EyeWorld Asia-Pacific September 2012 Issue

36 September 2012 EWAP rEfrActivE Dr. Tomita uses LASIK Xtra, which combines a riboflavin ophthalmic solution with Avedro’s KXL UVA irradiation system for CXL (pictured here) during LASIK. Source: Minoru Tomita, MD EyeWorld explores the “obvious next use” for corneal crosslinking C orneal collagen crosslinking (CXL) is well known as an effective way to strengthen and stabilize the cornea in ectatic and keratoconic patients. Minoru Tomita, MD, executive director, Shinagawa LASIK Center, Tokyo, Japan, believes that using CXL as prophylaxis with LASIK is the obvious next use, especially considering that LASIK reportedly weakens the cornea anywhere from 20-40%. Dr. Tomita uses LASIK Xtra (Avedro, Waltham, Mass., USA), which combines a riboflavin ophthalmic solution (VibeX) with Avedro’s KXL UVA irradiation system for CXL during LASIK. LASIK Xtra has CE mark approval but is not commercially available in the U.S. “Patients who choose LASIK Xtra are getting the benefits of prevention of keratoectasia and regression after LASIK,” he said. “By performing crosslinking to regain the corneal conditions as closer to the strength at the pre- op stage, there is the potential to prevent iatrogenic ectasia from happening,” Dr. Tomita continued. “Published papers have also reported the more corneal tissue ablated by LASIK, the thinner the cornea gets, which results in a higher likelihood of regression (myopic shift) due to the weakened cornea. When the cornea becomes strong after LASIK with crosslinking, it is likely to mitigate the occurrence and conditions of regression.” Dr. Tomita recommends the procedure for patients who are at risk for iatrogenic ectasia, such as high myopes who need a large amount of cornea ablated, patients with atopic dermatitis with less than 480 microns corneal thickness pre-op, or those who are at high risk for developing keratoconus or keratoectasia. Never too thin? Since CXL’s primary purpose is to stiffen and stabilize, can it be deduced that adding the procedure to LASIK means surgeons will be able to operate on thinner corneas—ones they previously wouldn’t have considered for the procedure? Despite positive outcomes in ectasia and keratoconus patients, Dan Z. Reinstein, MD, medical director, London Vision Clinic, thinks that might be a bit of a leap. “This implies, but does not prove, that we can do LASIK on thinner corneas if we also simultaneously crosslink, but it has to be proven,” Dr. Reinstein said. “To date, there is no good method of measuring the biomechanical stiffening effects of crosslinking; no machine seems to be able to pick up the changes with a parameter that we can actually measure. The area of research is still young.” Dr. Reinstein said a 2010 study by Daniel Kampik, MD , clinical Crosslinking and LASIK: Prophylaxis of the future? by Jena Passut EyeWorld Staff Writer research associate, and colleagues at University College London, Institute of Ophthalmology, showed that CXL does not change the LASIK ablation rate. “It does change nomograms, so this is a consideration if one wants to combine the two procedures,” he said. risks and benefits Avoiding ectasia is the primary benefit of combining CXL and LASIK, but a more predictable effect of LASIK has “yet to be proven,” according to R. Doyle Stulting, MD, Woolfson Eye Institute, Atlanta, and professor of ophthalmology, Emory University, Atlanta, Ga., USA. “Indications for the combination might include eyes at risk for ectasia, but some argue that PRK [photorefractive keratectomy] is a better procedure for those individuals,” Dr. Stulting said. He added that he doesn’t see a benefit to promoting routine CXL at the time of LASIK because of the downsides, including cost, risk of infection, additional surgical time, and risk of endothelial cell damage. “Many would argue it is not a good idea for eyes at risk for ectasia because they would be better served by CXL and PRK,” Dr. Stulting said. “They might also argue that it is not a good idea for eyes not at risk for ectasia.” Even the ectasia benefit remains to be seen, said retired Navy Capt. Steve C. Schallhorn, MD, former director, Cornea Service & Refractive