiple small pieces. This has usually occurred after scoring furrows in the nucleus to make the crack a simple step. Having bite-size pieces allows a safer procedure with ease of maneuverability but also clearly decreases the phacoemulsification time because as the pieces are brought down to ever smaller and smaller bite-size chunks, they often aspirate without ultrasound. Newer approaches using mechanical forces almost exclusively chop the nucleus into bite-size pieces eliminating or dramatically decreasing reliance upon ultrasound energy [2, 3]. This has been called by various names such as chop or snap or quick chop; however, the common theme for all of these approaches is mechanically splitting the nucleus without ultrasound into multiple bite-size pieces. When the pieces are small enough, ultrasound is only necessary to assist aspiration and the ultimate in mechanical energy use is to chop the nucleus into pieces so small that they can be aspirated without any ultrasound whatsoever. A new mechanical force that decreases even the small amount of ultrasound needed to assist in aspiration is with phaco chop using the second instrument to mash the pieces onto the ultrasound tip. By using slight mechanical pressure and high aspiration levels even larger pieces are often aspirated without difficulty. Mashing onto the tip with a little patience will eliminate all residual fragments without any ultrasound need (or laser or sonic energy). Ultrasound, therefore, is used minimally and only for some efficiency and is not necessary for elimination of even the hardest of the cataract pieces. Such reasoning for me has resulted in a technique with a specially-designed chopper (fig. 1) for horizontal chop with very hard nuclei with a 0° ultrasound tip used to impale the nucleus near the wound and the chopper used to cleave the nucleus cleanly in half. The first bite-size piece is removed with the chopper, usually less than 1/8 th of the total nucleus, and then mashed into the ultrasound tip with only brief bursts of ultrasound energy used only if necessary. The remaining smaller piece is then chopped into multiple small fragments usually
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Fig. 1. A 21-gauge experimental irrigating chopper, especially designed by the author for hard cataracts, that can be placed through a 0.8-mm incision (available from ASICO).
never less than four or five such that only brief bursts or often no ultrasound is necessary when both chopping and mashing are used in combination. With the first half finished, the second half can either be rotated to 180° or simply pushed so that both sides are exposed such that the chopper is placed on one side of the heminucleus and the ultrasound tip on the other side. Again, a combination of chopping and mashing, cutting the second half into at least five pieces and usually more, results in an extremely efficient procedure with minimal or no ultrasound energy used. The evolution of this technique clearly eliminates or substantially decreases ultrasound reliance such that the increased risk in association with ultrasound is virtually eliminated. The efficiency and utility is so obvious that the use of phacoptemesis or of laser would seem to add little or nothing to the overall efficiency or safety profile. Furthermore, in cases with very hard mature cataracts, the corneas with minimal ultrasound time are impressively clear suggesting minimal damage to the cornea. This prompted a new approach to cataract surgery in the face of corneal decompensation (Fuchs’ corneal dystrophy or old trauma). There has been controversy about such corneas, in particular in cases of Fuchs’ dystrophy, about whether or not cataract extraction alone should occur when the cataracts are clinically significant and the corneas are still quite clear or a combination of cataract extraction with corneal transplantation should occur. It has been well known that cataract surgery will often tip these corneas into bullous keratopathy requiring secondary penetrating keratoplasty. Most cataract surgeons have had cases of Fuchs’ dystrophy in which the cornea seemed quite clear before surgery and yet failed after surgery. At issue, therefore, was whether or not this new approach to cataract surgery could result in minimal corneal endothelial damage in cases of Fuchs’ dystrophy. We have had 2 cases with this new approach and both have had impressive results. Case 1: A 73-year-old retired general surgeon with Fuchs’ dystrophy and cataract had progressive loss of vision with difficulty functioning. He had sought three consults who had
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recommended penetrating keratoplasty at the time of cataract surgery due to the hardness of the cataract and the extent of his endothelial changes. He came to me specifically wondering if cataract surgery alone might not be possible and avoid the difficulties in association with penetrating keratoplasty. My evaluation found profound endothelial changes; however, there were no posterior folds in Descemet’s membrane and no epithelial edema throughout the day. There was a 3⫹ nuclear sclerosis in both eyes with best-corrected vision in the right eye of 20/60 and 20/50 in the left eye. We proceeded with minimal ultrasound-assisted phaco aspiration using phaco chop (right eye ultrasound time of 1 s and ⬍2 s in the left eye) and mash with a corneal scleral tunnel and retrobulbar anesthesia and use of viscoat to provide greater protection for the endothelial surface. Both corneas showed minimal edema on the first postoperative day with 20/25 uncorrected vision in the right eye and 20/40 uncorrected vision in the left eye. Within 2 weeks both corneas had cleared completely of any edema and were easily refracted to 20/20. The patient has been followed for over 1 year without any edema or difficulty. Case 2: A 68-year-old white male was referred for consideration of penetrating keratoplasty and cataract removal due to Fuchs’ dystrophy and a visually significant cataract. Visual acuity was 20/50 best corrected in both eyes. Although this patient had significant corneal endothelial changes, again, there was no epithelial edema throughout the day and no folds in Descemet’s membrane. It was decided to use phaco chop with mash and no ultrasound energy in either eye for his 2⫹ nuclear sclerosis. On the first postoperative day both corneas had epithelial edema (right eye 2⫹, left eye 1–2⫹). Visual acuity was 20/200 uncorrected and 20/80 corrected in the right eye and 20/70 uncorrected and 20/50 corrected in the left eye. Both corneas were clear and correctable to 20/20 by 2 weeks after surgery. Further follow-up is minimal to date.
Although this series is preliminary and small, certainly these results are impressive in patients with significant cataracts and Fuchs’ corneal changes. With the evolution of this technique, the ultrasound energy is turned off and the corneas have responded with minimal changes. If such are the results in such fragile corneas, then normal corneal endothelial changes should be minimal or nonexistent. We will complete prospective specular microscopy studies. While irrigation is an important mechanical force, its effect is generally negative in that the irrigation flow comes around our phaco needle often short circuiting the aspiration flow and moving particles away from our emulsification tip until we can get them in the central vortex of aspiration. We have developed this so that we can have a one-handed approach to phacoemulsification and to cool the tip to decrease the incidence of wound burns. With a combination of phaco chop and mashing the nucleus to largely eliminate or significantly decrease the use of ultrasound energy, there is no reason to have irrigation around our phaco needle. This has prompted a series of studies in regard to using an irrigating chopping instrument and a second bare phaco needle utilizing two stab incisions. Any approach such as this requires careful evaluation of the risk of creating wound burns and also whether or not we can maintain a deep anterior chamber.
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The phaco chopper is based upon 19-gauge tubing with four sets of irrigation holes such that if the first two are blocked in the nucleus then the second two holes will maintain the chamber. This combination easily delivered 80 ml/min of flow unimpeded. The irrigating chopper was introduced in eye bank eyes through a slit incision, and the bare 0° phaco needle was introduced through a second slit incision both approximately 1 mm long. Using the Allergan Sovereign machine with irrigation and aspiration at 15 ml/min and ultrasound starting at 50% power and increased in 10% increments, we continuously measured the wound temperature using a thermistor and looked for evidence of any wound burn (always noted at 45–50°C). We looked at continuous phaco and burst mode both in the unoccluded and the occluded state. Even with continuous full phaco energy, a burn could only be created in the unoccluded state at 100% energy after 160 s and in the occluded state at 80% energy in about a minute. Using a burst mode, at 100% energy, we could create a phaco burn after 42 s occluded. Intraocular pressure was monitored throughout the procedure at every 30-second interval and intraocular pressure was continuously maintained to at least 18 mm Hg showing that we had no trouble maintaining a deep chamber with good intraocular pressure in either the occluded or unoccluded states. Using an irrigating phaco chopper, the irrigation forces are now unopposed and very powerful. Any fragments immediately go to the phaco tip without having to chase nuclear fragments around the anterior chamber. There is some fluid loss from both wounds, which helps cool the phaco needle; small particles do come into that area, however, most pieces flow to the greatest outflow which is through the phaco needle. Now, irrigation alone with exquisite safety can be used to sweep nuclear particles off the capsule or out of the fornices eliminating the need to chase such particles with the much more dangerous phaco needle. This should enhance our safety and now allow wound sizes so small that they will again depend upon the size of the intraocular lens needed for insertion! This will push the technology for ever smaller intraocular lenses. One added benefit is the ability to swap sites for the phaco needle in complicated or difficult cases. In conclusion, we have determined that the use of mechanical forces is the single most important step in regard to our efficiency in cataract surgery. This either dramatically diminishes or eliminates ultrasound reliance in cataract surgery. This improves efficiency and safety by minimizing capsular, iris, or corneal endothelial damage. Such an approach (being able to perform cataract surgery through two small slit incisions with no or minimal ultrasound reliance) would seem to make either laser energy or phacoptemesis unimportant in the evolution of cataract extraction.
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Acknowledgments Supported in part by a grant from Research to Prevent Blindness, Inc., New York, N.Y., to the Department of Ophthalmology and Visual Sciences, University of Utah.
References 1 2
3
Pingree M, Crandall AS, Olson RJ: Cataract surgery complications in one year at an academic institution. J Cataract Refract Surg 1999;25:705–708. DeBry P, Olson RJ, Crandall AS: Phaco chop and divide and conquer cataract extraction: A prospective comparison of phacoemulsification energy. J Cataract Refract Surg 1998;24: 689–692. Wong T, Hingorani M, Lee V: Phacoemulsification time and power requirements in phaco chop and divide and conquer nucleofractis techniques. J Cataract Refract Surg 2000;26:1374–1378.
Randall J. Olson, MD, Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, 50 North Medical Drive, Salt Lake City, UT 84132 (USA) Tel. ⫹1 801 585 6622, Fax ⫹1 801 581 3357, E-Mail
[email protected]
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Management of the Mature Cataract Samuel Masket Jules Stein Eye Institute, UCLA, Los Angeles, Calif., USA
The mature cataract may represent one or both of two clinical entities. The cortical mature cataract (fig. 1) has opaque, milky white, (potentially) liquefied cortex that, at surgery, obscures the red reflex and the nature of the underlying lens nucleus. The nuclear mature cataract (fig. 2) contains an ultrafirm and visibly dark lens nucleus in which an epinucleus cannot be easily delineated and little to no cortex remains; it may consist virtually of ‘rock-hard’ nuclear lens material and lens capsule. Given that a very dark cataract can obscure the red reflex and that a white cataract may harbor an ultradense nucleus, there may be crossover between the two entities. Mature cataracts pose certain challenges to the surgeon and add surgical outcome risks to patients. Because phacoemulsification may be anything but routine in these cases, ophthalmologists have historically considered alternative surgical methods when faced with mature cataracts of either type. Nevertheless, observant presurgical evaluation, careful surgical planning, and skillful and diligent surgical technique can combine (with good fortune) to afford the patient the opportunity for rapid visual and physical recovery by means of small incision cataract surgery. Patients contemplating surgery for a mature cataract should be counseled regarding the likelihood for increased surgical time, a slower recovery of vision postoperatively, and an increased risk for intraoperative complications. Likewise, the surgeon must be properly prepared for the increased demands necessary for successful small incision surgery in these cases. This article was first published in Fishkind WJ (ed): Complications in Phacoemulsification. New York, Thieme Medical Publishers, 2001, pp 109–115. Reprinted with permission.
Fig. 1. Cortical mature white cataract. Note the white lens. Additionally, an iridodialysis can be noted to the left indicating the traumatic nature of this cataract.
Fig. 2. Nuclear mature cataract. Note absence of red reflex and firm greenish brown nucleus that extends to the lens periphery.
Cortical (Intumescent) Mature Cataracts
The etiology of the cortically mature cataract is generally unknown, but the condition is characterized by hydration of lens cortex sufficient for the cortical
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lens fibers to become swollen and opaque milky white. In the extreme case the lens cortex becomes fully liquefied, leaving only a small firm floating nucleus within a sac of white fluid; this rare special condition is referred to as a morgagnian cataract. It is uncertain why certain cataracts become cortically mature unless a specific rent in the capsule can be identified. However, the likely final common pathway is the mixture of aqueous humor with lens material. Cases without demonstrable trauma or physical openings in the lens capsule have, most likely, imbibed aqueous through the ordinarily semipermeable lens capsule. In these cases the lens generally swells, inducing an increased hydrostatic or ‘intralenticular pressure’. Lens swelling may be sufficient to cause narrowing of the chamber angle and the potential for phacomorphic glaucoma. Raised pressure within the capsular bag (or the eye) is but one factor that can complicate surgery in this group of patients. Capsulorhexis can be very difficult, given that the capsule may be very friable and readily tear to the equator, since the capsule is ‘stretched’ by the increased water content of the lens. Furthermore, the surgeon is hindered by the absence of the red reflex, making capsulorhexis yet more challenging. Finally, these case types may be problematic since the density of the nucleus is obscured and cannot be evaluated until after the anterior capsule has been opened. Should the nucleus be very hard, phacoemulsification presents added risks since no epinucleus is present and the milky cortex may tend to wash out, leaving no protective cushion for the posterior capsule during the emulsification process. The surgical approach to the cortically mature cataract begins with the preoperative evaluation. Gross presurgical vision testing can be assessed with two-point white light discrimination, perception of color with bright light, and entoptic phenomena. Additionally, the condition of the corneal endothelium should be evaluated with specular microscopy or slit lamp examination, since it may be necessary to elevate the nucleus into the anterior chamber during surgery, should the capsulorhexis fail, the posterior capsule rupture, etc. If the nucleus is very firm and the endothelium poor, emulsification in the anterior chamber may be contraindicated. Lastly, the preoperative evaluation should rule out phacolysis with lens-induced inflammation and secondary elevation of intraocular pressure. In that case intensive topical steroids and/or ocular hypotensive agents may be necessary prior to surgery. Phacomorphic angle closure from an intumescent white lens may require laser iridotomy prior to surgery. Anterior capsulorhexis remains the most important and the most challenging aspect of the surgery. Generally, if one can complete the capsulorhexis, all else is likely to succeed. The factors that make the capsulorhexis difficult, as discussed above, include poor visibility and the friable nature of the capsule, particularly if it is under tension from increased hydrostatic pressure within the capsular bag. The surgical ‘game plan’ must consider these issues.
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Table 1. Methods to enhance visibility during capsulorhexis
Alter microscope parameters Increase magnification Reduce focus speed Reduce zoom speed Reduce X-Y speed Turn off room lights Liberal use of viscoagent Side lighting – retinal endoilluminator Stain the anterior capsule Indocyanine green (ICG) Trypan blue Fluorescein sodium Methylene blue Gentian violet Brilliant green Autologous blood
Table 1 lists the presently available options for increasing visibility during the capsulorhexis. The surgeon should alter the parameters of the microscope, increasing magnification and slowing the motorized changes in magnification, zoom, and X–Y position. In that manner the cut edge of the capsule may be kept in the surgeon’s view. Additionally, reducing the ambient room lighting will eliminate glare and improve the visibility of the events occurring in the anterior chamber. Another commonly encountered problem of visibility may occur when the capsule is first punctured, as liquefied cortex may escape from the capsular bag and mix with the aqueous or the viscoagent. This may be prevented by ‘overfilling’ the anterior chamber with a highly retentive viscoagent prior to initiating the capsule tear. This also helps to avoid peripheralization of the capsulotomy by creating a tamponade against the rapid escape of milky cortex arising from high ‘intralenticular’ pressure. Additionally, when working with an intumescent white cataract, the surgeon may consider making a small circular capsulotomy initially and enlarging it later when the risks of peripheralization are reduced. Should cortex enter the chamber during capsulorhexis, and preclude an adequate view, it may be necessary to move it out of the way with additional viscoelastic or evacuate it with the I/A handpiece or cannula. Viscoelastic agents vary in their clinical behavior according to their chemical composition. Although individual stages of the surgery may require different viscocharacteristics, the optical clarity, cohesiveness, and high viscosity of Healon 5 (Pharmacia-Upjohn) at zero shear make it an excellent agent for capsulorhexis in cases with white cataract. However, once the emulsification process is initiated, a dispersive viscoagent may be useful to protect the
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endothelium and capsule if the nucleus is firm; Viscoat (Alcon) performs well under these circumstances, but might reduce visibility as it traps bubbles and liquefied lens cortex. The key factor in determining successful completion of a circular anterior capsulotomy (capsulorhexis) in cases with white mature cataracts is visualization of the anterior capsule and the advancing torn edge of the capsule. Historically, the use of a retinal endoilluminator, held tangential to the limbus, has been helpful in aiding the capsule tear (fig. 3a, b) [1]. Nevertheless, in my own experience, the endoilluminator method succeeds in less than 100% of cases. More recently, vital staining of the anterior capsule with either indocyanine green (ICG) or trypan blue has been popularized; this method is virtually always successful. ICG is readily available as an intravenous agent for retinal angiography and renal and hepatic imaging. Horiguchi et al. [2] have developed a system for its dilution, preparation and use in cataract surgery. It is essential to follow the prescribed method, as ICG can be modestly toxic to the corneal endothelium. As initially reported by Melles et al. [3], trypan blue is an excellent stain for the anterior capsule in cases of mature cataract. It is commercially available as a liquid in sterilized unit dose vials, is less costly than ICG, safe with respect to the endothelium and provides excellent contrast between the stained capsule and the underlying opaque or milky white lens cortex, as can be noted in figure 4. Given its advantages, trypan blue has become the method of choice for management of cortically mature cataracts. Nonetheless, it is presently unavailable in the USA, as the FDA has not evaluated it or approved its use. Other dyes for capsule staining (table 1) are either more toxic or less efficacious. Following capsule staining, the capsule tear should be initiated under a retentive viscoelastic in the center of the anterior lens capsule in order to prevent peripheralization at the outset of the capsulotomy. Furthermore, if liquefied cortex escapes from the lens and obscures an adequate view, it is wise to aspirate the material or push it aside with additional viscoagent. In rare situations, all of the liquefied cortex may exude from the capsule bag and require removal before the capsulotomy can be completed; in such cases, after evacuating the cortex, the capsule can be filled with viscoelastic, making the surgery technically feasible. Hydrodissection is often unnecessary in cases of white cataracts, as the liquefaction process may have sufficiently eliminated cortical-capsular adhesions. The surgeon should attempt to rotate the nucleus after capsulorhexis; if the nucleus is immobile, cautious hydrodissection is necessary (fig. 5). Given the friable nature of the capsule in these cases, hydrodissection must be approached with great care in order to prevent rupture of the capsule; small aliquots of BSS should be injected very slowly to prevent elevation of lens hydrostatic pressure. Furthermore, cases with recent trauma are likely to have a
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Fig. 3. a Intraoperative view of mature cataract with poor view of capsular and anterior cortical details. b Retinal endoilluminator placed tangential to the limbus creates sclerotic scatter and markedly improved view of the capsular and cortical details.
capsule rent which may be extended with aggressive hydrodissection; posterior lens dislocation is an unfortunate, but possible sequel. On the other hand, a case of old trauma may demonstrate a fibrotic lens capsule (membranous cataract) and partially absorbed lens cortex. Hydrodissection may not be possible in cases of this nature.
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Fig. 4. Intraoperative view of capsulorhexis after staining of the anterior capsule with trypan blue. Note that the capsule is easily visualized and contrasts well with the underlying white cortex.
Fig. 5. Following capsulorhexis, careful hydrodissection may be performed with a blunt cannula to avoid tearing the fragile anterior capsule.
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Nuclear emulsification may be carried out with the most appropriate strategy for the given case; nuclear chopping methods reduce the total amount of ultrasound necessary for lens disassembly. Care must be taken to avoid damage to the anterior capsule rim, the equatorial capsule, and the posterior capsule. Occasional addition of viscoelastic during the emulsification process can be very protective. Also, the nuclear fragments and sharp edges should be brought away from the posterior capsule and into the central aspect of chamber before emulsification; the center offers the furthest distance from both the posterior capsule and the corneal endothelium. If the lens nucleus is particularly dense and no cortex remains, anterior chamber or iris plane emulsification should be considered, although the presurgical status of the corneal endothelium must be factored. In very rare circumstances, it might be safest to remove the nucleus manually, particularly if capsular integrity is compromised. Cortex removal following nuclear emulsification is rarely challenging in cases with white cataracts. Nevertheless, it is common to encounter resistant fibrotic plaques on the posterior capsule. These may be left alone, or, in rare circumstances, a posterior capsulorhexis may be performed. Following ‘cortical clean-up’, lens implantation can be performed routinely. Postoperative management should present no unusual hurdles unless preoperative lens induced inflammation or elevation of IOP continue after surgery.
What to Do When Things Go Wrong
The most frequent complication, as it were, is failure to complete a smoothedged continuous tear anterior capsulotomy. The capsulotomy may be completed by the ‘can-opener’ method or by starting another capsulorhexis in the opposite direction, if possible. Added care must be taken when carrying out nuclear emulsification in cases without continuous capsulotomy. Given generally poor visibility, a friable capsule, little to no cortical or epinuclear cushion, my preference is to bring the nucleus into the anterior chamber with a ‘tire-iron’ maneuver, using the viscoelastic agent with its cannula. Anterior chamber emulsification is performed unless the lens is extraordinarily dense and/or the endothelium significantly compromised preoperatively. Under those circumstances, manual removal of the nucleus is a safer option. In that case, it may be wise to abandon the temporal clear corneal incision and prepare a sclerocorneal incision superiorly for best wound and astigmatism management. Also, removal of the nucleus, in this situation, is properly managed with a vectis, loop, or spoon rather than by expression since the firm, large nucleus may tear the capsule or rupture zonules during the expression maneuver. In fact, cases of this nature are at added risk for posterior dislocation of the nucleus during attempted expression.
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The Nuclear Mature (Brunescent) Cataract
Brunescent nuclear cataracts can progress to very advanced stages while producing little apparent loss of visual function. Most patients with nuclear cataract experience reduced distance vision, notice difficulty seeing at night and complain of glare symptoms. These cases generally have increased nuclear opalescence mixed with other forms of cataract. However, in some eyes the nucleus changes very gradually from clear to dark brown or black, passing through stages of yellow to deep red. In some of these cases, particularly those without nuclear opalescence, there is little distortion, glare, or relative loss of night vision; the patients are often tolerant of the slowly evanescent reduction in contrast sensitivity and color perception associated with this cataract type. The net result is that the surgeon may be confronted with the paradox of a very advanced cataract and a relatively asymptomatic patient. On one hand, cataract extraction should be performed before the surgery becomes extraordinarily risky, yet the patient may perceive little need for the proposed surgery, even though visual function may be significantly reduced. A nuclear cataract may be considered as mature when an epinucleus cannot be defined with routine hydrodelineation. Additionally, the maturation process may advance to where lens cortex is minimal, or, nearly nonexistent. These cases present added challenges intraoperatively with regard to the capsulorhexis, hydrodissection, and lens emulsification in particular. Furthermore, even in cases without surgical complication, there is the potential for prolonged recovery of vision postoperatively, owing to an increased likelihood for transient corneal edema following prolonged phacoemulsification.
Surgical Management
Surgical treatment for cases with nuclear mature cataracts begins with careful presurgical evaluation and planning. Certain factors must be considered. These include the depth of the anterior chamber and the preoperative condition of the corneal endothelium. Prolonged emulsification time, almost unavoidable with advanced brunescent cataracts, will place a significant burden on the survival of the cornea, should the chamber be shallow or the endothelium already compromised. Likewise, lengthy emulsification might be accompanied by significant zonular traction with an attendant potential for long-term complications, particularly if the presurgical condition of the zonules is compromised, as in some cases with pseudoexfoliation. Therefore, in light of these few examples alone, preoperative examination should be considered as an integral part of the surgical management of nuclear mature cataracts.
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Capsulorhexis can be challenging should the red reflex be obscured by the extraordinary density of the lens nucleus. In that case, it is advisable to consider any or all of the ‘tricks’ for enhanced visibility of the capsulotomy in cases with white mature cataracts (see above). The capsulotomy should be generous in size, perhaps larger than usual in order to avoid damage to the anterior capsular rim during emulsification and to facilitate removal of the nucleus from the capsule bag should it be necessary for any reason (ruptured posterior capsule, etc.). I generally aim for a centered anterior circular capsulorhexis of 6.0 mm or more with these cases, whereas in the routine situation I prefer the capsulotomy to be roughly 5.0–5.5 mm. Hydrodissection must be carried out with great caution. In the ‘garden variety’ cataract case, the epinucleus and cortex can act as a reservoir for the injected fluid during the hydrodissection. However, in the situation of a mature nuclear cataract, there is little more than a thin lens capsule and a firm nucleus (fig. 2). As a result, there is no cushion or ‘sponge’ to absorb excess fluid as it is injected during hydrodissection; a bolus of BSS, having no opportunity to be absorbed, can ‘blow out’ the thin posterior capsule. Alternatively, if the BSS is injected slowly and in judicious amounts, the fluid can cleave the nucleus from the cortex and capsule without incident. Nuclear emulsification will take added time, care, and patience when compared with the routine situation. When planning the surgical day, one should recognize that phacoemulsification of mature cataracts potentially takes longer than for typical cases. Recognizing and planning for the needed extra time will relieve, to some extent, the added stress of dealing with cases of this nature. While there has been a general trend toward nuclear chopping and away from traditional ‘divide and conquer’ sculpting methods for nuclear disassembly, chopping of very dense nuclear cataracts can be difficult and potentially dangerous, given that most chopping instruments are not sharp enough or long enough to adequately penetrate a very dense nucleus. Furthermore, the added torque needed to chop a large ‘rock-hard’ nucleus is likely to add undesirable stress on the zonules. Therefore, I prefer to sculpt and hemidivide nuclear mature cataracts before chopping the segments (fig. 2). Sculpting is facilitated by using a tip with an increased cutting angle for greater efficiency. Also, use of increased emulsification energy will facilitate the sculpting process which should be carried out deeply into the central nucleus. The latter maneuver allows the nucleus to be ‘cracked’ for disassembly. Furthermore, when sculpting a firm nucleus, only a small amount of tissue should be removed with each pass in order to avoid zonular stress. A worthwhile adage suggests that ‘nuclear tissue should be removed rather than moved’ during sculpting. Finally, I add a highly retentive dispersive viscoagent (Viscoat, Alcon) to the chamber on several occasions during the emulsification process. This technique yields added
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protection to the cornea and capsule during surgery, but increases the risks for incisional burns. During nuclear sculpting I partially debulk the center of the lens and create a central trough which is used for the initial crack, creating two heminuclei. Should the nucleus fail to crack, it is generally necessary to sculpt deeper. Hard cataracts are notoriously difficult to divide as the lens is noted to have ‘leathery’ posterior bridges and adhesions when cracking is attempted. Surgeons attempt a variety of personal tricks when confronted with a ‘noncracking’ nucleus. Following successful hemidivision of the nucleus, the two pieces may be sculpted and divided or chopped, varying with conditions, equipment, and the surgeon’s experience. For very dense cataracts I prefer to sculpt and divide into four or more equal size pieces before removing any of the segments, since it is easier to rotate the lens as a single unit. Prior to removing the fragments I add viscoelastic to the chamber. The segments are brought forward with a spatulated instrument through a paracentesis. I attempt to raise the sharp angulated portion of the nuclear piece away from the posterior capsule rather than have it sweep against the capsule and risk capsule rupture. I employ high vacuum fluidics to facilitate aspiration and I bring the free nuclear piece into the center of the chamber, so that emulsification can be carried out in the deepest portion of the chamber, giving the greatest possible protection to the cornea and the posterior capsule. In order to prevent wound burn during this case type, it is necessary to work with an incision of adequate width, allow adequate BSS (chilled) exchange, clear a path through the viscoagent (with irrigation and aspiration) prior to emulsification, and avoid (prolonged) tip occlusion by using ‘pulsed phaco’ when removing the quadrants. As a rule, newer, reduced dimension microtips are not ideal for emulsification of cases of this type since the tip occludes readily, potentially risking wound burn, and the small internal diameter of the tip prolongs removal of the bulky, dense cataract. Following nuclear emulsification, cortex removal and lens implantation should be routine. Small incision cataract surgery provides rapid and stable optical recovery [4]. Advantages accrue to the patient, to the surgeon, and to society. Fortunately, by adhering to the above guidelines and suggestions, patients with mature cataract of both types may, in many cases, be managed as routine and can expect excellent return of visual function after surgery.
References 1 2
Mansour AM: Anterior capsulorhexis in hypermature cataracts (letter). J Cataract Refract Surg 1993;19:116 –117. Horiguchi M, Miyake K, Ohta I, Ito Y: Staining of the lens capsule for circular continuous capsulorrhexis in eyes with white cataract. Arch Opthalmol 1998;116:535–537.
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3 4
Melles GRJ, de Waard PWT, Pameyer JH, Beekhuis WH: Trypan blue capsule staining to visualize the capsulorhexis in cataract surgery. J Cataract Refract Surg 1999;25:7–9. Masket S, Tennen DG: Astigmatic stabilization of 3.0 mm temporal clear corneal cataract incisions. J Cataract Refract Surg 1996;22:1451–1455.
Prof. Dr. Samuel Masket, Private Office, 2080 Century Park East, Suite 911, Los Angeles, CA 90067 (USA) Tel. ⫹1 310 229 1220, Fax ⫹1 310 229 1222, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 97–105
Phacoemulsification in the Vitreous Cavity José Mª Ruiz-Moreno, Jorge L. Alió Alicante Institute of Ophthalmology, Alicante, and Department of Ophthalmology, Miguel Hernández University, Medical School, Alicante, Spain
The phacoemulsification technique described by Kelman [1] in the 1960s is at the present moment the technique of choice for the surgical treatment of cataract [2]. Among its most important complications we should mention the dislocation of the nucleus lens or a fragment of the same in the vitreous cavity. Although it forms a not very frequent complication, it does pose an important problem for the surgeon and the patient, since in these cases an important inflammatory reaction appears and a very high incidence of glaucoma, uveitis and retinal problems such as cystoid macular edema and retinal detachment [3–5]. The loss of nucleus in the vitreous is produced either by rupture of the posterior capsule or by rupture of zonular fibers [6]. The published incidence of this complication is very variable, oscillating between 0.4 and 18% [7], generally in relation to the learning curve of the surgeon in the use of phacoemulsification techniques [8]. Three-port pars plana vitrectomy is at the moment the best strategy for resolving this problem [9–11], although there are various alternatives to it. We report here our experience in the extraction of the dislocated nucleus in the vitreous by means of vitrectomy and phacoemulsification in the vitreous cavity.
Patients and Methods Patients Twelve patients aged between 59 and 78 years (average 70 ⫾ 8.7) were operated on by vitrectomy with phacoemulsification for the extraction of the nucleus or fragments of the same from the vitreous cavity in the Instituto Oftalmológico Alicante by one surgeon (JMR-M). In all cases the patients had been operated on for cataract by clear cornea phacoemulsification
Fig. 1. Dislocated hard nucleus in the vitreous cavity.
Fig. 2. Dislocated nucleus and cortical material in the vitreous cavity. technique, there being 6 men and 6 women. Those patients who presented only dislocation of cortex material have been excluded. In no case had an intraocular lens been implanted. The time lapse between the cataract surgery and vitrectomy varied between 1 and 24 days (average 13 ⫾ 10). Six of the patients presented a dislocation of more than 80% of the nucleus according to our exploration with indirect ophthalmoscopy and 6 of them between 80 and 50% of the nucleus (fig. 1, 2).
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On previous evaluation, 9 patients presented an increase of intraocular pressure, 7 inflammatory reactions from mild to severe, 1 case presented a mild corneal edema and in no case was there a vitreous hemorrhage. In all cases the nucleus or its fragments were visible by indirect ophthalmoscopy.
Indications for Surgery The primary indication for vitrectomy was in all cases the decrease of visual acuity due to vitreous opacification generated by the presence of the nucleus and the inflammatory reaction. The cases with a rise in the intraocular pressure were treated by topical medication as was the associated inflammatory reaction in some of them. In 1 case a mild corneal edema existed which did not enable a detailed visualization of the fundus eye, delaying the vitrectomy surgery for 24 days, the date by which the cornea had recovered sufficient transparency to perform the vitreous surgery without problems.
Surgical Technique We performed three-port pars plana vitrectomy under local anesthesia (peribulbar) on an outpatient basis. At the same time we used a 30° light pipe pick to help us in the manipulation of the nucleus within the vitreous cavity and a wide field visualization system. As a first step we performed a complete vitrectomy starting it by completely eliminating the residual cortical lens material and prolapsed vitreous in the anterior chamber cleaning thoroughly all the vitreous fibers which might have remained attached to the corneal incision. After that we filled the anterior chamber with viscoelastic material to protect the corneal endothelium. We paid special attention to thoroughly cleaning the remains of the cortical material from under the iris and in the capsular remains, trying to preserve these as much as possible for the implantation of a posterior chamber intraocular lens. A complete vitrectomy is mandatory to avoid the incarceration of vitreous strands in the phacoemulsification tip with tractions on the retina and interferences with its aspiration. The second step consisted in lifting the nucleus and the residual cortical material (on occasion the cortical material mixed with the vitreous has been eliminated with the vitrectomy tip) by means of the injection of perfluorocarbon liquid, to place the nucleus in the center of the vitreous cavity (fig. 3). The use of this product offers us two advantages: the first protects the retina from possible impacts produced by the projection of hard nuclear fragments during its phacoemulsification and protects the retina reflecting at the surface of the perfluorocarbon bubble the ultrasound energy, provided that the sound probe is not immersed in the liquid [12]. We then proceeded to phacoemulsify the nucleus (fig. 4, 5) by means of the ultrasound tip ‘Micro Tip’ (the diameter of the same without infusion is 0.9 mm) using a bimanual technique with the 30° endoillumination pipe pick, with low ultrasound energy, pulsed mode, employing the following parameters: energy 75% in lineal mode, aspiration 200 mm Hg and 10 pps. During this step we avoided the appearance of burns in the sclerotomy by means of the continuous escape of infusion liquid by the same, since its size (1.4 mm, 20 G) is greater than the size of the Micro Tip needle (0.9 mm), allowing the escape of the liquid through it. The third and last step of surgery consists in the implantation of an intraocular lens (foldable if possible) by the reopening of the corneal incision (clear cornea) on the capsular
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Fig. 3. Injection of a bubble of perfluorocarbon liquid in the vitreous (arrows).
Fig. 4. Phacoemulsification of the nucleus by means of the ultrasound tip ‘Micro Tip’ using bimanual technique with the 30° endoillumination pipe pick, with low ultrasound energy.
remains (fig. 6, 7), if they permit a sufficiently stable base. Subsequently we eliminated the perfluorocarbon liquid and carried out a minute exploration of the peripheral retina by indentation (the use of wide field during surgery gives complete control of the whole vitreous cavity). On finding a retinal tear, we proceed to its endophotocoagulation and fluid gas exchange.
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Fig. 5. Phacoemulsification of the nucleus in the vitreous cavity.
Fig. 6. Implantation of a foldable posterior chamber intraocular lens on the capsular remains.
Results
Of the 12 cases we reached a final best corrected visual acuity (BCVA) of 5/10 or better in 5. In 6 cases the final BCVA obtained varied between 4/10 and 1/10. Only in 1 case was the final BCVA of 0.05 due to the existence of high myopic atrophic maculopathy. One case required treatment with
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Fig. 7. Posterior chamber intraocular lens at the end of vitrectomy and phacoemulsification to extract a nucleus from the vitreous cavity (arrows: capsulorhexis).
panretinophotocoagulation (endolaser) during vitrectomy since the patient was diabetic with preproliferative diabetic retinopathy. Intraoperatively in 1 case we detected the existence of a retinal tear in the upper temporal quadrant (right eye), proceeding to its treatment with endolaser and fluid gas exchange, without retinal detachment in the early postoperative period and until now. In 10 of the 12 cases we implanted a posterior chamber intraocular lens on the capsular remains. In 1 case the intraocular lens was not implanted since the patient was highly myopic and there was not sufficient capsular support. In another case these remains did not permit a sufficiently stable base for the intraocular lens implantation. Consequently it was implanted in the anterior chamber (fig. 8). In the postoperative period in no case did corneal edema appear, topical treatment being necessary to control the intraocular pressure in a continuous way in 3 cases. One patient developed in the early postoperative period (35 days) regmatogenous retinal detachment by retinal tear in the lower nasal quadrant which was treated by scleral buckling, vitrectomy with fluid gas exchange and tear endophotocoagulation, achieving a flat retina and reaching a final BCVA of 0.2.
Comment
As we have already indicated previously, the dislocation of the nucleus or a fragment of it in the vitreous cavity is an infrequent complication (between 0.4 and
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Fig. 8. Anterior chamber intraocular lens 30 days after vitrectomy and phacoemulsification to extract a nucleus from the vitreous cavity.
