Cross Linking

Halting keratoconus progression

Overview

Corneal collagen cross linking, CXL, is a treatment that strengthens the cornea to halt the progression of keratoconus and other corneal ectatic disorders, such as ectasia after laser refractive surgery. The cornea is soaked with riboflavin, vitamin B2, and then exposed to ultraviolet A light, which causes the riboflavin to generate reactive oxygen species that form additional chemical bonds between collagen fibers, increasing corneal stiffness. The technique was developed at the Technical University of Dresden in the late 1990s by researchers including Theo Seiler, Eberhard Spoerl, and Gregor Wollensak, and it was approved in the United States in 2016. In the standard epithelium off protocol, the outer epithelium is removed first to allow riboflavin penetration, while transepithelial and accelerated protocols are variations designed to improve comfort or shorten treatment. Cross linking aims to stabilize the cornea rather than reverse existing steepening, and it has reduced the need for corneal transplantation in keratoconus. It is sometimes combined with other procedures such as topography guided PRK.