What it is
In keratoconus, the cornea gradually thins and bulges into a cone shape, causing blurred, distorted vision and frequently changing glasses power. Corneal collagen cross-linking (also called C3R or CXL) strengthens the cornea: riboflavin (vitamin B2) drops are applied and the cornea is exposed to a controlled dose of ultraviolet-A light, which creates new bonds — “cross-links” — between its collagen fibres.
Who it's for
People, often teenagers and young adults, with keratoconus that is getting worse, or with corneal weakening after refractive surgery (called ectasia). It works best at an early stage, before the cornea becomes too thin or scarred. Suitability depends on corneal thickness and a detailed corneal evaluation.
What to expect
A pre-operative evaluation includes a visual acuity check, corneal topography and tomography, corneal thickness measurement, and an assessment of how the keratoconus has been progressing. The eye is numbed with drops, and one of two techniques is used: in conventional (epithelium-off) C3R, the thin outer layer of the cornea is removed first so that the riboflavin (vitamin B2) drops can penetrate the cornea; in transepithelial (epithelium-on) C3R, this outer layer is left in place and the drops are delivered through it. The cornea is then exposed to a controlled dose of UV-A light. A soft “bandage” contact lens may be placed at the end, particularly with the epithelium-off technique. You go home the same day with someone to accompany you.
Recovery
Discomfort, watering, light sensitivity and blurred vision are common for a few days while the surface heals, and vision may stay blurry for some weeks. Use the prescribed antibiotic and lubricating drops, avoid rubbing or pressing on your eyes, and do not wear contact lenses until your doctor advises. The aim is to stop or slow the cornea getting worse rather than to improve vision, so it does not remove the need for glasses or contact lenses.
Frequently asked questions
Will cross-linking improve my vision?
Its main aim is to stop keratoconus from getting worse. Some people see a small improvement, but most still need glasses or contact lenses.
Why should I avoid rubbing my eyes?
Frequent eye rubbing is linked to keratoconus getting worse. If your eyes itch, ask your doctor about treating the allergy instead.
Medically reviewed by Dr. Sweta Patro