Eyeworld

EW FEATURE 38 by Maxine Lipner Senior EyeWorld Contributing Editor Talking DALK for stromal disease DALK procedure making inroads in the U.S. F or many years full-thick- ness penetrating kerato- plasty (PK) has been the primary option for patients with severe stromal disease. However, deep anterior lamellar ker- atoplasty (DALK) has been coming on strong, particularly in countries outside of the United States, accord- ing to David D. Verdier, M.D., Verdier Eye Center, Grand Rapids, Mich. "We are behind much of the rest of the world when it comes to DALK," Dr. Verdier said. "In Europe, the Middle East, and Singapore, DALK is performed much more fre- quently." Dr. Verdier points to Eye Bank Association of America data, which in 2009 put anterior lamellar procedures at just 2% of transplants performed in the U.S., compared with 55% for PK and 43% for en- dothelial keratoplasty. What's holding practitioners back? Edward J. Holland, M.D., professor of ophthalmology, University of Cincinnati, and director, cornea service, Cincinnati Eye Institute, thinks that from the start, those in other parts of the world were more attuned to the procedure. "The in- terest started in the Middle East, in Europe, and in Asia," he said. "While we were always interested in doing DALK for stromal disease, the problem was interface haze, so we basically abandoned it. But other parts of the world kept trying to per- fect the procedure, mostly out of ne- cessity." Now the DALK technique is be- ginning to offer up real dividends. "I think that the techniques of the big bubble, Anwar's, and others that allow us to get a good dissection down to Descemet's make this pro- cedure for stromal disease far supe- rior to what we can do with penetrating keratoplasty," Dr. Holland said. "However, U.S. sur- geons have been complacent for the most part. This has a steep learning curve, it is a difficult operation to master, and it takes more time than PK." In addition, many surgeons have become wedded to familiar PK. "They say, 'I do a very good PK, this is what I've been doing for the last 20 years, why should I change?'" Dr. Holland said. George J. Florakis, M.D., clini- cal professor of ophthalmology, Co- lumbia University, New York, sees a host of things holding practitioners back from embracing DALK. He pointed out there is already the PK procedure for corneal transplanta- tion, which works very well. "Many of us have done it for many years and do it well," Dr. Florakis said. "At least in some studies, it offers better visual acuity with a full-thickness corneal transplant than DALK." There are, of course, other studies that show the opposite to be true. Also, practitioners have become very skilled at PK. "Because we've been doing it for such a long time, we're good at it," he said. "It's not a very good reason, but the practical- ity is we're in our comfort zone with PK." DALK is also technically difficult to master. "Sadeer Hannush [M.D., attending surgeon, Cornea Service] at Wills Eye Hospital [Philadelphia] once said that this is the toughest new operation that he had to learn since fellowship, about 20-25 years ago," Dr. Florakis said. "It's techni- cally difficult with a fairly high con- version rate." He pointed out that many who attempt a DALK ulti- mately end up converting to a full- thickness transplant anyway. During a recent meeting of the Northeast Cornea Society, which Dr. Florakis attended, 14 prominent cornea sur- geons were informally polled. The conversion rate there was found to be from 30-50%, depending upon where they were in the learning curve. In addition, some of the poten- tial benefits of DALK remain unstud- ied. "Many of the DALK advantages are theoretical; they haven't been proven with statistics or papers," Dr. Florakis said. "But they are probably real." For example, he points to peo- ple saying there's no endothelial re- jection with DALK because no endothelium is being replaced. Even without study this makes sense. Dr. Florakis noted that another sticking point might be that the DALK procedure has not quite come into its own yet. "It may be a great procedure, and maybe it's still in the development stage," he said. "When it becomes more developed and per- haps new instruments emerge or something changes about it, more people will feel comfortable doing it." He thinks perhaps some practi- tioners are wearied by the idea of having to master yet another tech- nique. "We just got over learning en- dothelial keratoplasty," Dr. Florakis said. "That took a lot out of us." While those who just completed their fellowships may take this in stride, others who have been in practice for decades are less likely to be embrace DALK over tried-and- true PK. "We've done regular full- thickness transplants essentially the same way since the 30s," Dr. Florakis said. It has also become clear that DALK is a time-consuming proce- dure to perform. "It takes two to three times longer than a PK," Dr. Florakis said. "Ambulatory surgical centers and even hospitals in the present economic environment may not like that." After all that, the practitioner may end up doing a PK anyway. "You spend 2 hours working DALK and have to convert, and you've al- ready taken 2-3 hours of OR time," he said. From a tissue perspective there's not much need for DALK in the U.S. "Unlike other countries where good donors with fresh and healthy en- dothelial cells may be hard to come by, in the U.S. we generally have good tissue," Dr. Florakis said. "For example, if I have a 25- year-old keratoconus patient who I want to do DALK on, you know that he could reasonably expect a good cornea within a month or 6 weeks, " he said. In another country, without a good donor network, it could take years to get a cornea with good en- dothelium. Also, in terms of payment, there's not any inducement for prac- titioners to undertake the more diffi- cult DALK procedure. "We get paid less even though it's more work since it's really a lamellar kerato- plasty rather than a PK," Dr. Florakis said. "There is no code for DALK right now, and so the code that we have to use because we're not going full thickness is for lamellar kerato- plasty." Historically speaking, lamellar keratoplasty—shaving off part of the cornea and sewing on a new one— was considered not as risky as going into the eye to do a PK. "Obviously things have changed, but the codes have not caught up with DALK yet," Dr. Florakis said. The importance of transitioning While there are still some draw- backs, Dr. Verdier thinks DALK has come to a place where it can no longer be overlooked by U.S. sur- geons. He sees some inherent as- pects to the procedure that give it a distinct leg up over PK. "The advantage is that you can retain the patient's own endothe- lium, and the endothelium is the one part of the cornea that can't re- generate its own cells," Dr. Verdier said. "If you run out of endothelial cells you end up with a cornea that decompensates." With PK, endothelial cell loss is par for the course. "We know that with penetrating keratoplasty, the cell loss is significant," he said. "In low to moderate risk corneas, 70% of the endothelial cells are lost in the first 5 years." "Not only does an approxi- mately 30% loss of endothelial cells occur in the first year, what is really February 2011 CORNEA May 2011 AT A GLANCE • In the U.S. in 2009, only 2% of corneal transplants were done using an anterior lamellar approach • Much of the rest of the world has already adopted the DALK proce- dure • Some U.S. surgeons are deterred by the fact that DALK is a technically difficult procedure with a steep learning curve • Many surgeons remain entrenched and are reluctant to leave their comfort zone of performing PK • With DALK, key concerns about graft rejection and late endothelial failure are vastly reduced • The DALK procedure is likely to last the patient's lifetime • The worst thing that will happen with a failed DALK is that it will be converted to a traditional PK

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