Five‐year results of a prospective, randomised, contralateral eye trial of corneal crosslinking for keratoconus

Background Few studies have evaluated corneal crosslinking (CXL) in a prospective, randomised fashion. This study aimed to determine the efficacy and safety of CXL to reduce the progression of keratoconus. Methods Prospective, unmasked, randomised, contralateral eye controlled trial at a tertiary eye centre. Participants : Individuals with bilateral progressive keratoconus. One eye from each subject was randomised to CXL and the contralateral, untreated eye acted as the control. Primary outcome measure : change in maximum keratometry. Secondary outcome measures : uncorrected distance visual acuity, spectacle corrected distance visual acuity, spherical equivalent refraction, simulated keratometry, corneal astigmatism, minimum pachymetry and complications. Results Thirty‐eight individuals (mean age 21.1 ± 6.7 years) were enrolled with one eye treated with CXL. At 5 years, there was a mean decrease in maximum keratometry of treated eyes (−1.45 ± 2.25 D) compared to an increase among the controls (1.71 ± 2.46 D; p  < 0.001). There were significant differences between the treated and control groups in the mean change of Steep SimK (−1.07 ± 1.22 vs. 0.96 ± 1.97 D; p  < 0.001), Flat SimK (−0.61 ± 1.34 vs. 0.43 ± 1.12 D; p  < 0.001), corneal astigmatism (−0.45 ± 1.31 vs. 0.63 ± 1.52 D; p  < 0.01) and minimum pachymetry (−32.49 ± 26.32 vs. −13.57 ± 24.11 μm; p  < 0.01). Complications included sterile infiltrates ( n  = 2), microbial keratitis ( n  = 1), persistent corneal haze/scarring at 5 years ( n  = 4) and loss of ≥2 lines of corrected distance visual acuity ( n  = 3). Conclusions CXL is an effective and relatively safe intervention to halt or reduce the progression of keratoconus in the majority of eyes for at least 5 years.