[Ultraviolet crosslinking in the treatment of keratoconus in patients with thin corneas]

Corneal collagen cross-linking (CXL) is a procedure that aims to halt the progression of corneal ectasia in keratoconic eyes. It is achieved by inducing cross-links in the corneal stroma and extracellular matrix by exposing it to ultraviolet-A (370 nm) irradiation while it is filled with photosensitizer (riboflavin). According to the conventional protocol, the recommended de-epithelialized corneal thickness should be higher than 400 μm in order to avoid radiation damage to the corneal endothelium. However, in progressive keratoconus, corneal thickness is often close to or lower than this threshold of 400 μm, which limits the application of cross-linking for these patients. The present article reviews the different protocols of cross-linking for thin corneas, their advantages and disadvantages. At present, clinical research on modified cross-linking protocols is still limited due to the methodology and a low number of patients involved. Thus, comparative randomized controlled studies with long-term follow-up are necessary to confirm the safety and effectiveness of several CXL protocols and identify the most efficient one.