Corneal collagen cross-linking: a review

Abstract

The aim was to review the published literature on corneal collagen cross-linking. The emphasis was on the seminal publications, systemic reviews, meta-analyses and randomized controlled trials. Where such an evidence did not exist, selective large series cohort studies, case controlled studies and case series with follow-up preferably greater than 12 months were included. Riboflavin/Ultraviolet A (UVA) corneal collagen cross-linking appears to be the first treatment modality to halt the progression of keratoconus and other corneal ectatic disorders with improvement in visual, keratometric and topographic parameters documented by most investigators. Its precise mechanism of action at a molecular level is as yet not fully determined. Follow-up is limited to 4-6 years at present but suggests continued stability and improvement in corneal shape with time. Most published data are with epithelium-off techniques. Epithelium-on studies suggest some efficacy but less than with the epithelium-off procedures and long-term data are not currently available. The use of Riboflavin/UVA CXL for the management of infectious and non-infectious keratitis appears very promising. Its use in the management of bullous keratopathy is equivocal. Investigation of other methodologies for CXL are under investigation.

Keywords: Corneal collagen cross-linking; Entrecruzamiento del colágeno corneal; Keratoconus; Queratocono.

Figure 1

Difference topographic map of an eye with keratoconus 4 years after epithelium off CXL showing the typical picture of flattening of the apex of the cone (green colour) with some slight steepening of the adjacent superior hemi-meridian (orange colour). Such changes are associated in an improvement in corneal higher order aberrations, especially vertical coma, and accompanying enhancements in visual performance.