18%) [7], that is usually associated with phacoemulsification more frequently than other forms of cataract extraction [5, 8], with a likely relationship to the surgical experience of the surgeon performing the technique [5]. Various factors favor the appearance of this complication apart from learning the technique [5, 13], such as capsular pseudoexfoliation, hard nucleus and previously vitrectomized eyes [2]. The treatment of the nucleus fragments remains controversial. Small fragments well tolerated without uveitis, glaucoma or loss of visual acuity can be followed, however, the delay in eliminating the lens remains may induce chronic glaucoma [3, 14], chronic inflammation or cystoid macular edema [3]. Nevertheless, vitrectomy obtains better functional results in the long term than the nonoperated eyes, despite a better a priori tolerance [10]. In the same way vitrectomy achieves less incidence of glaucoma and uveitis compared with the previtrectomy evaluation [9, 15]. Using the technique of three-port pars plana vitrectomy, two methods have been suggested to eliminate the nucleus or its fragments from the vitreous cavity. The first consists in lifting the nucleus after vitrectomy by means of injection of perfluorocarbon liquid up to the pupillary plane and to extract it reopening the corneal or sclerocorneal incision [16–18]. After the protection of the corneal endothelium with viscoelastic material, the nucleus is extracted with the handle [2]. This process has been recommended for very hard nuclei or when regmatogenous retinal detachment coexists [16]. However, it has two disadvantages in our opinion: firstly, having to open the capsulorhexis if it exists,
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with the consequent loss of support for subsequent implantation of a posterior chamber intraocular lens and, secondly, the reopening of the corneal incision implies additional endothelial trauma and induction of astigmatism (the incision must be large enough to allow the exit of the nucleus) [19]. The second method is the elimination of the nucleus and its fragments by phacoemulsification in the vitreous cavity [4, 6, 7, 10, 11, 20]. The advantages of this technique are: maintenance of the capsulorhexis [4], non-reopening of the corneal incision [4, 19] and good control of intraocular pressure during the whole procedure by separate infusion port [6]. However, the use of ultrasound in the vitreous cavity implies risks. Retinal damage may occur when ultrasound is used at therapeutic intensities [21]. Histological studies have shown that acoustic energy at low intensities induces lesions in the outer and inner segments of photoreceptors cells. These lesions appear as a discrete pigment reaction visible by indirect ophthalmoscopy [21]. With a greater energy level we can produce a retinal tear and with high energy level we can cause rupture of all the layers of the retina, with tear of choroidal vessels and bleeding into the vitreous cavity [21]. In our series, 41.5% of the cases have reached a final BCVA of 5/10 or better. These results are comparable to those published in series similar to ours in which the authors obtain between 32 and 68% of cases with 5/10 or better [2, 3, 7, 13]. However, 50% only reached between 4/10 and 1/10 and in 1 case the final BCVA was 0.05. Similar results were also obtained by others [2]. The incidence of regmatogenous retinal detachment in our series (1 case, 8.3%) is the same as the data published for retinal detachment after this technique from 5 to 17% [4, 6, 7, 11]. The use of topical medication to control the intraocular pressure was necessary in 25% of our cases. Other authors have needed chronic medication for glaucoma between 7 and 25% [4, 6, 7, 11]. There is no agreement in the published data with the time lapse between cataract surgery and vitrectomy. In our opinion, vitrectomy must be carried out as soon as possible provided that the visualization conditions are sufficient to perform the vitreous surgery without problems, maintaining the control of inflammation and intraocular pressure with topical medication until vitrectomy. Similarly, we prefer that the anterior segment surgeon should not implant the intraocular lens, since the absence of the same enables us to perform a better cleaning of the anterior chamber and a better visualization. Conclusion
In our opinion the treatment of a dislocated nucleus or a fragment of it should be performed by an expert vitreoretinal surgeon. The technique of choice is vitrectomy with phacoemulsification of the nucleus in the vitreous cavity, Ruiz-Moreno/Alió
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followed by posterior chamber intraocular lens implantation. The use of perfluorocarbon liquids during the vitrectomy, although not necessary, protects the retina. References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
19 20 21
Kelman CD: Phaco-emulsification and aspiration. A new technique of cataract removal. A preliminary report. Am J Ophthalmol 1967;64:23. Leaming DV: Practice styles and preferences of ASCRS members – 1994 Survey. J Cataract Refract Surg 1995;21:378 –387. Blodi BA, Flynn HW Jr, Blodi CF, Folk JC, Daily MJ: Retained nuclei after cataract surgery. Ophthalmology 1992;99:41– 44. Morel C, Roman S, Metge F, Barale O, Quenot S, Sepulveda Y: Chirurgie des luxations nucléaires intravitréennes post-phacoémulsification. J Fr Ophtalmol 1998;21:170–175. Michels RG, Shacklett DE: Vitrectomy technique for removal of retained lens material. Arch Ophthalmol 1977;95:1767–1773. Röver J: Phacoemulsification of a nucleus in the vitreous cavity. J Cataract Refract Surg 1997;23: 985–989. Gilliland GD, Hutton WL, Fuller DG: Retained intravitreal lens fragments after cataract surgery. Ophthalmology 1992;99:1263–1269. Emery JM, McIntyre DJ: Extracapsular Cataract Surgery. St Louis, Mosby 1983, pp 340–358. Hutton WL, Snyder WB, Vaiser A: Management of surgically dislocated intravitreal lens fragments by pars plana vitrectomy. Ophthalmology 1978;85:176–189. Lambrou FH, Stewart MW: Management of dislocated lens fragments during phacoemulsification. Ophthalmology 1992;99:1260 –1262. Fastenberg DM, Schwartz PL, Shakin JL, Golub BM: Management of dislocated nuclear fragments after phacoemulsification. Am J Ophthalmol 1991;112:535–539. Movschovich A, Berrocal M, Chang S: The protective properties of liquid perfluorocarbons in phacofragmentation of dislocated lenses. Retina 1994;14:457–462. Kim JE, Flynn HW Jr, Smiddy WE, Murray TG, Rubsamen PE, Davis JL, Nicholson DH: Retained lens fragments after phacoemulsification. Ophthalmology 1994;101:1827–1832. Epstein DL: Diagnosis and management of lens-induced glaucoma. Ophthalmology 1982;89: 227–230. Peyman GA, Raichand M, Goldberg MF, Ritacca D: Management of subluxated and dislocated lenses with the vitrophage. Br J Ophthalmol 1979;63:771–778. Lewis H, Blumenkranz M, Chang S: Treatment of dislocated crystalline lens and retinal detachment with perfluorocarbon liquids. Retina 1992;12:299–304. Van Effenterre G, Lemer Y, Lacotte JL et al: Luxation postérieure du cristallin ou d’un implant. Traitement chirurgical utilisant un perfluorocarbone liquide. J Fr Ophtalmol 1992;15:337–342. Greve MDJ, Peyman GA, Mehta NJ, Millsap CM: Use of perfluoroperhydrophenanthrene in the management of posteriorly dislocated crystalline and intraocular lenses. Ophthalmic Surg 1993;24: 593–597. Ruiz-Moreno JM: Repositioning dislocated posterior chamber intraocular lenses. Retina 1998;18: 330–334. Wong D, Briggs MC, Hickey-Dwyer MU, McGalliard JN: Removal of lens fragments from the vitreous cavity. Eye 1997;11:37– 42. Bopp S, El-Hifnawi ES, Bornfeld N, Laqua H: Retinal lesions after transvitreal use of ultrasound. Fortschr Ophthalmol 1991;88:442– 445.
Prof. Dr. José Mª Ruiz-Moreno, Instituto Oftalmológico de Alicante, Universidad Miguel Hernández (Vitreo-Retinal Unit), Avenida de Denia 111, E–03015 Alicante (Spain) Tel. ⫹34 902 333 344, Fax ⫹34 965 260 530, E-Mail
[email protected]
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Capsular Tension Ring as Adjuvant in Phacoemulsification Surgery Gonzalo Muñoz, Jorge L. Alió Alicante Institute of Ophthalmology, Alicante, and Department of Ophthalmology, Miguel Hernández University, Medical School, Alicante, Spain
The surgical management of the cataract in the presence of significative zonular dehiscence represents a real challenge for the ophthalmic surgeon. The adjunctive therapy in addressing subluxated cataracts is use of a capsular tension ring. First introduced in 1991, the capsular tension ring is a polymethyl methacrylate (PMMA) incomplete ring-shaped intraocular implant with expanded ends that contains positioning holes. When it is placed in the capsular bag, which is approximately 10.0 mm in diameter, the ring stretches the bag, delivers the forceps applied to any point of the bag to the entire zonular apparatus, and protects individual zonules from excessive stretching [1]. It also makes the surgery safer by maintaining the capsular bag in place during all the phases of the phacoemulsification [2, 3]. In the long term, the capsular tension ring counteracts the centripetal force of constriction of the capsulorhexis made by metaplasia and fibrosis of residual epithelial cells of the remaining anterior capsule. The capsular tension ring may also have a role in the prevention of posterior capsule opacification depending upon the design of its borders [4]. Band-shaped endocapsular rings may also provide better outcomes in pediatric cataract surgery [5]. Finally, there are especially designed capsular rings with integrated tinted sector shields that can be used in the case of aniridia or iris colobom.
Methods Case 1 A 52-year-old man with high myopia in both eyes came seeking for refractive surgery. Preoperative examination yielded an uncorrected visual acuity of 20/400 in both eyes.
Fig. 1. Right eye, patient 1. Complete closure of the anterior capsule opening by a fibrous plaque 2 months after phacoemulsification and IOL implantation without capsular tension ring in a highly myopic eye (⫺21 sph, ⫺2 cyl 180°).
Spectacle-corrected visual acuity was 20/40 in his right eye with a refraction of –21 sph, –2 cyl 180°, and 20/40 in his left eye with a refraction of –21 sph, –1.5 cyl 10°. Anterior segment examination disclosed unremarkable conditions and applanation tonometry was 20 mm Hg in both eyes. Posterior segment examination showed normal optic discs with moderate diffuse atrophy of the retina not affecting the macula. Axial length was 31.5 mm in his right eye and 30.9 mm in his left eye. The patient was scheduled for bilateral nonsimultaneous clear lens extraction with intraocular lens (IOL) implantation. The right eye was operated first, using a standard phacoemulsification technique under topical anesthesia. Capsulorhexis of 6 mm was made and after removal of the lens and cortical material, efforts were made to clean the residual lens epithelial cells from the remaining anterior capsule as much as possible. A foldable acrylic hydrophilic IOL of ⫹2D (Stabibag, Ioltech, La Rochelle, France) was implanted in the bag. The postoperative course was uneventful, with uncorrected visual acuity of 20/40 and spectacle-corrected visual acuity of 20/30 with a refraction of –1 sph, –1 cyl 180°. However, 2 months after surgery the patient presented with a drop of vision in his operated eye. Uncorrected and spectacle-corrected visual acuity were 20/200, and anterior segment examination disclosed a complete closure of the anterior capsule opening by a fibrous plaque (fig. 1). YAG-laser anterior capsulotomy was performed, and the patient recovered vision to the level of the immediate postoperative period. Six months after the first surgery, the patient underwent clear lens extraction in his left eye using the same surgical technique, but implanting a 12-mm PMMA capsular tension ring (Tensiobag, Ioltech) before the insertion of a foldable acrylic hydrophilic IOL of ⫹3D (Stabibag, Ioltech). Postoperative course was uneventful, with uncorrected visual acuity of 20/40 and spectacle-corrected visual acuity of 20/30 with a refraction of ⫺0.75 sph, ⫺0.75 cyl 110°. Six months after surgery, anterior segment examination under full dilation of both eyes showed clear media, with anterior capsulotomy in his right eye (fig. 2) and a round 6-mm capsulorhexis in his left eye (fig. 3).
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Fig. 2. Right eye, patient 1. After YAG laser anterior capsulotomy.
Fig. 3. Left eye, patient 1. Round 6-mm capsulorhexis 6 months after phacoemulsification and IOL implantation with a 12-mm capsular tension ring in a highly myopic eye (⫺21 sph, ⫺1.5 cyl 10°).
Case 2 A 63-year-old woman with bilateral subluxated cataracts of unknown etiology came seeking for surgery. Preoperative exam yielded an uncorrected visual acuity of counting fingers in both eyes. Spectacle-corrected visual acuity was 20/80 in her right eye with a refraction of ⫺16 sph, ⫺3 cyl 80°, and 20/400 in her left eye with a refraction of ⫺23 sph,
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Fig. 4. Right eye, patient 2. Subluxated nuclear cataract with 150° of dehiscence affecting the inferior zonula. ⫺3.5 cyl 100° due to profound amblyopia. The patient complained of right eye monocular diplopia. Anterior segment examination disclosed a subluxated nuclear cataract in her right eye with 150° of dehiscence affecting the inferior zonula (fig. 4). Her left eye showed a subluxated cataract with a 90° dialysis in the inferior zonula. In both eyes the anterior hyaloid was intact with no vitreous prolapse in the anterior chamber, but iridodonesis and phacodonesis were evident. Applanation tonometry was 22 mm Hg in both eyes. Posterior segment examination disclosed pale optic discs and moderate diffuse atrophy of the retina sparing the macula in the right eye. The left eye showed posterior staphyloma with extreme chorioretinal atrophy affecting the macula. Axial length was 29.7 mm in her right eye and 33.6 mm in her left eye. Available options included intracapsular lens extraction with anterior chamber angle-supported or iris-fixated IOL implantation, phacoemulsification with a sutured posterior chamber IOL, or IOL implantation following the use of an endocapsular ring, the latter being the chosen option. The patient was scheduled for bilateral simultaneous cataract surgery with IOL implantation. The right eye was operated first, using phacoemulsification technique under peribulbar anesthesia. After filling the anterior chamber with viscoelastic, a 5.5-mm capsulorhexis was made taking advantage of the intact zonules to provide countertraction. After limited hydrodissection with a 27-gauge cannula a 12-mm diameter PMMA scleral-fixated capsular tension ring (Type 1 L, Morcher GmbH, Stuttgart, Germany) was implanted and secured to the sclera at the 6 o’clock position just in the middle of the zonular dehiscence (fig. 5a–f). Scleral fixation of the endocapsular ring made the lens recentered on the pupil, while the capsular bag expanded and provided enough countertraction to continue with surgery. Removal of the lens and cortical material was made using low vacuum, low aspiration and low infusion. Finally, a foldable acrylic hydrophobic IOL of ⫹5 D (Acrysoft MA60, Alcon, Tex., USA) was implanted into the capsular bag. The left eye was operated using the same technique but a 12-mm PMMA capsular tension ring (Tensiobag,
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Fig. 5. Different steps during the implantation of the Cionni’s ring (surgeon’s view). a Capsulorhexis is performed. b A double-armed 10/0 prolene suture passed through the fixation hook of the ring is introduced through the incision, enters the pupil and staying anterior to the anterior capsule exits the eye through the ciliary sulcus and the previously created scleral incision, with the aid of a 25-gauge needle. c The Cionni’s ring is introduced in the capsular bag. d The fixation hook is rotated toward the center of the zonular dehiscence, with subsequent recentration of the subluxated nucleus. e After scleral fixation of the ring, the phacoemulsification has been completed, and the recentered capsular bag is filled with viscoelastic. f Final aspect, with IOL in the bag and perfect centration of the implant.
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Fig. 6. Right eye, patient 2. Retroillumination image shows a 2-mm superior decentration of the IOL. Note the Cionni’s ring in the inferior periphery of the capsular bag.
Ioltech) was implanted but not fixated to the sclera because it provided enough capsular support. A foldable acrylic hydrophilic IOL of ⫺3D (Corneal) was implanted into the capsular bag, and one haptic was positioned into the area of zonular dehiscence due to the amount of dialysis present. Stability of the IOL was assessed by performing the ‘bounce-back’ test which consisted on deliberate decentration with spontaneous recentration of the lens. The postoperative course was uneventful, and 6 months after surgery the patient attained an uncorrected visual acuity of 20/40 in her right eye and counting fingers in her left eye due to severe amblyopia. Anterior segment biomicroscopy revealed a 2-mm superior decentration of the IOL in her right eye (fig. 6), while IOL centration in her left eye was very good (fig. 7). No monocular diplopia was present.
Discussion
The capsular tension ring is manufactured from one-piece PMMA and is available in different sizes depending on the purpose of their use and the size of the eye where it is going to be implanted. They are distributed by many of the companies that make intraocular lenses, including Morcher, Ioltech, Corneal and Ophtec. Capsular tension rings are available in diameters ranging from 10 to 12 mm. The most commonly used are the 10 and 11 mm, whereas the 12 mm one is reserved for eyes with axial length higher than 28 mm. Recently, endocapsular rings as small as 9 mm have been designed for pediatric use. When the ring is in the packaged container the diameter is higher than when it is inserted in the
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Fig. 7. Left eye, patient 2. Retroillumination image shows a well-centered IOL in the capsular bag.
capsular bag. For instance, for the 12-mm Morcher type 14 A capsular tension ring the diameter outside the eye is 14.5 mm, but it is 12 mm when inserted and perfectly round in the capsular bag. The haptic thickness varies according to the axial length of the eye: for emmetropic eyes the recommended thickness are 0.15–0.20 mm which makes the capsular tension ring very flexible and easy to implant (Tensiobag of Ioltech, Morcher capsular tension rings type 14 and 14C, Ophtec type PC275). For eyes with high myopia and great tendency toward capsule retraction the recommended thickness is 0.20 mm which makes the ring rigid enough to prevent shrinkage of anterior and posterior capsule (Morcher capsular tension ring type 14 A, Ophtec type PC276). In order to prevent posterior capsule opacification, rings 0.20 mm in thickness and 0.70 mm in width can be used (Ophtec types PC277-278). Finally, in the case of aniridia and iris colobom, special capsular tension rings with complete or partial iris diaphragm can be used for dimming the iris defect and provide relief of photophobia (Morcher types 94 G-L-S and 96 G-L-S for colobom; Morcher type 50C for aniridia). Indications for capsular tension ring are: (1) weak zonules or subluxated cataracts; (2) intraoperative partial zonular rupture; (3) prevention of the anterior capsular contraction syndrome in eyes at high risk; (4) prevention of opacification of the posterior capsule; (5) aniridia or iris colobom, and (6) pediatric cataract to prevent fibrosis and IOL decentration (table 1). The most common indications for capsular tension rings are pseudoexfoliation syndrome, high myopia and subluxated lens including traumatic cataract with zonular dialysis and
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Table 1. Indications for capsular tension ring implantation Intraoperative zonular desinsertion Localized zonulolysis or weakness Generalized zonular weakness demonstrated by iridodonesis and phacodonesis Lens subluxation: Pseudoexfoliation, Marfan syndrome, Weill-Marchesani syndrome, homocystinuria Traumatic zonular dialysis Small capsulorhexis associated with poor mydriasis Prevention or reposition of IOL decentration caused by zonular dehiscence Prevention of anterior capsule contraction syndrome: high myopia, pseudoexfoliation, retinosis pigmentaria, capsule contraction in the fellow eye Prevention of opacification of the posterior capsule Eyes at risk of photocoagulation or expected vitreoretinal surgery after cataract surgery Aniridia or iris colobom Pediatric cataract surgery Intraocular measuring gauge
Marfan syndrome [2, 3, 6]. Other conditions associated with subluxated lens include homocystinuria and Weill-Marchesani syndrome [7]. Contraindications for the use of the capsular tension ring are: (1) capsule rupture with vitreous loss due to the possibility of posterior dislocation of the ring; (2) incomplete or instable capsulorhexis because of the risk of posterior tear when implanting the ring; (3) use of a plate-haptic IOL without fenestrations due to the risk of anterior dislocation because of the outward force of the ring, and (4) small eyes with very narrow angles for the increased possibility of angle closure [2]. In the case of zonular dialysis, when zonular weakness is noted preoperatively, the capsular tension ring should be inserted into the capsular bag after capsulorhexis and careful hydrodissection but before beginning phacoemulsification so that the bag maintains an endoskeleton once the lens is removed, preventing capsular bag collapse and vitreous herniation [3]. If an unsuspected zonular dehiscence occurs intraoperatively, the capsular ring can be implanted immediately to avoid further unzipping of the zonules and possible vitreous prolapse. When the capsular ring is used in order to prevent anterior capsule contraction syndrome or posterior capsule opacification, it is implanted just before implanting the IOL and after completing posterior capsule polishing. The capsular ring can be implanted using an especially designed injector or with the aid of a forceps and a spatula (table 2). The capsular bag is expanded with viscoelastic and the ring is slipped into the incision and fed under the capsulorhexis with the aid of angulated forceps. It is important to introduce the leading edge of the ring under the anterior capsule to be able to rotate the ring and introduce it completely in the capsular bag. An instrument such as a buttonhole
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Table 2. Actions of the capsular tension ring Circular expansion of the capsular bag Increased centrifugal force to the zonula Stabilization of the capsular bag during the phacoemulsification Inhibition of migration of lens epithelial cells Reduced risk of capsular fibrosis Reduced risk of capsular shrinking Stabilization of the IOL in the short and in the long term
spatula, Lester or Sinskey hook can be introduced through the side-port incision usually created at 2 o’clock and the ring can be gently pushed in a rotatory fashion against this instrument to avoid excessive pressure against the capsulorhexis edge. If a stop is noticed when the ring is rotated it is usually due to capsule pushing by the leading edge of the ring. In this situation, it is better to go back and introduce a small quantity of viscoelastic to expand the capsular bag in that area and then continue rotating the ring without pushing the capsular bag. The implantation of the ring is extremely easy provided that the capsular bag is full of viscoelastic. Recently, Cionni and Osher [8] introduced the scleral fixation of the endocapsular ring in order to prevent further zonular disinsertion and future dislocation of the IOL in eyes with large zonular fiber loss, usually more than 150°. For the implantation of the Cionni’s ring a scleral incision of 1 mm is made opposite to the cataract incision and in the middle of the zonular dehiscence, coincident with the meridian where the zonules are considered to be intact, at 2 mm posterior to the limbus. Before implantation a double-armed 10/0 prolene suture is passed through the eyelet of the fixation hook of the ring. Viscoelastic is injected between the anterior capsule and the undersurface of the iris at the area of zonular weakness. Both needles are passed through the incision, entering the pupil and staying anterior to the anterior capsule are advanced posterior to the iris. The needles exit the eye through the ciliary sulcus and the previously created scleral incision, with or without the aid of a 25-gauge needle passed through the scleral incision. The needles should exit the globe 1 mm apart from each other. Before inserting the ring in the capsular bag it is important to make sure that the fixation hook courses into a plane anterior to the rest of the ring. The fixation hook should capture itself anterior to the capsulorhexis while the rest of the ring remains within the capsular bag. The ring should be rotated so that the hook reaches the axis where the fixation sutures exit the eye. When the hook is in the middle of the zonular dehiscence and anterior to the capsulorhexis edge, tension on the fixation sutures is applied so that centration of the lens is
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Table 3. Signs of loose or broken zonules Preoperative Phacodonesis or iridodonesis Lens center is not coincident with pupil center Significative subluxation of the lens Presence of vitreous in the anterior chamber Iris bulging from vitreous Very deep anterior chamber Significative pseudoexfoliation of the lens Intraoperative Radial folds when puncturing the anterior capsule Excessive movement of the lens during capsulorhexis Unusual movement of the lens during hydrodissection or hydrodelineation Difficulty for nuclear rotation Excessive posterior displacement of the lens when starting irrigation Vitreous herniation around the lens
achieved. A temporary or permanent knot is made, the knot is buried and the suture is covered with conjunctiva. Significant zonular dialysis makes phacoemulsification and cortical aspiration difficult even for the experienced surgeon (table 3). Hence, although endocapsular rings help to perform a safer surgery in the presence of zonular weakness, the use of such devices should only be considered in the case of surgeons familiar with the techniques employed in cataracts with loose zonules: bimanual capsulorhexis, low fluid-dynamics phacoemulsification, and use of viscoelastic to prevent vitreous prolapse and to assist in viscodissection and manipulation of the nucleus [6]. Of utmost importance is not to overpressurize the eye at any time during surgery, especially after peribulbar injection, after expansion with viscoelastic before capsulorhexis, and during phacoemulsification itself using excessively high bottle height. It is usually difficult to perforate the anterior capsule to begin the anterior capsulotomy, and radial folds are early signs of zonular weakness at this step. During the capsulotomy, special care is required not to unzip weakened fibers. Ideal capsulorhexis size is about 5.5 mm in these cases, because it leaves a relatively small amount of lens epithelial cells while maintaining the IOL into the bag. The capsular tension ring permits cortical cleaving hydrodissection and hydrodelineation, but the ring usually holds much of the cortex pressed up against the capsular fornices, requiring aditional force to remove the cortex. Anterior capsule contraction syndrome consists on the shrinkage of the capsulorhexis opening from the proliferation and metaplasia of residual lens
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epithelial cells which transform into myofibroblastic-like cells. A fibrous membrane extends from the inner and also from the outer surface of the anterior capsule to the IOL center, and when it contracts the anterior capsule is shrunken and the capsulorhexis opening is closed [9]. Postoperative capsular bag shrinkage may lead to IOL decentration or tilting, impairing visual acuity or causing monocular diplopia. Complete closure of the anterior capsule opening may also occur and consequently reduce visual acuity and increase the difficulty to explore or treat eventual diseases of the posterior segment of the eye [10–12]. Anterior capsule contraction is a relatively common finding in eyes with pseudoexfoliation and also in eyes with high myopia [13]. The weakness of the zonular apparatus has a major role in this progressive contraction of the anterior capsule opening, but also in these conditions a breakdown in the ocular-blood barrier has been reported which may increase inflammatory response and promote fibrous membrane formation [9,14]. Other risk factors for anterior capsule contraction include myotonic dystrophy [15], retinitis pigmentosa [16], history of uveitis and any other condition in which significative zonular weakness is present. The use of silicone IOL is associated with higher incidence of anterior capsule phimosis in comparison with other materials such as acrylic or PMMA IOLs [17]. In all these situations, the use of an endocapsular ring should be considered. There have been attempts to design loopless IOLs which exactly fit the capsular bag in order to prevent capsular bag shrinkage, but the large size of this kind of IOL requires a larger incision and may induce significant astigmatism [18]. Intraocular lenses with loop shapes that conform to that of the capsular bag are not successful in mantaining the circular contour of the bag [19], whereas animal studies have shown that the capsular tension ring maintains the round shape of the capsular bag both in vitro and in vivo, preventing excessive capsular shrinkage and fibrosis [20, 21]. Risk factors for anterior capsule contraction syndrome are additive, and progressive and even complete closure has been reported despite the use of a capsular tension ring [22, 23]. Posterior capsule opacification is the most common complication associated with decreased vision after uneventful cataract surgery. A capsular tension ring designed with a sharp cross section creates a discontinuous bend in the equatorial capsule. It has been demonstrated that lens epithelial cells do not migrate over an abruptly discontinuous bend in the posterior capsule, and hence an endocapsular ring with sharp cross section helps to prevent the opacification of the posterior capsule [24]. Increasing the width of the capsular tension to 0.7 mm and creation of a rectangular edge results in the so-called capsular bending ring [4]. This band-shaped, sharp-edged capsule bending ring prevents the anterior capsule from coming into contact with the posterior capsule, and so the epithelial cells underneath the anterior capsule do no undergo fibrous metaplasia, reducing the incidence of opacification of the posterior capsule. This kind
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of endocapsular ring has been used successfully to enhance the safety of posterior chamber IOL implantation in pediatric cataract surgery, and to reduce capsule opacification in this population [5]. Rounded endocapsular rings on cross section may not have such an important impact in reducing capsular fibrosis [20, 24]. The capsular bending ring also inhibits lens epithelial cell migration based on the principle of compression inhibition: cell proliferation is prevented by mechanical compression [21]. An anterior circular capsulotomy slightly smaller than the optic diameter together with the use of a band-shaped, sharp-edged capsular tension ring decreases the incidence of fibrous metaplasia with fibrous strand and contracture of the posterior capsule, and also preserves the barrier effect of the IOL and the capsule after YAG laser capsulotomy. The capsular bending ring has been especially proposed for cases that need good fundus visualization for photocoagulation or expected vitreoretinal surgery after cataract surgery [4]. In summary, the capsular tension ring enhances the safety of phacoemulsification in the presence of zonular dialysis minimizing the stretching of the intact zonular fibers, facilitates IOL implantation, prevents IOL decentration and resists contraction of the capsular bag reducing the incidence of both anterior capsule contraction syndrome and secondary cataract. As a general rule, cataract surgery with small zonular dialysis can be performed using routine phacoemulsification technique although the use of a capsular tension ring is highly recommended. When the dehiscence is 90–120°, it is mandatory to insert an endocapsular ring to perform the phacoemulsification of the cataract safely. When faced with zonular dehiscences ⬎120° the use of a scleral fixated capsular tension ring should be considered prior to the phacoemulsification. Anterior capsule contraction syndrome and posterior capsule opacification can be prevented with the use of the band-shaped, sharp-edged capsular bending ring, which may also facilitate cataract surgery in pediatric patients. The capsular tension ring together with the modified capsular bending ring enlarge the surgical options in cataract surgery. References 1 2 3 4 5
Sun R, Gimbel HV: In vitro evaluation of the efficacy of the capsular tension ring for managing zonular dialysis in cataract surgery. Ophthalmic Surg Lasers 1998;29:502–505. Fine IH, Hoffman RS: Phacoemulsification in the presence of pseudoexfoliation: Challenges and options. J Cataract Refract Surg 1997;23:160–165. Gimbel HV, Sun R, Heston JP: Management of zonular dialysis in phacoemulsification and IOL implantation using the capsular tension ring. Ophthalmic Surg Lasers 1997;28:273–281. Nishi O, Nishi K, Menapace R: Capsule-bending ring for the prevention of capsular opacification: A preliminary report. Ophthalmic Surg Lasers 1998;29:749–753. Dick HB, Schwenn O, Pfeiffer N: Implantation of the modified endocapsular bending ring in pediatric cataract surgery using a viscoadaptive viscoelastic agent. J Cataract Refract Surg 1999; 25:1432–1436.
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6 7 8 9
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23 24
Cionni RJ, Osher RH: Endocapsular ring approach to the subluxed cataractous lens. J Cataract Refract Surg 1995;21:245–249. Groessl SA, Anderson CJ: Capsular tension ring in a patient with Weill-Marchesani syndrome. J Cataract Refract Surg 1998;24:1164–1165. Cionni RJ, Osher RH: Management of profound zonular dialysis or weakness with a new endocapsular ring designed for scleral fixation. J Cataract Refract Surg 1998;24:1299–1306. Kurosaka D, Ando I, Kato K, Oshima T, Kurosaka H, Yoshino M, Nagamoto T, Ando N: Fibrous membrane formation at the capsular margin in capsule contraction syndrome. J Cataract Refract Surg 1999;25:930–935. Hansen SO, Crandall AS, Olson RJ: Progressive constriction of the anterior capsular opening following intact capsulorhexis. J Cataract Refract Surg 1993;19:77–82. Davison JA: Capsule contraction syndrome. J Cataract Refract Surg 1993;19:582–589. Joo CK, Shin JA, Kim JH: Capsular opening contraction after continuous curvilinear capsulorhexis and intraocular lens implantation. J Cataract Refract Surg 1996;22:585–590. Hayashi H, Hayashi K, Nakao F, Hayashi F: Anterior capsule contraction and intraocular lens dislocation in eyes with pseudoexfoliation syndrome. Br J Ophthalmol 1998;82:1429–1432. Küchle M, Nguyen NX, Hannappel E, Naumann GO: The blood-aqueous barrier in eyes with pseudoexfoliation syndrome. Ophthalmic Res 1995;27(suppl 1):136–142. Newman DK: Severe capsulorhexis contracture after cataract surgery in myotonic dystrophy. J Cataract Refract Surg 1998;24:1410–1412. Hayashi K, Hayashi H, Matsuo K, Nakao F, Hayashi F: Anterior capsule contraction and intraocular lens dislocation after implant surgery in eyes with retinitis pigmentosa. Ophthalmology 1998; 105:1239–1243. Hayashi K, Hayashi H, Nakao F, Hayashi F: Reduction in the area of the anterior capsule opening after polymethylmethacrylate, silicone, and soft acrylic intraocular lens implantation. Am J Ophthalmol 1997;123:441–447. Tetz MR, O’Morchoe DJ, Gwin TD, Wilbrandt TH, Solomon KD, Hansen SO, Apple DJ: Posterior capsular opacification and intraocular lens decentration. II. Experimental findings on a prototype circular intraocular lens design. J Cataract Refract Surg 1988;14:614–623. Meur G: A new capsule supported intraocular lens. Ophthalmic Surg 1987;18:395–396. Nagamoto T, Bissen-Miyajima H: A ring to support the capsular bag after continuous curvilinear capsulorhexis. J Cataract Refract Surg 1994;20:417–420. Hara T, Hara T, Sakanishi K, Yamada Y: Efficacy of equator rings in an experimental rabbit study. Arch Ophthalmol 1995;113:1060–1065. Strenn K, Menapace R, Vass C: Capsular bag shrinkage after implantation of an open-loop silicone lens and a poly(methylmethacrylate) capsule tension ring. J Cataract Refract Surg 1997;23: 1543–1547. Faschinger CW, Eckhardt M: Complete capsulorhexis opening occlusion despite capsular tension ring implantation. J Cataract Refract Surg 1999;25:1013–1015. Nishi O, Nishi K, Mano C, Ichihara M, Honda T: The inhibition of lens epithelial cell migration by a discontinuous capsular bend created by a band-shaped circular loop or a capsule-bending ring. Ophthalmic Surg Lasers 1998;29:119–125.
Prof. Dr. Gonzalo Muñoz, Instituto Oftalmológico de Alicante, Universidad Miguel Hernández, Avenida de Denia 111, E-03015 Alicante (Spain) Tel. ⫹34 902 333 344, Fax ⫹34 965 260 530, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 119–130
Optical Coherence Biometry Wolfgang Haigis University Eye Hospital, Würzburg, Germany
With optical coherence biometry (OCB), also termed partial coherence interferometry (PCI), laser interference biometry (LIB) or laser Doppler interferometry (LDI), an innovative optical method for measuring axial lengths has recently become available as a possible alternative to commonly applied ultrasound biometry. In the IOLMaster [7, 14, 18], introduced in autumn 1999 by Carl Zeiss Jena, this new distance-measuring technique is combined with a classical measurement setup to determine central corneal curvatures together with a slit image-based method to measure anterior chamber depths. All three measurements are noncontact procedures – easy to apply for the examiner and well acceptable for the patient. With these measurement facilities, all data necessary for the calculation of intraocular lenses is thus acquired by one stand-alone device. The system software allows IOL calculation with all popular formulas and includes databases for IOL and surgeon data. The application of PCI to measuring human ocular dimensions dates back to the mid-1980s, when Vienna physicist Fercher [2] performed the first optical axial length measurement in vivo. Since autumn 1997, our laboratory (Biometry Department of the University Eye Hospital, Würzburg) has been involved in the development and transformation of this fascinating new technique into clinical applications [5, 7, 9, 13, 14].
Measurement Principle
In the IOLMaster, a laser diode is mounted in one arm of a Michelson interferometer setup (fig. 1). An infrared laser beam ( 780 nm) of short
LS
M" E"
d
E'
C
E"R
M' 2L
R
L
2d E'R E"C
LS Light source with short coherence length M', M" Interferometer mirrors PD Photodetector L Distance to be measured
E'C
PD
Fig. 1. Principle setup of a dual-beam partial coherence interferometer [after 3, 9].
coherence length is emitted onto a beam splitter which produces two coaxial beams by means of a fixed reference mirror and a moving measurement mirror. These beams are directed into the eye, where they are reflected at the cornea and the retina. Interference between the reflected beam components occurs if the delay between each other is equal to the optical path length of the eye. The resultant intensity distribution is sensed by a photodetector and recorded as a function of the displacement of the measurement mirror. The accuracy of this technique stems from the fact that the mirror position can be determined very precisely. Due to using coaxial beams, the optical measurement is insensitive against longitudinal eye movements.
Optical and Acoustical Biometry
Axial lengths measured by ultrasound and laser interference are not directly comparable (fig. 2). To obtain a ‘good’ echogram, the sound beam must impinge vertically onto all segmental interfaces within the eye. This can be achieved along the geometrical (optical) axis of the eye. With PCI biometry relying on fixation, the direction of measurement is along the visual axis.
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ILM RPE
AL op AL ac
Fig. 2. Optical (ALop) and acoustical (ALac) axial lengths: different distances in different directions: ALac anterior corneal vertex to internal limiting membrane (ILM); ALop intersection of visual axis with anterior cornea to retinal pigment epithelium (RPE).
Furthermore, whereas an ultrasound axial length extends from the anterior corneal vertex to the inner limiting membrane (ILM), an optical axial length is confined by the retinal pigment epithelium, because this is where the dominant reflection usually originates [11]. Thus, optical (ALop) and acoustical (ALac) axial lengths are different distances from different directions. With RT denoting the retinal thickness we may write to a first approximation: ALop ⬇ ALac RT
Another difference stems from the fact that ultrasound allows simultaneous segmental measurements of the eye, not so – at least with the present IOLMaster hardware – optical coherence biometry. Although ACD and lens thickness measurements have been reported in the literature [1], these measurements were carried out separately and not simultaneously during axial length determination. This is due to the small amount of light returning from the obliquely intersected lens surfaces along the line of sight [1]. It may, however, well be that future PCI equipment will also offer this modality. Until then – equivalent to applying a mean velocity in ultrasound – a mean (group [17]) refractive index nPCI (1.3549 [11]) has to be used in order to translate the measured optical path length (OPL) into a geometrical eye length (ALop), i.e.: ALop OPL/nPCI
Up to now, all clinical experience in IOL implantation and refractive outcome is built on ultrasound data. To make this vast experience available for
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AL op (mm)
26
24
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20 20
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26
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AL ac (mm)
Fig. 3. Optical and acoustical biometry: PCI axial length ALop (Zeiss) vs. immersion US axial length ALac (GBS).
optical biometry (and vice versa), it was necessary to determine the relationship between optical path lengths measured by PCI and the respective ultrasound axial lengths. In a pilot study with one of the IOLMaster’s prototypes (‘ALM’) comparing axial lengths of more than 600 eyes, the following relation was found [5, 7, 13, 14]: ALop OPL/1.3549 0.9571 ⴢ ALac 1.3033
As an ultrasound reference instrument, a high precision Grieshaber Biometric System (GBS) was used at 10 MHz in immersion technique which is known to be superior in accuracy to the commonly applied contact coupling method. This instrument allows simultaneous segmental measurements with a spatial resolution of 22 m and a reproducibility of 2224 m. The correlation between optical and acoustical eye lengths is excellent (99%) as can be seen from figure 3. Optical axial lengths, as expected, were longer than acoustical ones (by 0.30 0.17 mm on an average [7]). The difference was found to be more pronounced in short eyes which can be explained by an underestimation of the lens thickness in these eyes as a consequence of using an average refractive index. Today, the regression line shown above is wired into the market version of the Zeiss IOLMaster which thus emulates an immersion ultrasound instrument – as far as the displayed axial length values are concerned – with the high precision of PCI technology.
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In a follow-up study [unpubl. data] an IOLMaster individual out of the regular production line was rechecked with 101 patients against our high precision immersion ultrasound system. With a correlation coefficient of 98.8%, the following dependance between indicated axial lengths ALIOLMaster on the IOLMaster and immersion ultrasound reference values ALimmUS from the GBS was found: ALIOLMaster 1.0006 ⴢ ALimmUS 0.0337
If the average standard deviation for five consecutive axial length measurements is taken to be a measure for reproducibility, we obtained values of 22 24 m for the GBS ultrasound immersion measurements and 23 15 m for the IOLMaster [6, 8, 9]. In another study [8], based on 146 comparative axial length measurements between IOLMaster and GBS, a mean difference ALIOLMaster – ALimmUS of 10 19 m (median 10 m, range 770 to 420 m) was found.
