JAN 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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60 EW MEETING REPORTER January 2013 Reporting continued from page 59 Reporting live from the 2012 Asia Cornea Society meeting, Manila Editors' note: This Meeting Reporter contains original reporting by the EyeWorld news team from the 2012 Asia Cornea Society meeting in Manila. daunting as economic issues typically are in the region, this may not necessarily be insurmountable—the use of precut tissue from a central eye bank, for instance, offers one solution—but there are clinical challenges as well, including: 1. The technically challenging procedure is even more challenging in Asian eyes, which tend to be smaller, with greater vitreous pressure. 2. The main indication for keratoplasty in the region is pseudophakic bullous keratopathy (PBK); the procedure has been documented to have lower survival and more complications in these cases compared with cases performed for the typical indication in Western countries—Fuchs' dystrophy. Nonetheless, said Prof. Tan, the procedure is gaining some ground in the region. In Singapore, 77% of keratoplasty cases in 2012 were lamellar. And while it is technically more difficult, their experience further supports the procedure's advantages. Successful DSAEK, he said, is all about control. Every step in the development of the procedure, such as in terms of the donor insertion phase—from taco folding to insertion with the EndoGlide (Angiotech, Vancouver, B.C.) that Prof. Tan himself helped develop—has been about improving control. And yet in order to take the next step, it is often necessary to relinquish the same control that has brought you to the point at which it is possible to take that step. Or something. DMEK must be among the most extreme forms of selective lamellar keratoplasty ever conceived to date, a procedure in which the tissue to replace is confined to the endothelium, separated from the donor at the Descemet's membrane. This, said Prof. Tan, means harvesting and handling tissue that is even thinner and, subsequently, more difficult to control than the thinnest DSAEK. Regardless, Frank Price, M.D., Indianapolis, thinks that there is unquestionably a role for DMEK in Asia. Apart from the potential of providing the best possible visual quality of any EK procedure to date, in a very basic sense, DMEK is the next, possibly ultimate, step in the natural progression of EK: By avoiding the creation of an interface, an additional layer where there would not normally be one, DMEK may be the first procedure to truly restore the normal corneal architecture. While techniques for donor preparation and insertion as well as post-op management can be improved, the results Dr. Price currently achieves with the procedure are far superior to the results of any form of DSAEK. Sites from around the world that frequently prepare donor tissue for DMEK have donor tissue loss rates less than 1%—at least as good as donor tissue loss rates for ultrathin DSAEK. The cell loss rates Dr. Price has seen with DMEK are comparable to cell loss rates at other sites in the U.S. performing DSAEK. In addition, in some cases, it is possible that reported rates of cell loss were exaggerated by the method used for counting cells by eye banks. Dr. Price believes that DMEK will continue to be the best option for most of the U.S. and Asia until viable methods for simply injecting endothelial cells or stimulating the regeneration of the patients' own endothelial cells are developed. Editors' note: Prof. Tan helped develop the Tan EndoGlide, but has no financial interests in the device. Dr. Price has no financial interests related to his comments. Redefining corneal architecture The big bubble technique has always been presumed to cleave the cornea at the Descemet's membrane. But this might not always be the case. After a series of observations involving the procedure, Harminder S. Dua, M.D., Nottingham, U.K., began to suspect the existence of a distinct layer in the posterior stroma that is different from the Descemet's membrane. Prof. Dua devised a simple test for his hypothesis: He performed the big bubble technique on four whole globes and 21 sclero-corneal discs. The paper, in press, was the subject of his plenary lecture at the meeting. He found that performing the technique results in one of three types of bubbles: Type 1 emerges centrally, forming a well-circumscribed central dome 7-8.5 mm in diameter. Type 2 is thin-walled, begins peripherally, resulting in a bubble with a much larger diameter. Type 3 mixes the characteristics of the two. With a type 1 bubble, the Descemet's membrane can be peeled off entirely, histologically intact, without bursting the bubble. Peeling View this video at www.EWrePlay.org/ ACS2012 Donald Tan, M.D., Singapore, president of the Asia Cornea Society and the Cornea Society, summarizes the talks given at the Advanced Keratoplasty Symposium, which kicked off the meeting, sponsored by the Cornea Society.

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