EyeWorld Asia-Pacific March 2011 Issue

7 EW FEATURE March 2011 Minefields & Battles by Chiles Aedam R. Samaniego EyeWorld Asia-Pacific Senior Staff Writer Insights on ophthalmology from a special symposium at the SNEC 21st Anniversary International Meeting T he ophthalmology lingua franca is steeped in military metaphors: instruments, devices, and drugs constitute the ophthalmologist’s “armamentarium” or “arsenal”; refractive endpoints are “targets”; cataract surgery techniques are “strategies”. It isn’t likely that very many surgeons have thought about the way the field is thus metaphorically structured, but, as a symposium held at the end of the Singapore National Eye Centre (SNEC) 21st Anniversary International Meeting revealed, paying close attention to this way of thinking can lead to insightful discussion. At the symposium, Ronald Yeoh, MD (Singapore), invited a panel of experts from around the world to think of ophthalmic cases in terms of “minefields” and “battles”. Battles, he said, are those cases in which “you know you’re in trouble” from the start; cases which present obvious challenges to the ophthalmologist even before treatment begins. These cases are expected to be challenging from the outset. Minefields, on the other hand, appear to be straightforward, sometimes even routine cases in the beginning; initially hidden variables only become evident—perhaps even obvious, in retrospect—during the course of treatment. These cases thus have the potential to dramatically, often unexpectedly become challenging as treatment proceeds. The symposium was structured into ophthalmic subspecialties, with two speakers assigned to each subspecialty—one to present a “minefield”, another to present a “battle”. Pitfalls in cataract surgery Perhaps the “most critical area” that presents a potential minefield in cataract surgery is the creation of the continuous curvilinear capsulorhexis (CCC), said Graham Barrett, MD (Australia). Even a small tear in the anterior rhexis which “doesn’t seem to be a major problem at the time” can extend posteriorly, allowing vitreous to present in the anterior chamber and potentially causing nuclear fragments or even the entire nucleus to drop, he said. “The first thing you need to understand is the vector forces,” said Dr. Barrett. This understanding is usually largely intuitive, but is in fact addressed directly by each technique used in the creation of the CCC. For instance, he said, the injection of viscoelastic and the use of infusion are techniques to counteract the outward vector forces that result from zonular traction, vitreous pressure, and intralenticular pressure. Dr. Barrett identified four main factors that predispose an eye to rhexis tears: poor visibility; increased intralenticular pressure; weak zonules; capsular abnormalities. The “commonest cases” of poor visibility involve mature cataracts in which it is difficult to see the edge of the rhexis; corneal haze can also limit visualization. In these cases, Dr. Barrett recommended using capsular stains. “It’s best to be prepared and to use a capsular stain,” he said. “You’ll maintain visibility throughout the entire course and create an intact rhexis.” Mature cataracts don’t just present visibility problems; intumescent cataracts also have increased intralenticular pressures. Upon puncturing the capsule, the surgeon will note the egress of cortical material through the puncture. In such cases, it’s best to aspirate some of this material to reduce the pressure in the lens before proceeding with the rhexis. In case of zonular weakness, Dr. Barrett prefers using forceps to make the rhexis. The forceps allow him to lift the capsule and move the capsule edge tangentially. Finally, a fibrotic capsule may need to be dealt with using a good pair of scissors. However, it isn’t always possible to avoid rhexis tears. In case of a tear, Dr. Barrett recommends redirecting the rhexis, reversing the pull on the rhexis flap—the so-called “rescue maneuver” previously described by Dr. Brian Little; in some cases, it may be necessary to restart the rhexis entirely. Toric in a torrid situation Chee Soon Phaik, MD (Singapore), is well known at ophthalmology meetings for her skill in dealing with cataract surgery “battles”. The case she presented at this symposium had some of the metaphorical elements of a minefield, but would certainly present a challenge to the average cataract surgeon: a patient, who happened to be a lawyer, with a previous diagnosis of amblyopia severe enough to get him exempted from Singapore’s National Service, presented at her clinic with a posterior subcapsular cataract. Biometry also revealed significant astigmatism, and her calculations led her to recommend a 9-D toric implant; it was a case, then, that needed a fine degree of care and skill: posterior subcapsular cataracts are attended by an increased risk of posterior capsular rupture; a toric lens in this case seems a brave choice, since an uncomplicated surgery is particularly important to ensure good refractive outcomes. An uncomplicated surgery is not what Dr. Chee got. During surgery, Dr. Chee noticed that the cataract, unusually, was much denser on one side. While slowly and carefully performing her capsulorhexis through a 1.8-mm incision, she nonetheless observed a pupil snap. This put her on guard; she had not yet seen a tear in the posterior capsule, but she knew that she needed to proceed with continued on page 8 Getting ready for Minefields & Battles Source: Singapore National Eye Centre