What is Cornea Cross-linking (CXL)?

Collagen cross-linking is a relatively new treatment for Keratoconus that uses a photosensitizing agent, riboflavin (vitamin B2) & ultraviolet light (UVA, 365nm) exposure. It was developed about ten years ago in Germany by Dr. Theo Seiler. Since then, many countries have approved the CXL procedure for treatment of Keratoconus. CXL is currently in Phase II FDA trials in the US (http://clinicaltrials.gov/ct2/show/NCT00647699).

In extensive experimental studies (including biomechanical stress & strain measurements) researchers have demonstrated a significant increase in corneal rigidity / stiffness after collagen cross-linking using this riboflavin/UVA treatment. The 3 & 5 year results of Dresden clinical study in human eyes has shown the stop of progression of Keratoconus in all treated eyes. (Wollensak G. Crosslinking treatment of progressive keratoconus: New Hope. Current Opinion in Ophthalmology 2006; 17: 356 – 360)

The treatment is performed under topical anesthesia. The skin (epithelium) of the surface of the cornea is partially scratched, followed by application of Riboflavin eye drops for 30 minutes. The eye is then exposed to UVA light for 30 minutes. After the treatment, antibiotic ointment is applied and an eye-pad is worn overnight until the next day when the surface of the eye has healed. Oral analgesics are required for the first 1 -2 days.

Collagen cross-linking treatment is not a cure for keratoconus. Instead, it aims to halt the progression of Keratoconus. This is important to understand. Patients will continue to wear glasses or contact lenses (although a change in the prescription may be required) following the cross-linking treatment. The main objective of CXL is to stop the progression of Keratoconus, thus preventing further deterioration in vision and the need for cornea transplant.

In advanced Keratoconus where the corneal thickness is below 350 microns, CXL may not be performed because of possible damage by the UVA light to other parts of the eye.