Comparison between three protocols of corneal collagen crosslinking in adults with progressive keratoconus: Standard versus accelerated CXL for keratoconus

Objective: The study aimed to compare eye outcomes between the standard and accelerated corneal cross-linking (CXL) protocols over a 1-year follow-up, and assess whether the accelerated protocols are non-inferior to the standard. Methods: A retrospective cohort study including patients older than 18 years diagnosed with progressive keratoconus who underwent a CXL procedure. The primary outcome was defined as an increase of more than 1.5 diopter (D) in Kmax. The analysis included intra- and inter-group comparisons assessing differences in eye characteristics before and 12 months after the procedure. Furthermore, we assessed whether the accelerated procedures were non-inferior to the standard regarding Kmax change after 12 months. Results: Eighty-four patients included in the study of which 23, 37 and 23 underwent the standard CXL (group I), 10-min. (group II) and the 3-min. (group III) accelerated procedures, respectively. Intra-group comparison before and after 12 months of mean Ksteep and anterior corneal astigmatism showed significant improvement only for group I (–0.3D decrease for both). Inter-group comparison showed better results after 12 months for group I (–0.9 ± 1.2) compared to group III (0.1 ± 0.8) in Ksteep, Kmean (–0.5+1. vs 0.1+0.7, respectively) and anterior astigmatism (–0.5 + 0.9 vs 0.3+1.1, respectively). We could not declare that the accelerated CXLs are non-inferior to the standard ( p-value = 0.11 and 0.15). Conclusion: The standard CXL showed better results for keratometry and astigmatism in comparison with the accelerated. Therefore, the wide use of the accelerated CXL should be considered and reviewed for longer follow-up time and larger sample size in focus on the visual acuity parameters.