Keratoconus is the progressive thinning of the cornea, and corneal cross-linking (CXL) can successfully treat it. The application of riboflavin and UV light to the cornea generates highly reactive free radicals that cross-link molecules in the cornea (principally collagen), stiffening and strengthening it and thereby slowing or halting the disease’s progression.
But with CXL, thin corneas – often the corneas in most need of treatment – can cause big headaches. There is a good reason why the standard Dresden protocol for CXL is restricted to corneas with a thickness of >400 µm. Thinner corneas risk UV light penetrating deeper and damaging endothelial cells at the base of the cornea. As these cells cannot regenerate, surgeons performing CXL have had to find ways of making these thin corneas temporarily thicker (e.g. swelling the cornea with hypo-osmolar riboflavin or applying a contact lens to the cornea). These methods certainly complicate the procedure and add an element of uncertainty too. It doesn’t have to be this way.
Our research work has enabled us to build a validated model of how the four main components of the CXL technique (UV energy, UV irradiation time, riboflavin concentration, and oxygen pressure) interact to stiffen the cornea. This allows us to determine not just the stiffening effect of any given combination of the main components of CXL, but how deep the effects of CXL using personalized UV irradiation will be. In other words, a personalized UV illumination profile – helpfully, with a shorter irradiation time – can be used to treat thinner corneas, tailored to each patient’s eye, simplifying and speeding the treatment of thin corneas with CXL.