Efficacy of Corneal Collagen CXL for Treatment of Keratoconus: Systematic Review and Meta-Analysis
Purpose
To examine the efficacy of cross-linking (CXL) for the treatment of keratoconus (KCN).
Methods
A systemic literature review and meta-analysis on ocular functional and structural parameters of patients with keratoconus, undergoing cross-linking procedure. Using PubMed and the Web of Knowledge, a literature search was performed for relevant peer-reviewed publications on population-based studies. Data was analyzed using the R software (Meta library) and heterogeneity was assessed using Cochran's Q and I2 with the random or fixed models according to heterogeneity.
Results
We found a change in visual acuity, equivalent to 1-2 Snellen lines, 3 months or more after the CXL. Changes were more pronounced in the uncorrected visual acuity. Topography parameters were changed (0.6-1 diopters) 12 to 24 months following CXL in some parameters. Refractive cylinder changed by -0.4 to -0.7 diopters. Endothelial cell density was reduced in about 100-200 cells/mm2 in the first 3 months after CXL but returned to normal values afterwards. Corneal thickness was reduced by 10-20 µm in the year after CXL, then thickening towards normal after 24 months.
Conclusion
CXL improves vision in keratoconus. Topography and refraction changes were of low amplitude, in few parameters, and appeared late after the procedure. Acuity may improve by reduction of high order aberrations caused by the corneal shape, which is driven by healthier physical properties of the corneal stroma.