Keratometry and ACD Measurement with the IOLMaster
As an all-in-one-instrument, the Zeiss IOLMaster also features a keratometry module as well as the facility to measure anterior chamber (ACD) depth. For these two measurements, however, classical optical techniques are applied. Corneal curvatures are conventionally deduced from the positions of the images of 6 infrared light-emitting diodes (LEDs) illuminating the cornea in a hexagonal pattern. ACD is determined from a slit image of the anterior ocular segment with the help of sophisticated image analysis software. It is measured from the anterior corneal vertex to the anterior vertex of the lens, just like an ultrasound ACD would be measured. In fact, IOLMaster ACDs are calibrated against immersion ultrasound ACDs on the basis of more than 800 comparative measurements which have been carried out in our laboratory. Thus, with respect to an ACD measured ultrasonically in contact coupling mode, the IOLMaster ACD is likely to be a bit longer (0.1–0.2 mm), since it is not affected by a possible globe impression as might be the case in contact ultrasound. In an already mentioned study [8], IOLMaster keratometry results were compared to those obtained with an Alcon (Renaissance Series) handheld keratometer. A mean difference (IOLMaster – handheld keratometer) of the average corneal radius of 10 50 m was found for 154 patients (median 10 m, range 200 to 130 m). Additionally, a comparison between IOLMaster ACDs (n 151) and the respective immersion ultrasound data obtained with the GBS was carried out yielding a mean difference (IOLMaster – GBS) in ACD values of 30 180 m (median 0 m, range 400 to 680 m).
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SNR
10
9
8 10/1/00 11/1/00 12/1/00 13/1/00 14/1/00 15/1/00 16/1/00 17/1/00 18/1/00 Date
Fig. 4. ‘Learning curve’ for axial length measurement with the Zeiss IOLMaster: improvement of signal-to-noise ratio (SNR) as time progresses.
Observer Dependance and Learning Curve
In contact echography, which is widely used for axial length determination, the measured value depends, inter alia, on the experience of the examiner. An experienced examiner will e.g. exert less pressure on the eyeball than a beginner; hence, he or she will produce slightly longer axial lengths with less data scatter when repeating the measurement. To check the inter- and intra-examiner variability for the IOLMaster measurement modes, 4 examiners (2 experienced ones, 2 beginners) measured axial length, anterior chamber depth and mean corneal radius of 29 volunteers at three different times. Results for repeated measurements by one and the same examiner (intra-examiner variability) were 10.9 m for axial length, 31.9 m for ACD and 11.3 m for corneal radius. For different examiners measuring one and the same patient/volunteer (inter-examiner variability), the respective values were 11.8 m for axial length, 37.7 m for ACD and 13.4 m for corneal radius. Similar results have been published by Vogel et al. [19]. In terms of reliability, the following results were deduced: 100.0% for axial length, 97.8% for ACD and 99.6% for corneal radius measurements. A criterion for measurement quality in optical coherence biometry is the ratio of the usable interference signal relative to background noise (signalto-noise ratio – SNR). The higher the SNR, the better the measurement. Learning to apply this new biometry technology thus implies trying to achieve high SNR values. An example for a ‘learning curve’ in terms of mean SNR of five consecutive measurements on a test sphere, repeated on subsequent days by an absolute novice, is shown in figure 4.
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Optical Biometry and IOL Calculation
Optical biometry with the Zeiss IOLMaster – as has already been mentioned – produces axial lengths as if stemming from an immersion ultrasound measurement. However, although known to be less precise, the contact ultrasound method is the procedure which is mostly used for axial length determination. Accordingly, manufacturers’ constants for the calculation of intraocular implant lenses are meant for and adapted to contact ultrasound data. Therefore, it is of utmost importance to adjust the published IOL constants (like e.g. the A constant or the ACD constant) to optical biometry – individually for any given intraocular lens type. This can be done on the basis of pre- and postoperative clinical data. We have shown [9] that after proper individualization of lens constants there is virtually no difference between refractive results based on optical coherence biometry and high precision immersion ultrasound. Optimization of IOL constants for optical biometry is one of the main concerns of EULIB – the European User Group for Laser Interference Biometry. EULIB is an independent interest group of scientists and users, working in the field of optical biometry or applying this technique clinically. Founded in autumn 1999, EULIB can be contacted through its website at www.augenklinik.uni-wuerzburg.de/eulib. From the EULIB site, general information regarding PCI biometry as well as the clinical application of the Zeiss IOLMaster can be obtained. Also, a spreadsheet form designed to accept pre- and postoperative clinical data for the purpose of constants’ optimization can be downloaded [20]. Patient data sent back via this form are processed in our laboratory to produce optimized IOL constants for all popular IOL formulas. The results are then published on the EULIB site [21] (see fig. 5). The necessary adjustments e.g. in A constants for the SRK/T formula are typically of the order of 0.6 D, ranging from 0.2 to 1.3 D. This can be seen from figure 5, if only lens type results for n 50 are considered. Generally, immersion-based IOL constants are higher than constants for contact ultrasound. This is due to the fact that a ‘contact’ axial length which would lead to a correct IOL power will be measured longer in immersion which then would call for a weaker IOL if the IOL constants were not set to higher values.
Advantages and Disadvantages of Optical Biometry
Optical biometry is definitely advantageous over ultrasound biometry in cases of staphylomatous ocular backwalls [12, 16]. With ultrasound it is often difficult to decide among different axial length results from e.g. a highly
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a01.03; a10.40; a20.10
pACD5.51
pACD5.32
A117.4
a01.16; a10.40; a20.10
a0-0.954; a10.244; a20.206
a01.38; a10.40; a20.10
pACD5.43
Allergan SI30 NB
A118.4
Alcon SA30AL (*)
a01.29; a10.40; a20.10
pACD5.45
A118.0
A118.4
Alcon SA30AL
a01.26; a10.40; a20.10
pACD5.91
Allergan SI40 NB
A118.4
Alcon SA30AL
a01.81; a10.40; a20.10
pACD5.68
pACD5.24
A118.9
Alcon AcrySof MA30BA
a01.50; a10.40; a20.10
pACD6.11
A118.0
A118.9
Alcon AcrySof MA30BA
a01.582; a10.084; a20.157
pACD5.64
Allergan SI40 NB
A118.9
Alcon AcrySof MA60BM
a01.42; a10.40; a20.10
HofferQ/Holl.2
pACD5.18
A118.9
Acritec 12C
Haigis
Alcon SA60AT (*)
Nominal
IOL
sf1.60
sf1.52
sf1.46
sf1.43
sf1.62
sf1.63
sf1.66
sf2.10
sf1.89
sf2.36
sf1.91
Holl.1
A118.6
A118.5
A118.4
A118.4
A118.7
A118.8
A119.4
A119.1
A119.9
A119.2
SRK/T
A118.5
A118.7
A118.6
A118.9
A118.9
A119.7
A119.3
A120.5
A119.5
SRK II
Optimized IOL Constants for the ZEISS IOLMaster (as of November 15, 2001): (Please note: constants are preliminary, especially if n 50! For details how to create your own tentative constants, please see below).
The following table may be downloaded and fed directly into the IOLMaster. For details click here.
ULIB User Group for Laser Interference Biometry
[7] [9]
33
[2]
[3]
[3]
[7]
[5]
[8]
215
267
25
240
102
49
[7]
[2]
227 134
[2]
Ref. 16
n
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A118.0 A118.0 A116.7 A118.5 A118.5 A118.4 A118.4 A118.0 A118.4 A118.3 A118.0 A118.0 A118.5 A118.5
Allergan SA40 Array
Allergan SI55
Allergan PS60 ANB
Corneal BR110
Corneal BR110
Domilens Siflex4
Domilens Flex65L
Gen. Innov. XP-55
Lenstec LS-106
Pharm.-Upj. CeeOn 911A
Pharm.-Upj. 808C
Rayner 755 U
Staar AQ 2010
Staar AQ 2010
a01.56; a10.40; a20.10
a01.42; a10.40; a20.10
a01.60; a10.21; a20.11
a01.64; a10.40; a20.10
a00.283; a10.311; a20.155
a01.61; a10.40; a20.10
a01.00; a10.40; a20.10
a01.36; a10.40; a20.10
a01.12; a10.40; a20.10
a01.51; a10.40; a20.10
a01.25; a10.40; a20.10
a01.15; a10.40; a20.10
a00.78; a10.40; a20.10
a00.63; a10.40; a20.10
a01.12; a10.40; a20.10
a00.83; a10.40; a20.10
pACD5.77
pACD5.60
pACD5.42
pACD5.79
pACD5.47
pACD5.84
pACD5.24
pACD5.59
pACD5.38
pACD5.65
pACD5.48
pACD5.46
pACD5.00
pACD4.85
pACD5.35
pACD5.05
sf2.02
sf1.78
sf1.67
sf2.03
sf1.70
sf2.07
sf1.46
sf1.76
sf1.65
sf1.86
sf1.65
sf1.65
sf1.26
sf1.10
sf1.57
sf1.28
A119.3
A118.8
A118.8
A119.3
A118.8
A119.4
A118.4
A118.8
A118.8
A119.0
A118.7
A118.7
A118.2
A117.9
A118.6
A118.2
A119.7
A119.0
A119.0
A119.9
A119.2
A119.8
A118.7
A118.8
A119.4
A119.3
A119.0
A118.9
A118.4
A118.1
A118.8
A118.4
49
111
98
[6]
[7]
[1]
[2]
[2]
279 86
[2]
[2]
[2]
[2]
[2]
[4]
[2]
[2]
[2]
[2]
[2]
33
111
21
39
19
40
18
20
117
164
23
Fig. 5. Optimized IOL constants for optical biometry with the Zeiss IOLMaster as published by EULIB – the European user Group for Laser Interference Biometry – on their website www.augenklinik.uni-wuerzburg.de/eulib.const.htm (EULIB has recently changed its name into ULIB paying tribute to the fact that it has evolved into a global community with colleagues from all over the world).
Constants are given without any legal responsibility!
A118.4
A118.0
Allergan AR40
Allergan ClariFlex
Result of axial length measurement: Ultrasound Laser interference
nasal
AL 27.06 mm AL 29.19 mm
SNR 7.5 AL 29.19 n 1.3549 14
40
mm
Fig. 6. Ultrasound B scan and optical A scan of a staphylomatous eye: an intraocular lens calculated from ultrasound biometry produced a 4 D refractive surprise.
myopic eye. Since optical biometry measures along the visual axis, the PCI results are more reliable as long as the patient is able to fixate. An example is shown in figure 6. A patient presented a myopic refractive surprise of 4 D in the right eye. His axial length was 27.06 mm by ultrasound, 29.19 mm by PCI. IOL calculation had been based on the ultrasound length. The refractive surprise is fully explained by the difference between acoustical and optical axial lengths. Another application where optical biometry is superior to classical ultrasound is the measurement of pseudophakic and silicone oil filled eyes. Every medium along the propagation path of light affects the optical path length by its individual propagation velocity (expressed in its group refractive index). Compared to a normal phakic eye, a pseudophakic eye will thus have a different optical path length. In ultrasound, opposite to PCI, propagation velocities of IOL materials are considerably different from those of ocular tissues. Therefore, considerable correction factors are needed for measuring e.g. a pseudophakic axial length by ultrasound, ranging typically from 0.6 mm for silicone to 0.4 mm for PMMA lenses [4]. For optical biometry, on the other hand, typical pseudophakic correction factors [10] are of the order of 0.1 mm and nearly independent of IOL material. The same applies to silicone oil filled eyes: a normal eye with its vitreous cavity completely filled with silicone oil, measured as phakic eye will seemingly be some 0.7 mm too long when using PCI. The same eye measured with ultrasound in phakic mode will also appear to be too long – this time however by some 8.9 mm [unpubl. data].
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The evident advantage of optical biometry is of course its ease of use both for patient and examiner due to its noncontact mode of operation. No topical anesthesia is needed, no possible infection hazard involved. (Infrared) light, however, must be able to pass through the eye and return back to the PCI instrument. Therefore, a certain amount of transparency along the propagation path is mandatory with no obstructions blocking out the light. Furthermore, a minimum in fixation is needed. This requires cooperation on the side of the patient. Sometimes a measurement may not be possible due to very dense cataracts as well as general inabilities to cooperate. From our experience with more than 2,500 eyes (mostly unpublished data yet) some 5–15% of patients in a university hospital surrounding cannot be measured optically. In one study [14], no PCI measurements were possible in 58 eyes out of 678 (9%). Similar results between 7 and 12% are reported in the literature [18]. Among the reasons for optical biometry to fail were inability to cooperate (fixate), tremor, respiratory distress, severe tear film problems, keratopathy, corneal scarring, mature cataract, nystagmus, lid abnormalities, vitreous hemorrhage, membrane formation, maculopathy and retinal detachment. Finally, some possible pitfalls in optical biometry should also be mentioned. An A-scan from an ultrasound biometry device – although the instrument was not designed for ultrasound diagnosis – still carries some diagnostic information, since echoes of neighboring structures and tissues along the path of the sound beam are also displayed. The IOLMaster interferogram, however, shows no such information but rather a small window into retinal reflectivity. Thus, without careful interpretation, optical signals may hide possible pathologies. It may e.g. happen, as we have recently demonstrated, that good quality signals of high SNR acceptable as good axial length measurements turn out to actually stem from a detached retina [15]. It takes a trained person and clinical background information to avoid traps like this. In summary: Optical coherence biometry as available today in the Zeiss IOLMaster is easy to use for the operator and well acceptable for the patient since it is a noncontact procedure without the need for local anesthetics and without possible hazards which are characteristic for contact methods. By means of its wired-in calibration curves, the instrument simulates precise segmental immersion ultrasound measurements. Its accuracy is equivalent to high precision immersion ultrasound and superior to the commonly used applanation method. The innovative technique may well become a routine method for IOL calculation in cataract surgery in cases of ‘normal’ cataract eyes without additional pathologies with visual acuities 0.1. For some 5–15% of cataract patients, PCI fails out of different reasons. In these cases ultrasound will continue to be the method of choice. The same is true for all other biometrical applications apart from axial length determination.
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References 1
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Drexler W, Baumgartner A, Findl O, Hitzenberger CK, Sattmann H, Fercher AF: Submicrometer precision biometry of the anterior segment of the human eye. Invest Ophthalmol Vis Sci 1997;38: 1304–1313. Fercher AF, Roth E: Ophthalmic laser interferometer. Proc SPIE 1986;658:48–51. Fercher AF, Mengedoht K, Werner W: Eye length measurement by interferometry with partially coherent light. Optics Lett 1988;13:186. Haigis W: Biometrie; in Straub W, Kroll P, Küchle HJ (eds): Augenärztliche Untersuchungsmethoden. Stuttgart, Enke, 1995, pp 255–304. Haigis W, Lege B: Optical and acoustical biometry. ASCRS/ASOA Meeting, Seattle, April 1999. Haigis W, Lege B: First experiences with a new optical biometry device. XVIIth Congress of the European Society of Cataract and Refractive Surgeons, Vienna, September 1999. Haigis W, Lege B: Ultraschallbiometrie und optische Biometrie; in Kohnen T, Ohrloff C, Wenzel M (eds): 13. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, Frankfurt 1999. Köln, Biermann, 2000, pp 180–186. Haigis W, Lege B: Akustische und optische Biometrie im klinischen Einsatz; in Wenzel M, Kohnen T, Blumer B (eds): 14. Kongress der Deutschsprachigen Gesellschaft für IntraokularlinsenImplantation und refraktive Chirurgie, Luzern, February 2000. Köln, Biermann, 2000, pp 73–78. Haigis W, Lege B, Miller N, Schneider B: Comparison of immersion ultrasound biometry and partial coherence interferometry for IOL calculation according to Haigis. Graefes Arch Clin Exp Ophthalmol 2000;238:765–773. Haigis W, Lege B: Konstanten für die optische Biometrie. 98. Tagung der Deutschen Ophthalmologischen Gesellschaft DOG, Berlin, September 2000. Hitzenberger CK: Optical measurement of the axial eye length by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1991;2:616–624. Hoffmann PC, Schulze KC: IOL-Berechnung mittels Laserinterferenz- und Ultraschallbiometrie bei hochmyopen Augen. Klin Monatsbl Augenheilkd 2001;218(suppl 1):8. Lege B, Haigis W: Optical biometry – First clinical experiences. ASCRS/ASOA Meeting, Seattle, April 1999. Lege B, Haigis W: Erste klinische Erfahrungen mit der optischen Biometrie; in Kohnen T, Ohrloff C, Wenzel M (eds): 13. Kongress der Deutschsprachigen Gesellschaft für IntraokularlinsenImplantation und refraktive Chirurgie, Frankfurt 1999. Köln, Biermann, 2000, pp 175–179. Lege B, Haigis W: Probleme der optischen Biometrie in Fällen gravierender Pathologie entlang der visuellen Achse. Klin Monatsbl Augenheilkd 2001;218(Suppl 1):9. Lege B, Haigis W: Laserinterferenzbiometrie und konventionelle Ultraschallbiometrie in staphylomatösen Augen; in Wenzel M, Kohnen T, Blumer B (eds): 14. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, Luzern, February 2000. Köln, Biermann, 2000, pp 92–94. Pancharatnam S: Partial polarisation, partial coherence and their spectral description for polychromatic light. II. Proc Indian Acad Sci 1963;57:231. Schrecker J, Strobel J: Optische Achsenlängenmessung mittels Zweistrahl-Interferometrie; in Kohnen T, Ohrloff C, Wenzel M (eds): 13. Kongress der Deutschsprachigen Gesellschaft für IntraokularlinsenImplantation und refraktive Chirurgie, Frankfurt 1999. Köln, Biermann, 2000, pp 169–174. Vogel A, Dick HB, Krummenauer F, Pfeiffer N: Reproduzierbarkeit der Messergebnisse bei der optischen Biometrie: Intra- und Interuntersucher-Variabilität; in Wenzel M, Kohnen T, Blumer B (eds): 14. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, Luzern, February 2000. Köln, Biermann, 2000, pp 85–91. www.augenklinik.uni-wuerzburg.de/eulib/dload.htm www.augenklinik.uni-wuerzburg.de/eulib/const.htm Dr. rer. nat. Wolfgang Haigis, Universitäts-Augenklinik, Josef-Schneider-Strasse 11, D–97080 Würzburg (Germany) Tel. 49 931 201 5640, Fax 49 931 201 2454, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 131–140
Optical Biometry in Cataract Surgery Oliver Findl a, Wolfgang Drexler b, Rupert Menapace a, Barbara Kiss a, Christoph K. Hitzenberger b, Adolf F. Fercher b a
Universitätsklinik für Augenheilkunde und Optometrie, Allgemeines Krankenhaus Wien und b Institut für Medizinische Physik, Universität Wien, Austria
The most critical step to attain the desired refractive outcome after cataract surgery is the precise preoperative measurement of axial length [1, 2]. At present this biometric measurement is performed with the ultrasound A-scan echo-impulse technique (US). Studies based on preoperative and postoperative US biometry demonstrated that 54% of the error in predicted refraction after implantation of an IOL is attributed to axial length measurement errors, 8% to corneal power measurement errors, and 38% to errors in the estimation of the postoperative ACD [1]. A measurement error of axial eye length of 100 m would result in a corresponding postoperative refractive error of 0.28 D [1, 3]. Accurate biometry could improve the predictability of IOL power and therefore refractive outcome by approximately 30% for the SRK formula [4]. Hence, a more accurate axial eye length determination has been postulated as the greatest contributor to improve IOL power prediction [4]. US biometry enables the measurement of axial length with a longitudinal resolution of typically 150–200 m and an accuracy of approximately 100–150 m [5–8]. Among the US techniques, applanation ultrasound is the most commonly used technique for ocular biometry today [9]. Since this technique needs direct contact between the transducer and the eye, the cornea is indented, and the anterior chamber depth as well as the axial eye length is shortened as compared to the more accurate, but also more uncomfortable and cumbersome, water-immersion ultrasound technique. With the latter technique, the transducer has no direct contact to the cornea. Significant differences between applanation and immersion ultrasound axial eye length measurements of 0.14–0.36 mm have been reported [10]. For both ultrasound techniques, a possible mismatch between the measurement axis and the visual axis of the eye may influence their results.
In the last decade, a new noninvasive optical biomedical imaging technology, called optical coherence tomography (OCT), has been developed. It is analogous to conventional ultrasonic pulse-echo imaging (US A- and B-mode), except that OCT does not require direct contact with the tissue being investigated and that it measures echo delay and intensity of infrared light reflected back from internal tissue interfaces rather than using acoustic waves. OCT is based on an optical measurement technique known as partial coherence interferometry (PCI). Since the velocity of light is high, echo delay times cannot be measured directly and interferometric techniques have to be employed. The first medical application of this technique was biometry of the eye described by Fercher and Roth [11] in 1986. Since then, two related versions of this technique have been developed for noninvasive high-precision and high-resolution biometry and tomography in ophthalmology [12–15]. A special version of this interferometric technique, called dual beam PCI that eliminates any influence of longitudinal eye motions during measurement by using the cornea as a reference surface, was used to perform first axial eye length measurements in vivo of normal eyes [16], as well as corneal thickness and thickness profile measurements [17, 18]. Recently, Zeiss has developed a commercially available biometry equipment using this optical biometry technique (IOL Master, Zeiss). Apart from the high precision of measurement of axial length with this modality, this unit is supposed to be easy to use for clinical routine. This chapter gives a short overview of the technique and applicability of the novel optical biometry technique. Results of clinical studies on refractive outcome after optical biometry for cataract surgery and on IOL position in pseudophakic patients will be summarized.
Measurement Technique The principle of the dual beam version of PCI has been described in detail in previous chapters [11, 16, 19]. Briefly, an external Michelson interferometer splits an infrared light ( 855 nm) beam of high spatial coherence but very short coherence length into two parts, forming a coaxial dual beam (fig. 1). This dual light beam, containing two beam components (1, 2) with a mutual time delay of twice the interferometer arm length difference (2d) illuminates the eye and both components are reflected at several intraocular interfaces which separate media of different refractive indices. For the measurement of axial eye length, for example, reflection sites are the anterior surface of the cornea (C) and the retinal pigment epithelium (R). If the delay of these two light beam components – produced by the interferometer – equals an intraocular distance within the coherence length of the light source, an interference signal (called PCI signal) is detected, being similar to US A-scans, but with a very high resolution (12 m) and precision (0.3–10 m), the latter being more than one order of magnitude better than that of US biometry.
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Fig. 1. Sketch of the scanning version of the dual beam partial coherence interferometer. The eye is illuminated via an external interferometer, that produces a coaxial, dual beam. Reflected signals from the eye, for example (C1, C2, R1, R2) are superimposed on and detected by a photodetector. A PCI signal of the optical distance (OL) indicating the optical axial eye length is depicted. Measurements at a specific angle between vision axis and measurement direction, or along a completely linear or circular scan are performed using a computer-controlled scanning mirror and special scanning optics [from 22]. Since PCI yields optical distances, these need to be divided by the group refractive indices of the respective ocular media to obtain geometrical distances [16, 20]. A single A-scan to perform an axial eye length measurement takes about 0.5 s.
Refractive Outcome after Cataract Surgery
To demonstrate the applicability of PCI for biometry in cataract patients, a first study was performed on a total of 196 eyes of 100 patients measuring axial eye length [21]. That study showed that measurement of axial length is possible in eyes with cataract of varying intensity. In a further study, this technique was shown to perform accurate biometry in 85 cataract eyes, having the potential to improve the refractive outcome of cataract surgery by 27% using the SRK II power formula when compared to applanation ultrasound [22] (fig. 2). The possible mean absolute error for postoperative refraction achieved with PCI
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biometry was 0.49 D, compared to 0.67 D with US biometry. Further improvement of refractive outcome could be obtained by using third-generation IOL power formulas [23] (fig. 3). Precision of PCI biometry was better than that of applanation US by a factor of more than 10. Axial eye length measured with the two techniques differed by a mean of 460 m. These differences were probably due to the indentation of the cornea by the applanation US technique and the different reflection sites of sound and light in the retina. We also found a difference between PCI and US in measured crystalline lens thickness. This difference was significantly correlated with cataract intensity as graded semiquantitatively. In those eyes with high-grade nuclear cataract, US lens thickness measurements were significantly thinner than with PCI. The optical biometry technique seems to be less influenced by intensity, or hardness, of nuclear cataract than the US technique. All these studies were performed with a laboratory prototype of PCI. In a recent study, we compared the laboratory prototype of dual beam PCI with the commercial prototype of this novel optical biometry technique [24]. We could show that both optical devices measure similar axial eye lengths. The correlation between both optical techniques was excellent (r2 0.99). The precision, however, was significantly better with the laboratory prototype. The reason for this might be the different bandwidths of the superluminescent diodes used. In comparison to immersion ultrasound, the optical technique measures axial eye length longer by approximately 200 m. The median difference
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between PCI and IUS was 186 m. The systematic differences between optical and acoustic techniques are mainly due to the different reflection site in the retina [21, 22]. Ultrasound measures up to the inner limiting membrane, whereas with PCI the maximum interference pattern from the retina is detected at the interface of the photoreceptor layer to the retinal pigment epithelium. Furthermore, the mismatch of the beam axis and the visual axis during US measurements may cause a deviation of axial eye length measurements between biometry methods. This is in accordance with the results of our previous study comparing PCI to applanation and immersion ultrasound techniques. Such a mismatch does not happen in optical biometry since the patient fixates the measuring beam. The precision of PCI was also significantly better than that of the ultrasound technique. Though, with PCI, outliers have also been detected. The reason could be fixation problems of the patients, so that measurements were not repeated at exactly the same point on the retina. We were not able to attain measurements with the commercially available equipment in several eyes (6 of 55, i.e. 11%). Five patients had dense cataracts or fixation problems because of macular degeneration. The presence of dense posterior subcapsular cataract seems to be a special problem for measurements with the Zeiss equipment. We have not had difficulties measuring these eyes with the laboratory prototype. Possible reasons are the shorter wavelength and lower power of the laser light used in the Zeiss IOL Master.
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In a recent randomized trial, we compared the refractive outcome after biometry with optimized immersion ultrasound and the prototype of the commercially available IOL Master [25]. Ninety eyes of 45 patients with age-related cataract were included. For each patient the first eye was randomly assigned to receive an IOL using the Holladay intraocular lens power formula based either on optical or immersion-US biometry. The alternative biometric technique was used for the contralateral eye. Refractive outcome as assessed 3 months postoperatively was not significantly different between the two biometry techniques. Refractive outcome in cataract patients using the prototype of the commercially available laser interferometer is as good as that achieved with optimized immersion ultrasound. To summarize, the optical technique has a higher precision of measurement than the US technique. Measurements can be carried out with more comfort for the patient, without contact to the cornea and therefore minimizing the risk of infection. The assessment of axial eye length with this technique is time-saving, easy to use, quick to learn and appears adequate for clinical routine.
Pseudophakic Measurements
When performing US measurements of pseudophakic eyes, the implant material causes multiple artifacts at the posterior lens surface and in the vitreous, disturbing the interpretation of the A-scan, and therefore the precise determination of intraocular distances [26]. In contrast to US, biometry of pseudophakic eyes performed with PCI does not suffer from this problem, since it uses light instead of sound. Attached to the interferometer is a fully computer-controlled scanning unit which makes it possible to direct the measurement beam at various angles with respect to the vision axis [27] (fig. 1). To stabilize the visual axis, a fixation light is offered directly to the investigated eye. Typical PCI signals – so-called optical A-scans – of the anterior segment of the same eye before and after cataract surgery are shown in figure 4. These optical A-scans are similar to those obtained by conventional ultrasound, but show very narrow signal peaks, allowing much higher precision and resolution of measurement. In figure 4, the PCI-signal intensity is plotted versus the optical distance to the anterior corneal surface. Four main peaks, arising from light reflected at the anterior and posterior corneal and anterior and posterior crystalline lens (top) and IOL (bottom) surfaces can be distinguished, indicating the optical corneal thickness, anterior chamber depth, crystalline lens (top) and IOL (bottom) thickness, respectively. In the cataract lens (top) peaks probably caused by light reflected at the cortex-nucleus interfaces are also detected. In contrast to ultrasound biometry, no artifacts due to the IOL material are seen with the PCI technique in the pseudophakic eye (bottom).
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Fig. 4. Measurement of the anterior segment of eye 1 day before (top) and 12 weeks after (bottom) cataract surgery. The interference fringe contrast (intensity) is plotted as a function of the optical distance to the anterior corneal surface. Signal peaks indicating the corneal thickness, anterior chamber depth, crystalline (cataract) lens as well as intraocular lens are depicted. In the cataract lens (top) peaks probably caused by light reflected at the cortex-nucleus interfaces are also detected. In contrast to ultrasound biometry, no artifacts due to the implant material are detected by the PCI technique in the pseudophakic eye (bottom) [from 30].
Another example of the anterior segment measurement of a pseudophakic eye is depicted in figure 5 (top). Due to the high resolution of the scanning version of PCI, an additional peak, indicating a signal arising from the posterior lens capsule, enables the detection and precise quantification of the lenscapsule distance (LCD) [28]. The precision and resolution of PCI is more than 20 times better than conventional ultrasound. Therefore, accurate determination of the effective IOL position after cataract surgery is possible. Hence, the IOL-dependent constants, needed for IOL power calculation formulas in cataract surgery, can be determined more precisely. The high precision (4 m) and high resolution (12 m) of the scanning version of PCI allows highly accurate measurement of effective lens position of different IOLs and a precise quantification of a LCD when present [28].
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Fig. 5. Partial coherence interferometric A-scan of anterior segment of a pseudophakic patient before (top) and after (bottom) Nd:YAG capsulotomy. Note the additional lens capsule peak (arrow) before capsulotomy which disappears after capsulotomy [from 29].
The presence of a LCD is a possible risk factor for after-cataract, since it allows migration of lens epithelial cells and formation of Elschnig pearls between IOL and capsule (no space – no cells hypothesis). In many instances a LCD can be detected by careful slit lamp examination, but quantification is not possible. Also, detection may be difficult or impossible with small LCDs, or with some IOL styles depending on the optical characteristics of the optic material. PCI can detect and very precisely quantify a central LCD, if present. The incidence of a LCD was roughly the same for different IOL designs studied, including 1-piece as well as 3-piece silicone and acrylic IOLs, and amounted to approximately 20% for each IOL style [28]. By quantifying LCD, future modifications of IOL design may be assessed more accurately to help reduce the incidence of a lens-capsule gap, and consequently reduce lens epithelial cell migration and, therefore, regeneratory after-cataract. In another study, we could show that Nd:YAG capsulotomy caused a backward movement of the IOL in all 32 patients studied [29] (fig. 5). The extent of IOL movement was small with a mean of 25 m. However, some eyes showed a greater extent of movement with an accompanying slight hyperopic shift in
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refraction. One-piece plate haptic IOLs showed significantly more backward movement than 3-piece IOLs. Currently, one of our main interests is the effect that capsule shrinkage has on IOL anterior chamber depth after surgery. An aim is to find IOL designs that show the least variability in postoperative change of anterior chamber depth, and can therefore be predicted the best in terms of effective lens position, or postoperative refraction. Another interest is the movement of IOLs induced by contraction of the ciliary muscle, or pseudophakic accommodation. Several prototype ‘accommodating’ IOL designs are under development that are supposed to allow reading with distance correction because of a forward movement of the IOL optic with ciliary muscle contraction. PCI is a powerful tool for such studies, because of its high reproducibility for measuring IOL position in pseudophakic patients. Concluding, biometry using PCI can be performed in cataract and pseudophakic eyes with a precision and resolution that is much better than that of conventional ultrasound. Therefore, accurate determination of the effective IOL position after cataract surgery is possible. Hence, IOL-dependent constants, needed for most of the IOL power calculation formulas in cataract surgery, can be determined more precisely. Furthermore, LCD, a possible risk factor for aftercataract, can be detected and quantified with this novel technique. Finally, optical biometry is a novel examination technique that offers a high degree of comfort to the patient and examiner, since biometry can be performed within a short time. In addition, it is a noncontact method with no need for local anesthesia and a reduced risk of corneal infection.
References 1 2 3 4 5 6 7 8 9
Olsen T: Sources of error in intraocular lens power calculation. J Cataract Refract Surg 1992;18: 125–129. Boerrigter RM, Thijssen JM, Verbeek AM: Intraocular lens power calculations: The optimal approach. Ophthalmologica 1985;191:89–94. Olsen T: Theoretical approach to intraocular lens calculation using gaussian optics. J Cataract Refract Surg 1987;13:141–145. Holladay JT, Prager TC, Ruiz RS, Lewis JW, Rosenthal H: Improving the predictability of intraocular lens power calculations. Arch Ophthalmol 1986;104:539–541. Binkhorst RD: The accuracy of ultrasonic measurement of the axial length of the eye. Ophthalmic Surg 1981;12:363–365. Schachar RA, Levy NS, Bonney RC: Accuracy of intraocular lens powers calculated from A-scan biometry with the echo-oculometer. Ophthalmic Surg 1980;11:856–858. Olsen T: The accuracy of ultrasonic determination of axial length in pseudophakic eyes. Acta Ophthalmol (Copenh) 1989;67:141–144. Bamber J, Tristam M: Diagnostic ultrasound; in Webb S (ed): The Physics of Medical Imaging. Bristol, Hilger, 1988, pp 319–388. Leaming DV: Practice styles and preferences of ASCRS members – 1997 survey. J Cataract Refract Surg 1998;24:552–561.
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Olsen T, Nielsen PJ: Immersion versus contact technique in the measurement of axial length by ultrasound. Acta Ophthalmol (Copenh) 1989;67:101–102. Fercher AF, Roth E: Ophthalmic laser interferometer. Proc SPIE 1986;658:48–51. Fercher AF, Mengedoth K, Werner W: Eye length measurement by interferometry with partially coherent light. Optics Lett 1988;13:186 –188. Huang D, Swanson EA, Lin CP, Schuman JS, Stinson WG, Chang W, Hee MR, Flotte T, Gregory K, Puliafito CA et al: Optical coherence tomography. Science 1991;254:1178–1181. Huang D, Wang J, Lin CP, Puliafito CA, Fujimoto JG: Micron-resolution ranging of cornea anterior chamber by optical reflectometry. Lasers Surg Med 1991;11:419–425. Fercher AF: Optical coherence tomography. J Biomed Opt 1996;1:153–173. Hitzenberger CK: Optical measurement of the axial eye length by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1991;32:616 – 624. Hitzenberger CK, Drexler W, Fercher AF: Measurement of corneal thickness by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1992;33:98–103. Hitzenberger CK, Baumgartner A, Drexler W, Fercher AF: Interferometric measurement of corneal thickness with micrometer precision. Am J Ophthalmol 1994;118:468–476. Drexler W, Hitzenberger CK, Sattmann H, Fercher AF: Measurement of the thickness of fundus layers by partial coherence tomography. Opt Eng 1995;34:701–710. Drexler W, Hitzenberger CK, Baumgartner A, Findl O, Sattmann H, Fercher AF: Investigation of dispersion effects in ocular media by multiple wavelength partial coherence interferometry. Exp Eye Res 1998;66:25–33. Hitzenberger CK, Drexler W, Dolezal C, Skorpik F, Juchem M, Fercher AF, Gnad HD: Measurement of the axial length of cataract eyes by laser Doppler interferometry. Invest Ophthalmol Vis Sci 1993;34:1886 –1893. Drexler W, Findl O, Menapace R, Rainer G, Vass C, Hitzenberger CK, Fercher AF: Partial coherence interferometry: A novel approach to biometry in cataract surgery. Am J Ophthalmol 1998;126: 524–534. Findl O, Drexler W, Menapace R, Heinzl H, Hitzenberger CK, Fercher AF: Improved prediction of intraocular lens power using partial coherence interferometry. J Cataract Refract Surg 2001;27: 861–867. Kiss B, Findl O, Menapace R, Wirtitsch M, Drexler W, Hitzenberger CK, Fercher AF: Biometry of cataract eyes using partial coherence interferometry: A clinical feasibility study of the commercial prototype. J Cataract Refract Surg 2002;126, in press. Kiss B, Findl O, Menapace R, Wirtitsch M, Petternel V, Drexler W, Rainer G, Georgopoulos M, Hitzenberger CK, Fercher AF: Refractive outcome of cataract surgery using partial coherence interferometry and ultrasound biometry: A clinical feasibility study of a commercial prototype II. J Cataract Refract Surg 2002;126, in press. Naeser K, Naeser A, Boberg-Ans J, Bargum R: Axial length following implantation of posterior chamber lenses. J Cataract Refract Surg 1989;15:673–675. Drexler W, Hitzenberger CK, Fercher AF: A scanning-laser interferometer for fundus profile measurement of the eye. Proc SPIE 1993;2083:363–371. Findl O, Drexler W, Menapace R, Bobr B, Bittermann S, Vass C, Rainer G, Hitzenberger CK, Fercher AF: Accurate determination of effective lens position and lens-capsule distance with 4 intraocular lenses. J Cataract Refract Surg 1998;24:1094–1098. Findl O, Drexler W, Menapace R, Georgopoulos M, Rainer G, Hitzenberger CK, Fercher AF: Changes in intraocular lens position after neodymium: YAG capsulotomy. J Cataract Refract Surg 1999;25:659 – 662. Findl O, Drexler W, Menapace R, Hitzenberger CK, Fercher AF: High precision biometry of pseudophakic eyes using partial coherence interferometry. J Cataract Refract Surg 1998;24: 1087–1093. Dr. Oliver Findl, Universitätsklinik für Augenheilkunde, Allgemeines Krankenhaus Wien, Währinger Gürtel 18–20, A–1090 Wien (Austria) Tel. 431 40400 7901, Fax 431 40400 7881, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 141–146
White-to-White Corneal Diameter Measurements Using the Eyemetrics Program of the Orbscan Topography System Li Wang a, b, Gerd U. Auffarth a a b
Department of Ophthalmology, Ruprecht Karls University, Heidelberg, Germany, and Cullen Eye Institute, Baylor College of Medicine, Houston, Tex., USA
Measurement of the horizontal corneal diameter (‘white-to-white’) yields important clinical information for diagnostic purposes (i.e. microcornea, relative anterior microphthalmus, etc.) as well as for surgical procedures, such as implantation of anterior chamber IOLs (AC-IOLs) in phakic eyes for refractive purposes or implantation of AC-IOLs in aphakic eyes [1–13]. There are different methods for white-to-white measurements. One of the (semi)automated means are topography systems based on the slit lamp principle, such as the Orbscan system. The Orbscan system offers apart from corneal topography maps additional features like measurement of the anterior chamber depth and the corneal diameter [3, 4]. The following study evaluates the accuracy of white-to-white measurements using the eyemetrics subprogram of the Orbscan topography system.
Methods The Orbscan topography system is a 3D scanning slit beam system for analyzing corneal surfaces as well as structures of the anterior segment (iris, lens). Surface data points are measured in the x-, y- and z-axes creating color-coded true surface topography maps. The cornea is therefore scanned limbus to limbus by a calibrated slit beam. Forty independent images are required by the calibrated videocamera with up to 240 data points per slit. Therefore, up to 9,000 data points on each surface provide a maximal resolution to within 2 m in the central zone [3, 4].
