Corneal Cross-Linking and Safety Issues

PURPOSE: To compile the safety aspects of the corneal collagen cross-linking (CXL) by means of the riboflavin/UVA (370 nm) approach. MATERIALS AND METHODOLOGY: Analysis of the current treatment protocol with respect to safety during CXL. RESULTS: The currently used UVA dose density of 5.4 J/cm(2) and the corresponding irradiance of 3 mW/cm(2) are below the known damage thresholds of UVA for the corneal endothelium, lens, and retina. Regarding the photochemical damages due to the free radicals the damage threshold for endothelial cells is 0.35 mW/cm(2). In a 400μm thick corneal stroma saturated with riboflavin, the irradiance at the endothelial level is about 0.18 mW/cm(2), which is a factor of 2 smaller than the damage threshold. CONCLUSION: As long as the corneal stroma treated has a minimal thickness of 400 microns (as recommended), neither corneal endothelium nor deeper structures such as lens and retina will suffer any damages. The light source should provide a homogenous irradiance avoiding hot spots.