JAN 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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46 EW International January 2013 International outlook Strengthening corneas in Singapore by Matt Young EyeWorld Contributing Writer Surgeon explains why and how he performs crosslinking during many LASIK procedures C rosslinking, while considered investigational in the U.S., is widely available throughout most of the world. Over the past decade, crosslinking has become the standard of care for patients with keratoconus as well as those with induced ectasia following refractive surgery. It was just a matter of time until clinicians familiar with the technique of crosslinking started to consider prophylactic use in all patients undergoing corneal refractive surgery. The expansion of indication for use from a disease treatment into routine use with LASIK has not been without controversy. As with many new treatments over the years, clinical use often precedes validation by clinical trials. Could LASIK Xtra be appropriate for all patients? At this point, we can't be sure. While many of us are waiting for validation of the safety and efficacy of the technique, we can certainly learn from the early experience of others. In this month's "International outlook," we feature a practice in Singapore that has made crosslinking a routine offering for LASIK patients. John A. Vukich, M.D., international editor normal LASIK procedure and his reasons for taking such steps toward more stable corneas and ones that do not regress visually. hile there are known risk factors for ectasia after LASIK, analysis of such factors continues to remain controversial. Scoring systems can lead to incorrect predictions of risk factors that—let's face it—still aren't entirely understood. Even as surgeons attempt to screen out bad LASIK candidates from good ones, corneal crosslinking is—in some countries—allowing surgeons to stabilize many more corneas during the LASIK procedure. At least that's what Jerry Tan, F.R.C.S., believes. Dr. Tan, consultant eye surgeon, Jerry Tan Eye Surgery, Singapore, has been performing follow-up for patients who have undergone corneal crosslinking during LASIK for the last nine months. He is among a select group of surgeons performing this procedure outside of the U.S., where the procedure has yet to gain approval from the FDA. Dr. Tan performs Lasik Xtra (Avedro, Waltham, Mass.), which involves corneal crosslinking, on corneas potentially at risk for ectasia, on hyperopic LASIK patients as well as on very high myopes. "At present, there is no major complication we see," Dr. Tan said. Dr. Tan explained step by step how the procedure compares to a Despite practicing Lasik Xtra over the course of the past year, Dr. Tan readily admits that the body of scientific literature supporting the procedure could be stronger. "At the present moment, there are few papers that have been written on Lasik Xtra regarding hyperopia," Dr. Tan said. Several peer-review articles have favorably discussed Lasik Xtra for high myopia, many just appearing in the later half of 2012. Meanwhile, discussion of Lasik Xtra for hyperopia appears more prevalently not in peer-reviewed literature, but at ophthalmic meetings and in trade articles. That said, in Dr. Tan's hands, the procedure seems to be working well for hyperopic patients. "Nobody knows why hyperopic LASIK seems to be more stable [with Lasik Xtra]," Dr. Tan said. "The cornea profile seems to be better." For its part, Avedro says that Lasik Xtra preserves "corneal biomechanical integrity" in company literature. Essentially, a riboflavin formula is applied to the cornea during LASIK along with UVA illumination in order to bring about crosslinking with the intention of strengthening the cornea. Using topography, Dr. Tan said these hyperopic corneas post-surgery with Lasik Xtra look better—i.e., "shapes are beautiful"—compared to W Risks vs. benefits LASIK Xtra is performed. Singapore Source: Jerry Tan, F.R.C.S. non-Lasik Xtra procedures. He also feels there is less regression occurring among Lasik Xtra cases—a notorious occurrence among standard hyperopic LASIK cases. High myopes also tend to experience significant regression after LASIK, but not with Lasik Xtra, Dr. Tan said. In fact, while standard LASIK patients experience a "wow" factor almost immediately post-op, that effect tends to diminish with regression over the course of weeks and months in high myopes. With Lasik Xtra, it's just the opposite, Dr. Tan said. A small amount of myopia tends to remain immediately postop, and vision continues to improve to plano until about the threemonth follow-up period, he said. "The patients tell me they see better and better," Dr. Tan said. "So I am getting late-onset 'wows.'" Dr. Tan much prefers late-onset "wows" to regression, and so do his patients, he said. Patients potentially at risk for ectasia (i.e., young patients, those with thinner corneas, etc.) also appreciate the added potential safety that crosslinking allows. In my hands Normally, corneal ectasia develops anywhere from two to four years after LASIK and even as late as 10 years post-op, Dr. Tan said. "This is something very difficult to predict in normal eyes," Dr. Tan said. "So I do [Lasik Xtra] on all high myopes, and all patients who have a residual corneal thickness of 250300 microns in the stromal bed underneath the flap. I tell the patient, 'I think you need Lasik Xtra just in case I make the cornea too weak.' Most of them say, 'If it's no risk to me, I just get a bit of insurance.'" As noted earlier, Dr. Tan also performs Lasik Xtra on hyperopes. Normally, Dr. Tan starts out the LASIK procedure with IntraLase (Abbott Medical Optics, Santa Ana, Calif.). He makes a 100-110 micron flap. Dr. Tan applies the riboflavin (without dextran) for 45 seconds to the stroma, rinsing any excess from the flap. Then he puts the flap back. Dr. Tan applies UV light (30 mW/cm2) to the cornea for 45 seconds. Afterward, he waits an addi-

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