Fig. 1. Screenshots of a sequence of the eyemetrics analysis of white-to-white measurement. The eyemetrics subprogram of the Orbscan software provides an autodetection of the pupillary margin as well as the limbus, thus creating the white-to-white measures. We evaluated 26 eyes of 13 healthy volunteers with the Orbscan system (System Orbscan I, Orbtek Inc., Salt Lake City, Utah, USA). Figure 1 demonstrates the steps of how the calibrated video image is processed for corneal diameter measurements. Two control measures were done using a ruler with micrometer scale (MM) and the millimeter scale of a Goldmann perimeter (GP).
Results
The average corneal diameter was 12.01 ⫾ 0.35 mm with the Orbscan, 11.97 ⫾ 0.35 mm control MM and 11.93 ⫾ 0.35 mm control GP (fig. 2).
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Fig. 2. Mean values and standard deviation of corneal diameter measurements. There are virtually no differences.
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Fig. 3. Correlation: corneal diameter Orbscan versus micrometer ruler measurement. Good correlation with a coefficient of determination of 0.859.
Spearmann rank order correlation was r ⫽ 0.91 (p ⬍ 0.0001) Orbscan vs. control MM and 0.93 (p ⬍ 0.0001) Orbscan vs. control GP. Linear regression analysis revealed a coefficient of determination (⫽square of correlation coefficient) of 0.87 Orbscan vs. control MM and 0.93 Orbscan vs. control GP, as well as 0.84 control MM vs. control GP (fig. 3–5). Figure 6 represents problematic cases. In one picture the video image is blurred and not aligned because of eye and lid movement. In the other picture the image is too dark and contrast detection is quite difficult.
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Fig. 4. Correlation: corneal diameter Orbscan versus Goldmann measurement. Good correlation with a coefficient of determination of 0.936.
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Fig. 5. Correlation: micrometer ruler measurement versus Goldmann measurement. Good correlation with a coefficient of determination of 0.842.
Discussion
The Orbscan topography system offers a white-to-white measurement of the horizontal corneal diameter with its implemented eyemetrics program. Measurements show very accurate and reproducible data. Compared to two control
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Fig. 6. Problematic image analysis. Left: the video image is blurred and not aligned because of eye and lid movement; right: the image is too dark and contrast detection is quite difficult.
measurements there were very good correlations and coefficients of determination. The mean values were virtually identical. A disadvantage of the system is that the accuracy depends on the quality of the captured video image. This image is automatically drawn from the images that were accessed during the slit scanning process of the cornea. There is no possibility to switch images in the program. If the image is blurred or distorted due to eye or lid movements, the analysis does not work properly. Nevertheless, this system offers a complete workup on a refractive patient to give also additional information such as the white-to-white data and anterior chamber depth when planning phakic IOLs. Sizing of phakic anterior chamber lenses can be planned directly and not during surgery. This applies of course also to conventional anterior chamber lenses for secondary implantation or for planned intracapsular cataract surgery. References 1 2 3 4 5
Arne JL, Lesueur LC: Phakic posterior chamber lenses for high myopia: Functional and anatomical outcomes. J Cataract Refract Surg 2000;26:369–374. Assetto V, Benedetti S, Pesando P: Collamer intraocular contact lens to correct high myopia. J Cataract Refract Surg 1996;22:551–556. Auffarth GU, Biazid Y, Tetz MR, Völcker HE: Measuring anterior chamber depth with the Orbscan topography system: A reliability study. J Cataract Refract Surg 1997;23:1351–1355. Auffarth GU, Wang Li, Völcker HE: Keratoconus evaluation using the Orbscan topography system. J Cataract Refract Surg 2000;26:222–228. Auffarth GU, Wesendahl TA, Apple DJ: Are there any indications for clinical use of anterior chamber intraocular lenses (AC IOLs) in the 1990s? An analysis of 4,104 explanted AC IOLs. Ophthalmology 1994;101:1913–1922.
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Fechner PU, Haigis W, Wichmann W: Posterior chamber myopia lenses in phakic eyes. J Cataract Refract Surg 1996;22:178– 824. Kaya V, Kevser MA, Yilmaz OF: Phakic posterior chamber plate intraocular lenses for high myopia. J Refract Surg 1999;15:580–585. Marinho A, Neves MC, Pinto MC, Vaz F: Posterior chamber silicone phakic intraocular lens. J Refract Surg 1997;13:219 –222. Perez-Santonja JJ, Bueno JL, Zato MA: Surgical correction of high myopia in phakic eyes with Worst-Fechner myopia intraocular lenses. J Refract Surg 1997;13:268–281. Saragoussi JJ, Puech M, Assouline M, Berges O, Renard G, Pouliquen YJ: Ultrasound biomicroscopy of Baikoff anterior chamber phakic intraocular lenses. J Refract Surg 1997;13:135–141. Trindade F, Pereira F, Cronemberger S: Ultrasound biomicroscopic imaging of posterior chamber phakic intraocular lens. J Refract Surg 1998;14:497–503. Trindade F, Pereira F: Exchange of a posterior chamber phakic intraocular lens in a highly myopic eye. J Cataract Refract Surg 2000;26:773–776. Zaldivar R, Davidorf JM, Oscherow S: Posterior chamber phakic intraocular lens for myopia of –8 to –19 diopters. J Refract Surg 1998;14:294–305.
Gerd U. Auffarth, MD, Department of Ophthalmology, Ruprecht Karls University of Heidelberg, Im Neuenheimer Feld 400, D–69120 Heidelberg (Germany) Tel. ⫹49 6221 566 631, Fax ⫹49 6221 561 726, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 147–154
Injector Systems for Foldable Intraocular Lens Implantation Ekkehard Fabian AugenCentrum, Rosenheim, Germany
Cataract surgery as small-incision surgery is well accepted as standard. Very short visual rehabilitation, nearly no surgically induced cylinder, reduced postoperative intraocular inflammation, possibility of topical anesthesia and outpatient cataract surgery are arguments for small-incision cataract surgery. To insert foldable IOLs, incision sizes of 2.5–3.8 mm are recommended today [2–5, 8]. Since 1984, when Mike Bartel presented the first ‘folder’ [6], IOL implantation with inserter systems has been divided into three main steps: (1) take the IOL out of the package, (2) position the IOL into the folding device and (3) implant the IOL into the capsular bag. The great variety of injector systems reflects the diversity of IOLs and that the way out of the package into the capsular bag has not yet been optimally solved. There is even a great variety in the literature [1–8] with respect to the numbers a given IOL is implanted with or without an injector system. This depends not only on the injector system itself but also on presbyopia of the involved persons in the operating room. Three different injector systems for foldable IOLs are on the market – combinations of cartridges and injectors, singleuse monosystems and monosystems that can be resterilized (fig. 1, 2).
Material and Methods All systems need the manipulation of the IOL: with forceps the IOL has to be taken out of the package and positioned into the cartridge or into the folding chamber. A certain amount of viscoelastic material protects the IOL during injection. Advancing the IOL is done monomanually by pushing or bimanually by rotating the central cylinder.
Fig. 1. Cartridge-based reusable injectors (from left to right): Lens Injector Set (Duckworth & Kent), Monarch (Alcon), Microserter (Bausch & Lomb), Sensar (Allergan), Unfolder (Allergan) and Unfolder T (Allergan).
Fig. 2. Single-use injectors (from left to right): EasySert (Pharmacia), EasyPack (Ophtec), Staar, Staar and Mport (Bausch & Lomb).
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The tips of this central cylinder vary in respect to the diameter and to the overall design. The tip itself is made of metal, plastic or covered with a silicone sleeve. This depends on the diameter of the cartridge or the folding chamber and on the resistance of the IOL. The resistance of folding the IOL again depends on whether the process of folding and advancing the IOL is separated or not. The cartridge-based systems fold the IOL by closing the cartridge. This reduces the force needed to advance the IOL within the cartridge. The folding chamberbased systems exert more force on the IOL by folding and advancing the IOL in one step. The cartridges vary in inner and outer diameters, in material and in round, oval or hexagonal tip designs. This influences the unfolding of the IOL and the incision width. The characteristics of different injector systems (alphabetically listed by the name of the company) are described below: Alcon The ‘Monarch’ is provided for the Acrysoft 5.5-mm IOL. This system uses a flat, not foldable, single-use cartridge to be completely filled with viscoelastic material. The IOL is placed within the cartridge and the leading haptic is stretched forward whereas the trailing haptic points out of the cartridge. The handpiece plunger must meet the edge of the IOL optic. Bimanual screwing of the plunger folds the lens and rotating of the injector delivers the IOL by slow release into the capsular bag. Allergan The ‘Unfolder’ handpieces and cartridges of the silver series are provided for silicone lenses with 6.0-mm optics (SI30, SI40, SA40) and the gold series for silicone lenses with 5.5-mm optics (SI55). These systems use flat, foldable, single-use cartridges to be filled with a small amount of viscoelastic material and single-use silicone soft-tip sheath. Proper positioning of the IOL is indicated on the right wing of the cartridge. The bimanual implantation procedure by screwing the plunger and rotating the unfolder facilitates controlled unfolding of the IOLs and safe, direct placement into the capsular bag. The ‘Sensar’ unfolder handpiece and cartridge is provided for acrylic lenses (AR40). The foldable, single-use cartridge indicates on the left wing of the cartridge, how to position the IOL underfilled with viscoelastic material. The bimanual implantation procedure by screwing the plunger and rotating the unfolder facilitates very slow unfolding and rotating of the IOL into the capsular bag. Bausch & Lomb The ‘Microserter’ handpiece and cartridge is provided for silicone (LI40) and for acrylic (EasAcryl) lenses. Different foldable, single-use cartridges have to be used with viscoelastic material for the specific IOL. Very slow screwing of the plunger bimanually advances the IOL; positioning into and centration within the capsular bag sometimes has to be done with a push-pull instrument. The ‘Passport’ made for implantation for silicone lenses with plate haptic (C11) or with polyimide haptics is a single-use injector. The folding chamber is placed in front of the unit. After exact positioning of the IOL and closing of the folding chamber the tip of the injector has to meet the IOL optic very exactly. The ‘Mport’ as a one-piece, single-use instrument with loading deck, folding chamber and injector is provided for silicone lenses (Soflex 2). By closing the loading deck the IOL is
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folded in an M-like shape, advancing the plunger pushes the IOL forward, direct, monomanual implantation without rotation into the capsular bag is possible. Duckworth & Kent The ‘Lens Injector Set’ with injector, forceps and loading plate, which can be resterilized, is a one-piece instrument completely made of metal. Different models are provided for acrylic or silicone IOLs. This is an injector not produced and not delivered by an IOL company. After positioning the IOL into the injector chamber and closing it, the IOL is folded by pushing the plunger forward. Ophtec The ‘EasyPack’ as a one-piece, single-use injector with cartridge is provided for silicone lenses (PC410). The IOL is placed in the cartridge, filled with viscoelastic material, rolled into the cartridge and pushed by the plunger; the IOL is inserted monomanually into the capsular back. Pharmacia The ‘EasySert’ as a one-piece, single-use injector with integrated cartridge is provided for silicone lenses (SeeOn Edge). After exact positioning the IOL and closing the folding chamber, the three-faceted plunger has to push the IOL to roll and to inject it simultaneously. First the plunger has to be screwed bimanually and second it has to be pushed monomanually.
Results
Cartridge-Injector Systems for IOLs with Plate Haptics (Microserter, Passport II) This type of IOL (silicone: C11, Bausch & Lomb, AA-4203VF, Staar; acrylic: EasAcryl*1, Bausch & Lomb) can be easily positioned into the cartridge of the Microsert (bimanual) injector or into the Passport II (monomanual). There is no need for rotation of the Passport II itself. The implantation of this IOL into the capsular bag is better controlled with the injector than with forceps; with higher diopters of the IOL, unfolding is also somewhat uncontrolled with the injector, advancing of the IOL performed by folding and injecting through a 2.5-mm incision. Cartridge-Injector Systems for Three-Piece Silicone IOLs (Microserter, EasyPack) These silicone IOLs (Soflex, Bausch & Lomb; PC140, Ophtec) can be implanted monomanually with pushing injectors (EasyPack) and bimanually with screwing injectors (Microserter). Positioning of the IOL into the rods of the cartridge has to be controlled, the haptics have to be set in the right direction (leading haptic forward, trailing haptic backwards out of the cartridge) thus
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making the whole loading procedure more demanding. Insertion of the IOL is facilitated because the injector does not have to be rotated. Cartridge System for Three-Piece Silicone IOLs (Unfolder, Unfolder Silver/Gold, Unfold Silver T) These silicone IOLs with high index of refraction (SI40, SI55, SA40, Allergan) have to be implanted bimanually with a screwing injector. The bevel cutaway of the cartridge has to point to the left, the leading haptic is positioned into the bag, the injector itself is rotated counterclockwise, whereas the plunger is rotated clockwise during implantation of the silicone-covered tip. One has to rewind the rod to engage the trailing loop with the rod to place it also into the capsular bag. At the end of the learning curve for the bimanual counterrotating implantation process, this is the most controlled release of a silicone IOL into the capsular bag. The IOL can even be retracted when it is half way out of the rod. The Unfolder Silver T has wider threads to make the delivery of the IOL easier and to synchronize the rhythm of rotating the unfolder and injecting the IOL into the capsular bag. The implantation can be accomplished through 3.2-mm (silver series) or 2.9-mm (gold series) incisions. Cartridge System for Three-Piece Acrylic IOLs (Unfolder Sapphire) This acrylic IOL (AR40, Allergan) has to be implanted with the screwing ‘Unfolder Sapphire’ injector. Exact positioning of the IOL into the cartridge before folding is important. A slightly higher resistance with a less enrolled acrylic IOL has to be regarded. The IOL is released out of the rod very controlled because the unfolding of the IOL is slow. The IOL can be rotated with the unfolder for complete, direct positioning into the capsular bag. Bimanual counterrotating implantation has to be understood for safe delivery. In contrast to the silicone IOL unfolder, the plunger may not be retracted during the injection process to avoid damage of the haptic. The implantation can be accomplished through a 3.4-mm incision. Cartridge System for Three-Piece Acrylic IOL (Monarch) This acrylic IOL (Acrysoft 5.5 mm, Alcon) has to be implanted bimanually with the screwing Monarch injector. Exact positioning of the IOL into the cartridge before injecting is important. The cartridge has to be completely filled with viscoelastic material. The tip of the plunger has to meet the edge of the optic to advance the IOL, otherwise it will glide over the IOL. The implantation can be accomplished through a 3.4-mm incision. Injector Set for Three-Piece Acrylic IOL (Lens Injector Set DK 7705-1) This system is delivered for different IOLs (acrylic and silicone three-piece). The loading plate and the forceps facilitate the placing of the IOL into the IOL
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chamber. After closing the chamber the IOL cannot be seen during monomanually advancing because of the metal-type rod. This sharp-edged rod needs an incision opening of 3.8– 4.0 mm. Single-Use Injectors for Three-Piece Silicone IOLs (EasyPack, EasySert, Mport) The three-piece silicone IOL (SeeOn Edge 911A, Pharmacia) has to be positioned very exactly on a plane or the bottom of the injector chamber (EasyPack) covered with viscoelastic material. Special care has to be taken to position the haptics after closing the injector chamber. Another follow-up of injecting, first screwing and then pushing, facilitates a monomanual procedure. The IOL can be implanted directly into the capsular bag through a 3.4-mm incision. The three-piece silicone IOL (PC 410, 415, 420, Ophtec) can be implanted monomanually. The IOL can open after leaving the rod without rotation of the injector, but the IOL opens quickly, nearly uncontrolled. The cartridge-based system (EasySert) can be implanted through a 3.2-mm incision. The three-piece silicone IOL (Soflex 2, Bausch & Lomb) has to be positioned very exactly into the loading deck. After closing the drawer, the IOL is compressed M-like in the injector chamber. The leading haptic has to be pulled forward before the well-positioned plunger can push the IOL. With its M-like lens fold the IOL comes out on plane, there is no tumbling. The IOL can be implanted directly into the capsular bag through a 3.3-mm incision.
Discussion
Injector-based implantation devices appeared on the market in 1984. Mike Bartel [6] suggested a so-called ‘folder’ for foldable IOLs. Other injector systems like ‘Prodegy’ (Allergan) and ‘Disk Lens Injector’ (Geuder) disappeared from the market again. In the last 2 years some new single-use injectors have been introduced. But still most of the foldable three-piece IOLs are implanted with forceps although some disadvantages of the forceps implantation – manipulation of the IOL, touch of the conjunctiva, incision size to be enlarged – can be minimized with injector implantation. Most of the foldable one-piece silicone IOLs (C11, EasAcryl*1, Bausch & Lomb; AA-4203VF, Staar) are implanted with injectors. These systems are easy to load, the positioning of the IOL into the cartridge needs no extra manipulations and the injection of the IOL into the capsular bag is possible in a one-step delivery and very predictable. Injectors and cartridges are different in dimensions and material. Thus they should only be used with that IOL they are developed for. The injectors can
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be differentiated in respect to their function. Screwing injectors are to be used bimanually, the plunger must be screwed at its end and the injector itself often has to be rotated in the opposite direction. Injectors where the IOL only has to be pushed forward can be used monomanually, thus leaving the other hand free for a second instrument. The tips of the plungers vary in respect to inner and outer diameters or form and the cartridges are adopted to the IOLs and to the plunger. The cartridges vary in respect to their bevel cutaway (aside – Allergan, down – Bausch & Lomb). Thus the cartridges can only be used with the injector belonging to the system and the specific IOL which is recommended for this system. With some cartridge systems (Unfolder, Allergan), the plunger is not long enough. Thus the plunger has to be withdrawn before rotating the IOL into the capsular bag (two-step delivery). This problem has been solved with the Unfolder Silver T. Another cartridge system (Monarch, Alcon) allows the direct implantation of the IOL with moving the plunger only forward (one-step delivery). During this maneuver the surgeon has to be very careful not to touch the iris or ciliary body on the opposite site. Injector systems with folding chamber (EasyPack, Mport, Passport II) track more attention to the positioning of the IOL into the chamber. Both haptics have to be positioned as pointed out (EasyPack, Pharmacia), the haptic has to be placed very exactly onto the plunger recess (Mport, Bausch & Lomb) or the plunger has to meet precisely the edge of the IOL optic (Passport). Preparing and loading the injector system can be performed by the operating room staff. Thus the surgeon has only to take over the loaded injector. This can reduce the time of exposure to air of the IOL, thus reducing the possibility of adhesion of dust to the lens material. Within all injector systems one still has to manipulate directly the IOL by forceps or other instruments. This is at least problematic for presbyopics, you cannot see it in a darkened operating room and you cannot manipulate it under the microscope without changing magnification and viewing angle. All IOL and/or injector producers should concentrate on efforts to minimize or to avoid such handlings with the IOL out of the package into the folding device. The best solution would be a closed system for the IOL from the package into the capsular bag. Working with injectors, reproducibility of implantation, safety in respect to an unharmed IOL do need a learning process. Handling of the system has to be trained before working with it in a human eye. Thus one has to learn that each injector system has its own characteristics and using them varies. Injector systems give advantages in respect to IOL isolation from ocular surface bacteria and debris, reproducibility of geometry and smaller size for wound width, implantation through small capsulorhexis, implantation into the capsular bag
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or sulcus with compromised capsular bag structures and prevention of crimping the haptics. Respecting recommendations for handling the injectors, the implantation with injector systems will be of benefit for the eye of the patient and for a well-controlled surgery.
References 1 2 3 4
5 6 7 8
Dick B, Eisenmann D, Fabian E, Schwenn O: Refraktive Kataraktchirurgie mit multifokalen Intraokularlinsen. Berlin, Springer, 1999. Fabian E, Dick B: Injektor-Systeme für die Implantation von faltbaren Linsen. OphthalmoChirurgie 2000;12:43–52. Kohnen T, Lambert RJ, Koch DD: Incision sizes for foldable intraocular lenses. Ophthalmology 1997;104:1277–1286. Kohnen T, Koch DD: Experimental and clinical evaluation of incision size and shape following forceps and injector implantation of a three-piece high-refractive-index silicone intraocular lens. Graefes Arch Clin Exp Ophthalmol 1998;236:922–928. Mackool RJ, Russel RS: Effect of foldable intraocular lens insertion on incision width. J Cataract Refract Surg 1996;22:571–574. Mazzocco TR, Davidson BM: Insertion technique and clinical experience with silicone lenses; in Mazzocco TR (ed): Soft Implant Lenses in Cataract Surgery. Thorofare, Slack Inc, 1986. Olson R, Cameron R, Hovis T, Hunkeler J, Lindstrom R, Steinert R: Clinical evaluation of the Unfolder. J Cataract Refract Surg 1997;23:1284–1389. Steinert RF, Deacon J: Enlargement of incision width during phacoemulsification and folded intraocular lens implant surgery. Ophthalmology 1996;103:220–225.
Priv.-Doz. Dr. Ekkehard Fabian, IOL Injector Systems, AugenCentrum Rosenheim, Luitpoldhaus, Bahnhofstrasse 12, D–83022 Rosenheim (Germany) Tel. ⫹49 8031 389 500, Fax ⫹49 8031 389 5038, E-Mail
[email protected]
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Incisions for Implantation of Foldable Intraocular Lenses Development of a New Caliper, Measurement of Incision Sizes, and Wound Morphology of the Cornea
Thomas Kohnen Department of Ophthalmology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
Cataract surgery and intraocular lens (IOL) implantation have changed dramatically over the past 20 years. Small-incision surgery using phacoemulsification has become the preferred method for cataract removal in the industrialized countries [16, 27, 40], and developments in wound construction have led to the routine use of sutureless, self-sealing tunnel incisions [9, 36]. Incision size, configuration and location are important determinants of wound stability [1, 7, 8, 10, 15], astigmatic changes [14, 18, 29, 34, 37] and visual outcome [4, 29] after cataract surgery. To further reduce incision size, foldable IOLs have been developed [21]. The development of foldable IOLs has permitted reduction in incision size by over 50% compared to that required for implantation of rigid poly(methylmethacrylate) (PMMA) IOLs. According to currently published IOL surveys [17, 27, 41], foldable IOLs have become the preferred choice for ophthalmic surgeons to replace the human crystalline lens. Materials used in the optics of modern foldable IOLs include silicone elastomers and hydrophobic and hydrophilic acrylate/methacrylate polymers [5, 13]. Foldable IOLs are constructed primarily in either three-piece or single-piece plate-haptic designs. A variety of surgical devices are currently used to insert foldable IOLs. Despite extensive interest in reducing the incision size for implanting foldable IOLs, only two published studies that actually measured incision sizes following foldable IOL insertion [19, 38] were available when the following research
projects were started. Both studies documented wound enlargement with insertion of selected silicone IOLs. The purpose of this study was: (1) to develop a new mechanical caliper, which could easily measure incision sizes in clinical and experimental settings; (2) to determine the smallest incision size required for insertion of a representative spectrum of foldable silicone, hydrophobic acrylic (soft acrylic) and hydrophilic acrylic (hydrogel) IOLs; and (3) to study wound stretching or incisional damage of both tight and appropriately sized incisions following forceps and injector insertion of foldable IOLs.
Patients, Material and Methods Experimental Studies The experimental studies were approved by the Institutional Review Board for Human Subject Research for Baylor College of Medicine and Affiliated Hospitals prior to commencement of the experiments. All experimental work was performed at the Cullen Eye Institute, Baylor College of Medicine, Houston, Tex., USA. Subjects (Part A) Sixty-nine fresh human cadaver eyes were obtained from several eye banks in the United States. The donors’ mean age was 81 years (range 69–102). Exclusion criteria were previous anterior segment pathology or intraocular surgery, which were confirmed by each eye bank’s protocol. The eyes were stored at 4–8°C until the experiments were performed and were grossly examined by us to confirm the absence of any anterior segment abnormality that might affect the outcome of this study. All surgeries were done within 48 h of death of the donors. Subjects (Part B) Ten fresh human cadaver eyes (6 for the incision size measurements, 4 for the scanning electron microscopy (SEM) evaluation) were obtained either from the Lions Eye Bank of Texas, Houston, Tex., USA or from the Central Florida Lions Eye Bank, Tampa, Fla., USA. The donors’ mean age was 79 years (range 68–93). Exclusion criteria were as described in Part A. Preparation of the Globes To thin the corneas, the eyes were placed for 20–30 min in hyperosmotic 15% dextran solution [2, 6, 39]. Corneal thickness between 500 and 650 m was confirmed using ultrasonic pachymetry (DGH 2000, DGH Technology, Frazer, Pa., USA) before the experiments were performed. The globes were fixated in an artificial eye holder, and a 23-gauge needle was passed through the optic nerve into the vitreous cavity. Infused balanced salt solution maintained the intraocular pressure, which was monitored with Schiotz tonometry to be between 10 and 20 mm Hg. To maintain corneal thinning until the eyes were used, a paracentesis was performed two clock hours away from the anticipated tunnel incision area, and 15% dextran solution was instilled to fill the anterior chamber.
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Table 1. Characteristics of foldable IOLs (in 20.5 D) and their implantation devices IOL
IOL characteristics
Refractive index
Implantation device
IOLAB LI41U (Soflex)
Three-piece, 6-mm optic silicone IOL with PMMA haptics and a total diameter of 12.5 mm
1.43
Livernois-McDonald implantation forceps (Katena)
Allergan SI-30NB
Three-piece, 6-mm optic silicone IOL with prolene haptics and a total diameter of 13.0 mm
1.46
Fine Universal II Folder (Rhein Medical)
Chiron C10UB
Plate-haptic 6-mm optic silicone IOL with a total diameter of 10.5 mm
1.41
Passport Foldable Lens Placement System, Model PS-30 (Chiron)
Staar AA-4203
Plate-haptic 6-mm optic silicone IOL with a total diameter of 10.5 mm
1.41
Microstaar Injector ⫹ Softtrans Injector 1-ICS (Staar)
Alcon MA60BM (Acrysof)
Three-piece, 6-mm optic soft acrylic IOL with PMMA haptics and a total diameter of 13.0 mm
1.55
Buratto implantation forceps, J2186.2 (e.janach)
Alcon MA30BA (Acrysof)
Three-piece, 5.5-mm optic soft acrylic IOL with PMMA haptics and a total diameter of 13.0 mm
1.55
Buratto implantation forceps, J2186.2 (e.janach)
Storz H60M (Hydroview)
Three-piece, 6-mm optic hydrogel IOL with PMMA haptics and a total diameter of 12.5 mm
1.47
Hydro-Inserter implantation forceps, SP7-52607 A (Storz)
Alcon SH30BC1 (Hydrosof)
One-piece, 5.5-mm optic hydrogel IOL with a total diameter of 12.0 mm
1.44
Hydrosof implantation forceps, 1NS440 (Alcon)
1
Formerly called IOGEL 2000SM.
Foldable IOLs and Implantation Devices (Part A) We wished to determine the smallest incision sizes permitting insertion and the actual incision size following insertion for eight different foldable IOLs, all with a power of 20.5 diopters (D). The foldable IOLs were 4 silicone (2 three-piece and 2 plate-haptic), 2 three-piece soft acrylic and 2 hydrogel (1 three-piece and 1 one-piece) IOL (table 1). In this experiment each IOL was inserted using implantation instrumentation that either was recommended by the IOL manufacturer or was commonly used by cataract surgeons (table 1).
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Fig. 1. Forceps to implant the foldable silicone IOL Allergan SI40NB (Fine Universal Folder II, Rhein Medical), experimental study Part B.
Foldable IOLs and Implantation Devices (Part B) The IOLs were model SI40NB™ (Allergan Medical Optics, Irvine, Calif., USA) with the following parameters: three-piece construction; 20.5-D, 6-mm silicone optics with a refractive index of 1.46; extruded PMMA haptics, and overall lens diameter of 13.0 mm. Further in the text the Allergan high-refractive silicone IOLs are described without the™ trademark sign. The implantation devices were either a forceps (Fine Universal Folder II, Rhein Medical) (fig. 1) or an injector (UNFOLDER™ AMO® PHACOFLEX II®, Allergan Medical Optics) (fig. 2). The UNFOLDER™ AMO® PHACOFLEX II® is further in the text called ‘Unfolder’. In the same eye, two insertions were performed on the horizontal meridian (determined by white-to-white measurements) through different incisions 180° apart, one with forceps, the other one with injector. The order of use of the implantation devices was determined in a randomized fashion. Measurements To make tunnel incisions of various sizes, stainless-steel, angled, bevel-up keratomes (A-OK Full Handle Slit Knives) were provided by Alcon. Several of the keratomes had to be custom manufactured for the studies. The widths of the keratome blades were 2.0, 2.25, 2.5, 2.75, 3.0, 3.2, 3.5, 3.7 and 4.0 mm. Preoperative measurement of the keratome widths revealed a deviation of ⫾0.05 mm. To measure the corneal tunnel dimensions, we modified an Osher internal incision caliper (K3-9012, Katena Products Inc., Denville, N.J., USA) by adding a screw mechanism to assure precise, stable positioning of the caliper arms (fig. 3). A vernier caliper with a digital display (Mitutoyo Corp., Tokyo, Japan) (fig. 3) was used to measure the actual external spread of the caliper arms (in hundredths of a millimeter); we did not use the gauge on the Osher caliper itself. In Part B, all incisions were also measured with a new caliper (Kohnen incision caliper, G-19136, Geuder, Heidelberg, Germany) (fig. 7–9), which was developed during this study for use in the clinical evaluation of incision size (see Results, Development of a New Caliper to Measure Incision Sizes). Surgical Procedure All procedures in the experimental studies were performed by one surgeon (T.K.) with the use of an operating microscope (Model Urban US-1, Storz, St. Louis, Mo., USA) in the Ophthalmic Microsurgical Laboratory, Baylor College of Medicine. The dextran solution in the anterior chamber was exchanged for a viscoelastic agent (Viscoat, Alcon, Ft. Worth, Tex., USA or Vitrax, Allergan Medical Optics). Using a diamond step-knife (Alcon), a groove 3.5 mm wide and 300 m deep was created at the limbus of the autopsy eye. To construct tunnel incisions of various sizes, we used stainless-steel, angled, bevel-up keratomes of different widths (2.75, 3.0, 3.2 and 3.5 mm) (A-OK Full Handle Slit Knives, Alcon). The keratomes were used to dissect rectangular corneal tunnel incisions with a radial length of Kohnen
158
a
b
c
d Fig. 2. Injector to implant foldable Allergan silicone IOL (UNFOLDER™ AMO® PHACOFLEX II® Implantation System, Allergan Medical Optics). a Cartridge with loaded three-piece high-refractive-index silicone IOL. b Insertion of the silicone IOL through the cartridge. c Implantation of the silicone IOL using the injector system. d In the experimental study Part B, the cartridges of the Unfolder were marked to allow a reproducible insertion length into the incision.
1.5 –2.0 mm [14, 38]. The approximate length of the incisions was confirmed by external measurement of the tunnel length using the modified Osher calipers (fig. 4a). A Seibel folder (I-12255, Icon, St. Louis, Mo., USA) was used to fold the three-piecedesign IOLs in two equal halves to allow comparable implantation conditions. The plate-haptic IOLs were folded with their respective silicone cartridges. Following the initial determination of the external and internal incision width, the foldable IOLs were inserted under viscoelastic substance protection into the anterior chamber – for three-piece IOLs with implantation forceps and for the plate-haptic IOLs with the injectors. The various instruments are summarized in table 1. The cartridges of the injectors were inserted 30–50% into the incision (fig. 2d). In these cadaver eyes the anterior chamber filled with viscoelastic substance was sufficiently deep to allow IOL insertion without restriction by the iris or crystalline lens. Determination of the Incision Sizes (Part A) Measurements were performed by inserting the caliper tips in the incision and then gently opening until modest tissue resistance was felt. For the measurements of external incision Incisions for Implantation of Foldable Intraocular Lenses
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Fig. 3. Modified Osher internal caliper (below) and digital caliper (above) used to determine external and internal incision sizes. width, the forceps were inserted until the tips extended no more than 0.5 mm into the incision (fig. 4b). For the measurements of internal incision width, the forceps were inserted until the tips were at or just central to the internal opening of the incision (fig. 4c). The incision width was first approximated in a pilot study. For each foldable IOL, 1–3 fresh cadaver eyes (a total of 15 eyes which were not included in the 48 eyes of the experimental study Part A) received corneal tunnel incisions starting at a width of 2.25 mm, and IOL insertion was attempted. The incisions were enlarged by 0.2 or 0.25 mm using the metal keratomes until the IOL could readily be inserted with minimal resistance. To determine the smallest incision size the cadaver eyes were randomized into 6 eyes for each of the eight different foldable IOLs tested in this study. The experiments with the 48 human cadaver eyes were started with incisions 0.5 mm smaller than the predetermined width obtained for each IOL model in the pilot study. Insertion was attempted with force, but in a way which still felt comfortable for the surgeon. The incisions were enlarged by 0.2 or 0.25 mm, depending on the keratome, until the IOL could be inserted. This incision is hereafter called ‘smallest possible pre-insertion incision’. Before each insertion attempt and following the final insertion, the external and internal incision widths were determined with the above-described calipers (fig. 4b, c). The internal incision size was also measured from the endothelial side after the cornea had been removed from the globe (fig. 4d). Three measurements were taken, and the mean value was used for statistical analysis. The measured incision widths are abbreviated in the following text as: (1) pre-insertion external ⫽ preinext; (2) post-insertion external ⫽ postinext; (3) pre-insertion internal ⫽ preinint; (4) post-insertion internal ⫽ postinint 1; (5) post-insertion internal after the cornea was removed ⫽ postinint 2. Determination of the Incision Sizes (Part B) To determine the differences between incision sizes permitting insertion and actual incision sizes following insertion, all incisions were measured before and after insertion of the IOLs. As we had determined the minimal incision size for insertion of a similar IOL in the experimental study Part A (Allergan Medical Optics SI30NB), IOL implantation was first
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a
b
c
d Fig. 4. Determination of the incision size for corneal tunnel incisions in a human autopsy eye. a External measurement of the tunnel length. b External measurement of the external wound width. c External measurement of the internal wound width (method A). d Internal measurement of the internal wound width after removal of the whole cornea following the IOL insertion (method B). attempted through 2.75-mm incisions. The incisions were enlarged by 0.2 or 0.25 mm using the metal keratomes until the IOL could readily be inserted with minimal resistance. This incision is hereafter also called ‘smallest possible pre-insertion incision’. Before each insertion attempt and following the final insertion, the external and internal incision widths were determined by inserting the caliper tips into the incision and then gently opening until modest tissue resistance was felt. Three measurements were taken, and the mean value was used for statistical analysis. Determination of Tissue Damage Following IOL Implantation (Part A) In a pilot study with two autopsy eyes, we implanted IOLs through the smallest possible incision and performed SEM of the endothelial surface of the incision. We found that insertion through a tight incision damaged corneal tissue more than a keratome incision alone. Therefore, each of four additional donor eyes received two corneal tunnel incisions adjacent to the limbus, 180° apart. One incision was created with a 3.0-mm keratome and the other with a 3.5-mm keratome. Two eyes each were implanted with a high-refractive-index
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three-piece silicone IOL (Allergan SI-30NB) of 20.5 D using a Fine Universal II folder and with a plate-haptic silicone IOL (Staar AA-4203) of 20.5 D using a Microstaar injector. Following IOL insertion, the corneas were removed from the globes, immediately immersed in Optisol GS (Chiron IntraOptics, Irvine, Calif., USA), stored over ice, and shipped by overnight express service to the National Vision Research Institute Laboratory, San Diego, Calif., USA. Upon receipt, the corneas were washed in 0.1 M cacodylate buffer, placed in 1/2 Karnovsky’s fixative for 8 h, and subsequently rewashed in buffer. Each cornea was then dissected into two pieces, postfixed in 2% osmium tetroxide for 2 h, and dehydrated in a graded series of ethanol. The tissue pieces were placed in 100% acetone and subjected to critical-point drying (Samdri-750, Tsoumis, Rockville, Md., USA). The dried specimens were mounted on viewing stubs, coated on their endothelial surface with a gold-palladium alloy to a depth of approximately 9 m, viewed in a Hitachi S-520 scanning electron microscope (Hitachi Ltd, Tokyo, Japan), and photographed with a Polaroid Type 55 PositiveNegative 4 ⫻ 5 instant sheet film (Polaroid, Cambridge, Mass., USA). Determination of Tissue Damage Following IOL Implantation (Part B) SEM of the endothelial surface of the cornea was used to assess tissue damage. Each of four donor eyes received two corneal tunnel incisions at the 3 and 9 o’clock position adjacent to the limbus. In two eyes, both incisions were created with a 3.0-mm keratome and in the other two eyes with a 3.2-mm keratome. In each of the four eyes, one IOL was inserted with the Fine forceps and one with the Unfolder. Following IOL insertion, the corneas were removed from the globes and were then processed as described in Part A.
Clinical Studies All clinical work was performed at the Department of Ophthalmology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany. Patients (Part A) In 12 consecutive cataract procedures (patients’ age 69.7 years, range 54–89 years), Allergan Medical Optics SI40NB IOLs of 18.0–24.5 D were implanted in a randomized fashion using the forceps or injector as described in the experimental study Part B (fig. 1, 2) and the incision sizes were determined intraoperatively using the newly developed incision caliper (Kohnen incision caliper, G-19136, Geuder, Heidelberg, Germany; figures 7–9; see Results, Development of a New Caliper to Measure Incision Sizes). Six eyes were implanted with each insertion method. Patients (Part B) In a prospective, randomized study, incision sizes were evaluated for 5.5-mm total optic foldable IOLs. Forty cataract cases were included in this study. The mean age of the patients was 67.3 years (range 55– 86). All eyes had no previous intraocular surgery or anterior segment pathology. Three different 5.5-mm total optic 3-piece foldable IOLs were used, two silicone IOLs (Pharmacia CeeOn 912, Allergan SI55NB), and one hydrophobic acrylic IOL (Alcon MA30BA). The refractive optic of the IOLs were different: 5.5 mm for the Pharmacia
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Fig. 5. 5.5-mm total optic foldable IOLs made of silicone and hydrophobic acrylic material. a Silicone IOL Pharmacia CeeOn 912. b Hydrophobic acrylic IOL Alcon Acrysof MA30BA. c Silicone IOL Allergan SI55NB. Table 2. Characteristics of the 5.5-mm total optic 3-piece foldable IOLs IOL
IOL characteristics
Optic, Optic, Total Refractive total (mm) effective (mm) diameter (mm) index
Haptics
Haptic angulation
Pharmacia CeeOn 912
Three-piece silicone IOL
5.5
5.5
12.0
1.43
White PMMA (CM® technology)
Allergan SI55NB
Three-piece silicone IOL
5.5
5.0
13.0
1.46
Blue core PMMA
Alcon Acrysof MA30BA
Three-piece hydrophobic acrylic IOL
5.5
5.5
12.5
1.55
Blue PMMA (Monoflex®)
10°
CeeOn 912 and the Alcon Acrysof MA30BA, 5.0 mm for the Allergan SI55NB IOL. Characteristics of the three foldable IOLs are shown in figure 5 and reported in table 2. The inclusion criteria into this study were IOL power between 20 and 30 D (table 3). From each IOL type, 10 lenses of different dioptric power were implanted using different implantation forceps (table 3, fig. 6). Additionally, 10 Allergan SI55NB IOLs were implanted with the AMO Unfolder injector (fig. 2).
