Corneal cross-linking is a relatively new procedure used to treat corneal diseases such as keratoconus, an eye condition that causes thinning of the cornea. The procedure involves applying a solution containing riboflavin (vitamin B2) to the cornea and then using ultraviolet light to strengthen the bonds between collagen fibers in the cornea. 

Corneal cross-linking helps to slow or stop the progression of the disease and prevent further vision loss. It can also reduce pain, improve vision, and restore normal shape to the cornea.