Abstract

The introduction of corneal collagen cross-linking (CXL) has become one of the major interventions designed to prevent the further progression of the disease by enhancing the corneal biomechanical stability. Although many studies have shown positive results, the inconsistency of long-term visual and topographic results made it important to evaluate them thoroughly by means of systematic synthesis. A meta-analysis and systematic review were conducted to determine the long-term effects of CXL in patients with progressive keratoconus. The inclusion criteria were randomized controlled trials and observational studies that reported visual acuity and corneal topographic outcomes with a follow-up period. Twelve articles with 1206 eyes were included. Meta-analysis showed that there was a significant improvement in maximum keratometry (Kmax) after CXL with a pooled mean difference of –1.16 diopters (95% CI: −1.45 to −0.87, p < 0.0001), which is an effective corneal flattening. The uncorrected visual acuity (UCVA) and the best-corrected visual acuity (BSCVA) were also significantly improved, with the difference of −0.15 (p = 0.0251) and −0.06 (p = 0.0181), respectively. The thickness of the corneas had a small yet significant decrease (−11.24 µm, p = 0.0355), but with a great heterogeneity among studies. Corneal collagen cross-linking has long-term effectiveness in the stabilization of keratoconus based on long-term corneal topography and visual acuity improvements. Although pachymetric results are inconsistent, the cumulative evidence in favor of CXL as a safe and effective intervention to stop the progression of the disease was present, and the benefits were found to be sustained over a long period of time in different patient groups.

Key words: Corneal cross-linking, progressive keratoconus, systematic review, meta-analysis, long-term visual, topographic outcomes