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5°
Table 3. Dioptric range of the implanted 5.5-mm total optic 3-piece foldable IOLs and their implantation devices IOL
Mean power of implanted IOLs, D average
range
Pharmacia CeeOn912
23.0
20.5–27.5
Alcon Acrysof MA30BA Allergan SI55NB
26.0
20.0–28.0
23.25
21.5–25.5
22.5
21.5–29.0
Implantation device
Nichamin implantation forceps (Katena) Buratto implantation forceps, J2186.2 (e.janach) a) Fine Universal II Folder (Rhein Medical) b) AMO Unfolder
a
b
Fig. 6. Forceps to implant the 5.5-mm total optic foldable IOL. a Nichamin implantation forceps (Rhein Medical) (Pharmacia CeeOn 912). b Buratto implantation forceps, J2186.2 (e.janach) (Alcon Acrysof MA30BA). c Fine Universal Folder II (Rhein Medical) (Allergan SI55NB).
c
Surgical Procedure All operations were performed by one surgeon (T.K.) using posterior chamber phacoemulsification through a temporal posterior limbal corneal tunnel incision under topical anesthesia. First, using a 0.7-mm steel knife, two paracenteses were performed ca. two clock hours on either side of the incision, and the aqueous humor was replaced with hyaluronic acid (either with Healon® or Healon® GV, Pharmacia, Uppsala, Sweden). There was no specific indication for the two different viscoelastic substances. A 500-m deep groove was made at the peripheral vascular arcade of the temporal cornea with a preset three-cut diamond step
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knife. Using a 3.0-mm clear-corneal diamond keratome (for forceps implantation of the Pharmacia CeeOn 912, the Alcon Acrysof MA30BA, and the Allergan SI40NB and SI55NB and injector implantation of the Allergan SI40NB using the AMO Unfolder) or a 2.5-mm metal keratome (for the injector implantation of the Allergan SI55NB using the AMO Unfolder), a rectangular limbal corneal tunnel incision with a radial length just under 2.0 mm was incised. Following continuous curvilinear capsulorhexis and multilamellar hydrodissection, the nucleus was emulsified with an in situ four-quadrant phacofracture technique. The cortical material was removed using a small-port bimanual irrigation/aspiration system (Koch/Kohnen bimanual A/I system, G-22100/1, Geuder) through the two-side port incisions, and the posterior capsule was vacuumed on a low aspiration setting. The viscoelastic agent (either Healon® or Healon® GV, Pharmacia) was reinjected to deepen the anterior chamber and to inflate the capsular bag. Using forceps or injector, implantation of the 3-piece foldable intraocular lenses was first attempted without enlargement. If this failed, a minimal enlargement of the incision was performed with the diamond or metal keratome. Following comfortable IOL implantation into the capsular bag, residual viscoelastic substance was removed with the bimanual tips, and the anterior chamber was deepened by injecting balanced salt solution (BSS®, Alcon Surgical Inc., Ft. Worth, Tex., USA) through a side-port opening. The wound was checked for leakage and if it was found not to be watertight, the stroma of the corneal tunnel incision was hydrated. All incisions were left sutureless. Determination of the Incision Sizes In each surgical case, the incision size was measured once at four different time points using the newly developed incision caliper (G-19136, Geuder) (see Results, Development of a New Caliper to Measure Incision Sizes): (a) after performing the limbal corneal tunnel incision; (b) following phacoemulsification; (c) before IOL implantation (which was equivalent to the previous measurement if the wound did not need to be enlarged, but was greater when further enlargement was necessary); and (d) after IOL implantation. The predicted incision sizes for the three different 5.5-mm total optic 3-piece foldable IOLs and the different implantation devices were predetermined for each IOL/insertion device combination in five cataract procedures before the beginning of the clinical study. According to the prefindings either a clear-corneal diamond keratome (for forceps implantation of the Pharmacia CeeOn 912, the Alcon MA30BA, and the Allergan SI40NB and SI55NB) or a 2.5-mm metal keratome (for the injector implantation of the Allergan SI40NB and SI55NB using the Unfolder) was used in the main study. To maintain the incision size of 2.5–2.6 mm during the phaco procedure (for the injector implantation of the Allergan SI55NB using the Unfolder) a smaller phaco-tip (Mini-Mega-Ultrasonic-Tip, G-24070, Geuder) was necessary. For the other procedures with an initial incision width of approximately 3.0 mm, a regular phaco-tip (Mega-Ultrasonic-Tip, G-24055, Geuder) was used. Statistical Analysis To determine if there was a significant effect of various IOL materials and designs and inserting foldable IOLs with injector or forceps, incision size measurements were assessed using one-way analysis of variance (ANOVA). When the ANOVA indicated that there was statistical significance (p ⬍ 0.05), the Tukey-Kramer multiple comparison test was used to detect significant differences between the means (p ⬍ 0.05). Both statistical analyses were performed with SAS software (JMP, SAS Institute, Inc., Cary, N.C., USA) [35].
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0.1-mm steps
24 3.5
9 Fig. 7. The caliper for small-incision cataract surgery can be sterilized, is suitable for intraoperative use, and is available in two ranges: 1.0–6.0 and 2.0–4.0 mm. Fig. 8. Design specifications of the caliper screw (range 1.0–6.0 mm). Fig. 9. Sketch of the small-incision caliper screw (range 2.0–4.0 mm) which shows the 0.1-mm measurement steps. The arrows indicate the motion of the screw. In this position, the caliper would measure an incision size of 3.5 mm.
Results
Development of a New Caliper to Measure Incision Sizes To measure incision sizes in clinical and experimental settings, a new mechanical caliper was developed (Kohnen incision caliper, G-19136, Geuder). The metal caliper is made out of two arms with fine tips (fig. 7). The length and
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Table 4. Comparison of internal incision sizes by two different methods1 IOL
Method A, mm2
Method B, mm3
IOLAB LI41U Allergan SI-30NB Chiron C10UB Staar AA-4203 Alcon MA60BM Alcon MA30BA Storz H60M Alcon SH30BC
3.79 (⫾0.07) 3.27 (⫾0.14) 3.27 (⫾0.04) 3.22 (⫾0.10) 3.75 (⫾0.10) 3.34 (⫾0.10) 3.53 (⫾0.04) 3.34 (⫾0.05)
3.90 (⫾0.11) 3.26 (⫾0.10) 3.31 (⫾0.08) 3.26 (⫾0.09) 3.79 (⫾0.13) 3.36 (⫾0.11) 3.51 (⫾0.10) 3.37 (⫾0.05)
1
One-way analysis of variance did not show statistically significant difference between the external and internal measurement of the internal incision size (p ⫽ 0.07). 2 Measurement performed with globe intact. 3 Measurement performed following removal of cornea.
angulation of the tips allow external and internal measurements of tunnel incisions. A screw connects the two arms of the caliper in the middle of the device (fig. 8). The instrument measures distances in the range of 1–6 mm in 0.1-mm steps. The device is produced for two ranges, 2–4 and 1–6 mm (fig. 8, 9). The thread of the screw is covered with a layer of silicone to allow inadvertent locking. Experimental Studies Incision Sizes (Part A) There was no significant difference between the two methods of measuring post-insertional internal incision size (table 4). Therefore, calculations were performed using the numbers obtained from method A (postinint 1), in which the post-insertional internal incision was measured from outside. In addition, although there were slight differences between the external and internal incision widths, the ANOVA indicated no statistically significant differences between those two measurements (table 5). Therefore, the mean of these two measurements was used to calculate the absolute and percentage enlargement (fig. 10, table 5). Pre-insertion incision widths ranged from 2.9–3.7 mm and increased to 3.2–3.8 mm following IOL insertion (table 5). Incisions enlarged after insertion in each case, ranging from 3.5 to 10.3% (mean 5.9%) for the lenses inserted with forceps and 10.6 to 11.2% (mean 10.9%) for those inserted with injectors. However, there was no statistically significant difference in the percentage enlargement among the different IOLs.
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Table 5. External and internal incision sizes for foldable IOLs measured in 48 cadaver eyes (6 per IOL) IOL (implantation device)
Incision location
Preoperative mm
Postoperative mm
Post.-Pre. mm
Enlargement %
IOLAB LI41U (forceps)
External Internal Mean
3.71 (⫾0.04) 3.70 (⫾0.02) 3.71
3.87 (⫾0.10) 3.79 (⫾0.07) 3.83
0.16 0.09 0.13
3.5
Allergan SI-30NB (forceps)
External Internal Mean
3.13 (⫾0.10) 3.04 (⫾0.09) 3.09
3.33 (⫾0.11) 3.27 (⫾0.14) 3.3
0.20 0.23 0.22
7.1
Chiron C10UB (injector)
External Internal Mean
3.06 (⫾0.18) 2.97 (⫾0.21) 3.02
3.37 (⫾0.05) 3.27 (⫾0.04) 3.22
0.31 0.30 0.32
10.6
Staar AA-4203 (injector)
External Internal Mean
2.98 (⫾0.18) 2.90 (⫾0.17) 2.94
3.32 (⫾0.07) 3.22 (⫾0.10) 3.27
0.34 0.32 0.33
11.2
Alcon MA60BM (forceps)
External Internal Mean
3.66 (⫾0.11) 3.62 (⫾0.12) 3.64
3.80 (⫾0.06) 3.75 (⫾0.10) 3.78
0.14 0.13 0.14
3.8
Alcon MA30BA (forceps)
External Internal Mean
3.19 (⫾0.13) 3.10 (⫾0.20) 3.15
3.41 (⫾0.09) 3.34 (⫾0.10) 3.38
0.22 0.24 0.23
7.3
Storz H60M (forceps)
External Internal Mean
3.24 (⫾0.10) 3.18 (⫾0.07) 3.21
3.55 (⫾0.07) 3.53 (⫾0.04) 3.54
0.31 0.35 0.33
10.3
Alcon SH30BC (forceps)
External Internal Mean
3.26 (⫾0.09) 3.23 (⫾0.09) 3.25
3.38 (⫾0.03) 3.34 (⫾0.05) 3.36
0.12 0.11 0.12
3.6
Statistically, there were three incision size classes for both the pre- and post- insertional assessments (table 6). The largest incisions were associated with the Alcon MA60BM and IOLAB LI41U lenses. The incisions required for insertion of hydrogel lenses (Alcon SH30BC and Storz H60M) were intermediate in size, though the Alcon SH30BH post-insertion incisions were comparable to those of the group with the smallest post-insertion incisions. The smallest incisions were associated with the remaining four lenses, which were not statistically different from each other, even though two were inserted with injectors (Chiron C10UB, Staar AA-4203) and two with forceps (Allergan SI-30NB, Alcon MA30BA).
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4.0 Pre-insertion
Incision size (mm)
3.8
Post-insertion
3.6 3.4 3.2 3.0 2.8 2.6 IOLAB LI41U
Allergan SI-30NB
Chiron C10UB
Staar Alcon AA-4203 MA60BM
Alcon MA30BA
Storz H60M
Alcon SH30BC
Fig. 10. Incision sizes (average of external and internal measurements) in 48 autopsy eyes undergoing insertion of eight different foldable IOLs (6 eyes per IOL), experimental study Part A.
Table 6. Statistical grouping1 of the pre- and postoperative incision size measurements IOL
preext
postext
preint
postint 1
Staar AA-4203 Allergan SI-30NB Chiron C10UB Alcon MA30BA Alcon SH30BC Storz H60M Alcon MA60BM IOLAB LI41U
A A A A B B C C
D D D D D E F F
G G G G H H I I
J J J J J K L L
1
Using the Tukey-Kramer test; incision sizes with the same letter in each column are not significantly different. A, D, G, J ⫽ smallest incision; B, E, H, K ⫽ intermediate incision; C, F, I, L ⫽ largest incision.
Incision Sizes (Part B) The mean external and internal tunnel widths for the smallest possible incision before IOL insertion were 3.05 and 3.02 mm with the forceps and 3.06 and 3.01 mm with the Unfolder, respectively (table 7). Following implantation, the mean external and internal incisional widths were 3.33 and 3.33 mm with
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Table 7. External and internal incision sizes for implantation of SI-40NB IOLs using forceps (Fine Universal Folder II) and injector (Unfolder) (6 implantations per device) Insertion device
Fine Universal II Folder (forceps) Unfolder (injector)
Incision site
Incision size, mm
Enlargement
before IOL insertion
after IOL insertion
mm
%
External Internal Mean
3.05 (⫾0.07) 3.02 (⫾0.03) 3.035
3.33 (⫾0.07) 3.33 (⫾0.04) 3.33
0.28 0.31 0.295
9.0
External Internal Mean
3.06 (⫾0.04) 3.01 (⫾0.04) 3.025
3.32 (⫾0.08) 3.33 (⫾0.07) 3.325
0.26 0.32 0.29
8.8
the forceps and 3.32 and 3.33 mm with the Unfolder. The differences between the external and internal incision widths were negligible, and the ANOVA indicated no statistically significant differences between those two measurements (table 7). Therefore, the mean of these two measurements was used to calculate the absolute and percentage enlargement. The comparison of the incision sizes before and after IOL insertion between the two devices were not statistically significant different. The enlargement following IOL insertion through the smallest possible incision was 9.0% when using the forceps and 8.8% when using the Unfolder. The incision enlargements were not statistically significant different between the forceps and injector groups. SEM Study of the Incisions (Part A) The results of the SEM analysis of the morphology of the endothelial surface of the incisions in the six specimens (with and without IOL implantation) can be summarized as follows: (1) Insertion through a tight incision damaged corneal tissue more than a keratome incision alone. (2) Tearing of Descemet’s membrane and corneal stroma appeared at the lateral borders of the smaller, tight incisions following IOL insertion (fig. 11 vs. 12 and fig. 13 vs. 14). (3) There was some herniation of corneal stromal tissue into the anterior chamber in the 3.0-mm incisions following IOL insertion, and this appeared to be more extensive in corneas implanted with the injector insertion device than with the forceps (fig. 11, 12). The corneal stroma appeared to retain some memory of the shape of the injector after it had been withdrawn from the incision (fig. 11A). This persistent tissue distortion was also noted with inspection of the tighter incisions intraoperatively with the surgical microscope (fig. 15).
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Fig. 11. 3.0-mm corneal tunnel incision in a cadaver-eye cornea following plate-haptic IOL (Staar AA-4203) insertion with a cartridge/injector system. The limbus is in the upper left-hand side of the photographs (E ⫽ endothelium). a The low magnification gives an overview of the shape of the incision. Descemet’s membrane appears to be torn at the inferior border of the incision. Stromal collagen has herniated into the anterior chamber, mainly along the upper border of the incision. Both lateral margins show evidence of tearing and disruption of Descemet’s membrane. SEM. Orig. magn. ⫻ 45. b The higher magnification of the right lateral border demonstrates the tearing of the incision. SEM. Orig. magn. ⫻ 180.
Fig. 12. 3.5-mm corneal tunnel incision in a cadaver-eye cornea (same as in figure 4) following plate-haptic IOL (Staar AA-4203) insertion with a cartridge/injector system. The limbus is again in the upper left-hand side of the photographs (E ⫽ endothelium). a The overview of the incision shows bulging of stromal tissue in the upper part of the incision. The cut edge of Descemet’s membrane is smooth and continuous and the lateral borders show little if any evidence of tearing. SEM. Orig. magn. ⫻ 45. b The higher magnification of the left edge demonstrates almost no tearing of the incision. SEM. Orig. magn. ⫻ 180.
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Fig. 13. 3.0-mm corneal tunnel incision in a cadaver-eye cornea following forceps insertion of a high-refractive-index three-piece silicone IOL (Allergan SI-30NB). The limbus is in the upper left-hand side of the photograph (E ⫽ endothelium). Unlike the two previous incisions (fig. 12, 13), the extent of stromal herniation into the anterior chamber is minimal, but there is evidence of tearing of the lateral borders of the incision (arrows). SEM. Orig. magn. ⫻ 45.
Fig. 14. 3.5-mm corneal tunnel incision in a cadaver-eye cornea (same as in figure 14) following forceps insertion of a high-refractive-index three-piece silicone (Allergan SI-30NB). The limbus is in the upper left-hand side of the photograph (E ⫽ endothelium). There is some mild herniation of corneal tissue into the anterior chamber, but the lateral edges of the incision are sharply defined, suggesting that corneal tearing is absent in this tissue. SEM. Orig. magn. ⫻ 45.
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Fig. 15. Appearance of an incision after forceful insertion of a plate-haptic IOL using an injector.
SEM Study of the Incisions (Part B) 3.0- vs. 3.2-mm incisions: For forceps and injector insertion, the 3.0-mm incisions revealed more tearing of the lateral incision borders and Descemet’s membrane than the 3.2-mm incisions (fig. 16). In all four specimens, there was bulging or herniation of intrastromal tissue into the anterior chamber; this was much more pronounced in the 3.0-mm than in the 3.2-mm incisions. Forceps vs. injector: Comparing the forceps and injector groups, there was no difference in the morphology of the incisions. Clinical Studies Part A In 12 consecutive cataract procedures, the incision sizes before and after IOL implantation were 3.23 (⫾0.10 SD) mm (range 3.1–3.4) and 3.36 (⫾0.06) mm (range 3.3–3.4) with the forceps and 3.12 (⫾0.08) mm (range 3.0–3.2) and 3.22 (⫾0.10) mm (range 3.1–3.3) with the injector, respectively (table 8). The incision sizes for forceps and injector groups were statistically significant different before (p ⬍ 0.005) and after implantation (p ⬍ 0.05); however, the incision enlargement (comparison of incision sizes before and after IOL insertion) was not statistically significant for the two devices. Part B In the 40 cataract procedures the tunnel width (in mm) pre- and postimplantation was 3.32 (⫾0.06) and 3.42 (⫾0.06) for the Pharmacia CeeOn 912 using Nichamin implantation forceps, 3.28 (⫾0.09) and 3.42 (⫾0.09) for the
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Fig. 16. SEM study of endothelial surface of corneal tunnel incisions of cadaver eyes following insertion of SI40NB IOLs. The limbus is in the upper left-hand side of the photographs. Orig. magn. ⫻ 45. a 3.0-mm corneal tunnel incision after insertion with forceps. b 3.2-mm corneal tunnel incision after insertion with forceps. c 3.0-mm corneal tunnel incision after insertion with injector. d 3.2-mm corneal tunnel incision after insertion with injector. a, c 3.0-mm incisions: Descemet’s membrane appears to be torn at the borders of the incision. Stromal collagen has herniated into the anterior chamber and the lateral margins show evidence of tearing. The morphology of the incisions is similar after either forceps or injector implantation. b, d 3.2-mm incisions: The borders of Descemet’s membrane are smooth and continuous, and the lateral borders show minimal if any evidence of tearing. The appearance of the incisions is similar after either forceps or injector implantation.
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Table 8. Incision sizes measured during 12 cataract procedures using forceps (Fine Universal Folder II) and injector (Unfolder) insertions of SI-40NB IOL (6 implantations per device)
Incision After phacoemulsification Before IOL implantation After IOL implantation Enlargement
Fine Folder (forceps), mm
Unfolder (injector), mm
2.96 (⫾0.05) 3.06 (⫾0.05) 3.23 (⫾0.10) 3.36 (⫾0.06) 4.0%
3.01 (⫾0.04) 3.08 (⫾0.10) 3.11 (⫾0.08) 3.21 (⫾0.09) 3.2%
Significance
p ⬍ 0.005 p ⬍ 0.05
Alcon Acrysof MA30BA using Buratto implanation forceps, 3.0 (⫾0.07) and 3.1 (⫾0.05) for the Allergan SI55NB using a Fine Universal II Folder, and 2.66 (⫾0.08) and 2.81 (⫾0.11) for the Allergan SI55NB using the AMO Unfolder, respectively (table 9). The incision sizes before and after IOL implantation were statistically significantly different for the groups (table 10). The enlargement (comparison of incision sizes before and after IOL implantation) was very similar in all four study subgroups with a calculated value of 3–5% (table 9). The incision sizes for the Pharmacia CeeOn 912 and the Alcon MA30BA were not statistically significant different before and after implantation (table 10). However, these two IOLs were statistically significant different in pre- and postimplantation incision size to the Allergan SI55NB IOL implantations. Additionally, the Allergan SI55NB implantation with the AMO Unfolder was associated with statistically significant smaller incision sizes than implantation with the Fine Universal II Folder (tables 9, 10). It should be mentioned that the average dioptric power in this study was the highest in the MA30BA group and lowest in the SI55NB Unfolder group (table 3).
Discussion
Development of a New Caliper to Measure Incision Sizes In a recent clinical study the incision sizes of cataract wounds were measured with several devices. Steinert and Deacon [38] used incision gauges to verify the incision size. Such gauges require in most cases several measurements and can slightly enlarge the wound. Mackool [19] used an Osher internal caliper, whose accuracy had been verified against a standard steel millimeter ruler. This caliper has an incremental scale of 0.5 mm, and therefore requires
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Table 9. Incision sizes measured during 40 cataract procedures using forceps and injector implantation of 5.5-mm total optic 3-piece IOLs (10 implantations per IOL and device) Pharmacia CeeOn 912 (Nichamin forceps) mm
Alcon Acrysof MA30BA (Buratto forceps) mm
Allergan SI55NB (Fine Folder) mm
Allergan SI55NB (AMO Unfolder) mm
Incision
3.02 (⫾0.06)
3.01 (⫾0.03)
2.97 (⫾0.07)
2.59 (⫾0.05)
After phacoemulsification
3.09 (⫾0.07)
3.13 (⫾0.05)
3.00 (⫾0.07)
2.65 (⫾0.09)
Enlargement (due to phacoemulsification)
0.07 (2.3%)
0.12 (4.0%)
0.03 (1.0%)
0.06 (2.3%)
Necessary enlargement
100%
80%
0%
10%
Before IOL implantation
3.32 (⫾0.06)
3.28 (⫾0.09)
3.00 (⫾0.07)
2.66 (⫾0.08)
Enlargement (due to diamond or keratome cut)
0.23 (7.4%)
0.15 (4.8%)
0.00 (0%)
0.01 (0.4%)
After IOL implantation
3.42 (⫾0.06)
3.42 (⫾0.09)
3.10 (⫾0.05)
2.81 (⫾0.11)
Enlargement (due to implantation)
0.1 (3.0%)
0.14 (4.3%)
0.1 (3.3%)
0.15 (5.6%)
Table 10. Statistical grouping1 of the pre- and postimplantation incision size measurements IOL
Pre
Post
Pharmacia CeeOn 912 Alcon Acrysof MA30BA Allergan SI55NB (Fine Folder) Allergan SI55NB (AMO Unfolder)
A A B C
D D E F
Pre ⫽ Preimplantation; Post ⫽ Postimplantation. 1 Using the Tukey-Kramer test; incision sizes with the same letter in each column are not significantly different.
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some estimation of the measurement on the part of the observer. In the experimental studies of our investigations, we have used a modified Osher and vernier calipers to precisely study the incision dimensions with an accuracy of 0.01 mm. This modified Osher caliper also measures with an accuracy of 0.5-mm steps and therefore requires a vernier caliper for more precise values. Unfortunately, this method is too time consuming for clinical studies, and therefore this new device was developed. The practicability of the new instrument was evaluated in the clinical part of this research project for forceps and injector implantation of 3-piece highrefractive-index silicone IOLs (Part A) and for 5.5-mm total optic foldable IOLs (Part B). In Part A, the measurements were first performed with the modified Osher and vernier calipers and were then repeated with the new device. An accuracy of 0.1 mm was found. An advantage of this device compared to incision guages [38] and the modified Osher caliper/vernier caliper system is that only one maneuver is necessary to determine the incision size. With the appropriate surgical experience, enlargement of the incision can be avoided. However, only an optically driven measuring device could totally eliminate the ocular tissue with the forcep tips which might enlarge the tunnel dimensions. For currently used small-incision cataract techniques and available foldable IOLs the new caliper should be preferably used with a measurement range of 2– 4 mm (fig. 9). In summary, this new caliper facilitated easy and atraumatic intraoperative measurement of incision sizes for small-incision surgery with an accuracy of 0.1 mm. Experimental Studies We believe that there are three major conclusions to be derived from the experimental study Part A: First, implantation of foldable IOLs through the smallest possible corneal tunnel incision enlarges the wound. This increase in wound size is accompanied by tearing or disruption of corneal stromal tissue and Descemet’s membrane, whereas appropriately sized incisions show minimal if any insertional tissue damage (fig. 11–14). The clinical impact of this tissue injury is uncertain, but it is our clinical impression that stretched incisions are less likely to be self-sealing and more often require a suture in order to achieve wound closure. Second, this study demonstrates that there are statistically significant differences in incision sizes required for implantation of various foldable IOL/inserter combinations. Following implantation of the 8 foldable IOLs, actual incision sizes ranged from 3.2 to 3.8 mm (experimental study Part A). Three categories of final incision sizes were found: (1) 3.2–3.4 mm: Allergan SI-30NB, Chiron C10UB, Staar AA-4203, Alcon MA30BA, and Alcon SH30BC; (2) 3.5 mm:
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Table 11. Relationship between actual IOL optic diameter and mean postoperative incision size (calculated for a 20.5-D IOL) IOL
IOL optic size
Ratio of IOL optic diameter to incision width, mm
Staar AA-4203 Allergan SI-30NB Chiron C10UB Storz H60M Alcon SH30BC Alcon MA30BA Alcon MA60BM IOLAB LI41U
6.0 6.0 6.0 6.0 5.5 5.5 6.0 6.0
1.84 1.82 1.81 1.70 1.64 1.63 1.59 1.57
Storz H60M; and (3) 3.8 mm: IOLAB LI41U and Alcon MA60BM. Comparing the two three-piece silicone IOLs (IOLAB LI41U and Allergan SI-30NB), the latter, with its high-refractive-index silicone and a smaller refractive optic size (5.3 vs. 6.0 mm), could be implanted through a smaller incision. Although both plate-haptic silicone IOLs tested in this study have a lower refractive index than the two three-piece silicone IOLs (1.41 vs. 1.43/1.46), our data suggest that the use of an injector reduces the incision size required for implantation of these IOLs (clinical study Part A). The soft acrylic IOLs have the highest refractive index of all tested lenses and therefore have the smallest central thickness. The larger incision sizes found for the 6-mm optic acrylic IOL (Alcon MA60BM) compared to most of the other 6-mm optic IOLs suggests that soft acrylic IOL material is not as compressible or pliable as silicone or hydrogel material. There was no clear correlation between optic size and post-insertional incision size. The ratio of millimeters of IOL optic diameter per millimeter of incision was highest for the high-refractive-index silicone IOL and the two plate-haptic IOLs, and lowest for the IOLs that needed a 3.8-mm incision for insertion (table 11). For several IOLs the actual refractive part of the IOL is smaller than the total diameter of the IOL optic. Therefore, another way to evaluate required incision sizes is to calculate the ratio of millimeters of refractive optic diameter per millimeter of incision; this analysis shows a different ordering of the IOLs (table 12). Third, the study suggests that, when implanting IOLs through the smallest possible incisions, there may be qualitative differences in the induced tissue changes depending upon whether forceps or injectors are used. Although these conclusions are only drawn based on two different IOLs (Allergan SI-30NB, Staar AA-4203) and two different implantation devices (Universal Fine II Folder and Microstaar injector) in 6 fresh human cadaver eyes, the SEM images
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Table 12. Relationship between refractive IOL optic diameter and mean postoperative incision size (calculated for a 20.5-D IOL) IOL
IOL refractive optic size
Ratio of refractive IOL optic diameter to incision width, mm
Storz H60M Chiron C10UB Alcon MA30BA Allergan SI-30NB Staar AA-4203 Alcon MA60BM IOLAB LI41U Alcon SH30BC
6.0 5.5 5.5 5.3 5.25 6.0 6.0 5.0
1.70 1.66 1.63 1.60 1.60 1.59 1.57 1.49
suggest that the increase in incision size following injector implantation is associated with greater tissue damage and that the corneal stroma appears to retain some memory of the shape of an injector. There was also a trend toward greater quantitative enlargement of incisions following the use of injectors (10.9% for injectors vs. 5.9% for forceps). We recognize that there are limitations to the cadaver eye model for studying incision sizes following cataract surgery, but clinical studies have already shown comparable results between in vivo and in vitro surgery [19]. Recently, Steinert and Deacon [38] examined intraoperative cataract wound size and demonstrated that the incision enlarges at each step of the procedure – after entry with a keratome, after phacoemulsification and after IOL implantation. For clear corneal tunnel incisions, they found that the final incision sizes for high-refractive-index three-piece and plate-haptic silicone IOLs were 3.31 and 3.34 mm, respectively. They concluded from their study that irreversible incision stretching or tearing occurs, rather than reversible elastic incision deformation. Our laboratory, measurements and SEM evaluation indicate that the distortion seen during insertion of foldable IOLs through tight incisions is accompanied by wound enlargement and damage to corneal structures. We conclude, therefore, that the cornea’s capacity for true elastic deformation is limited and that the cornea is injured by excessive stretching. In the experimental study Part B, additional information was obtained for forceps and injector implantation: First, the study again demonstrated that IOL insertion through an excessively tight incision can damage corneal structures (fig. 4). In Part A we had evaluated by SEM the difference between 3.0- and 3.5-mm incisions for a high-refractiveindex silicone IOL (Allergan Medical Optics SI30NB) and found tearing in the
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smaller incision. In the study Part B the tighter incisions (3.0-mm) again showed greater disruption of corneal tissue than the larger incisions (3.2-mm). Second, in our study, the occurrence of corneal damage was more dependent on the incision size before implantation than on the implantation device. Either the forceps or the injector caused comparable tissue damage if the incisions were too small. Third, the experimental evaluation revealed that insertion of this IOL through a tight incision tears and/or deforms corneal tissue and thereby enlarges the wound by ca. 9%. The enlargement of the incision in the clinical investigation (Part A) was only 3.2 and 4.0%. In the experimental study, incisions were enlarged in 0.25/0.2-mm increments until smooth insertion was possible. In the clinical study Part A, a 3-mm wound was also enlarged minimally, but in a less controlled manner using a diamond knife. This may explain for the greater preinsertion wound width in the clinical series, and thus for the reduced amount of wound enlargement. One further possible explanation for this disparity is that, compared to living tissue, cadaver eye tissue sustains greater tearing or deformation from the incisional enlargement required to implant the IOL. This may therefore indicate a modest limitation of the cadaver eye model for studying incision sizes. However, another potential explanation for the differential incisional enlargement might be the type of blades used. In the cadaver eyes, the incisions were made with steel knives, whereas in the clinical study a diamond knife was used. Radner et al. [32] recently showed that the IOL implantation through 3.0-mm clear corneal incisions made with steel keratomes produced corneal trauma that was considerably more severe than implantation through 3.2-mm wide steel blade incisions or 3.0-mm diamond incisions. Another study by this group [31] demonstrated that cutting corneal tissue with diamond tips caused less tissue damage than expanding the incisions with blunt caliper tips. Thus the smaller amount of incisional enlargement in the clinical arm of our study Part A might be simply due to the use of the diamond knife. Additional clinical study will be required to verify this hypothesis.
Clinical Studies The silicone IOL used in clinical study Part A allows the smallest possible incisions currently achievable for three-piece, 6-mm optic IOLs. Olson et al. [26] recently found in a clinical evaluation of the Unfolder that the new injector provided a controlled IOL implantation through incisions ranging from 2.7 to 3.2 mm in width. In their study, the incision sizes increased as a result of IOL implantation, with widths ranging from 2.9 to 3.3 mm. Their results are comparable to the incision sizes determined in our current investigation. In our clinical study and Olson’s evaluation, the incision sizes using the injector were
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smaller than those required for forceps implantation with this IOL (table 8). We suspect that additional refinement of the design of injector systems might further reduce the incision size required for IOL implantation; however, the amount of reduction is not likely to exceed 0.5 mm with the current IOL design, since the IOL itself comprises the majority of material introduced into the wound when using the Unfolder. Most of the IOLs studied in previous [24, 26, 38] and in our investigations were 6-mm total optic IOLs. Recently, 5.5-mm total optic foldable IOLs have been available, with one reason being a predicted decrease in postinsertion incision size. In the current investigation (clinical study Part B), incision sizes of 2.8–3.4 mm were found for 5.5-mm total optic 3-piece foldable IOLs. This is a decrease in the range of incision sizes compared to the 3.1–3.9 mm in studies investigating 6-mm IOLs [24–26, 38]. The incision sizes for 5.5-mm total optic IOLs obtained in other studies are comparable to the findings of the current investigation. For example, incision sizes for the Alcon Acrysof MA30BA were as follows: 3.38 ⫾ 0.10 mm in the experimental study Part A, 3.4 ⫾ 0.13 mm in a clinical study [25], and 3.42 ⫾ 0.09 mm in the current clinical investigation. The results from these experimental and clinical investigations were quite similar. Beside our studies (experimental study Parts A ⫹ B) several studies have recently shown that the wound progressively enlarges during the various steps of small-incision cataract surgery [19, 31–33, 38]. It was found that implantation of foldable IOLs through the smallest possible corneal tunnel incision enlarged the wound, and this enlargement was accompanied by tearing or disruption of corneal stromal tissue and Descemet’s membrane, whereas appropriately sized incisions showed minimal if any insertional tissue damage. When implanting IOLs through the smallest possible incisions, a qualitative differences in induced tissue changes was seen, depending upon whether forceps or injectors were used. All investigators observed that the smallest possible incision enlarged during the implantation process. Sufficient enlargement of the wound before IOL implantation is therefore recommended. To investigate the impact of an implantation device the SI55NB IOL was implanted with an injector (AMO UNFOLDER Implantation Systems) and with forceps especially designed for this IOL (Fine Universal II Folder). A statistical difference was found for the incision sizes before and after IOL implantation (table 9). A difference between forceps and injector implantation was also found for 6-mm optic high-refractive-index silicone IOLs (Allergan SI30NB, SI40NB) in our experimetal study Part B and in another previous study [26]. The smallest incision sizes associated with using forceps were 3.31 mm [38], 3.36 mm (table 8) and 3.32 mm [24], whereas with the Unfolder the incison sizes were 3.21 mm (table 8) and 3.1 mm [26].
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Fig. 17. Injector systems (AMO® UNFOLDER Implantation System) for implantation of the Allergan three-piece highrefractive-index silicone IOLs: Comparison of the SI55NB and SI40NB cartridge tips side by side showing a difference in orifice and tip shaft (see Discussion).
The Unfolder cartridges for implantation of the Allergan SI40NB and SI55NB three-piece high-refractive-index silicone IOLs are shown in figure 17. Different cartridges and metal injectors are used for the IOLs. The differences in the injectors are: (1) The SI55NB orifice and tip shaft are 0.127 mm smaller relative to both the inside and outside diameters. (2) The SI55NB tip shaft has a more gradual taper at the distal end, making it slightly more parallel until about half way down the tip. Other than that, they are identical. The distal orifices are round while the proximal ends are more elliptical, with the transition gradually occurring throughout the tip. The slight changes of the tips for the Allergan SI40NB and SI55NB three-piece high-refractive-index silicone IOLs and the different diameters of the IOL (5.5 vs. 6 mm) allowed a decrease in incision size of ca. 0.4 mm (3.2–2.8 mm). Another factor which influences incision size is dioptric power of the IOL [24]. We only used in the clinical study Part B IOLs with a dioptric power of 20 D and higher, because we feel that the 5.5-mm total optic IOLs are too small for myopic eyes. This is even more problematic with IOLs which only have a refractive optic of 5.0 mm like the Allergan SI55NB. Also the IOLs were only implanted in eyes with smaller pupils to prevent optic edge glare [11]. Additionally the capsulorhexis size was always smaller than the overall optic to cover the IOL body with anterior capsule. The groups were too small to perform a statistical analysis to correlate IOL power and incision size. With respect to the slight differences found in the study of Moreno-Montañés [24], a larger number of cases need to be investigated to show a real difference for different IOL powers. From the clinical study Part B of 5.5-mm total optic foldable IOLs, several conclusions can be drawn: (1) The average incison size for 5.5-mm total optic 3-piece foldable IOLs (2.8–3.4 mm) is smaller than for 6-mm total optic 3-piece foldable IOLs (3.1–3.9 mm) [24–26, 38].
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Table 13. Relationship between actual (total) IOL optic diameter and mean postimplantation incision size IOL
Total IOL optic size, mm
Ratio of total IOL optic diameter to incision size, mm
Allergan SI55NB (AMO Unfolder) Allergan SI55NB (Fine Folder) Alcon Acrysof MA30BA Pharmacia CeeOn 912
5.5 5.5 5.5 5.5
1.96 1.77 1.61 1.61
Table 14. Relationship between refractive (effective) IOL optic diameter and mean postimplantation incision size IOL
Refractive IOL optic size, mm
Ratio of refractive IOL optic diameter to incision size, mm
Allergan SI55NB (AMO Unfolder) Alcon Acrsof MA30BA Allergan SI55NB (Fine Folder) Pharmacia CeeOn 912
5.0 5.5 5.0 5.5
1.78 1.61 1.61 1.61
(2) The incision width of 2.81 mm after IOL implantation of the Allergan SI55NB using an Unfolder is the smallest postimplantation incision currently documented in the peer-reviewed literature. (3) For the same lens model, incision size associated with the implantation using an injector is less than using forceps. (4) There is no clear correlation between the refractive index of the IOL material and post-insertional incision size. Although the high-refractive-index silicone IOL (refractive index of 1.46) showed a smaller incision size than the Pharmacia silicone IOL with a refractive index of 1.43, the incision size for the high-refractive-index (1.55) hydrophobic acrylic IOL was equal to the Pharmacia silicone IOL with a refractive index of 1.43. (5) The ratio of millimeters of total IOL optic diameter per millimeter of incision was highest for the high-refractive-index silicone IOL implanted with the AMO Unfolder injector (table 13). (6) However, another way to evaluate required incision sizes is to calculate the ratio of millimeters of refractive optic diameter per millimeter of incision, because the actual refractive part of the IOL can be smaller than the total diameter of the IOL optic. This analysis shows a different ordering of the IOLs (table 14).
