Photochemical corneal collagen cross‑linkage using riboflavin and ultraviolet A for keratoconus and keratectasia

The procedure

The aim of the procedure – which is sometimes known as CXL – is to stop your keratoconus getting any worse by making the cornea stiffer. It isn't clear exactly how it works but it might make the bonds between the collagen fibres (cross‑links) in the cornea stronger. It also isn't clear how long the benefits last.

The way the procedure is done varies, but local anaesthetic is used and it usually takes an hour to an hour and a half with no need for a stay in hospital. Riboflavin (vitamin B) eye drops are put on the eye before and during the procedure, during which UV\u2011\A light is shone onto the surface of the cornea. It is done on 1 eye at a time and may be repeated.

The difference between the epithelium‑on and epithelium‑off procedures is that in the epithelium‑off procedure, the layer of cells on the surface of the cornea (the epithelium) is removed with a spatula to expose the layer of cornea to be treated and to help the riboflavin eye drops to be absorbed. In the epithelium‑on procedure, the layer of cells is not removed but may be thinned using a chemical. It takes longer for the riboflavin eye drops to be absorbed in this form of the procedure.

While the cornea is healing, you will normally be given antibiotics and anti-inflammatory eye drops (to reduce any redness, swelling, heat or pain) and you may be given a bandage contact lens (a type of non-magnifying contact lens that protects the cornea) to use for a few days.

Corneal collagen cross‑linking can be done at the same time as procedures to improve eyesight, such as implanting an artificial lens.