Ricerc@Sapienza

Considering the oxygen diffusion barrier constituted by the epithelium, we reported differences in the corneal stromal demarcation line depth (rather than in CXL efficacy) secondary to the lower stromal penetration of riboflavin and to the ultraviolet-A light shielding effect of the intact corneal epithelium in transepithelial CXL protocols. As a consequence, we further agree that there is not a clear correlation between CXL effectiveness and corneal stromal demarcation line depth, and there is still much to understand in this direction.