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The implantation of all three IOLs using the forceps shows the same results; the high-refractive-index silicone IOL implanted with the Unfolder still provides the best ratio (table 14).
Conclusions
Numerous clinical studies have reported incision sizes following cataract extraction and IOL implantation [3, 4, 12, 14, 18, 20, 22, 23, 28, 30, 37], but the actual incision sizes postoperatively were not measured. Since these measurements are the basis for further evaluation of the procedures (e.g., calculation of induced astigmatism or corneal topographical changes), determination of the true postoperative incision size is important before its impact on other variables can be accurately assessed. Our studies demonstrate that incisions enlarge following foldable IOL insertion through the smallest pre-insertional incision. Incision sizes following insertion of foldable IOLs ranged from 2.8 to 3.8 mm. The results of these studies can assist surgeons in choosing an adequate incision size for atraumatic implantation of foldable IOLs through self-sealing tunnel incisions. To determine the correct incision size in clinical studies, the incision width must be carefully measured following IOL implantation.
Acknowledgments The author would like to thank Douglas D. Koch, MD, Cullen Eye Institute, Baylor College of Medicine, Houston, Tex., USA, Richard J. Lambert, PhD, DVM, Alcon Laboratories, Inc, Ft. Worth, Tex., USA, and Jim Deacon, PhD, Allergan Medical Optics, Irvine, Calif., USA, for their help in designing and performing the study, Robert W. Lambert, PhD, and Perry S. Binder, MD, National Vision Research Institute, San Diego, Calif., USA, for the scanning electron microscopy studies and Alexander S. Kogan, Baylor College of Medicine, Houston, Tex., USA, and Rolf Palme, Department of Ophthalmology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany, for the photography artwork.
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Priv.-Doz. Dr. med. Thomas Kohnen, Department of Ophthalmology, Johann Wolfgang Goethe University, Theodor-Stern-Kai 7, D–60590 Frankfurt am Main (Germany) Tel. ⫹49 69 6301 6739, Fax ⫹49 69 6301 3893, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 187–194
Scheimpflug Imaging of Modern Foldable High-Refractive Silicone and Hydrophobic Acrylic Intraocular Lenses Martin Baumeister, Jens Bühren, Thomas Kohnen Department of Ophthalmology, Johann Wolfgang Goethe University, Frankfurt am Main, Germany
Scheimpflug photography was first introduced into ophthalmic diagnostics by Niesel [23, 24] and Brown [4], mainly as a standardized method to obtain reproducible slit images of the human lens for cataract research. Hockwin and Dragomirescu [6] constructed the first Scheimpflug camera with a rotating slit illumination to obtain images of all lens meridians. Since then, Scheimpflug imaging has been used for various purposes in the diagnostics of the anterior eye segment. In 1989, Sasaki et al. [29] developed a method of determining tilt and decentration of posterior chamber intraocular lenses (IOLs) by two Scheimpflug slit images taken at orthogonal slit axes. We investigated three different types of three-piece foldable IOLs using this technique.
Patients and Methods In 24 cataractous eyes (7 female, 17 male; 12 right eyes, 12 left eyes; mean age 69.8 (57–90) years) continuous curvilinear capsulorhexis, phacoemulsification, bimanual irrigation and aspiration and IOL implantation were performed. In all cases hyaluronic acid (Healon or Healon GV, Pharmacia, Erlangen, Germany) was used as viscoelastic substance. The demographics of the single groups are shown in table 1. There was no other ocular pathology in any of the cases. All surgeries were done by the same surgeon (T.K.) using topical anesthesia and a self-sealing temporal limbal tunnel incision. No complications occurred during surgery or postoperatively. Three types of foldable IOLs were implanted: Allergan SI40 (fig. 1a, b), 3-piece biconvex high-refractive silicone IOL with polymethyl methacrylate (PMMA) haptics (n ⫽ 5), Pharmacia 911A (fig. 2a, b), 3-piece biconvex high-refractive silicone IOL with polyvinylidene fluoride haptics (n ⫽ 14), Alcon AcrySof MA60BM (fig. 3a, b),
Fig. 1. Allergan SI40 (high-refractive silicone IOL, 6-mm optic, PMMA haptics). a Overview. b Scheimpflug slit image. Fig. 2. Pharmacia CeeOn 911A (high-refractive silicone IOL, 6-mm optic, polyvinylidene fluoride haptics). a Overview. b Scheimpflug slit image. Fig. 3. Alcon AcrySof MA60BM (hydrophobic acrylic IOL, 6-mm optic, PMMA haptics). a Overview. b Scheimpflug slit image.
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Table 1. Demographics of the examined patients
Eyes, n Sex, m/f Age, years (mean ⫾ SD) Left/right
Allergan SI40NB
Pharmacia 911A
Alcon MA60BM
5 5/0 70.1 ⫾ 6.0
14 8/6 71.6 ⫾ 8.6
5 4/1 67.6 ⫾ 5.0
3/2
7/7
2/3
3-piece hydrophobic acrylic IOL with PMMA haptics (n ⫽ 5). All IOLs had an optic diameter of 6.0 mm and C-loop haptic design. The postoperative IOL position was measured 6 and 12 months after surgery using a rotating digital charge-coupled device Scheimpflug camera connected with a personal computer (EAS-1000, Nidek Co., Gamagori, Japan) that allowed digital processing of the obtained images. After maximal pupil dilation, two Scheimpflug slitlamp images of each IOL were taken at slit angles of 90 and 180°. The anterior and posterior surfaces of the cornea and the IOL were marked on the computer monitor to determine the visual axis of the eye and the optical axis of the IOL. The tilt of the IOL optic axis compared to the visual axis, the distance between the IOL vortex and the visual axis and the anterior chamber depth (ACD) were calculated. The differences among the three groups and the periodic changes in each group were compared by single-factor analysis of variance. Differences with a p value ⬍0.05 were considered statistically significant.
Results
The amount of decentration of the three IOLs is shown in table 2. No statistical significance could be detected. Table 3 shows the degree of optic tilt. Although the Alcon AcrySof IOL showed slightly less tilt than the others, the differences between the IOLs were not statistically significant. Table 4 shows the ACD in the three groups. As for the other two parameters, a statistically significant difference was not detectable.
Discussion
Scheimpflug photography of IOLs has been performed mainly for two purposes: (1) Biometrical assessment of lens position (tilt and decentration) and positional stability (changes in lens position over time). (2) Monitoring of posterior capsule opacification (PCO) (light scattering from the posterior lens capsule).
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Table 2. Amount of decentration (mm) of the examined IOLs 6 and 12 months after surgery (mean ⫾ SD)
Allergan SI40NB Pharmacia 911A Alcon MA60BM p value
6 months
12 months
0.16 ⫾ 0.08 0.30 ⫾ 0.21 0.24 ⫾ 0.18 0.25
0.22 ⫾ 0.12 0.25 ⫾ 0.13 0.44 ⫾ 0.36 0.15
Table 3. Amount of IOL tilt (degrees) 6 and 12 months after surgery (mean ⫾ SD)
Allergan SI40NB Pharmacia 911A Alcon MA60BM p value
6 months
12 months
3.89 ⫾ 1.45 3.91 ⫾ 1.94 2.54 ⫾ 1.46 0.31
3.16 ⫾ 1.39 3.72 ⫾ 2.09 2.69 ⫾ 2.01 0.58
Table 4. Anterior chamber depth (mm) in the examined eyes 6 and 12 months after surgery (mean ⫾ SD)
Allergan SI40NB Pharmacia 911A Alcon MA60BM p value
6 months
12 months
3.94 ⫾ 0.27 3.82 ⫾ 0.17 3.93 ⫾ 0.63 0.41
4.04 ⫾ 0.20 3.90 ⫾ 0.20 4.14 ⫾ 0.44 0.20
Various types of anterior and posterior chamber IOLs have been developed for correction of aphakia and, more recently, as phakic implants to correct refractive errors. By the use of foldable IOLs, it has become possible to significantly reduce the incision size for IOL implantation [17]. Therefore, foldable IOLs have become increasingly popular among cataract surgeons [22]. The major advantages of the reduced incision size are faster visual rehabilitation and minimized induced astigmatism. With high-refractive silicone lenses, incision sizes ⬍3 mm can be achieved [16]. Postoperative complications and refractive changes due to lens tilt and displacement have been reported [5, 18, 20].
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An IOL decentration of ⬎1.0 mm or an optic tilt of ⬎5° have been considered to cause clinically significant impairment of visual quality [9]. Earlier studies reported tilt and decentration as main complications of foldable IOLs in comparison to rigid PMMA IOLs [1, 5]. There is a variety of methods to determine tilt and decentration of IOLs and to measure changes in postoperative IOL position [2, 18, 19, 27]. The Scheimpflug photography as applied by Sasaki et al. [29] has been proven to be a valuable tool for in vivo measurements. Optic tilt and decentration are calculated as deviation of the optic axis of the IOL from the optic axis of the eye (selected as the connecting line between the center of the anterior surface curvature and the geometrical center of the pupil) from two Scheimpflug slit images taken at angles of 180 and 90°. This method has been incorporated in the software of the EAS-1000 anterior eye segment analysis system from Nidek that was released in 1991 [28]. For this reason, almost all studies that involve Scheimpflug photography of IOLs were performed using this imaging system. Several studies have been conducted using this technique. Hayashi et al. [11] compared tilt and decentration between one-piece and three-piece PMMA IOLs and found no significant differences regarding the optic tilt but better centration in the one-piece IOL than in the three-piece IOL with flexible haptics. Another study of the same authors, however, revealed no significant differences in tilt and decentration between rigid PMMA IOLs and silicone and acrylic soft IOLs [9]. The same group compared tilt and decentration in one-piece PMMA IOLs that were either scleral-suture fixated, sulcus-fixated or implanted in the capsular bag and found a significantly higher degree of dislocation in the suturefixated group [13]. Wang et al. [32] examined the positional changes of PMMA and silicone IOLs after phacoemulsification and in-the-bag implantation and found no differences in postoperative stability. Our comparison of two silicone and one acrylic foldable IOLs likewise detected no significant differences for tilt and decentration and confirmed the previous findings. Hayashi and co-workers [8, 10, 12] conducted several studies about IOL stability in eyes with abnormal preoperative conditions and found increased tilt and decentration of the IOL in eyes with pseudoexfoliation, glaucoma and retinitis pigmentosa. Yang et al. [33] detected no significant differences in postoperative IOL position between eyes with primary angle-closure glaucoma and a normal control group. A conclusion that can be drawn from these results is that the postoperative stability of modern IOLs depends not as much on the IOL material and design as on the surgical technique applied (in-the-bag, sulcus-fixated, scleral-suture fixated) and on the preoperative pathologies of the operated eye (glaucoma, pseudoexfoliation, retinitis pigmentosa).
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PCO as a postoperative complication of phacoemulsification and IOL implantation remains a major issue in cataract surgery [31]. Most techniques for objective quantification of PCO use evaluation of retroillumination photographs [7, 26, 30]. Lasa et al. [21] first developed a method of documenting PCO by means of Scheimpflug photography. However, this system found no wider application in clinical studies because it involved only the central 1-mm zone of the IOL optic. Hayashi et al. [14] presented a technique of PCO quantification by averaging the density values of the posterior capsule in Scheimpflug images taken on different meridians. They found this to be a valid and reliable method but pointed out that some improvements had yet to be made to establish this system as a routine technique. A close attachment of the posterior lens capsule to the IOL optic is seen as an important factor for PCO prevention [25]. Scheimpflug photography allows for documentation of changes in the distance between IOL optic and posterior capsule [15]. Klos et al. [15] reported about Scheimpflug evaluation of changes in IOL material such as the ‘glistenings’ in acrylic IOLs. Recently, we published a study on Scheimpflug imaging of phakic anterior and posterior chamber IOLs (pIOL) for correction of refractive errors [3] and could show that this is a valuable tool for the postoperative monitoring of position and stability of the implants and of possible cataract development in the human lens that could be caused by phakic IOLs. Conclusion
Centration in the capsular bag achieved with modern three-piece foldable IOLs is excellent and comparable with that of PMMA IOLs. Scheimpflug photography offers a noncontact biometric method that is fast and easy to perform and has been proven suitable for routine examinations of phakic and pseudophakic IOLs. References 1 2 3
4 5
Allarakhia L, Knoll RL, Lindstrom RL: Soft intraocular lenses. J Cataract Refract Surg 1987;13: 607–620. Auran JD, Koester CJ, Donn A: In vivo measurement of posterior chamber intraocular lens decentration and tilt. Arch Ophthalmol 1990;108:75–79. Baumeister M, Bühren J, Schnitzler EM, Ohrloff C, Kohnen T: Scheimpflug-fotografische Untersuchungen nach Implantation phaker Vorder- und Hinterkammer-Intraokularlinsen: Erste Erfahrungen. Klin Monatsbl Augenheilkd 2001;218:125–130. Brown N: Slit-image photography. Trans Ophthalmol Soc UK 1969;89:397–408. Chen TT: Clinical experience with soft intraocular lens implantation. J Cataract Refract Surg 1987;13:50 –53.
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6
7 8 9 10
11
12 13
14 15
16 17 18 19 20 21 22 23 24 25 26 27 28 29
Dragomirescu V, Hockwin O, Koch HR, Sasaki K: Development of a new equipment for rotating slit image photography according to Scheimpflug’s principle; in Hockwin O (ed): Gerontological Aspects of Eye Research. Basel, Karger, 1978, pp 118–130. Friedman DS, Duncan DD, Munoz B, West SK, Schein OD: Digital image capture and automated analysis of posterior capsular opacification. Invest Ophthalmol Vis Sci 1999;40:1715–1726. Hayashi H, Hayashi K, Nakao F, Hayashi F: Anterior capsule contraction and intraocular lens dislocation in eyes with pseudoexfoliation syndrome. Br J Ophthalmol 1998;82:1429–1432. Hayashi K, Harada M, Hayashi H, Nakao F, Hayashi F: Decentration and tilt of polymethyl methacrylate, silicone, and acrylic soft intraocular lenses. Ophthalmology 1997;104:793–798. Hayashi K, Hayashi H, Matsuo K, Nakao F, Hayashi F: Anterior capsule contraction and intraocular lens dislocation after implant surgery in eyes with retinitis pigmentosa. Ophthalmology 1998; 105:1239–1243. Hayashi K, Hayashi H, Nakao F, Hayashi F: Comparison of decentration and tilt between onepiece and three-piece polymethyl methacrylate intraocular lenses. Br J Ophthalmol 1998;82: 419–422. Hayashi K, Hayashi H, Nakao F, Hayashi F: Intraocular lens tilt and decentration after implantation in eyes with glaucoma. J Cataract Refract Surg 1999;25:1515–1520. Hayashi K, Hayashi H, Nakao F, Hayashi F: Intraocular lens tilt and decentration, anterior chamber depth, and refractive error after trans-scleral suture fixation surgery. Ophthalmology 1999;106: 878–882. Hayashi K, Hayashi H, Nakao F, Hayashi F: Reproducibility of posterior capsule opacification measurement using Scheimpflug videophotography. J Cataract Refract Surg 1998;24:1632–1635. Klos KM, Richter R, Schnaudigel O, Ohrloff C: Image analysis of implanted rigid and foldable intraocular lenses in human eyes using Scheimpflug photography. Ophthalmic Res 1999;31: 130–133. Kohnen T: Incision sizes with 5.5-mm total optic, 3-piece foldable intraocular lenses. J Cataract Refract Surg 2000;23:1765–1772. Kohnen T, Lambert RJ, Koch DD: Incision sizes for foldable intraocular lenses. Ophthalmology 1997;104:1277–1286. Korynta J, Bok J, Cendelin J: Changes in refraction induced by change in intraocular lens position. J Refract Corneal Surg 1994;10:556–564. Kozaki J, Tanihara H, Yasuda A, Nagata M: Tilt and decentration of the implanted posterior chamber intraocular lens. J Cataract Refract Surg 1991;17:592–595. Lakshminarayanan V, Enoch JM, Raasch T, Crawford B, Nygaard RW: Refractive changes induced by intraocular lens tilt and longitudinal displacement. Arch Ophthalmol 1986;104:90–92. Lasa MS, Datiles MB 3rd, Magno BV, Mahurkar A: Scheimpflug photography and postcataract surgery posterior capsule opacification. Ophthalmic Surg 1995;26:110–113. Leaming DV: Practice style and preferences of ASCRS members – 1999 survey. J Cataract Refract Surg 2000;26:913–921. Niesel P: Spaltlampenphotographie der Linse für Messzwecke. Ophthalmologica 1966;152: 387–395. Niesel P: Spaltlampenphotographie mit der Haag-Streit-Spaltlampe 900. Ophthalmologica 1966; 151:489–504. Nishi O: Posterior capsule opacification. 1. Experimental investigations. J Cataract Refract Surg 1999;25:106–117. Pande MV, Ursell PG, Spalton DJ, Heath G, Kundaiker S: High-resolution digital retroillumination imaging of the posterior capsule after cataract surgery. J Cataract Refract Surg 1997;23:1521–1527. Phillips P, Perez-Emmanuelli J, Rosskothen HD, Koester CJ: Measurement of intraocular lens decentration and tilt in vivo. J Cataract Refract Surg 1988;14:129–135. Sasaki K, Sakamoto Y, Shibata T, Emori Y: The multi-purpose camera: A new anterior eye segment analysis system. Ophthalmic Res 1990;22(suppl 1):3–8. Sasaki K, Sakamoto Y, Shibata T, Nakaizumi H, Emori Y: Measurement of postoperative intraocular lens tilting and decentration using Scheimpflug images. J Cataract Refract Surg 1989; 15:454–457.
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30 31 32 33
Tetz MR, Auffarth GU, Sperker M, Blum M, Volcker HE: Photographic image analysis system of posterior capsule opacification. J Cataract Refract Surg 1997;23:1515–1520. Tetz MR, Nimsgern C: Posterior capsule opacification. 2. Clinical findings. J Cataract Refract Surg 1999;25:1662–1674. Wang MC, Woung LC, Hu CY, Kuo HC: Position of poly(methylmethacrylate) and silicone intraocular lenses after phacoemulsification. J Cataract Refract Surg 1998;24:1652–1657. Yang CH, Hung PT: Intraocular lens position and anterior chamber angle changes after cataract extraction in eyes with primary angle-closure glaucoma. J Cataract Refract Surg 1997;23: 1109–1113.
Priv.-Doz. Dr. med. Thomas Kohnen, Department of Ophthalmology, Johann Wolfgang Goethe University, Theodor-Stern-Kai 7, D–60590 Frankfurt am Main (Germany) Tel. ⫹49 69 6301 6739, Fax ⫹49 69 6301 3893, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 195–201
Does the PCO Preventing Square Edge Concept Apply to Acrylic-Hydrophilic Intraocular Lenses? Stéphane Jaullery, Philippe Sourdille Centre Hospitalier Intercommunal Tarbes and Clinique Sourdille, Nantes, France
Postcataract operation lens epithelial cell (LEC) migration and transformation create various forms of capsular opacification, resulting in visual acuity loss. Modifying the design of current intraocular lenses (IOLs) by cutting sharp rectangular edges on the haptics and optic has proven experimental and clinical efficiency. Hara et al. [1] proposed in 1991 an ‘equator ring’ to maintain a complete circular contour of the capsular bag equator. The ring had a square section and an experimental decrease in LEC migration was noted. Nishi and co-workers [2–4] related the effect to the capsular bend created by the sharp edge, and demonstrated a similar action with acrylic and PMMA optic material. Nishi et al. [2–4] and Menapace et al. [5] designed a square capsular tension ring which, in addition to mechanical actions, is efficient in PCO prevention. The combination of acrylic and hydrophilic materials has been proposed to benefit both from the resistance of acrylic and from the greater foldability and ease of insertion of hema, creating a very ‘user-friendly’ material. Different combinations of hema and acrylics have been proposed, with a hydrophilicity ranging from 18 to 34%. These IOLs share great mechanical properties and longterm stability. But they have also been reported to have a higher rate of PCO (fig. 1, 2) and a case of calcium deposit on the surfaces of an 18% hema optic (Hydroview, Storz) has recently been published by Werner et al. [6]. Could the square edge design of haptics and optic on a mixed acrylichydrophilic IOL prevent LEC migration and solve the related problems?
Fig. 1. First-generation ACR6 – round edges, nonangulated haptics: LEC proliferation at the capsulorhexis margin and on the posterior capsule.
Fig. 2. ACR6 SE – angulated haptics (10°) sharp edge technology: both anterior and posterior capsules are transparent at 8 months.
Material and Methods IOL Characteristics The lens is a copolymer of hydroxyethylmethacrylate (HEMA) and methylmethacrylate (MMA). The hydrophilicity percentage is 26%, refractive index is 1.46. Resistance to tearing is superior to 2 mPa, 3 times superior to hema and equivalent to silicone. It is a
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one-piece lens, with an overall diameter of 12.5 mm. The haptics have a posterior angulation of 10°. Haptics and optic have a square edge (90°). The lens is manufactured by Cornéal SA, Pringy, France.
Experimental Surgery We conducted an experimental study at the Bascom Palmer Eye Institute (Miami, Fla., USA): two groups of 8 young pigmented rabbits each were unilaterally implanted with an Acrysof (Alcon) IOL or with the modified IOL (ACR6D SE, Cornéal). Surgery consisted of a 2-mm wide clear cornea incision followed by a 4.5–5 mm capsulorhexis, lens matter extraction by infusion-aspiration, opening of the surgical entry to 4 mm, in the bag IOL insertion and closing of the wound with 10/0 nylon stitch. Two animals of each group were euthanized at postoperative days 7, 14, 21 and 28 and fixed in formalin or glutaraldehyde for Miyake’s view and histology readings. No statistical difference in PCO level was found among the groups at any of the four time periods. The optical zone was consistently more transparent with the ACR6D SE than with the acrylic IOL. No clinical or histological foreign body reaction, such as giant cells, were observed with any of the implants at any of the postoperative periods. The effect of the square edge could be demonstrated. No contact inhibition effect was observed with either material. Vacuoles were documented in the PEA-MMA (Acrysof) material.
Clinical Study Two different groups of patients were enrolled independently in two different centers. In all cases a hydrophilic acrylic IOL (ACR6D SE, Cornéal) was implanted. Group 1: 102 cataractous eyes of 102 patients, average age 76.4 (range 45–93) years. 13% had associated ocular pathologies: drusen, ARMD, glaucoma, diabetes. The surgical technique consisted of 4-mm unsutured temporal clear cornea incision, 4.5–5 mm capsulor-hexis, phacoemulsification, polishing of posterior capsule, in the bag implantation (forceps). Average best corrected preoperative visual acuity (BCVA) was 0.26. Average power of the IOL was 22.4 D (average constant 120). One surgeon (S.J.) operated. The postoperative regimen consisted of topical dexamethasone indomethacin 3 times a day for 1 month. Group 2: 58 cataractous eyes of 52 patients, average age 70.5 (range 42–94) years. 47 eyes were diagnosed with cataract only. Seven of these presented with various degrees of ARMD and drusen. Two had uveitis, there was 1 case of trauma, and 2 diabetes. Nine eyes had a combined operation cataract glaucoma, 2 eyes had a combined cataract penetrating keratoplasty (PK). Average preoperative BCVA was 0.25 (SD 0.13). Average IOP was 16.44 (range 7–26) mm Hg. The surgical technique for cataract only was identical to group 1, combined glaucoma operations were nonpenetrating trabecular surgery done at the 12 o’clock position and separate temporal incision for cataract extraction. In the 2 PK cases the lens was removed through the corneal trephine. All IOLs were implanted in the bag. There was no intraoperative complication in the groups. Average power of the IOL was 23.4 D (average constant 120). One surgeon (Ph.S.) operated. The postoperative regimen consisted of dexamethasone indomethacin 3 times a day for 2 weeks, and then indomethacin alone (3 times) for 4 weeks (dexamethasone was prolonged for a further 2 months in case of combined PK).
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Results
Group 1: All 102 patients were followed up at least 1 year, and 11 patients were re-examined at 18 months. 100% have a BCVA 0.5, 92% are 0.8, 68% are 1 (20/20). Best cases group (excluding 13% of eyes because of associated pathologies): 100% are 0.8, 78% are 1 (20/20). Average postoperative refraction is 0.2 D (refraction ranging from 1.25 to 1), stable during the whole follow-up period. 15% of patients demonstrated some nonprogressive deposits on the posterior capsule, they were related to incomplete intraoperative polishing of the capsule. One patient had a one-line drop of visual acuity, and 1 had a two-line drop (nonprogressive). The posterior capsule behind the optic remained clear, with no progression of LECs. Densification of the capsulorhexis margin was observed in less than 10% of the cases, without any cell proliferation on the anterior surface of the optic. No YAG capsulotomy had to be performed. The EPCO score was calculated for the 11 patients at 18 months and was 0.0207 (SD 0.12). This extremely low score corroborates the slit lamp results. Group 2: All 58 patients were followed up for at least 8 months. Ten patients were re-examined at 1 year. Average BCVA was 0.86 (results ranging from 0.2 to 1 according to the associated pathologies). Average postoperative refraction was 0.32 D (refraction ranging from 1.25 to 1.25), stable after 2 weeks and during the whole follow-up period. Average postoperative IOP was 13.25 (range 10–22) mm Hg without treatment. No patient demonstrated any LEC progression behind the optic and the blocked LECs could consistently be seen at the equator of the optic (fig. 3–5). Two central capsular folds were documented, without VA decrease. Densification of the capsulorhexis margin was noted in 7 eyes, without any cell proliferation on the anterior surface of the optic. No YAG capsulotomy was performed. Special attention was paid to capsule contact with the optic of the IOL, and to its stability. This was analyzed by slit lamp and by the Eye Analyzer System (EAS, Nidek). The frontal distance of the IOL was measured from the center of the posterior cornea to the center of the optic anterior surface. This remained stable between the first week, the first month and the third month, with respective distances (expressed in mm) of 4.33 (SD 0.43), 4.32 (SD 0.31) and 4.18 (SD 0.35). No tilt, nor decentration could be detected. Contact of the anterior capsule with the anterior surface of the optic was absent in 57/58 eyes during the first week, absent in 48/58 during the first month and absent in 13/58 at 3 months. Contact of the posterior capsule at the center of the optic was absent in 54/58 eyes during the first week, absent in 37/58 during the first month and absent in 4/58 at 3 months. This absence of contact was only true for the central 3 or 4 mm of the optic. The equatorial zone had a consistent and firm contact.
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Fig. 3 and 4. ACR6 SE – 10 months: blockage of LEC migration at the optic edge. Fig. 5. ACR6 SE – 12 months: blockage of accumulated LECs at the optic edge.
Discussion
Globally these experimental and clinical results demonstrate the clinical safety and efficiency of the new IOL. No membrane or cellular formation was detected on the anterior or posterior surface of the optic. No deposit of any kind was noted on the surfaces or inside the IOL. The experimental comparison with the current ‘gold standard’ in terms of PCO prevention (Acrysof, Alcon) was logical and positive. But the highly active reproliferation of rabbit capsular bags is a limit to transposition of experimental surgery results in humans. Despite this limitation, our data, including histology readings, indicate an excellent tolerance and some decrease in lens regeneration, with a consistent greater posterior capsule clarity in the ACR6 SE group. Our two groups of clinical results are not comparable: Group 1 has more standard indications of cataract operations, with VA results far above the FDA requirements. This group also demonstrated a clinically absent PCO during the 18-month follow-up period. Group 2 has been designed as a combination of various indications, potentially subject to more postoperative inflammation and to various ocular reactions than straightforward cataract cases. The average postoperative VA is lower, as expected, but no adverse reaction has been noted. It is currently possible to document PCO very precisely: slit-lamp examination to assess capsule contact with IOL optic and haptics, LEC migration from the equator of the capsular bag, and capsular transparency between the equator and the optic will identify any early or secondary proliferation transformation of the LECs. EPCO software analysis offers a reproducible and objective measurement, and can be used in multicentric studies to compare surgical techniques, IOL designs and materials. The absence of anterior capsule-IOL optic contact will prevent LEC proliferation on the anterior surface of the optic, whether they come from the anterior capsule (early migration), or from the germinative zone of the equator (secondary migration). If the contact is durably absent the anterior capsule will remain transparent, and no anterior LEC migration is possible. Since the stability of the IOL does not rely on this adherence, no complication will occur from such an anatomical situation. On the contrary, the earlier the contact between with the posterior capsule and the posterior surface of the optic, the more efficient the prevention of LEC migration and transformation between the optic and the biologically active lens capsule. Assessment of consistent and total posterior contact by increased vaulting of the optic becomes a must of implantology. While we are still expecting a clinically acceptable chemical treatment for the prevention of LEC migration and transformation, we now have a larger choice of IOLs that significantly decrease the incidence of PCO and the incidence of YAG capsulotomy.
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References 1 2
3 4 5 6
Hara T, Hara T, Yamada Y: ‘Equator’ ring for maintenance of the completely circular contour of the capsular bag equator after cataract removal. Ophthalmic Surg 1991;22:358–359. Nishi O, Nishi K, Sakanishi K: Inhibition of migrating lens epithelial cells at the capsular bend created by the rectangular optic edge of a posterior chamber intraocular lens. Ophthalmic Surg Lasers 1998;29:587–594. Nishi O, Nishi K: Preventing posterior capsule opacification by creating a discontinuous sharp bend in the capsule. J Cataract Refract Surg 1999;25:521–526. Nishi O, Nishi K, Wickstrom K: Preventing lens epithelial cell migration using intraocular lenses with sharp rectangular edges. J Cataract Refract Surg 2000;26:1543–1549. Menapace R, Findl O, Georgopoulos M, Rainer G, Vass C, Schmetterer K: The capsular tension ring: Designs, applications and techniques. J Cataract Refract Surg 2000;26:898–912 Werner L, Apple DJ, Escobar-Gomez M, Ohrstrom A, Crayford BB, Bianchi R, Pandey SK: Postoperative deposition of calcium on the surfaces of a hydrogel intraocular lens. Ophthalmology 2000;107:2179–2185.
Dr. Philippe Sourdille, Clinique Sourdille, 3, place Anatole France, F–44040 Nantes (France) Tel. 33 251 833 245, E-Mail
[email protected]
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Kohnen, T (ed): Modern Cataract Surgery. Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 202–208
Posterior Capsule Opacification after Implantation of Polyfluorocarbon-Coated Intraocular Lenses: A Long-Term Follow-Up Gerd U. Auffarth, Marcus Ries, Manfred R. Tetz, Ute Faller, Klio A. Becker, Il-Joo Limberger, Hans E. Völcker Department of Ophthalmology, Ruprecht Karls University, Heidelberg, Germany
Surface modifications of intraocular lens (IOL) optics have been developed in order to enhance biocompatibility and prevent cell adhesion. In the last 10 years the quality of production of IOLs has reached a high level [1–4]. A variety of new IOL materials with different surface modifications were developed [1, 4–6]. Heparin surface-modified IOLs have been reported to reduce cell adhesion and to enhance biocompatibility because of their highly hydrophilic surface characteristics. Highly hydrophobic surfaces are also supposed to reduce cell adhesion. In this paper we have tested whether polyfluorocarbon (Teflon)coated IOLs (PFC-IOL) have a positive influence on the development of posterior capsule opacification (PCO) in comparison to standard PMMA-IOLs.
Patients and Methods In this prospective, randomized trial, 48 eyes of 48 patients underwent cataract surgery with implantation of an IOL between 1991 and 1992. Twenty-five patients received a PFCIOL (Alcon Surgical Cilco Model AR50BZ) and 23 patients a standard PMMA-IOL (Style CVC1U0) of equal design without any coating. We evaluated the PCO development of these patients 4–6, 10–14 and 46–52 months after implantation [5, 7]. PCO formation was evaluated using a standardized photographic image analysis system developed by Tetz et al. [8] (fig. 1). Therefore, we took standardized photographs of the IOLs using Zeiss® Fotospaltlampe Model 40 SL/P in maximum drug-induced mydriasis. The PCO
Fig. 1. Image analysis system (EPCO) for evaluation of PCO behind the IOL.
values were calculated by multiplying the area of opacification of the IOL optic (0–100% 0–1.0) with a graduated PCO value (0– 4). Statistical analysis was performed calculating mean values, standard deviation, analysis of variance and Kruskall-Wallis analysis of variance for nonparametric data using Microsoft Excel 4.0 and Systat 5.03 for Windows™.
Results
Twenty-four patients could be examined 4 years postoperatively (14 PFC, 10 controls). Both patient groups did not show any differences in terms of mean age or postoperative follow-up and corrected distance acuity (fig. 2, 3, table 1). The PCO value increased from 0.31 in the first year after implantation to 1.5 after 46 months (PFC-IOL) and from 0.31 to 1.2 (standard PMMA-IOL), respectively (fig. 4–6). Both IOLs showed no significant difference referring to the PCO expression at any examination time (table 1, fig. 4 – 6). PCO values after 4 years showed a great range between 0 and 3.6 for both groups (fig. 6). A Nd:YAG capsulotomy
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Corrected distance visual acuity
1.0
0.5
PFC group Control group
0.1 5
12
48
Follow-up (months)
Fig. 2. Development of visual acuity over 4 years.
1
Visual acuity
0.5
p = 0.54
0.1 PFC group
Control group
Fig. 3. Mean visual acuity in both patient groups.
was performed in 2 of 14 patients with PFC-IOL and in 1 of 10 patients with standard PMMS-IOL.
Discussion
PCO is the important long-term complication after extracapsular cataract extraction with implantation of a posterior chamber lens [1, 2, 4]. In the literature,
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Table 1. Patient data
Patients, n Age, years Time postoperatively, months Visual acuity PCO value
PFC group
Control group
Significance
14 78.1 8.14 46.7 2.13
10 75.3 7.69 47.4 6.52
p 0.95* p 0.72*
0.6 0.33 1.5 1.02
0.7 0.41 1.2 0.83
p 0.54* p 0.58*
*Not significant.
PCO value (area density)
1.6 PFC group
1.4
Control group 1.2 1 0.8 0.6 0.4 0.2 0 5
12 Postoperative follow-up (months)
48
Fig. 4. Development of PCO 4 years after implantation.
development of PCO after an extracapsular technique varies from 3 to 50% 2–5 years after implantation [2, 5, 9–17]. Reasons for different frequencies of PCO development depend for example on different observation times and different age distributions of the evaluated patient groups. This could be explained by the influence of ocular, extraocular, systemic factors and different methods of PCO evaluation [18]. It is known that the implantation of a posterior chamber lens into the capsular bag reduces the expression of PCO [2, 8–13, 15, 16]. Moreover, biconvex optical design and a sufficient contact between the optic and posterior part of the capsular bag decrease the development of PCO [2, 9–13, 15, 16]. In this long-term study an examiner-independent, standardized PCO evaluation method developed by Tetz et al. [18] was used to analyze the influence of PFC surface modification on PCO development (fig. 1). Both patient groups
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PCO value (area density)
4
3
2 p 0.58 1
0 PFC group
Control group
Fig. 5. Mean values of PCO 4 years after cataract extraction. Difference between PFCIOL group and standard PMMA-IOL group was not statistically significant (p 0.58, Mann-Whitney U test).
PFC group
35
Control group
Frequency (%)
30 25 20 15 10 5 0
0–0.5
0.51–0.10 1.01–1.5 1.51–2.0 2.01–2.5 2.51– 3.0 3.01– 3.5
3.51–4.0
PCO value (area density)
Fig. 6. PCO values 4 years after cataract extraction. PCO values of the PFC-IOL group and standard PMMA-IOL group show a similar range from 0 to 3.6.
could be compared because they did not show any differences in terms of mean age, follow-up time or systemic conditions which could influence the expression of PCO, like diabetes mellitus [17], pseudoexfoliation syndrome [6], retinitis pigmentosa [19] and so on. Patients with PFC-IOLs presented with equal functional results compared to those with standard PMMA-IOL. A difference in PCO formation could not be detected between the groups. The low rate of capsulotomy can be explained by the good acuity of vision from 0.6 to 0.7. A specific coating of IOL with equal
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optical-functional results which reduces the PCO development would be an elegant solution for the PCO problem. PFC-coated optical surfaces could not help decrease the rate of PCO in this study. References 1 2 3
4 5
6 7
8
9 10
11 12
13
14 15 16
Apple DJ, Kincaid MC, Mamalis N, Olson RJ: Intraocular Lenses. Evolution, Designs, Complications, and Pathology. Baltimore, Williams & Wilkins, 1989. Apple DJ, Solomon KD, Tetz MR, Assia EI, Holland EY, Legler UF, Tsai JC, Castaneda VE, Hoggatt JP, Kostick AM: Posterior capsule opacification. Surv Ophthalmol 1992;37:73–116. Auffarth GU, Schmidt JA, Wesendahl T, Recum AV, Apple DJ: Surface characteristics of intraocular lens implants: An evaluation using scanning electron microscopy and three-dimensional topographical profilometry. Long-Term Effects Med Implants 1993;3:321–332. Apple DJ, Auffarth GU, Peng Q, Visessook N: Foldable Intraocular Lenses: Evolution, Clinicopathologic Correlations and Complications. Thorofare, Slack Inc., 2000. Tetz M, Greiner C, Blum M, Faller U, Völcker HE: Zellbesiedlung und Hinterkapseltrübung bei Polyfluorocarbon beschichteten Hinterkammerlinsen – erste klinische Ergebnisse; in Robert YCA, Gloor B, Hartmann C, Rochels R (eds): Transactions. 7. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation (DGII), Zürich 1993. Berlin, Springer, 1993, pp 344–350. Zetterström C: Incidence of posterior capsule opacification in eyes with exfoliation syndrome and heparin-surface-modified intraocular lenses. J Cataract Refract Surg 1993;19:344–347. Faller U, Tetz MR, Blum M, Greiner C, Völcker HE: Endothelzellverlust bei Polyfluorocarbon beschichteten Intraokularlinsen; in Pham DT, Wollensak J, Rochels R, Hartmann C (eds): Transactions. 8. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation (DGII) Berlin 1994. Berlin, Springer, 1994, pp 336–339. Tetz MR, O’Morchoe DJC, Gwin TD, Wilbrandt TH, Solomon KD, Hansen SO, Apple DJ: Posterior capsular opacification and intraocular lens decentration. II. Experimental findings on a prototype circular intraocular lens design. J Cataract Refract Surg 1988;14:614–623. Born C, Ryan D: Effect of intraocular lens optic design on posterior capsular opacification. J Cataract Refract Surg 1990;16:188–192. Davis P, Hill P: Inhibition of capsule opacification by convex surface posterior three-piece all PMMA C-loop lenses: A fellow eye and same lens study. Eur J Implant Refract Surg 1989;1: 237–240. Davis PL, Hill P, Coffey A: Convex posterior PMMA implants: Do PMMA vs. prolene haptics alter capsular opacity? Eur J Implant Refract Surg 1991;3:127–130. Götting J, Knorz MC, Seiberth V, Münch D: Nachstarrate mit bikonvexen und konvexplanen IOLs – Eine prospektive Studie; in Wenzel M, Reim M, Freyler H, Hartmann C (eds): 5. Kongress der Deutschen Gesellschaft für Intraokularlinsen-Implantation (DGII). Berlin, Springer, 1991, pp 698–703. Hansen SO, Solomon KD, McKnight GT, Wilbrandt TH, Gwin TD, O’Morchoe DJ, Tetz MR, Apple DJ: Posterior capsular opacification and intraocular lens decentration. I. Comparison of various posterior chamber lens designs implanted in the rabbit model. J Cataract Refract Surg 1988;14:605– 613. Morrell AJ, Pearce JL: Cataract surgery with posterior chamber lens implantation in patients aged 20–45. Eur J Implant Refract Surg 1989;1:85– 87. Nishi O: Incidence of posterior capsule opacification in eyes with and without posterior chamber intraocular lenses. J Cataract Refract Surg 1986;12:519–522. Tetz M, Imkamp E, Hansen SO, Solomon KD, Apple DJ: Experimentelle Studie zur Hinterkapseltrübung und optischen Dezentrierung verschiedener Hinterkammerlinsen nach intrakapsulärer Implantation. Fortschr Ophthalmol 1988;85:682– 688.
