Efficacy, Safety, and Outcomes following Accelerated and Iontophoresis Corneal Crosslinking in Progressive Keratoconus

Purpose: To investigate the outcomes of accelerated (A-CXL) and iontophoresis (I-CXL) corneal crosslinking in a large retrospective cohort with progressive keratoconus. Methods: This retrospective observational cohort study included consecutive patients treated by A-CXL (9 mW/5.4 J/cm(2)) or I-CXL with a minimal follow-up of 12 months. Visual acuity, manifest refraction, topography, specular microscopy, and corneal optical coherence tomography (OCT) were evaluated at baseline and at the last visit. Progression was defined as an increase in the maximum topographic keratometry (Kmax) of 1D. Results: 302 eyes of 241 patients with a mean age of 25.2 ± 7.5 years were included from 2012 to 2019: 231 and 71 eyes in the A-CXL and I-CXL groups, respectively. The mean follow-up was 27.2 ± 13.2 months (maximum: 85.7 months). Preoperatively, the mean Kmax was 51.8 ± 4.0D, with no differences between groups. Mean topographic measurements and spherical equivalent remained stable during the follow-up. At the last visit, CXL failure was reported in 60 eyes (19.9%): 40 (14.7%) versus 20 (28.2%) in A-CXL versus I-CXL, respectively, p = 0.005. The likelihood of progression after CXL was significantly higher following I-CXL: RR = 1.62, CI95 = [1.02 to 2.59], p = 0.04. Demarcation line presence at 1 month was positively correlated with higher efficacy of CXL, p = 0.03. No endothelial damage was reported, especially in 51 thin corneas (range = 342–399 µm). Conclusions: A-CXL seems more effective than I-CXL in stabilizing keratoconus; this is to be taken into account when a therapeutic indication is posed according to the aggressiveness of the keratoconus.