EyeWorld Asia-Pacific March 2012 Issue

39 EW CORNEA March 2012 Anxiously awaiting corneal crosslinking by Enette Ngoei EyeWorld Contributing Editor With the treatment closer to FDA approval in the U.S., EyeWorld looks at the details of corneal crosslinking in practice C orneal collagen crosslinking as the standard of care treatment for progressive keratoconus and post-LASIK ectasia has been available in Canada for more than 4 years and in Europe for even longer. In the U.S., there are several clinical trials being conducted, and the one that’s closest to resolution is one sponsored by Avedro Inc. (Waltham, Mass., USA), said Eric D. Donnenfeld, MD , co-chairman, Cornea, Nassau University Medical Center, East Meadow, NY, USA. “That data has been submitted to the FDA, and we’re looking forward to seeing that approved,” he said. An effective treatment Keratoconus is the second most common cause of corneal transplants in the United States, and with crosslinking, it can virtually be eliminated, Dr. Donnenfeld said. The document of literature shows that corneal crosslinking overwhelmingly stops the progression of keratoconus or ectasia and that there’s a mean of approximately 1.0 to 2.0 D of flattening of the cornea as well, he said. While the data on post-LASIK ectasia patients is not quite as good as with keratoconic patients, it’s still good, Dr. Donnenfeld said. R. Doyle Stulting, MD , Woolfson Eye Institute, Atlanta, Ga., USA, who is involved with clinical trials sponsored by Topcon Medical Systems (Oakland, NJ, USA), also said the treatment is very effective, based on international data. Raymond Stein, MD , medical director, Bochner Eye Institute, Toronto, Canada, whose practice was the first in Canada to become involved with corneal crosslinking, said, “We’ve been doing it for 4-and-a-half years, and we’ve treated approximately 2,500 eyes in that period. We haven’t seen any patient who’s shown progression, and we’ve treated patients as young as 10 years of age.” The majority of his patients are between 18 and 30, but he has also treated patients whose ages range from 10 all the way up to 60. “It’s an extremely effective procedure at preventing progression,” Dr. Stein said. Who should be treated and when Dr. Donnenfeld said that any patient who has progressive disease should be treated. “Any patient who is showing worsening ectasia by keratometry often verified by refraction should be treated, and the earlier you treat patients, the better the prognosis,” he explained. He added that patients who have advanced disease generally aren’t as eligible for treatment because these are patients who have very steep corneas, over 60 D, patients with apical thinning with corneas thinner than 400 microns, and patients with apical scarring. Dr. Stulting is of the same opinion: “Anyone who has keratoconus or corneal ectasia should be treated at the time of diagnosis. Perhaps some of those people will not progress, but I think the risk/benefit ratio for the treatment favors a decision to treat everyone once a diagnosis is made.” There’s also no age limit on how young patients can be treated, Dr. Donnenfeld said. “I’ve treated patients as young as 14 years of age and as old as 60. The real key is whether the disease is progressing and if we can stop it from progressing safely. The same goes for refractive surgery patients,” he said. In Europe, the general guideline is to wait for progression before treating, Dr. Stein said. “But our thought in Canada is that if someone develops keratoconus at an early age, the chance [of progression] is close to 100%, and the earlier you do the treatment, the better the visual prognosis because it basically locks everything in place and prevents deterioration of best corrected visual acuity.” In Canada, patients between the ages of 10 and 28 are recommended treatment even without evidence of progressive disease, he said. However, in patients over 28, some progression is usually documented, with follow-ups every 3-6 months. Topographic analysis is performed and if there is some further thinning or progressive steepening, crosslinking will be performed, Dr. Stein said. As for post-LASIK patients, Dr. Stein said they tend to respond or progress a little differently than the keratoconus patients. They tend to progress over time even if they’re older, whereas when keratoconus patients get to about 35 or 40 years of age, their corneas are usually fairly stable. So for these patients, intervention treatment is recommended at any age without having to have a second instrument showing progression, Dr. Stein said. Crosslinking as prophylactic treatment With very little hard data to show the safety and efficacy of the prophylactic treatment of patients at risk of ectasia using corneal crosslinking, the jury is out right now, Dr. Donnenfeld said. “I’m convinced that if you crosslink patients who are at risk of developing ectasia, they won’t develop ectasia. My concern is that crosslinking, which is known to flatten the cornea, will change the visual results of LASIK or PRK, and the results will not be as good with crosslinking as they are without,” he explained. A prospective trial needs to be conducted, he said. But at present, he is not crosslinking patients who have come in for LASIK because of the lack of knowledge in this area and the fact that crosslinking is not approved in the United States, he said. He added: “I think it’s very reasonable in the United States to treat patients who have a therapeutic need for visual rehabilitation and the prevention of ectasia progression, but prophylaxis is a different level of treatment and one that I’m not comfortable performing today until we have more knowledge about the outcomes.” According to Dr. Stulting, prophylaxis for ectasia in refractive surgery may have a role in selected cases where there is an increased risk for ectasia. However, he would not do it across the board, he said. For Dr. Stein, while the concept is interesting, he said the question is whether it is right to do crosslinking when the incidence is about 1 in 3,000. “Surgeons certainly could make a case for crosslinking patients, whether they crosslink all patients or they crosslink patients who are at higher risk or patients with thinner corneas, slightly irregular topographies, family history of keratoconus, and higher refractive corrections. We have not done this yet,” he said. He wants to make sure from the data that there isn’t an increase in complications from the laser portion. “For example, if there is a delay from putting the flap back down because surgeons have irrigated continued on page 44