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17
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Tetz MR, Lehrer I, Klein U, Völcker HE: Cataracta secundaria bei Diabetes Mellitus; in Pham DT, Wollensack J, Rochels R, Hartmann C (eds): 8. Kongress der Deutschen Gesellschaft für Intraokularlinsen-Implantation (DGII). Berlin, Springer, 1994, pp 398–406. Tetz MR, Auffarth GU, Sperker M, Blum M, Völcker HE: Evaluation of a photographic image analysis system for PCO scoring. J Cataract Refract Surg 1997;23:1515–1520. Auffarth GU, Peng Q: Posterior capsule opacification: Pathology, clinical evaluation and current means of prevention. Ophthalmic Pract 2000;18:4:172.
Gerd U. Auffarth, MD, Department of Ophthalmology, Ruprecht Karls University of Heidelberg, Im Neuenheimer Feld 400, D–69120 Heidelberg (Germany) Tel. 49 6221 566 631, Fax 49 6221 561 726, E-Mail
[email protected]
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Piggyback Intraocular Lens Implantation James P. Gills, Robert E. Fenzl St. Luke’s Cataract and Laser Institute, Tarpon Springs, Fla., USA
The piggyback lens implantation strategy, implanting two intraocular lenses (IOLs) in one eye (fig. 1), can be used to treat both high hyperopia [1–5] and extremely high myopia [6], and as a secondary technique to treat pseudophakic refractive errors to avoid the risks associated with lens exchange [3, 5, 7]. Piggybacking IOLs requires a close attention to phacoemulsification technique, both because of the population that usually receives piggyback IOLs, and because of the long-term complications that can arise with two IOLs implanted in the bag.
Piggybacks in High Hyperopes
Measurements and Calculations The highly hyperopic patient presents the cataract surgeon with two potential problems. The first is the possibility of surgical complications that may arise from the structural nature of the hyperopic eye. The second is implanting adequate power while maintaining good optical quality and an accurate refraction. Patients with short axial lengths often have very small anterior segments. About 20% of eyes with axial length ⬍21 mm have disproportionately small anterior segment sizes [8]. In cases with shallow anterior chambers, we are less able to utilize clear-corneal incisions (CCIs) because 2.5 mm takes up more area in a small cornea. Predicting and fitting the correct IOL power in highly hyperopic patients is even more challenging due to the difficulties in obtaining accurate measurements in short eyes, and the limitations of power formulas. Accurate measurement of axial length in hyperopic eyes is especially important since any error is greatly magnified in proportion to the length of the eye. Yet it is in short eyes
Fig. 1. Insertion of anterior piggyback IOLs.
that accurate measurements are most difficult to obtain. Ultrasound axiometers are calibrated with average velocities for normal length eyes. These velocities are incorrect for short eyes, causing significant measurement errors [9]. Performing applanation biometry is frequently difficult in short eye cases with a shallow anterior chamber because it can be difficult to distinguish the initial ‘bang’ echo from the iris and establish perpendicularity. Decreasing the ultrasound gain may be necessary when this occurs so each echo can be visualized but doing so can make the scan more difficult to perform. The most significant problem with applanation biometry is that the cornea is easily indented even in the hand of the most skilled ultrasound technician. Even the slightest indentation can cause significant measurement errors which are magnified when the eye is short [9–11]. Immersion biometry can provide superior results in these cases [12]. First, it is impossible to applanate the cornea. Thus, by its very nature, immersion is more reliable. Second, it allows visualization of the corneal echoes. In order to obtain the most accurate measurement, the skilled ultrasound technician will watch for consistency of echo height, axial length, lens thickness, and anterior chamber depth readings. Optimizing axial length measurements does not guarantee the desired outcome. In a study one of the authors (J.P.G.) performed with Dr. Jack Holladay [9], several hyperopic patients were examined and more detailed anatomical measurements were taken. In most cases the short eye cases had normal anterior segment dimensions (corneal diameter, keratometry, and anterior segment length). The ‘abnormality’ was a foreshortened axial length due to a shortened posterior segment.
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Based on these observations we can conclude that most third-generation power formulas systematically generate hyperopic errors in power calculation among most short eye cases because they shorten the expected anterior chamber depth to the lens as a function of the axial length [8]. Thus they all predict the position of the lens to be too far anterior, resulting in a hyperopic error. Holladay [8] has reported that prediction accuracy in short eyes is significantly improved with the Holladay-2 formula, which uses extra measurements to take into account the sometimes unusual anatomy often found in high hyperopes. He reported a decrease in mean absolute error among short eye cases from about 4.5 D with other formulas to a little less than 1 D with the Holladay-2 formula. About 4% of eyes with average total axial lengths have anterior segment sizes which are large or small relative to the posterior segment and may also benefit from the use of a power formula based on more measurements. Furthermore, when the ‘piggyback’ technique is used in high hyperopes, power calculations must be adjusted again. By measuring the distance from the iris to the IOL vertex, Holladay and Gills [9] determined that the anterior-most lens is in the usual position while the posterior-most lens is pushed back, causing additional hyperopic error. Apparently the anterior lens pushes the posterior lens further back due to the elastic nature of the capsular bag. Thus, additional power must be factored into the equation. The Holladay-2 formula provides such adjustments [8]. For these reasons, the Holladay-2 formula is the formula of choice for piggyback implantation lens power calculation. We have found improved accuracy in our piggyback cases after switching to this formula [13]. Surgical Technique All patients undergoing cataract surgery receive a thorough explanation of the type of anesthesia to be used, what to expect during surgery, and the risks involved with surgery. This is especially important with high hyperopes since compliance during surgery is critical. Topical anesthesia can be used for these patients, just as for cases with average axial lengths. However managing complications is certainly more difficult under topical anesthesia, and high hyperopes are at greater risk for certain complications such as shallow anterior chambers; iris prolapse; pupillary block while the pupil is dilated, which can result in a hard eye; and choroidal effusion or fluid misdirection which can increase the pressure in the eye. Many surgeons may prefer regional anesthesia for these cases. For primary piggyback cases, we use either two PMMA single-piece biconvex IOLs with an optic size of 5.5 mm, or one plate-haptic silicone lens (with the majority of the power) in the bag and one three-piece silicone lens in the sulcus (minimal power). By combining these two silicone IOLs, better centering is often obtained and there is less chance of IOL dimpling. We generally
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use a self-sealing scleral-tunnel incision in these cases, but if the anterior chamber is a normal size, a clear-corneal incision is possible. If PMMA lenses are used, then a scleral-tunnel incision is necessary, as the incision length must accommodate the 5.5-mm optic, and a 5.5-mm clear-corneal incision would have an increased risk of infection. If we are able to perform a clear-corneal incision, we use a 2.5-mm incision length and implant the silicone IOLs. The incision is placed in the steep meridian to correct pre-existing astigmatism. In some cases limbal or corneal relaxing incisions are also performed to correct pre-existing astigmatism [8]. One IOL is bag fixated with the secondary IOL in the sulcus to prevent interlenticular opacification that can be seen with both IOLs bag fixated. Phacoemulsification is more challenging in a short eye. One of the challenges that may arise during phacoemulsification is pupillary block. Increased IOP from choroidal effusion or fluid misdirection is more common in hyperopic eyes and can cause a progressive shallowing of the anterior chamber as the eye hardens. Short eyes are at greater risk for expulsive hemorrhage. Another complication associated with a short eye is iris prolapse when the phaco tip is inserted.
Secondary Piggyback Implantation for Over- or Underpowered Pseudophakes
If the patient is pseudophakic and under- or overpowered in the contralateral eye, a second IOL can be implanted under topical anesthesia to provide the needed corrective power. There is no need for a removal/exchange, which would be traumatic and increases the risk for retinal tears, cystoid macular edema, and cyclodialysis, and is associated with posterior or anterior capsule rupture, decreasing capsular support. Also, since the original IOL is fixed, there is no concern over the possibility that the IOL will change position as can happen after an exchange and there is no need to determine why the power is wrong (calculation mistake, IOL power incorrectly marked, etc.). The necessary corrective power is provided by implanting a second IOL of appropriate power with haptics fixated in the sulcus. Underpowered cases can have a low-power lens implanted, while in overpowered cases, a minus-powered lens can be used. The refraction is used to determine the power requirement. For secondary piggyback implantation, we use the Holladay II software for calculating the power; however, we have found that for overpowered pseudophakes, the appropriate IOL is approximately equal in power to the spherical equivalent.
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Table 1. Our lens choices for secondary piggybacks Underpowered pseudophakes lenses STAAR AQ5010 Silicone, convex/plano, 6.3-mm optic, three-piece IOL Diopter range: plano to ⫹4 (1-D steps) STAAR AQ2010V Silicone, biconvex, 6.3-mm optic, three-piece IOL Diopter range: ⫹5 to ⫹9 (1-D steps); ⫹9.5 to ⫹30.5 (0.5-D steps) Storz P547UV PMMA, equiconvex, 6.0-mm optic, sulcus, one-piece IOL Diopter range: plano to 34.0 (0.5-D steps) Storz P359UV PMMA, equiconvex, 5.5-mm optic, one-piece IOL Diopter range: plano to 45 (0.5-D steps) Overpowered pseudophakes lenses STAAR AQ5010 Silicone, convex/plano, 6.3-mm optic, three-piece IOL Diopter range: –1.0 to –4.0 (1-D steps) Storz P547 UV PMMA, equiconvex, 6.0-mm optic, one-piece IOL Diopter range: ⫺1.0 to ⫺18.0 (1-D steps)
Our lens choices for secondary cases are presented in table 1. The availability of the STAAR AQ5010 silicone IOL in low-powered and minus-powered lenses allows for secondary piggyback implantation through a 2.5-mm clearcorneal incision.
Intralenticular Opacification
Intralenticular opacification (ILO), a long-term complication of piggyback lenses has recently been reported [14 –17]. ILO is cellular growth between piggybacked lenses, which is often characterized as Elschnig pearl formation, and may even result in a fibrous membrane formation between the lenses. Interlenticular opacification has been reported primarily in acrylic lenses with long-term follow-up, although it has also been seen in PMMA and silicone piggybacks [14 –17]. Gayton [17] has reported an incidence of ILO of 43% among his acrylic piggybacks and 22% among his PMMA piggybacks. He has reported a number of cases with thick, opaque membranes that have severely impacted vision and
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Fig. 2. Interlenticular opacification, or cellular ingrowth into the piggyback lens interface.
required surgical removal. Moreover, both Gayton [17] and Shugar [15] have reported a shift in refraction among cases with significant ILO. We conducted a study of all our piggyback cases with at least 2-year possible follow-up and examined them at slit lamp to determine the extent of the problem in our practice. We examined 50 eyes of 34 patients, 22 eyes with piggybacked PMMA lenses, 19 with silicone, and 9 with one PMMA and one silicone lens. We found 3 eyes, or 6%, showed signs of ILO, 2 with piggybacked PMMA (fig. 2) and 1 with mixed PMMA and silicone. In these 3 cases, we saw only mild interface growth, with no impact on visual function, no shift in refraction, and no symptoms of glare or shadows. We found no cases of ILO in double-silicone piggybacks, even with both in the bag. We found a much lower incidence and severity of ILO in our practice than reported by Gayton or Shugar, which may be due either to a difference in IOL material, since we do not use acrylic, or to a difference in surgical technique. Dr. Apple [14, 17] has implicated incomplete removal of epithelial cells as a possible cause of ILO. Since we routinely polish the capsule in all our cataract cases (fig. 3), we effect a more complete removal of lens epithelial cells at surgery, which may have significantly lowered our incidence of ILO. While we believe that polishing the capsule is an important step for all cataract cases, meticulous attention to removal of all epithelial cells is especially crucial in piggyback cases. While the causes of this complication are not yet
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Fig. 3. Polishing the capsule removes more lens epithelial cells and may reduce the incidence of interlenticular opacification.
well understood, and methods of treatment still under study, a careful polishing of the capsule and removal of all lens epithelial cells may significantly lower the incidence and severity of the problem.
References 1 2 3 4 5
6 7 8 9 10
Gayton JL, Sanders VN: Implanting two posterior chamber intraocular lenses in a case of microphthalmos. J Cataract Refract Surg 1993;19:776 –777. Gayton JL, Raanan MG: Reducing refractive error in high hyperopes with double implants; in Gayton JL (ed): Maximizing Results. Thorofare, Slack Inc, 1996, pp 139–148. Gills JP, Gayton JL, Raanan MG: Multiple intraocular lens implantation; in Gills JP, Fenzl R, Martin RG (eds): Cataract Surgery: State of the Art. Thorofare, Slack Inc, 1998. Shugar JK, Lewis C, Lee A: Implantation of multiple foldable acrylic posterior chamber lenses in the capsular bag for high hyperopia. J Cataract Refract Surg 1996;22:1368–1372. Gills JP: The implantation of multiple intraocular lenses to optimize visual results in hyperopic cataract patients and under-powered pseudophakes. Best Papers of Sessions, 1995 Symposium on Cataract IOL and Refractive Surgery Special Issue, 1996. Gills JP, Fenzl RE: Minus power intraocular lenses to correct refractive error in myopic pseudophakia. J Cataract Refract Surg 1999;25:1205–1208. Gayton JL, Sanders V, Van Der Karr M, Raanan MG: Piggybacking intraocular implants to correct pseudophakic refractive error. Ophthalmology 1999;1066:56–59. Holladay JR: Achieving emmetropia in extremely short eyes. Annual Meeting of the American Academy of Ophthalmology, Chicago 1996. Holladay JR, Gills JP, Leidlein JL, Cherchio M: Achieving emmetropia in extremely short eyes with two piggyback posterior chamber intraocular lenses. Ophthalmology 1996;103:1118–1123. Sanders DR, Retzlaff JA, Kraff MC: A-scan biometry and IOL implant power calculations; in Focal Points: Clinical Modules for Ophthalmologists. San Francisco, American Academy of Ophthalmology, 1995, vol 13, pp 1–14.
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11 12 13
14
15
16
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Holladay JT, Prager TC, Ruiz RS, Lewis JW: Improving the predictability of intraocular lens power calculations. Arch Ophthalmol 1986;104:539–541. Shammus HJF: A comparison of immersion and contact techniques for axial length measurement. Am Intraocular Implant Soc J 1984;10:444. Fenzl RE, Gills JP, Cherchio M: Refractive and visual outcome of hyperopic cataract cases operated on before and after implementation of the Holladay II formula. Ophthalmology 1998; 105:1759–1764. Gayton JL, Apple DJ, Peng Q, Visessook N, Sanders V, Werner L, Pandey SK, Escobar-Gomez M, Hoddinott DS, Van Der Karr M: Interlenticular opacification: Clinicopathological correlation of a complication of piggyback posterior chamber intraocular lenses. J Cataract Refract Surg 2000;26: 330–306. Shugar JK, Schwartz T: Interpseudophakos Elschnig pearls associated with late hyperopic shift: A complication of piggyback posterior chamber intraocular lens implantation. J Cataract Refract Surg 1999;25:863–867. Shugar JK, Keeler S: Interpseudophakos intraocular lens surface opacification as a late complication of piggyback acrylic posterior chamber lens implantation. J Cataract Refract Surg 2000;26: 448–455. Gayton JL, Apple DJ, Van Der Karr M, Sanders V: Refractive stability and long-term interlenticular membrane formation of piggybacked intraocular implants. J Cataract Refract Surg 2001 (in press).
Dr. James P. Gills, St. Luke’s Cataract and Laser Institute, 43309 US Highway 19N, PO Box 5000, Tarpon Springs, FL 34688 (USA) Tel. ⫹1 727 938 2020, Fax ⫹1 727 938 5606, E-Mail
[email protected]
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Multifocal Intraocular Lenses Charles Claoué a, Dipak Parmar b a DBCG, London and The North East London Eye Partnership, Whipps Cross University Hospital, London, and b Whipps Cross University Hospital, London and Moorfields Eye Hospital, London, UK
Why a Multifocal Intraocular Lens?
Whilst Jacques Daviel, ophthalmologist to Louis XV, may be the father of modern cataract surgery in that he invented cataract extraction, there is no doubt that leaving a subject aphakic is not a perfect optical solution. A major advance was the implantation of the first intraocular lens (IOL) by Sir Harold Ridley in London in 1949. However, these monofocal lenses did not allow good vision at all distances without supplementary correction usually worn as a spectacle lens. As our understanding of the optics of IOLs has improved, so advances in biometry have resulted in better refractive results. However, these have usually resulted in good unaided vision for distance, but the need for spectacles for reading due to the absolute presbyopia of the emmetropic eye with monofocal pseudophakia. Alternatively, a strategy known as ‘monovision’ has occasionally been employed in subjects with bilateral cataracts who undergo bilateral implantation of monofocal IOLs. The focus of one monofocal IOL is set for distance (preferably implanted in the dominant eye) and the other is set for near vision (by the optical outcome being targeted on a low myopic outcome), leading to satisfactory results in some subjects. However, other subjects find monovision unacceptable and often resort to wearing spectacles, since monovision provides only partial binocularity and may lead to loss of stereopsis. This contrasts with normal physiology, i.e. good vision for both near and distance without glasses, as experienced by the pre-presbyopic emmetrope. Many subjects still aspire to such vision, and welcome the opportunity to reduce (if not abolish) their spectacle dependency when lens surgery for cataract is required.
Multifocal IOLs were designed to improve near and intermediate vision without supplementary glasses, as well as provide distance vision, because they can produce a variable number of foci, either finite or infinite, depending on the lens design. A cortical elaboration process is believed to enable the subject to choose the image most clearly in focus [1]. This phenomenon is called ‘pseudoaccommodation’ and may depend in part on the Stiles-Crawford effect. Since multifocal IOLs always produce an in-focus and an out-of-focus image, and visual processing allows partial or total suppression of the out-of-focus image, it is not surprising that some subjects are aware of the ‘blur circles’, which are colloquially referred to as ‘haloes’. In this chapter, we review the designs and effectiveness of various marketed and investigational multifocal IOLs.
History of Multifocal IOL Development
Designs Multifocal IOLs are based on either refractive or diffractive optics and differ in design and material (table 1) [2]. All refractive IOLs use the total available light without losing any to higher order diffraction. The Array multifocal IOL (Allergan Surgical, Irvine, Calif., USA) and Domilens Progress 1 (Domilens, Lyons, France) are refractive designs that obtain multifocality from a change in optical refractive power in different areas of the IOL optic. This allows the lens to focus images from various distances onto the retina. The Array is a foldable, concentric, zonal-progressive design, with a series of repeatable, continual aspheric power distributions on the anterior surface of the lens (fig. 1a,b) [3]. It is distance-dominant and, therefore, appropriate for a distance-vision-dominant species. In an eye with an average pupil size, approximately 50% of incoming light is allocated to distance focus, 13% to the intermediate range, and 37% to the near image [2]. The Domilens Progress 1 is a one-piece, progressive, PMMA IOL. The Progress 1 optics are aspheric biconvex, with light allocated predominantly to the near image [4]. True Vista is a three-zone refractive bifocal IOL (designed by Storz Instrument Co., St. Louis, Mo., USA, and acquired by Bausch & Lomb Surgical, Claremont, Calif., USA). The biconvex IOL has a central (distance) zone, near annulus, and peripheral (distance) zone. The near annulus has an add power of 4 D [5]. Diffractive IOLs include the CeeOn 811E and Pharmacia 808X (Pharmacia Upjohn, Kalamazoo, Mich., USA), and 3M 825X and 815LE (designed by 3M,
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Table 1. Designs of multifocal IOLs (adapted from Steinert [2]) Design and model
Manufacturer
Material
Optics and features
Allergan Surgical (Irvine, Calif., USA)
Three-piece silicone
Domilens (Lyons, France)
One-piece PMMA
Zonal-progressive with repeatable, continual power distributions on anterior surface; aspherical; biconvex; distance dominant, 3.5 D add Progressive; aspheric; biconvex; near dominant
Bausch & Lomb (Claremont, Calif., USA)
PMMA
Three-zone (central distance, near annulus with 4 D add, peripheral distance); biconvex; distance dominant
Pharmacia Upjohn (Kalamazoo, Mich., USA) Pharmacia Upjohn
One-piece PMMA
3M 825X
Alcon (Fort Worth, Tex., USA)
Three-piece PMMA
3M 815LE
Alcon
One-piece PMMA
Bifocal diffractive surface on posterior side of optical body; biconvex; 4.0 D add Bifocal; UV absorbing; concentric diffractive microstructure superimposed on posterior surface of conventional refractive lens; 6.5 mm biconvex optic Meniscus-shaped optic; anterior spheric surface with multiple diffraction zones on posterior surface; 4.0 D add 27 concentric microslope rings onposterior surface; 3.5 D add
Refractive multifocal Array
Domilens Progress 1 Refractive bifocal True Vista
Diffractive bifocal CeeOn 811E
808X
One-piece PMMA
Minneapolis, Minn., USA and rights acquired by Alcon, Fort Worth, Tex., USA). Diffractive IOLs use a modified phase plate that creates constructive interference of light rays, thereby directing light to discrete near and far foci [3]. As a result of this design, most diffractive IOLs are bifocal. For most diffractive IOLs, approximately 41% of incoming light is allocated for distance and 41% for near vision. The remaining 18% of light cannot be focussed because it is lost to higher order diffraction, forming images that can never be visualized because they do not reach the retina.
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219
Zone 1
2.1 mm
Zone 2
2.1–3.4 mm
Zone 3
3.4–3.9 mm
Zone 4
3.9– 4.6 mm
Zone 5
Add power
4.6–4.7 mm
3.5 D Base power 2
a
1
01 Millimeters from center
2
Fig. 1. Array refractive multifocal IOL (Allergan Surgical). a Schematic of zonalprogressive lens design. b Photograph depicting aspheric rings on anterior surface (from Steinert et al. [3]).
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The following studies use Snellen, Snellen equivalent, or the decimal scale. The decimal scale ranges from 0.05, or 20/400 Snellen, to 1.0, or 20/20 Snellen. Effectiveness The effectiveness of multifocal IOLs can be measured in terms of distance visual acuity, near visual acuity, depth of focus, contrast sensitivity, visual symptoms, driving ability, independence from spectacles, subject satisfaction, and quality of life. The multifocal IOL reported on most often in the literature is the Array. It has been studied in comparisons with monofocal IOLs [3, 6–12], the Domilens Progress 1 refractive multifocal IOL [13], the CeeOn 811E [13, 14] and 3M diffractive bifocal IOLs [15–17] and a PMMA bifocal IOL from Bausch & Lomb [18] (table 2). The CeeOn 811E diffractive bifocal IOL was studied in a noncomparative trial [19], and the True Vista refractive bifocal IOL in several comparative and noncomparative trials [5, 20–22]. An investigational diffractive bifocal IOL, Pharmacia model 808X, was studied in comparative trials with a monofocal IOL of similar design [23, 24]. Distance Visual Acuity The effectiveness of monofocal IOLs on distance visual acuity is well characterized. The effectiveness of multifocal and bifocal IOLs on distance visual acuity has been measured in several clinical trials. Steinert et al. [3] evaluated the safety and effectiveness of the Array in a prospective, nonrandomized, multicenter, fellow eye comparative trial in the USA (n ⫽ 456). All subjects were implanted with the Array. The fellow eye was either phakic or implanted with a multifocal or monofocal IOL. At five of the sites, subjects participated in a paired-eye comparison trial, with an Array model SA40 in one eye and a PhacoFlex II model SI40NB silicone IOL (Allergan Surgical) in the fellow eye (n ⫽ 102). In this study, mean uncorrected (i.e. without spectacles) distance visual acuities at 1 year were 20/32 (Snellen) for the multifocal and 20/30 for the monofocal IOL. Uncorrected distance visual acuity of 20/20 or better was achieved by 18% (18 of 102) eyes with the multifocal IOL, and by 30% (31 of 102) eyes with the monofocal IOL (fig. 2). The mean best-corrected distance visual acuities were 20/25 for eyes with the multifocal IOL and 20/23 for those with the monofocal IOL, with a mean difference between eyes of 0.3 line (Snellen equivalent) (p ⬍ 0.002). Bestcorrected distance visual acuity of 20/20 or better was achieved by 49% (50 of 102) of eyes with the multifocal and by 59% (60 of 102) of eyes with the monofocal IOLs ( p ⫽ 0.002). Javitt and Steinert [12] measured visual function and quality-of-life outcomes in subjects implanted bilaterally with the Array multifocal IOL (n ⫽ 127)
Multifocal Intraocular Lenses
221
Claoué/Parmar
222
15
Pieh, 1998
26 3
Jacobi, 1999 Steinert, 1999
10 14
29
7
P
6 19 9
Arens, 1999 Avitabile, 1999 Featherstone, 1999 Häring, 1999
Vaquero-Ruano, 1998 Grosskopf, 1998 Liekfeld, 1998
P P P
11 12 28 18
Javitt, 2000 Javitt, 2000 Yang, 2000 Lesueur, 2000
Retro.
P PR
P NR C
P NR P NR C
P R DM P R DM P P
Ref. Study design
Study
Array CeeOn 811E Array 3M 815LE Array
Array
Array Array Diffractive Array
50 26 24 29 12
50
31 29 29 102
Array 64 Array 127 Array 20 Array 24 P359 TUV 22 PMMA Array 21 CeeOn 811E 35 Array 33
60 118 –
Fellow eye 50
Not listed 85
PMMA
SI40NB
Not listed 15 – – Silicone 33
SI40NB SI40NB –
n
type
type
n
Monofocal IOL
Multi- or bifocal IOL
Table 2. Studies of multifocal and bifocal IOLs Contrast
✓ ✓
✓
✓ ✓ ✓
✓
✓ ✓
✓ ✓
✓
✓ ✓ ✓
✓ ✓ ✓ ✓ ✓
✓ ✓ ✓ ✓
✓
✓ ✓
dist. near acuity sensitivity
VA
✓ ✓ ✓ ✓ ✓
✓
✓
✓
✓ ✓
✓ ✓
Visual sympt.
✓
✓
Driving ability
✓ ✓
✓
Spectacle independ.
✓
✓
✓ ✓
✓ ✓
Satisf. & QOL
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223
16
30
23
24
31 21 20 5
Weghaupt, 1997
Weghaupt, 1996
Allen, 1996
Haaskjold, 1998
Ravalico, 1994 Knorz, 1994 Knorz, 1993 Knorz, 1993
P PC PC PC
PRC
PRC
P
P
P
P
CeeOn 811E 20 Progress 1 20 Array 20 MPC25NB 3M 825X 10 Array 13 SSM26NB 3M 815LE Array SSM26NB Array 14 SSM26NB Pharmacia 79 808X Pharmacia 115 808X Progress 1 20 True Vista 26 True Vista 446 True Vista 11 106
70
20
Monofocal 26 Monofocal 118 Monofocal 11
808D
808D
Silicone
✓ ✓
✓ ✓
✓
✓
✓
✓ ✓
✓ ✓
✓
✓ ✓
✓ ✓
✓ ✓ ✓
Spatial resolution threshold
✓
✓
✓
✓
✓ ✓
P ⫽ Prospective, R ⫽ randomized, NR ⫽ nonrandomized, DM ⫽ double-masked, C ⫽ comparative, QOL ⫽ quality of life, dist. ⫽ distance, sympt. ⫽ symptoms, satisf. ⫽ patient satisfaction
17
13
Weghaupt, 1998
Ravalico, 1998
Percent of eyes
100
80
⬎20/40 20/40
60
20/32 20/25 ⭐20/20
40
20
0 Multi
Mono Uncorrected
Multi
Mono Corrected
Fig. 2. Cumulative distribution of uncorrected and corrected distance vision at 1 year (from Steinert et al. [3]).
in comparison to subjects implanted bilaterally with a PhacoFlex II SI40NB monofocal IOL (n ⫽ 118). This prospective, randomized, double-masked, clinical trial was conducted at eight sites in the USA, seven sites in Germany, and one site in Austria. They reported mean uncorrected distance visual acuities of 20/21 (Snellen equivalent) in the subjects implanted with the multifocal IOL and 20/22 in subjects implanted with the monofocal IOL (p ⫽ 0.05). Bestcorrected distance visual acuities were 20/18 in both groups (p ⫽ NS). Javitt et al. [11] reported on the results of the seven clinical sites in Germany and one site in Austria in the above trial, in which 64 subjects were implanted with the Array and 60 with the PhacoFlex II model SI40NB monofocal IOL. They reported mean uncorrected binocular distance visual acuities of 20/21 (multifocal) and 20/22 (monofocal) (p ⫽ NS). Best-corrected binocular distance visual acuities were 20/18 and 20/17, respectively (p ⫽ NS). Lesueur et al. [18] found both the Array SA40N with the P359 TUV PMMA bifocal IOL (Bausch & Lomb) to have similar mean corrected distance visual acuities (0.6). Arens et al. [6] retrospectively evaluated binocular function after bilateral implantation of the Array multifocal (n ⫽ 21) or a monofocal IOL (n ⫽ 15). With distance correction, distance visual acuities were similar in multifocal and monofocal subjects for monocular and binocular vision. Without distance correction, distance acuity was significantly higher in the multifocal subjects for monocular vision. The monocular distance visual acuity was 0.53 ⫾ 0.19 for the Array multifocal lens and 0.41 ⫾ 0.27 for the monofocal lens (p ⬍ 0.05). The
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difference between binocular acuities was not significant. The authors suggested that this significant monocular difference may have been due to the intended visual outcome of myopia for the monofocal subjects and emmetropia for the multifocal subjects. Thus, the multifocal IOL caused no decrease in best-corrected distance acuity compared to the monofocal IOL, either monocularly or binocularly. Vaquero-Ruano et al. [7] reported no difference in mean distance vision between the Array multifocal (n ⫽ 50) and PMMA monofocal IOLs (n ⫽ 50). Kamath et al. [25] studied interesting subjects with cataract and concurrent eye diseases (e.g., macular degeneration, glaucoma, diabetic retinopathy). They found the Array multifocal IOL produced distance visual outcomes comparable to those of the PhacoFlex SI40NB silicone monofocal IOL. They concluded that these subjects benefited from the multifocality and that management of their eye diseases was not compromised by the nature of the IOL. Pieh et al. [15] found comparable distance visual acuity for the Array refractive multifocal IOL and the 3M 815LE diffractive bifocal IOL. The mean uncorrected distance acuity was 0.79 (Snellen decimal) with the refractive IOL and 0.61 with the diffractive. With best correction, mean distance visual acuity improved to 0.95 (refractive) and 0.96 (diffractive). Similarly, Liekfeld et al. [14] found no differences in distance visual acuity between the Array and the CeeOn 811E diffractive bifocal. Avitabile et al. [19] evaluated unilaterally implanted CeeOn 811E diffractive IOLs and found the mean uncorrected distance visual acuity to be 0.79 and mean corrected visual acuity 1.0. Allen et al. [23] compared a Pharmacia diffractive bifocal IOL, model 808X (n ⫽ 79), with a comparable monofocal (n ⫽ 70) of the same design without the diffractive microstructure superimposed on the posterior surface. All subjects achieved a best-corrected visual acuity of 0.5 or better. Eighty percent of the monofocal and 71% of bifocal subjects achieved best-corrected visual acuity of 1.0 or better. Knorz et al. [5] reported the findings of a small study of 44 patients. Eleven patients had a True Vista bifocal implanted in one eye and a monofocal AMO PC 65CNB (Allergan Surgical) in the fellow eye (bifocalmonofocal subset). Corrected distance acuity was not significantly different between the two eyes. Uncorrected distance acuity was significantly better in the True Vista eyes, but this may have been the result of the study design, in which the goal was to have some with-the-rule astigmatism in the monofocal eyes but emmetropia in the True Vista eyes. Knorz [20] reported the results of a European multicenter study of the True Vista bifocal IOL. Best-corrected distance acuity was 20/40 (Snellen) or better in 94% (259 of 275) at 4 – 6 months and 97% (185 of 191) at 7–11 months. In summary, the refractive multifocal IOLs, refractive bifocal IOL, and several diffractive bifocal IOLs provided distance vision comparable to monofocal IOLs.
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100
80 Percent of eyes
⬎J3 J3 J2 J1
60
ⱕJ1⫹
40
20
0
Multi Mono Uncorrected
Multi Mono Distance corrected
Multi Mono Best corrected
Fig. 3. Cumulative distribution of uncorrected and corrected near vision at 1 year (from Steinert et al. [3]).
Near Visual Acuity The Array multifocal IOL offered significantly better near visual acuity than the monofocal IOLs in several clinical studies. In the multifocal-monofocal subset of the Steinert et al. [3] study, mean uncorrected near acuities were 20/33 for eyes implanted with the Array multifocal IOL and 20/54 for eyes implanted with the SI40NB monofocal IOL at 1 year after surgery, with a mean difference of two lines (p ⬍ 0.0001). Uncorrected Jaeger (J) near visual acuity of J3 (20/40) or better was achieved by 86% (87 of 101) of eyes with the multifocal IOL, and by 49% (49 of 101) of eyes with the monofocal IOL (fig. 3). Uncorrected near visual acuity of J1 (20/20) or better was achieved by 47% (47 of 101) of eyes with the multifocal, and 12% (12 of 101) of eyes with the monofocal IOL. The distribution for near acuity with distance correction was similar to that for uncorrected near vision. Javitt and Steinert [12] found statistically significant differences between subjects implanted with multifocal IOLs and those with monofocal IOLs. Mean uncorrected near visual acuities were 20/26 (Array multifocal) and 20/40 (SI40NB monofocal) (p ⬍ 0.0001). Mean distance-corrected near visual acuities were 20/28 (multifocal) and 20/45 (monofocal) (p ⬍ 0.0001). Statistically significant differences in near visual acuities were reported by Javitt et al. [11]. In their study, mean uncorrected binocular near visual
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acuities were 20/25 (multifocal) and 20/41 (monofocal) (p ⬍ 0.001) and mean distance-corrected near visual acuities were 20/26 (multifocal) and 20/46 (monofocal) (p ⬍ 0.001). In subjects who had undergone extracapsular cataract extraction rather than phacoemulsification reported by Vaquero-Ruano et al. [7], eyes with the Array multifocal IOL had significantly better uncorrected and distance-corrected near acuities than eyes with a PMMA monofocal IOL (p ⬍ 0.001). However, it is obvious that postoperative astigmatism is more easily controlled with phacoemulsification, and this is undoubtedly the preferred technique for multifocal surgeons. Lesueur et al. [18] found the mean distance-corrected near visual acuity in the P359 TUV PMMA bifocal group (n ⫽ 22) to be significantly better than that of the Array SA40N group (n ⫽ 24) (p ⫽ 0.05). A retrospective evaluation of binocular function by Arens et al. [6] showed that near visual acuity for both monocular and subjects with bilateral Array multifocal IOLs (n ⫽ 21) was similar with or without distance correction. For subjects with bilateral monofocal (not identified) IOLs (n ⫽ 5) near visual acuity was greater without correction than with correction for both monocular and binocular vision. Without distance correction there was no significant difference between near visual acuity for multifocal and monofocal subjects for monocular and binocular vision; however, monocular acuity was slightly lower than binocular. With distance correction, near acuity for multifocal subjects was significantly higher than that for monofocal subjects for both monocular (0.75 ⫾ 0.36 vs. 0.34 ⫾ 0.19; p ⬍ 0.05) and binocular vision (0.91 ⫾ 0.31 vs. 0.52 ⫾ 0.21; p ⬍ 0.05). In contrast, Liekfeld et al. [14] found that near visual acuity and near visual acuity with distance correction was significantly better with the CeeOn 811E diffractive bifocal than the Array multifocal IOL at 4–6 weeks postoperatively (20/20 vs. 20/30) (p ⬍ 0.002). The better near visual acuity for the CeeOn may be attributed, at least partially, to the higher magnification created by an add of ⫹4 D, compared to an add of ⫹3.5 D for the Array. However, the higher add theoretically reduces the working distance (depth of field) and creates a greater disparity between the in-focus image and the out-of-focus blur circle created by the alternate foci. Avitabile et al. [19] found that 97% (34 of 35) of subjects with unilaterally implanted CeeOn 811E diffractive bifocals had uncorrected near visual acuity of J3 (20/40) or better. Also, Allen et al. [23] reported that the diffractive bifocal IOL, Pharmacia model 808X, performed better in tests of uncorrected near visual acuity and near acuity with distance correction than a comparable monofocal lens. Ninety-three percent of bifocal subjects could read J3 or better without correction and 99% with distance correction compared with 9 and 4%, respectively, for the monofocal IOL.
