Corneal Collagen Cross-Linking for Keratoconus and Ectasia BY JULIA T. LEWANDOWSKI, SENIOR ASSOCIATE EDITOR

Welcome to the final installment of Cataract & Refractive Surgery Today’s three-part series highlighting corneal ectasia. This article discusses corneal collagen cross-linking with riboflavin, the latest addition to our armamentarium for the treatment of keratoconus and for stabilizing corneal ectasia after keratorefractive surgery. Internationally, cross-linking is widely becoming an accepted treatment for these corneal pathologies. Clinical trials in the United States are coming to an end and, when completed, I hope will increase the availability of cross-linking in the near future. Because cross-linking can be performed in the clinical setting, it offers physicians and patients the benefits of speed and comfort. As we gain more experience with cross-linking, I believe we will significantly reduce the need for penetrating keratoplasty among most patients with progressive corneal thinning. Cross-linking strengthens the cornea by increasing the number of covalent bonds between collagen fibers. When riboflavin is activated by ultraviolet-A light (UVA; 3 mW/cm2), it promotes a free radical pathway that cross-links collagen and increases the cornea's strength by more than 300%. Riboflavin cross-linking is currently recommended only for corneas that are at least 400 μm thick, but a modified method that uses dextran-free riboflavin allows physicians to cross-link thinner corneas safely.1 A debate about the most efficient method for infusing riboflavin into the corneal stroma continues. The original clinical trials called for epithelial debridement of the central 7 to 9 mm of the cornea. Recently reported studies, however, suggest that applying tetracaine to the intact corneal surface preoperatively sufficiently disrupts the tight junctions between epithelial cells to promote the induction of riboflavin into the stroma. With either approach, the cornea should appear completely yellow under the slit lamp, and the aqueous should also demonstrate a yellow tint. The instillation of riboflavin generally takes about 30 minutes, after which the solution is activated by UVA (Peschke UV-X; Peschke Meditrade GmbH, Nuremberg, Germany). In many patients, this procedure not only stabilizes the process of ectasia, but also improves BCVA by one or two lines. I hope you enjoy this installment of “Peer Review,” and I encourage you to seek out and review the articles in their entirety at your convenience. —Mitchell C. Shultz, MD, Section Editor