Collagen cross-linking (sometimes called corneal cross-linking or corneal collagen cross-linking) is a procedure that was developed in 1998 to strengthen the cornea by promoting stronger connections among the collagen fibers contained in the cornea. CXL uses a combination of vitamin B eye drops and ultraviolet light to help encourage stronger bonding, or cross-linking, among the fibers in patients with keratoconus as well as patients who experience post-LASIK ectasia. Both conditions result in a weakened cornea that bulges outward, causing vision distortion. Ectasia is the hallmark of an eye disease called keratoconus, but it can also occur in people following certain types of refractive surgery including LASIK.
Corneal collagen crosslinking works by strengthening corneal tissue so the progression of ectasia (thinning) is reduced. The process involves saturating the deep layers of the cornea with vitamin B2 (riboflavin) solution and then activating it with UV light. The combination of vitamin B2 and UV light results in the formation of new bonds between collagen fibers.
The cross-linking procedure can be performed in one of two ways:
“Epithelial-off,” in which the upper layer of the cornea, called the epithelium, is removed to facilitate absorption of the vitamin B eye drops;
“Epithelial-on,” in which the epithelium remains intact and the drops are administered for a longer period of time to ensure adequate absorption.
Once the vitamin B has flooded the cornea, the eye is exposed to ultraviolet light for about a half hour while additional vitamin B drops are administered. Finally, a special contact lens is placed on the eye to serve as a bandage for the initial few days of healing.
Prior to your treatment, Dr. Cohen will perform a thorough evaluation of your eye including measuring the thickness of your cornea to ensure you're a good candidate for crosslinking.
He'll also perform corneal mapping, a technique used to determine the overall condition of your cornea. Once he determines crosslinking could be a good option for you, he'll place the vitamin B eye drops in your eyes and allow them to remain on your eye surface for a specific period of time depending on which approach (epithelial on or off) he's using.
Once Dr. Cohen determines the concentration of vitamin B2 is sufficient, he'll apply a UV light for about 30 minutes. Afterward, a bandage may be applied and you'll be given a prescription for antibiotic and anti-inflammatory eye drops. The entire procedure takes about an hour to an hour and a half to perform.
After your procedure, you'll need to use special antibiotic and anti-inflammatory drops to help prevent infection and discomfort, and you'll have frequent follow-up visits to ensure the eye is healing properly and to evaluate your results. The contact lens bandage will be removed after about three days once initial healing is well underway.
The best candidates are those who receive treatment before the cornea has become badly misshapen or before significant vision loss has occurred. Used early, CXL can help stabilize the cornea and in some cases, improve the shape of the cornea so vision is improved.