EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
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40 EW FEATURE Corneal crosslinking November 2013 Crosslinking for other conditions by Ellen Stodola EyeWorld Staff Writer AT A GLANCE • In addition to treatment for keratoconus, crosslinking is being explored as a possible option to treat infections, post-LASIK ectasia, corneal melts, infectious keratitis, and corneal edema. • Crosslinking for non-ectatic indications could be especially helpful if other treatments have failed. • It is important to proceed with caution or possibly not use crosslinking in patients with thin corneas or problems with epithelial healing. Possibilities for crosslinking are expanding, and it could be used to treat other conditions besides keratoconus C rosslinking, a popularly debated treatment currently seeking FDA approval, is mainly known to treat keratoconus, but it could be used for other conditions, and studies are beginning to show the effect that crosslinking can have for patients. Doyle Stulting, MD, PhD, director of the Stulting Research Center, Woolfson Eye Institute, and professor emeritus of ophthalmology, Emory University, Atlanta; Eric Donnenfeld, MD, clinical professor of ophthalmology, New York University Medical Center, New York; and Majid Moshirfar, MD, director of the Moran Eye Center's Refractive Surgery Program and Cornea Program, Salt Lake City, discussed some of the conditions that they believe crosslinking can be used for. What other conditions could crosslinking be considered for? "Crosslinking as we all know is effective for keratoconus, but if you want to go beyond keratoconus, it's also effective for post-LASIK ectasia, which is a variant of ectasia," Dr. Donnenfeld said. "There's a whole list of other conditions where crosslinking can be effective." Something that has been getting a lot of attention recently is using crosslinking to treat infections. "The Transepithelial crosslinking of a patient with visual fluctuation following RK Source: Eric D. Donnenfeld, MD riboflavin is absorbed into the infectious organism and the UV light causes release of free radicals, which kills the organism. For opportunistic infections that are not sensitive to current antimicrobial therapy, this appears to be a very reasonable option," Dr. Donnenfeld said. Crosslinking seems to be most effective against fungus and for certain unusual bacteria, he said. There are also studies looking into crosslinking used on Acanthamoeba. Dr. Donnenfeld said for some hard-totreat infections, it might be useful to explore crosslinking as a possible treatment option. In addition, crosslinking is proving to be a possible treatment for post-radial keratotomy visual fluctuation. "We've used it very successfully in patients who are significantly impacted by the visual fluctuation that occurs with radial keratotomy, with the vision changing during the course of the day," Dr. Donnenfeld said. Dr. Stulting also indicated that there are a number of conditions that crosslinking could be useful for. "CXL may be efficacious for corneal infections resistant to medical management, sterile corneal melts, corneal melts associated with infectious keratitis, corneal edema (e.g., Fuchs' and pseudophakic corneal edema), RK (fluctuating vision and progressive hyperopia), and pretreatment of eyes at risk for ectasia," he said. Dr. Moshirfar said there are possibilities for using crosslinking for corneal edema, pseudophakic keratopathy, bacterial keratitis, and fungal keratitis. However, the possibilities for success with these conditions are still being explored. Evidence to support expanded indications Dr. Stulting said there are published and peer-reviewed papers that support using crosslinking for all the conditions that he mentioned. "Several studies have been done now with animal models and in humans that have shown the efficacy of crosslinking on infections, and the use of ultraviolet light to kill bacteria has been well established in the literature and is used in a variety of different areas," Dr. Donnenfeld said. "It's used to sterilize water, for example, to sterilize foods, and it makes sense that it could be used for killing bacteria in the cornea as well." A number of case reports and case series discuss the expanded indications for crosslinking in a variety of conditions, Dr. Moshirfar said. "Much of the literature is filled with case series and case reports, but we still don't have a prospective controlled study to show the efficacy," he said. Although Dr. Moshirfar said crosslinking could be a good alternative for some conditions where other treatments have failed, it certainly has not reached the point to be considered the standard of care. Is crosslinking for non-ectatic indications successful? Measuring the success of crosslinking for non-ectatic indications has been limited so far. "We have been unable to evaluate the safety and efficacy of these indications because of limitations of FDA-controlled clinical studies," Dr. Stulting said. Dr. Donnenfeld said that he has found crosslinking successful to use against infections. "There have been some trials that have been performed in the United States that continued on page 42