EyeWorld Asia-Pacific September 2011 Issue

50 EW CORNEA September 2011 with a full-thickness transplant, “but patients don’t seem to mind,” he said. In Asian eyes, DSAEK for pseudophakic bullous keratopathy (PBK) is more common than Fuchs,’ mainly because Asians present at a later stage, said Donald T.H. Tan, FRCOphth, head and senior consultant, Singapore National Eye Centre, Singapore. “Surgery is more challenging in these eyes because there’s more haze during surgery and the visual outcomes are not as good,” Dr. Tan said, adding that socioeconomics is a predominant reason why people in China, Japan, or India present later than their US or European counterparts. Adding to the difficulty is the fact that Asian eyes are generally smaller, so surgeons are operating in much more confined spaces, he said. “We’ve learned from DSAEK surgery that visual loss from guttata is more severe than we ever suspected,” Dr. Terry said. “Fuchs’ dystrophy 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 situation 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 patients to have a visual loss to 20/60 [6/18] or 20/70 [6/21] because we now realize that if they’re 20/30 [6/9] in our room, they may be 20/60 or 20/100 [20/30] 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 procedure of choice for these patients, Dr. Vroman said. In 2005, the number of corneas distributed for EK procedures 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 number of full thickness corneal transplants 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 transplants 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 transplants. 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 latest 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 reported on PK for Fuchs.’” There are limitations to DSAEK, Dr. Price said, namely that very few have excellent visual outcomes. “Fuchs’ patients have viable endothelial 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 initially,” 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 endothelial cells just by performing the surgery, which indicates a need for better techniques, Dr. Tan said. Dr. Price said a comparison between 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 involved in cell counts, but it’s certainly no worse than PK.” In small eyes, the surgeon faces a shallow anterior chamber and much higher vitreous pressure. While most US surgeons opt for the “taco folding” technique for donor tissue, using that method in Asian eyes tends to lead to chamber collapse, Dr. Tan said. In Asian eyes, using a pull- through method with the Tan EndoGlide (Angiotech, Vancouver, BC, Canada) helps maintain the chamber. Although cell loss is a concern, endothelial rejection in EK procedures is “not all that common,” Dr. Vroman said. In general, patients are put on a tapering steroid dose from four times daily immediately after surgery to about once a day by 9 months. Most patients will need to remain on daily steroids, as Dr. Terry said a few studies have shown rejection rates increase once steroids are removed. Surgical pearls Although there are some similarities between DSAEK and cataract surgery, “you can’t fold a cornea or coil it up with impunity like you can an IOL; you’ll do damage. I say that because surgeons are trying to go through much smaller wounds now, like cataract surgery. They try to be astigmatically neutral, they try to use 3-mm incisions,” Dr. Tan said. Dr. Terry’s group has shown that smaller incisions will cause more endothelial damage than incisions around 5 mm. “Another aspect is that surgeons don’t like to operate on the sclera because you’ve got to open up the conjunctiva; they like clear corneal incisions like IOL surgery. But that’s more challenging because on the clear cornea there’s more astigmatism so they try to go smaller. Most surgeons today feel a scleral incision is safer in terms of the endothelium,” Dr. Tan said. He believes using a scleral tunnel incision, coupled with sutures and a larger incision, is safer for the endothelium. Successful DSAEK surgery is aided “by starting with good quality tissue,” Dr. Van Meter said. With eye banks being paid more for EK tissue preparation, PK tissue may be a lesser grade, he said. Graft dislocation can be a concern, he added, “and that comes from not getting the bubble big enough and eliminating the interface fluid”. A secondary concern is pupillary block, which can be managed by ensuring no air is left behind the iris. Dr. Vroman suggests surgeons should use a technique “that makes sense for your skill set”. In his Endothelial from page 49