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Knorz [20] reported best-corrected near acuity of 20/30 or better in 92% (250 of 272) of patients implanted with the True Vista IOL at 4–6 months postoperatively and in 87% (166 of 191) at 7–11 months. Knorz et al. [5] has also reported distance corrected near acuity was significantly better with the True Vista lens than the monofocal lens (p ⫽ 0.007) in the bifocal-monofocal subset of their small study. Snellen near acuity with near add was significantly lower with the True Vista than the monofocal IOLs (p ⫽ 0.008) but reading acuity was not significantly different. In summary, the Array multifocal IOL offers significantly better near visual acuity than monofocal IOLs, as expected from the optical design. A new bifocal PMMA design from Bausch & Lomb showed good results in an early study, as did the 808X from Pharmacia. The refractive bifocal True Vista and diffractive bifocal CeeOn offer good near visual acuity. Combined Distance and Near Visual Acuities In the multifocal-monofocal subset of the study by Steinert et al. [3], 77% (78 of 101) of eyes implanted with the Array multifocal IOL achieved the combined distance (20/40 or better) and near visual acuity (J3 or better) criteria, compared to 46% of eyes implanted with the SI40NB monofocal IOL. With best distance correction, a significantly higher percentage of multifocal eyes achieved both these acuity levels compared to monofocal eyes (81 vs. 48%; p ⬍ 0.0001). Thus, the Array multifocal IOL offers good acuity over a wider range of vision than a monofocal IOL. Javitt and Steinert [12] reported that more subjects in the Array multifocal IOL group achieved combined distance and near visual acuities of 20/40 or better and J3 or better than those in the SI40NB monofocal IOL group (p ⬍ 0.0001). These combined distance and near visual acuities were achieved by 96% (118 of 123) of subjects implanted with the multifocal and by 65% (71 of 109) of subjects implanted with the monofocal IOL. Javitt et al. [11] reported that more subjects in the multifocal IOL group achieved both 0.5 (20/40) or better binocular distance visual acuity and J3 or better uncorrected binocular near visual acuity at the final postoperative exam than those in the monofocal IOL group (p ⬍ 0.001). These were achieved by 97% (59 of 61) of subjects implanted with the multifocal and 66% (35 of 53) of subjects implanted with the monofocal IOL. Depth of Focus A major disadvantage of monofocal IOLs is that visual acuity is maximal at a distinct distance but then decreases with increasing defocus. In contrast, multifocal IOLs were designed to provide a wider range of visual acuity because of their multiple foci.
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In the sub-study analysis by Steinert et al. [3], the Array multifocal IOL had a significantly greater depth of focus compared to the SI40NB monofocal (p ⫽ 0.008) that was more pronounced in the near region, where a visual increase of approximately three lines occurred. Vaquero-Ruano et al. [7] demonstrated that the Array had a significantly broader depth of focus than the monofocal, especially in the near vision range from ⫺1 to ⫺3 D (p ⬍ 0.001). This is in agreement with Arens et al. [6] who found that subjects with bilateral Array multifocal IOLs (n ⫽ 21) had a significantly wider range of focus in the near region than subjects with bilateral monofocal (not identified) IOLs (n ⫽ 15) (p ⬍ 0.05). Furthermore, these subjects had a greater total range than the monofocal subjects for a visual acuity threshold of 0.5 (⫹1.0 to ⫺3.0 D vs. ⫹1.0 to ⫺1.0 D). The multifocal and monofocal IOLs provided almost identical depth of focus around emmetropia. The publication by Weghaupt et al. [17] showed that both the Array refractive multifocal and the 3M 825X diffractive multifocal IOL offer considerable depth of focus. The distance acuity peaks for the Array and the diffractive 825X were at Snellen decimal equivalents of 0.91 and 1.0, respectively; near acuity peaks were at 0.55 and 0.82, respectively. The diffractive IOL had statistically significant higher levels of visual acuity than the refractive IOL only in the defocused range of ⫺2.5 to ⫺4.0 D, consistent with the higher add for near in the diffractive compared to the refractive IOL (⫹4.0 vs. ⫹3.5 D). Visual acuity for both of these lens types was lowest in the intermediate range, with a shallow dip to 0.43 (Snellen decimal) at ⫺2.0 D for the refractive and 0.42 at ⫺1.5 D for the diffractive. Except for these dips, visual acuity of 0.5 or better was achieved with the refractive in the range of ⫹1.0 to ⫺3.5 D, and with the diffractive in the ⫹1.0 to ⫺4.0 D range. In a technically interesting paper, Ravalico et al. [13] examined range of vision by using high-pass resolution perimetry to assess the spatial resolution threshold in the central visual field of subjects implanted with either the refractive Array, refractive Domilens Progress 1, diffractive bifocal 811X (early model of CeeOn 811, Pharmacia Upjohn), or PMMA monofocal IOL. Each IOL type was implanted in 20 subjects. For distance vision, no significant differences were found between subjects with refractive multifocal IOLs or with monofocal IOLs, but subjects with the diffractive bifocal had a significantly higher (i.e., worse) spatial resolution threshold (p ⫽ 0.003). For intermediate vision, the Array had a significantly lower (i.e., better) threshold compared to the other IOLs (p ⬍ 0.01). The refractive Domilens Progress 1 was comparable to the monofocal for intermediate and near vision (p ⫽ NS). For near vision, the diffractive bifocal 811X had better spatial resolution than any of the other IOLs (p ⬍ 0.001); while the refractive monofocal Array performed better than either the refractive Domilens Progress 1 or the PMMA monofocal (p ⬍ 0.001).
Multifocal Intraocular Lenses
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In summary, the Array multifocal IOL had a greater depth of focus than monofocal IOLs in the near vision range. Both refractive and diffractive multifocal IOLs can provide considerable depth of focus and performance over a range of distances. Contrast Sensitivity The greater depth of focus for a multifocal IOL compared to a monofocal IOL (discussed above) is a tradeoff for the decreased image clarity that results from multifocal vision. Because multifocal optics distribute incoming light through several foci, out-of-focus images are generated that overlap the image of a distant focus thereby reducing image clarity, particularly at low contrast levels. In 43 of 67 subjects from the sub-study analysis by Steinert et al. [3], the Array IOL had significantly lower visual acuity than the SI40NB monofocal IOL at low contrast levels; however, there were no perceived disadvantages in visual function or subject satisfaction associated with this reduction. In return for the improved range of near and functional vision, subjects were apparently willing to accept the decrease in low contrast acuity. The study by Lesueur et al. [18] included two measures of contrast sensitivity, the CSV 1000 (Vector Vision) with 4 spatial frequencies and 8 different contrasts, and the Gradual (Opsia) with letters at variable contrasts and 3 levels of luminance. They reported better contrast sensitivity with the investigational P359 IOL (p ⬍ 0.001 with both tests). Vaquero-Ruano et al. [7] also reported significantly lower mean values of contrast sensitivity in the Array multifocal group compared to the PMMA monofocal group at low contrasts of 25 and 11% (p ⬍ 0.001). Arens et al. [6] reported no significant differences in best-corrected distance visual acuities between subjects with bilateral Array multifocal IOLs (n ⫽ 21) and subjects with bilateral monofocal (unidentified) IOLs (n ⫽ 15), either monocularly or binocularly, at contrast levels of 96, 50, or 25% (Regan Low Contrast Acuity Charts). At low contrast levels of 11%, however, the multifocal subjects had significantly lower sensitivity than the monofocal subjects for monocular vision (0.33 vs. 0.41, p ⬍ 0.05). Acuities for binocular vision at the 11% contrast level were 0.40 in the multifocal group and 0.47 in monofocal group, which were not significantly different. The authors speculated that neural summation of the two monocular responses might be responsible for the higher sensitivity observed at the low contrast level for binocular compared to monocular vision. Pieh et al. [15] compared contrast sensitivity and glare disability for the Array multifocal IOL (n ⫽ 12) and the 3M 815LE diffractive bifocal IOL (n ⫽ 29). A Brightness Activity Tester was used with stationary sinusoidal gratings at various spatial frequencies. At the lowest spatial frequencies
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(0.5, 1 cycles per degree) and at the highest (22.8 cycles per degree) there was no difference between groups. At 3, 6 and 11.4 cycles per degree, the diffractive bifocal reached 90–94% of the contrast sensitivity function of the Array multifocal; the difference was significant at 6 cycles per degree (p ⬍ 0.05). The slightly reduced contrast sensitivity for the diffractive bifocal compared to the Array refractive multifocal may be attributable to the different distributions of light for diffractive vs. refractive optics. Both Allen et al. [23] and Haaskjold et al. [24] compared contrast sensitivity of the Pharmacia 808X diffractive bifocal IOL to that of a monofocal IOL. Allen’s group reported that contrast sensitivity was lower with the bifocal IOL than the monofocal IOL in medium light, but the mean values in each group remained within the normal range at each of five frequencies tested. Haaskjold’s group also reported lower contrast sensitivity with the diffractive bifocal than the monofocal IOL. In the 11 patients with a True Vista IOL in one eye and monofocal in the fellow eye, Knorz et al. [5] found that, for both IOLs, contrast acuity values at far focus decreased with increasing pupil size. At high contrast (96%, 50%) with a dilated pupil, contrast acuity was similar for the True Vista and monofocal IOLs (p ⫽ NS). At low contrast (50%, 25%, 11%) with a dilated pupil, the differences were significant in favor of the monofocal lens (p ⭐ 0.07). It was also Knorz [20] who evaluated contrast acuity in a subgroup of best-case subjects in his larger study of 446 subjects. Subjects were evaluated in dim and bright light using the Regan Low Contrast Acuity Charts (96, 50, 25 and 11%). Contrast acuity with True Vista was comparable to that of the monofocal IOL for distance vision at 96, 50 and 25% contrast levels and was less than the monofocal IOL at 11% contrast level. Contrast acuity with True Vista was lower at near focus than at distance focus at all contrast steps tested and contrast acuity values at near focus were lower in bright light than in dim light. Knorz attributed the loss of contrast acuity in bright light to the smaller pupil size, which exposes a smaller area of the near annulus. In summary, the main drawback of a multifocal IOL is loss of contrast at low contrast levels that results from the distribution of incoming light to several foci. This problem was greater with diffractive than refractive IOLs. In clinical practice, it is almost unheard of for a subject with an Array IOL to notice the reduced contrast sensitivity which, although measurable, seems to be at a subclinical level. Visual Symptoms Steinert et al. [3] collected data on visual symptoms from study subjects by means of a questionnaire. Subjects were asked to report their experience with glare/flare, halos, night vision, blurred near vision, distorted near vision, blurred
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far vision, distorted far vision, depth perception, double vision (one eye), double vision (both eyes), or color distortion. There were no significant between-group differences for 8 of the visual symptoms. Subjects with the multifocal implant reported significantly more difficulty with haloes, glare/flare, and blurred far vision (p ⭐ 0.014). The percentages of multifocal vs. monofocal subjects who reported ‘severe difficulty’ with these phenomena were low: 15 vs. 6% for haloes, 11 vs. 1% for glare/flare, and 4 vs. 1% for blurred far vision. These generally low values combined with high subject satisfaction scores suggest that their occasional experience of these phenomena was an acceptable tradeoff for the benefits of multifocal vision. Javitt and Steinert [12] asked subjects in both IOL groups to rate glare disability (limitation in activities of daily living), degree of bother due to double or distorted vision, and degree of bother due to glare, haloes, or rings around lights. The rating scale was 0 (no limitation or bother) to 4 (extreme limitation or bother). No significant between-group differences were seen in glare disability or double or distorted vision. Subjects implanted with multifocal IOLs had significantly more bother with glare, haloes, or rings around lights than those implanted with monofocal IOLs (p ⬍ 0.0001). In a separate study, Javitt et al. [11] found that subjects implanted with the multifocal IOL experienced more nightflare and haloes than those with the monofocal IOL. However, Lesueur et al. [18] reported similar rates of haloes and glare in the two groups: 8% with the P359 lens and 9% with the Array. Dick et al. [8] compared multifocal and monofocal IOLs with respect to occurrence of photic phenomena (halo, flicker or forward-scattered light, glare). No differences were found between multifocal and monofocal IOLs for objective measures of these phenomena. Subjects also subjectively evaluated these symptoms by filling out a questionnaire. Nine of 28 multifocal and 3 of 27 monofocal subjects noticed light sensations (mainly haloes) that had not been present before surgery. However, the majority of subjects were not bothered by these sensations. Stereoacuity and aniseikonia following unilateral or bilateral implantation of the Array lens was evaluated by Häring et al. [26]. The unilateral and bilateral groups had similar stereoacuity, but distance and near aniseikonia were significantly less in the bilateral than the unilateral group. However, the authors concluded that the Array multifocal IOL allowed good binocular vision despite the simultaneous formation of multiple retinal images. Arens et al. [6] tested best visual acuity in three bright light conditions (comparable to: bright overhead commercial lighting, partly cloudy day, direct overhead sunlight) in 21 patients with bilateral Array multifocal IOLs and 15 patients with bilateral monofocal IOLs. For binocular vision, multifocal subjects had slightly better visual acuity in all three light conditions than the monofocal patients, but the differences were
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not statistically significant. For monocular vision, there were almost no differences between the multifocal and monofocal eyes. Therefore, no disadvantages were found for multifocal IOLs at any glare level tested with this method. Vaquero-Ruano et al. [7] found that the occurrence of ghost images and glare was similar in the Array multifocal (n ⫽ 50) and monofocal IOL subjects (n ⫽ 50). At 18 months after surgery, ghost images were reported by 6% of multifocal and by 2% of monofocal subjects; glare reported by 4 and 2%, respectively. However, all subjects found these visual symptoms were tolerable and none wished to have the IOL removed. In summary, certain visual symptoms such as glare, haloes, blurred vision, or ghosting may occur occasionally in subjects implanted with multifocal IOLs. These symptoms, however, appear to mild enough so as not to detract from overall subject satisfaction. Many subjects with monofocal IOLs implanted also note haloes and glare. Much of the skill in using multifocal IOLs is ensuring that subjects are reassured that ‘haloes’ are a ‘symptom’ that the IOL is ‘working properly’! If presented to the subject in this fashion, there is usually an immediate reduction of subject anxiety and a rapid adaptation to pseudo-accommodation. Driving Ability The effect of multifocal IOLs on driving ability at night and in other low contrast situations has been studied because of concern over the reduced visual acuity at low contrast levels and occurrence of glare symptoms reported in multifocal subjects. Featherstone et al. [9] conducted a novel driving study using the Iowa Driving Simulator in subjects with bilateral Array multifocal IOLs (n ⫽ 33) or bilateral monofocal IOLs (n ⫽ 33). Under three poor visibility conditions (clear weather at night with or without a glare source, fog), 30 different measures of driving performance were made. In 26 of the 30 (87%) comparisons, the Array multifocal and monofocal subjects had similar performances. In the 4 comparisons in which the Array multifocal group was lower than the monofocal group, the subjects with multifocal IOLs still performed, on average, within safety guidelines. The authors concluded that there were no consistent differences in driving performance and safety, but that multifocal subjects may have more difficulty in recognizing certain traffic signs while driving during the night or poor visibility conditions. Grosskopf et al. [10] prospectively assessed visual acuity under various contrast and glare levels in order to determine nighttime driving ability in subjects with beginning cataracts (n ⫽ 41), Array multifocal IOLs (n ⫽ 50), and monofocal IOLs (n ⫽ 85). According to the criteria of the German Ophthalmological Society, which are generally considered to be rather strict, only 38% of the multifocal subjects and 41% of the monofocal subjects met the standards
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100
Percent of subjects
80
60 Mono/Multi Bilat Multi 40
Unilat Multi
20
0 Near
Intermediate
Distance
Fig. 4. Subjects able to function without spectacles (from Steinert et al. [3]).
for nighttime driving ability. The authors concluded that elderly pseudophakic subjects and those with beginning cataracts should be informed that their nighttime driving ability may be impaired, even if their visual acuity is sufficient. Independence from Spectacles In the Array safety and efficacy study by Steinert et al. [3] the percent of subjects with bilateral multifocal IOLs who could function comfortably without spectacles were 93% for distance, 93% for intermediate, and 81% for near vision (fig. 4). These percentages were generally greater for subjects who had received bilateral Arrays. For near vision, a significantly higher percentage of subjects with bilateral multifocal IOLs could function comfortably without eyeglasses (81% (96 of 118)), compared to 56% (93 of 165; p ⬍ 0.001) of multifocal/monofocal subjects, or to 58% (56 of 97; p ⬍ 0.001) with unilateral monofocals. Thus, the full advantages of multifocality are more likely gained with bilateral implantation. If a subject requires cataract surgery and aspires to be spectacle-independent, then only implantation of multifocal IOLs can achieve this with preservation of stereopsis. Patient Satisfaction and Quality of Life Patient satisfaction at 1 year postsurgery in the study by Steinert et al. [3] was very high. More than 90% of subjects were moderately or very satisfied, and more than 90% of them would choose the same IOL again.
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Subjects in the multifocal IOL groups in the studies by Javitt and Steinert [12] and Javitt et al. [11] rated their vision without glasses better overall, at near, and at intermediate distances than subjects in the monofocal IOL groups (p ⭐ 0.05). Subjects with the Array demonstrated better visual function for near tasks and social activities and less spectacle dependency that subjects implanted with traditional monofocal IOLs. All 50 subjects with implanted Array IOLs in the study by Vaquero-Ruano et al. [7] were satisfied with the lens and their increased range of functional vision, even if they were not fully independent of spectacles. Brydon et al. [27] also found that subjects with bilateral Array IOLs were significantly more pleased with their improved vision than subjects with bilateral monofocals, based upon mean scores on the VF-14 index of visual function (p ⫽ 0.003). In subjects with unilateral implantation of the CeeOn 811E diffractive bifocal [19], 31% (11 of 35) were dissatisfied with their uncorrected distance and near vision; the authors suggest that this high dissatisfaction rate is related to the unilateral implantation. Of the other subjects, 43% (15 of 35) were satisfied and 26% (9 of 35) were highly satisfied. After best distance correction, 57% (20 of 35) were satisfied, 37% (13 of 35) were highly satisfied, and only 6% (2 of 35) were dissatisfied. Eighty-nine percent (31/35) of subjects said they would choose the same IOL for their fellow eye.
Conclusion
Multifocal IOLs more closely replicate the near to far vision of the prepresbyopic crystalline lens than monofocal IOLs and may well offer definite advantages over monofocal IOLs. Refractive multifocal IOLs, refractive bifocal IOLs and diffractive bifocal IOLs all showed distance vision comparable to monofocal IOLs. The Array refractive multifocal IOL provided significantly better near visual acuity and significantly greater depth of focus than monofocal IOLs. The Domilens Progress 1 refractive multifocal IOL provided intermediate and near visual acuity comparable to monofocal IOLs. The True Vista refractive bifocal IOL provided better uncorrected near vision and distance-corrected near vision than monofocal IOLs. The diffractive bifocal IOLs – CeeOn 811E, Pharmacia 808X, 3M 825X and 3M 815LE – provided good distance and near visual acuities. The diffractive optics, however, do not use all available light and this appears to have a negative impact on low contrast sensitivity. As for the future, we would hope for an injectable accommodative implant which would virtually mimic the physiological behavior of the lens – although this is clearly a distant wish at present.
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References 1 2 3
4 5
6 7 8
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12
13 14 15 16 17
18
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Ravalico G, Baccara F, Bellavitis A: Refractive bifocal intraocular lens and pupillary diameter. J Cataract Refract Surg 1992;18:594 –597. Steinert R: Visual outcomes with multifocal intraocular lenses. Curr Opin Ophthalmol 2000;11: 12–21. Steinert RF, Aker BL, Trentacost DJ, Smith PJ, Tarantino N: A prospective comparative study of the AMO Array zonal-progressive multifocal silicone intraocular lens and a monofocal intraocular lens. Ophthalmology 1999;106:1243–1255. Ravalico G, Parentin F, Sirotti P, Baccara F: Analysis of light energy distribution by multifocal intraocular lenses through an experimental optical model. J Cataract Refract Surg 1998;24: 647–652. Knorz MC, Claessens D, Schaefer RC, Sieberth V, Liesenhoff H: Evaluation of contrast acuity and defocus curve in bifocal and monofocal intraocular lenses. J Cataract Refract Surg 1993;19: 513–523. Arens B, Freudenthaler N, Quentin CD: Binocular function after bilateral implantation of monofocal and refractive multifocal intraocular lenses. J Cataract Refract Surg 1999;25:399– 404. Vaquero-Ruano M, Encinas JL, Millan I, Hijos M, Cajigal C: AMO Array multifocal versus monofocal intraocular lenses: Long-term follow-up. J Cataract Refract Surg 1998;24:118–123. Dick H, Krummenauer F, Schwenn O, Krist R, Pfeiffer N: Objective and subjective evaluation of photic phenomena after monofocal and multifocal intraocular lens implantation. Ophthalmology 1999;106:1878–1886. Featherstone KA, Bloomfield JR, Lang AJ, Miller-Meeks MJ, Woodworth G, Steinert RF: Driving simulation study: Bilateral Array multifocal versus bilateral AMO monofocal intraocular lenses. J Cataract Refract Surg 1999;25:1254 –1262. Grosskopf U, Wagner R, Jacobi F, Krzizok T: Contrast sensitivity and glare sensitivity in patients with monofocal or multifocal pseudophakic eyes (in German). Ophthalmologe 1998;95:432–437. Javitt J, Brauweiler HP, Jacobi KW, Klemen U, Kohnen S, Quentin CD, Teping C, Pham T, Knorz MC, Poetzsch D: Cataract extraction with multifocal IOL implantation: A multicenter clinical trial in Germany and Austria evaluating clinical, functional and quality-of-life outcomes. J Cataract Refract Surg 2000;26:1356–1366. Javitt JC, Steinert RF: Cataract extraction with multifocal IOL implantation: A multinational clinical trial evaluating clinical, functional and quality-of-life outcomes. Ophthalmology 2000; 107:2040–2048. Ravalico G, Parentin F, Pastori G, Baccara F: Spatial resolution threshold in pseudophakic patients with monofocal and multifocal intraocular lenses. J Cataract Refract Surg 1998;24:244–248. Liekfeld A, Walkow T, Anders N, Pham DT, Wollensak J: Prospective comparison of two multifocal lens models (in German). Ophthalmologe 1998;95:253–256. Pieh S, Weghaupt H, Skorpik C: Contrast sensitivity and glare disability with diffractive and refractive multifocal intraocular lenses. J Cataract Refract Surg 1998;24:659–662. Weghaupt H, Pieh S, Skorpik C: Multifocal intraocular lenses as an alternative in cataract surgery (in German). Wien Med Wochenschr 1997;147:298–301. Weghaupt H, Pieh S, Skorpik C: Comparison of pseudoaccommodation and visual quality between a diffractive and refractive multifocal intraocular lens. J Cataract Refract Surg 1998;24: 663–665. Lesueur L, Gajan B, Nardin M, Chapotot E, Arne JL: Comparison of visual results and quality of vision between two multifocal intraocular lenses. Multifocal silicone and bifocal PMMA. J Fr Ophtalmol (in French) 2000;23:355–359. Avitabile T, Marano F, Canino E, Biondi S, Reibaldi A: Long-term visual results of bifocal intra-ocular lens implantation. J Cataract Refract Surg 1999;25:1263–1269. Knorz MC: Results of a European multicenter study of the True Vista bifocal intraocular lens. J Cataract Refract Surg 1993;19:626– 634. Knorz MC, Koch DD, Martinez-Franco C, Lorger CV: Effect of pupil size and astigmatism on contrast acuity with monofocal and bifocal intraocular lenses. J Cataract Refract Surg 1994;20: 26–33.
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Knorz MC, Seiberth V, Ruf M, Lorger CV, Liesenhoff H: Contrast sensitivity with monofocal and bifocal intraocular lenses. Ophthalmologica 1996;210:155–159. Allen ED, Burton RL, Webber SK, Haaskjold E, Sandvig K, Jyrkkio H, Leite E, Nystrom A, Wollensak J: Comparison of a diffractive bifocal and a monofocal intraocular lens. J Cataract Refract Surg 1996;22:446– 451. Haaskjold E, Allen E, Burton R, Webber SK, Sandvig KU, Jyrkkio H, Leite E, Liekfeld A, Philipson B, Nystrom A, Wollensak J: Contrast sensitivity after implantation of diffractive bifocal and monofocal intraocular lenses. J Cataract Refract Surg 1998;24:653–658. Kamath GG, Prasad S, Danson A, Phillips RP: Visual outcome with the Array multifocal intraocular lens in patients with concurrent eye disease. J Cataract Refract Surg 2000;26:576–581. Häring G, Gronemeyer A, Hedderich J, de Decker W: Stereoacuity and aniseikonia after unilateral and bilateral implantation of the Array refractive multifocal intraocular lens. J Cataract Refract Surg 1999;25:1151–1156. Brydon KW, Tokarewicz AC, Nichols BD: AMO Array multifocal lens versus monofocal correction in cataract surgery. J Cataract Refract Surg 2000;26:96–100. Yang HC, Chung SK, Baek NH: Decentration, tilt, and near vision of the Array multifocal intraocular lens. J Cataract Refract Surg 2000;26:586 –589. Jacobi FK, Kammann J, Jacobi KW, Grosskopf U, Walden K: Bilateral implantation of asymmetrical diffractive multifocal intraocular lenses. Arch Ophthalmol 1999;117:17–23. Weghaupt H, Pieh S, Skorpik C: Visual properties of the foldable Array multifocal intraocular lens. J Cataract Refract Surg 1996;22(suppl 2):1313 –1317. Ravalico G, Baccara F, Isola V: Functional evaluation of a new type of intraocular lens: Domilens type Progress 1 (in French). J Fr Ophtalmol 1994;17:175–181.
Charles Claoué, MD, DBCG, PO Box 12650, London SE3 9ZZ (UK) Tel. ⫹44 020 8852 8522, Fax ⫹44 020 8852 8522, E-Mail
[email protected]
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Author Index
Masket, S. 85 Menapace, R. 131 Mester, U. 25 Muñoz, G. 106
Alió, J.L. 59, 97, 106 Anterist, N. 25 Arshinoff, S.A. 13 Attia, W.H. 59 Auffarth, G.U. 141, 202
Findl, O. 131 Fine, I.H. 32 Friedman, N.J. 74
Baumeister, M. 187 Becker, K.A. 202 Bellucci, R. 1 Bühren, J. 187
Haigis, W. 119 Hauck, C. 25 Hitzenberger, C.K. 131 Hoffman, R.S. 32
Claoué, C. 217
Jaullery, S. 195
Davis, E.A. 44 Dornbach, G. 41 Drexler, W. 131
Kammann, J. 41 Kiss, B. 131 Koch, D.D. 74 Kohnen, T. 74, 155, 187
Shalaby, A.M.M. 59 Sourdille, P. 195
Limberger, I.-J. 202 Lindstrom, R.L. 44 Löw, M. 25
Völcker, H.E. 202
Gills, J.P. 209 Olson, R.J. 79
Fabian, E. 147 Faller, U. 202 Fenzl, R.E. 209 Fercher, A.F. 131
Packer, M. 32 Parmar, D. 217 Ries, M. 202 Ruiz-Moreno, J.M. 97
Tetz, M.R. 202
Wang, L. 141
238
Subject Index
Anesthesia, see Topical anesthesia, cataract surgery Anterior chamber depth capsule shrinkage effects 139 IOLMaster measurement 123 Scheimpflug imaging 189, 190 Anterior chamber phacoemulsification comparison with phaco stop and chop best-corrected visual acuity 62, 71 corneal edema 62, 71 corneal thickness 68, 71 endothelial cell count 66, 67, 71 evaluation parameters (table) 64, 65 intraocular pressure 62, 63 laser flare cell meter count 65, 71 ultrasound time, power 62 historical perspective 59, 60, 68 indications 72 patient selection, evaluation 60 phacoemulsification techniques, popularity 68–70 postoperative treatment, follow-up 61, 62 technique 60, 61 Aspiration, phacoemulsification 80 Biometry, see Optical coherence biometry, Scheimpflug imaging, Ultrasound biometry Brunescent cataract, see Nuclear mature cataract Capsular tension ring actions 106, 113, 114, 117
anterior capsule contraction syndrome 115, 116 case studies 106–109, 111 indications 106, 112, 113 material 106, 111 posterior capsule opacification 116, 117, 195 scleral fixation 114, 115 sizes 111, 112 suppliers 111 zonular dialysis, signs of loose or broken zonules 115 Capsulorhexis, see also Cortical mature cataract, Tilt and tumble phacoemulsification ophthalmic viscosurgical devices 20–22 visibility enhancement techniques 88 Cocaine, topical anesthesia, cataract surgery 1 Cortical mature cataract anterior capsulorhexis 87–89 clinical features 85–87 complication management, surgery 92 cortex removal 92 hydrodissection 89, 90 morgagnian cataract 87 nuclear emulsification 92 preoperative evaluation 87 viscoelastic agent selection 88, 89 visualization, anterior capsule 89 Dispersive-cohesive viscoelastic soft shell technique, ophthalmic viscosurgical device utilization 14, 16
239
EasyPack, foldable intraocular lens injection 150, 152, 153 EasySert, foldable intraocular lens injection 150–152 Extracapsular cataract extraction, phacoemulsification comparison 59, 70, 71 Foldable lens, see Intraocular lens Fuchs’ dystrophy, ultrasound-assisted phaco aspiration case studies 81, 82 Healon, see Ophthalmic viscosurgical device, Viscoelastics Indocyanine green, anterior capsule visualization, mature cataract surgery 89 Intralenticular opacification, incidence with piggyback lens implantation 213–215 Intraocular lens biometry, see Optical coherence biometry, Scheimpflug imaging, Ultrasound biometry capsule shrinkage effects, anterior chamber depth 139 historical perspective 217 incisions, foldable lens implantation cadaver eyes, globe preparation for study 156 caliper development, incision size measurement design 166, 167 performance 175, 177 standard calipers 158 clinical studies factors affecting incision size 180–184 lens features 162, 163 measurement, incision size 165, 173–175, 180 patients 162, 163 statistical analysis 165 surgical procedure 164, 165 corneal damage, insertion through minimal incision 161, 162, 169, 170, 173, 178–180
Subject Index
incision size determination 159–161 intact globe versus removed cornea measurement 167–170 lens and implantation device type effects, incision size 157, 158, 168, 175, 177, 178, 180–184 minimum incision size studies 169, 170, 177, 178 rationale, foldable lenses and small incision size 155, 190 scanning electron microscopy, incisions 161, 162, 170, 173, 178, 179 surgical procedure 158, 159 injector systems, foldable lens implantation classification, inserter systems 147 EasyPack 150, 152, 153 EasySert 150–152 historical perspective 152 injection technique 147, 149, 153, 154 Lens Injector Set 150–152 lens specificity 152, 153 Microserter 149–151 Monarch 149, 151 Mport 149, 150, 152, 153 Passport 149, 150, 153 Sensar 149 Unfolder 149, 151 lens-capsule distance measurement 137, 138 multifocal intraocular lens, see Multifocal intraocular lens ophthalmic viscosurgical devices, implantation 20 piggyback intraocular lens implantation high-hyperopia treatment measurements and calculations 209–211 surgical technique 211, 212 indications 209 intralenticular opacification incidence 213–215 secondary implantation, over- or underpowered pseudophakes 212, 213
240
posterior capsule opacification, see Posterior capsule opacification posterior chamber intraocular lens implantation, vitreous cavity phacoemulsification 102 Scheimpflug imaging, foldable lenses anterior chamber depth 189, 190 decentration 189–191 lenses, evaluation 187, 189, 191 posterior capsule opacification 189, 192 technique 189 tilt 189–191 white-to-white measurement, see Orbscan topography system Intumescent cataract, see Cortical mature cataract IOLMaster anterior chamber depth measurement 123 instrumentation 119, 120 intraocular lens constant optimization 125–127 keratometry 123 observer dependence and learning curve 124 refractive outcome after cataract surgery compared with ultrasound biometry 135, 136 ultrasound axial length comparison and conversion 120–123
Mature cataract, see Cortical mature cataract, Nuclear mature cataract Microserter, foldable intraocular lens injection 149–151 Monarch, foldable intraocular lens injection 149, 151 Morgagnian cataract, see Cortical mature cataract Mport, foldable intraocular lens injection 149, 150, 152, 153 Multifocal intraocular lens advantages over monofocal lenses 235 designs models and manufacturers 218, 219, 235 refractive versus diffractive optics 218 effectiveness of models combined distance and near visual acuities 228 contrast sensitivity 230, 231 depth of focus 228–230 distance visual acuity 221, 224, 225 driving ability 233, 234 independence from spectacles 234 measures 221 near visual acuity 226–228 patient satisfaction and quality of life 234, 235 table 222, 223 visual symptoms 231–233 rationale for development 217, 218
Laser interference biometry, see Optical coherence biometry phacoemulsification safety 79 Lens Injector Set, foldable intraocular lens injection 150–152 Lidocaine, topical anesthesia for cataract surgery formulations 3, 4 gel 7 intraocular penetration 4, 5 side effects 5 sponges 8 systemic levels 4, 5 toxicity 5
Nuclear mature cataract clinical features 85, 93 definition 93 surgical management advantages 95 capsulorhexis 94 hydrodissection 94 nuclear emulsification 94 nuclear sculpting 94, 95 preoperative evaluation 93
Subject Index
Ophthalmic viscosurgical device, see also Viscoelastics advantages and limitations of classes 14, 16
241
Ophthalmic viscosurgical device (continued) applications anterior hyaloid face dissection from posterior capsule 19 capsulorhexis 20–22 cornea transplantation 20 intraocular lens implantation 20 partial filling, anterior chamber 20 phaco tumble techniques 19 trauma 20 trypan blue utilization 20, 22, 23 viscomydriasis 20 vitrectomy 21 wound blockade 21 classification 14, 15 dispersive-cohesive viscoelastic soft shell technique 14, 16 pseudoplasticity curves 18, 19 removal techniques 23, 24 types 13, 16 ultimate soft shell technique 21–23 viscoadaptive response to fluid turbulence 16–18 Optical coherence biometry, see also IOLMaster advantages over ultrasound biometry 125, 128, 129, 132–135, 137 dual beam partial coherence interferometry 132–136 historical perspective 110 intraocular lens constant optimization 125–127 lens-capsule distance measurement 137, 138 limitations 129 principles 132, 133 pseudophakic measurements 136–139 reference system 122 refractive outcome, cataract surgery 133–136 ultrasound axial length comparison and conversion 120–123 Orbscan topography system accuracy 142–144 instrumentation 141, 142 problem cases 143, 145 white-to-white measurement 141
Subject Index
Partial coherence interferometry, see Optical coherence biometry Passport, foldable intraocular lens injection 149, 150, 153 Phaco chop advantages 77, 78 anterior chamber phacoemulsification comparison, see Anterior chamber phacoemulsification chopping technique 76 complications 77 historical perspective 74, 75 instrumentation 75 patient selection 75 principles 75, 80 training 77 ultrasound assistance Fuchs’ dystrophy case studies 81, 82 irrigation forces 82, 83 rationale 80 technique 80, 81 Phacoemulsification, see Anterior chamber phacoemulsification, Capsular tension ring, Phaco chop, Phacotmesis, Staar Wave, Tilt and tumble phacoemulsification, Viscoelastics, Vitreous cavity phacoemulsification Phaco-out, see Anterior chamber phacoemulsification Phacotmesis indications 42, 43 principles 41 technique, phacoemulsification 41 tip size effects 42 Piggyback intraocular lens implantation, see Intraocular lens Posterior capsule opacification acrylic-hydrophilic intraocular lens studies of square edge prevention lens characteristics 196, 197 opacification, first-generation lenses 195 patient groups and outcomes 197, 198, 200 square edge concept 195 surgical technique 197 assessment techniques 200, 203, 204
242
capsular tension ring effects 116, 117, 196 incidence following lens implantation 204, 205 lens epithelial cell migration 195, 200 polyfluorocarbon-coated intraocular lens study functional outcomes 206, 207 opacification assessment 202–206 rationale 202 study design 202, 203 Scheimpflug imaging 190, 192 Retina, protection in vitreous cavity phacoemulsification 105 Scheimpflug imaging foldable lens imaging anterior chamber depth 189, 190 decentration 189–191 lenses for evaluation 187, 189, 191 posterior capsule opacification 189, 192 technique 189 tilt 189–191 historical perspective 187 Sensar, foldable intraocular lens injection 149 Staar Wave conventional surgical features 32, 33 instrumentation 32, 33 limitations of current ultrasonic tips 33, 34 Sonic technology advantages 34–36, 39 SuperVac tubing 36, 37, 39, 40 Wave Powertouch user interface 37–39 Tetracaine, topical anesthesia, cataract surgery 3 Tilt and tumble phacoemulsification advantages 54 capsulorhexis 44, 45, 52, 53 closure 51 corneal incision and approaches 49–51 cortex removal 55 historical perspective 44–46 hydrodissection 53–55
Subject Index
indications 46, 47 keratotomy 51, 52 posterior lens chamber seating 56 postoperative care 57 preoperative preparation anesthesia 47, 48 aperture drape 48 periocular prep 48 speculum separation, lids 48, 49 Storz Millennium utilization 55 variations in technique 57, 58 viscoelastic injection 53, 54, 56 selection 52 Topical anesthesia, cataract surgery advantages over injection 2 bilateral instillation 6 clinical experience, small incision surgery 8, 9 complications management 7 historical perspectives 1 instillation schedule 6 intraocular irrigation 6, 9 lidocaine formulations 3, 4 gel 7 intraocular penetration 4, 5 side effects 5 sponges 8 systemic levels 4, 5 toxicity 5 patient selection and instructions 6 postoperative instructions 7 receptor block principles 2, 3 requirements 2 surgical technique 6, 7, 10 tetracaine 3 tilt and tumble phacoemulsification 47, 48 Trypan blue anterior capsule visualization, mature cataract surgery 89 utilization, ophthalmic viscosurgical device 20, 22, 23 Ultimate soft shell technique, ophthalmic viscosurgical device utilization 21–23
243
Ultrasound, see Phaco chop, Phacoemulsification, Staar Wave Ultrasound biometry accuracy 131 applanation versus immersion axial eye length measurements 131, 210 optical axial length comparison and conversion 120–123 optical coherence biometry comparison 125, 128, 129, 132–135, 137 piggyback intraocular lens implantation measurements 210 Unfolder, foldable intraocular lens injection 149, 151 Viscoadaptive, see Ophthalmic viscosurgical device, Viscoelastics Viscoelastics classification 25 cornea guttata comparative study of phacoemulsification central corneal thickness outcomes 27–30 central endothelial cell outcomes 27, 28 study design 26, 27, 29 surgical technique effects on endothelial impairment 29
Subject Index
viscoelastic physical and chemical properties 26, 30 surgical trauma protection 28 tilt and tumble phacoemulsification injection 53, 54, 56 selection 52 Vitreous cavity phacoemulsification advantages over nuclear extraction 103, 104 best corrected visual acuity outcomes 101, 102, 104 complication incidence 97, 102, 103 indications 99 patient characteristics and selection 97–99, 104 posterior chamber intraocular lens implantation 102 retinal protection 105 three-port pars plana vitrectomy 99, 100 White-to-white measurement, see Orbscan topography system Zonular dialysis capsular tension ring indication 106, 112, 113, 117 signs of loose or broken zonules 115
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