Eyeworld

EW CORNEA 25 D espite the massive effort to study ectasia, both overseas and in the U.S., the rules for when and how to apply treatment remain mostly muddy. "On a practical level, it's hard for a practitioner to know what to do for ectasia patients, especially when treatment may call for crosslinking," said Louis E. Probst, M.D., chief laser surgeon and senior medical advisor, TLC Laser Eye Cen- ters, which has locations in Chicago; Madison, Wis.; and Tampa, Fla. Corneal collagen crosslinking with riboflavin is widely used in Eu- rope and other countries, as clinical trials and studies in the U.S. work to- ward FDA approval. Clinicians who believe their ectatic patients would benefit from crosslinking are faced with giving them a choice: partici- pate in a clinical trial, travel overseas to have the procedure done, or do nothing. But at what point do practition- ers offer this choice to patients? No one will currently put a threshold on the corneal thickness or degree of astigmatism that makes a patient a good candidate. "There's not any specific point at which you can say, 'This is ectasia or keratoconus or needs crosslinking or doesn't need crosslinking,'" said David R. Hardten, M.D., adjunct as- sociate professor of ophthalmology, University of Minnesota, Minneapo- lis. "There are a lot of multifactorial issues that come into play with it. That's part of what makes this area very difficult for us in trying to diag- nose this and decide. It's a very com- plicated decision-making process whether a patient might benefit from crosslinking." Dr. Hardten's practice currently is part of a clinical crosslinking trial by TopCon Corp. (Tokyo). Origi- nally, a clinical trial was being per- formed by Peschke Meditrade GmbH (Hunenberg, Switzerland). When the company stopped funding the trial, it sold the data to Avedro (Waltham, Mass.). "A lot of it is clinical judgment," he said about diagnosing ectasia. "It's based on both the anterior and posterior tomography testing, based on corneal thickness. Age plays some role in it." Talking to patients In his position as vice president of patient services for TLC Laser Eye Centers, Dallas, John Potter, O.D., F.A.A.O., has probably talked to more ectasia patients after refractive surgery than nearly anyone in the world. He said patients have a hard time tolerating contact lenses, and the idea of having a cornea trans- plant often doesn't sit well with them either. "Intacs (Additional Technology, Des Plaines, Ill.) are sometimes not very helpful, so often patients won't do anything," Dr. Potter said. "If in 2011 a doctor identifies someone with ectasia and it's pretty early on, crosslinking is appropriate. It's a simple treatment, it has very few side effects, and it may slow the pro- gression of ectasia. It's a hard thing for a surgeon to not want to do." by Jena Passut EyeWorld Staff Writer How and when to treat ectasia patients not always clear ful not to leave any bare sclera be- cause of the risk of scleral thinning or melting. "If someone has a large nasal and temporal pterygium from both sides or one that involves the visual axis, that plays a role in how aggres- sive I am," Dr. Palmon said. "Unless I was operating on a se- vere recurring pterygium, I wouldn't use mitomycin C," Dr. Verdier said. "It may depend on your population, but I've only had one recurrence in my career. I don't see as severe ptery- giums as people do in the Sunbelt." Although Dr. Rapuano gener- ally does not use MMC, he will use it if he is treating a recurrent case. Instead of intraoperative use, some surgeons prescribe MMC 0.02% four times a day for 7-14 days post-op to reduce recurrences, Dr. Verdier said. Unusual cases Not all cases qualify for typical pterygium surgery. Dr. Verdier is more cautious if he is suspicious of squamous cell carcinoma. "I just saw a pterygium that I thought could be squamous cell carcinoma. I'm going to do a biopsy before I re- move it. I don't want to take it off without first seeing if it's cancer- ous," he said. Other unusual cases would be patients with filtering blebs from glaucoma or other glaucoma-related issues. In these patients or in those with large pterygiums, where you would have to remove more tissue than you'd feel comfortable with, using an amniotic membrane might be a better choice, Dr. Verdier said. Surgeons are reviewing research that is investigating vascular en- dothelial growth factor inhibitors such as Avastin (bevacizumab, Genentech, South San Francisco) or Lucentis (ranibizumab, Genentech) injected or used topically to prevent recurrences, Dr. Palmon said. Pub- lished results so far have been mixed, he said. Surgical pearls If you're looking to perfect your pterygium technique, consider the following tips from Drs. Palmon, Rapuano, and Verdier: • Make sure to excise all of the in- flamed tissue, not just the portion over the cornea, Dr. Palmon said. • Do not leave any bare sclera if you use MMC, Dr. Palmon said. • Don't get too extensive in your removal efforts, Dr. Verdier said. Although you naturally want to remove the pterygium, he said he once caused double vision in a patient by going too far back with the dissection. "Once you get past the posterior to the rhexus mus- cles, especially if you go further back into orbital fat, you run an increased risk of scarring that can interfere with eye mobility," he said. "I get good or better results by not going 3-5 mm back from the limbus." • Use a diamond burr to smooth out the cornea, Dr. Rapuano rec- ommended. "I believe the smoother the cornea and limbus, the less chance there is of recur- rence," he said. • For similar reasons, Dr. Verdier recommends the use of a spatula or 64 Beaver blade parallel to the cornea but not cutting into the cornea. "You end up with smooth biologic tissue membrane. It's much better than if you just try and cut in." EW Editors' note: The doctors interviewed have no financial interests related to this article. Contact information Palmon: 239-768-0006, rpalmon@swfleye.com Rapuano: 215-928-3180, cjrapuano@willseye.org Verdier: 616-949-2001, daverdier@aol.com Pterygium continued from page 24 continued on page 26 A patient's pre- and post-collagen crosslinking topography Source: A. John Kanellopoulos, M.D. November 2011

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