Eyeworld

EW FEATURE 43 fact that Asian eyes are generally smaller, so surgeons are operating in much more confined spaces, he said. "We've learned from DSAEK sur- gery that visual loss from guttata is more severe than we ever sus- pected," Dr. Terry said. "Fuchs' dys- trophy patients can have very little in the way of corneal edema but yet still have significant glare problems, and vision drops off in a real-life sit- uation because the guttata disperses the light." Dr. Terry said patients with Fuchs' will complain "bitterly" about vision, even though in clinical exams there's not much in the way of stromal edema. "We don't have to wait for pa- tients to have a visual loss to 20/60 or 20/70 because we now realize that if they're 20/30 in our room, they may be 20/60 or 20/100 when they're trying to drive at night," he said. "We should be doing more glare testing, contrast sensitivity testing" because the guttata, not just the stromal edema, is limiting the vision. DSAEK has become the proce- dure of choice for these patients, Dr. Vroman said. In 2005, the number of corneas distributed for EK proce- dures by eye banks was 1,429; in 2006 that number rose to 6,027. In 2007, there were 14,159 donor corneas prepped for EK procedures; by 2009 a total of 18,221 tissues were distributed for EK use out of a total of 42,000, Dr. Vroman said. During that same period, the num- ber of full thickness corneal trans- plants dropped by more than half, from almost 46,000 in 2005 to 23,269 in 2009. Dr. Van Meter added there was a 9.5% increase from 2009-2010 in the number of eye bank tissue distributed for EK use (to 19,159). "There were more corneal trans- plants for Fuchs' this year [2010] than last year," Dr. Van Meter said. "One reason is we're treating Fuchs' much more aggressively than before EK became mainstream." He said about 85% of those with Fuchs' were treated via EK; the remaining 15% underwent full-thickness trans- plants. Eye banks prepared about 100 tissues for DMEK procedures in 2010, Dr. Van Meter said. Making DSAEK a success Regardless of technique, endothelial cell loss is a concern. Dr. Terry's lat- est data indicates Fuchs' patients will have less endothelial cell loss 5 years or more after surgery than those with PBK. Dr. Price has found that visual results after DSAEK "are as good or better than any results re- ported on PK for Fuchs.'" There are limitations to DSAEK, Dr. Price said, namely that very few have excellent visual outcomes. "Fuchs' patients have viable en- dothelial cells in the periphery," Dr. Terry said. Dr. Tan said the majority of cell loss will occur during the surgical procedure itself; hopefully the use of newer inserters will reduce that loss, he said. "That's the key, since most of the injury to the cells is during the insertion portion of the surgery," he said. Studies from Price et al. are showing the initial high level of cell loss tapers off early. "Cell loss stabilizes much faster in DSAEK, but it's much higher ini- tially," Dr. Tan said. "It's all about the technique at the moment." Some studies have found "very high levels of endothelial cell loss in DSAEK procedures, which defeats the whole purpose of doing the transplant," he said. Some surgeons are losing up to 40% of the endothe- lial cells just by performing the sur- gery, which indicates a need for better techniques, Dr. Tan said. Dr. Price said a comparison be- tween DSAEK eyes and the PK Corneal Donor Study (CDS) that evaluated cell loss showed that "even though 6-month cell counts were a lot lower for DSEK than the PK eyes in the Cornea Donor Study, the cell counts were approximately equal at 3 years, and by 5 years DSEK eyes had better cell counts than the PK CDS eyes. The point isn't that DSEK was better, because there's certainly some variability in- volved in cell counts, but it's cer- tainly no worse than PK." In small eyes, the surgeon faces a shallow anterior chamber and much higher vitreous pressure. While most U.S. surgeons opt for the "taco folding" technique for donor tissue, using that method in Asian eyes tends to lead to chamber col- lapse, Dr. Tan said. In Asian eyes, using a pull-through method with the Tan EndoGlide (Angiotech, Vancouver, B.C.) helps maintain the chamber. Although cell loss is a concern, endothelial rejection in EK proce- dures is "not all that common," Dr. Vroman said. 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