COLLAGEN CROSS-LINKING FOR THE TREATMENT OF INFECTIOUS KERATITIS

Abstract

Corneal infections are sight-threatening and remain to be a challenge for the ophthalmologist, especially if the infection resists medical treatment or complicates with corneal stromal melting. Corneal collagen cross-linking (CXL) is a relatively new technique of strenghthening corneal stroma that showed good results in cases of corneal ectatic conditions. There have been several trials of using this technique in combating corneal infections with variable results. This review releaved that CXL may be a safe and effective adjuvant for treating advanced infectious keratitis with corneal melting. Besides being an adjuvant therapy, it has been used as a salvage therapy for refractory keratitis showing relatively good results. CXL is most effective for infectious keratitis without deep corneal involvement. CXL seems promising in early, superficial bacterial and fungal keratitis as a primary therapy with the exclusion of viral infections. Several research groups are currently working on introducing new compounds that would increase the microbicidal efficacy currently achieved with riboflavin while allowing for a shorter treatment time relying on three mechanisms that occur during the light-activation of the chosen chromophore: 1-Intercalation of the chromophore (eg, riboflavin) with the nucleic acids of the pathogen and inhibition of replication. 2-Damage to the pathogen’s cell walls caused by massive amounts of reactive oxygen species. 3-Changes in the tertiary structure of the surrounding stromal collagen fibers, making it difficult for the collagenases to dock to their cleavage sites and exert their function. CXL may become an early and first-line treatment for infectious keratitis and with the development of a shortened treatment protocol, will be at least as effective as topical antimicrobial treatment. So future researches should evaluate whether repeating CXL can accelerate healing of different corneal ulcers and it may even be performed at the slit lamp by comprehensive ophthalmologists in the community.