Comparison of standard versus accelerated corneal collagen cross-linking for keratoconus: 5-year outcomes from the Save Sight Keratoconus Registry

Objective: To compare long-term effectiveness of Standard (UV intensity: 3 mW/cm², duration: 30 min) vs Accelerated (UV intensity: 9 mW/cm², duration: 10 min) corneal cross-linking (CXL) for stabilising keratoconus. 

Methods: Data for this observational study were captured through a web-based registry system from the routine clinical practice (15 sites across Australia, New Zealand and Italy). The outcomes were compared using mixed-effects regression models. A total of 100 eyes (75 patients) who had standard CXL and 76 eyes (66 patients) who had accelerated CXL, with a follow-up visit at five-year post-CXL were included. 

Results: Both CXL protocols were effective and safe in stabilising keratoconus and improving outcomes. The adjusted mean changes (95% CI) in outcomes were better in standard CXL than in accelerated CXL [visual acuity gain, 10.2 (7.9–12.5) vs 4.9 (1.6–8.2) logMAR letters; pinhole visual acuity 5.7 (3.5–7.8) vs 0.2 (−2.2 to 2.5) logMAR letters; Kmax −1.8 (−4.3 to 0.6) vs 1.2 (−1.5 to 3.9)D; K2 −0.9 (–2.2 to 0.3) vs 0.1 (−1.3 to 1.6)D; MCT –3.0 (−13.7 to 7.7) vs −11.8 (−23.9 to 0.4) µm (p values for visual acuity, pinhole visual acuity, Kmax: <0.05; for K2 and MCT: >0.05)]. The frequency of adverse events at the 5-year follow-up visit was low in both groups [standard, 5 (5%; haze 3; scarring 1, epithelial defect 1) and accelerated 3 (3.9%; haze 2, scarring 1)]. 

Conclusions: Both standard and accelerated CXL were safe and effective procedures for stabilising keratoconus in the long term. The standard CXL resulted in greater improvements in visual acuity and keratometry.