To evaluate the efficacy of collagen cross-linking with individualized fluence (sub 400 protocol) in keratoconus patient with ultrathin cornea.

Keratoconus is a chronic progressive ophthalmic disease that leads to bulging and thinning of the cornea, resulting in increasing irregular astigmatism and ultimately poor vision. The introduction of collagen cross inking (CXL) has changed the natural course of this disease and as a result reduced the need for corneal transplants.

Corneas with advanced disease that would likely benefit from undergoing CXL cannot be treated with the Dresden protocol because of corneal thickness less than 400 microns. The sub400 protocol approach in ultrathin corneas will broaden the range of indications of CXL and further decrease the need for corneal transplantations.