Corneal collagen crosslinking in keratoconus

Corneal collagen crosslinking (CXL) is, at present, the only treatment that can slow or even stop the progression of keratoconus. It uses riboflavin and ultraviolet A (UVA) to create covalent bonds ("crosslinks") between collagen fibrils thus increasing corneal rigidity. Although to date there has been no direct evidence of intrastromal corneal crosslinking, several studies have reported the safety and efficacy of the conventional CXL protocol. This protocol is indicated for progressive keratoconus with a minimal corneal thickness (without the epithelium) of at least 400 μm. It should be performed as early as possible in patients under 18 years with keratoconus or with post-LASIK ectasia. Because of the epithelial debridement, it may rarely induce complications such as infectious keratitis or stromal scars. A variety of new protocols is under investigation and may reduce the rate of these complications. In addition, combination of CXL with other surgical treatments (intracorneal ring segments or photorefractive keratectomy) may improve visual outcomes in patients with keratoconus. Finally, the antimicrobial and anti-edematous properties of CXL have been shown, suggesting new therapeutic indications of this procedure such as infectious keratitis or stromal edema in the future.