Evaluation of Iontophoretic Collagen Cross-linking for Early Stage of Progressive Keratoconus Compared to Standard Cross-linking: A Non-Inferiority Study

INTRODUCTION The purpose of this study was to evaluate the efficacy and safety of iontophoretic collagen cross-linking (I-CXL) compared to epithelium-off standard collagen cross-linking (CXL) in treating the early stages of progressive keratoconus. METHODS This retrospective cohort study at Oftaprof Clinic, Iasi, Romania included 40 eyes of 40 patients with progressive keratoconus stage I according to the Amsler classification who underwent I-CXL and the results were compared with a matched group of 40 eyes from 40 patients who received standard CXL. The follow-up period was 24 months. Uncorrected (UCVA) and corrected (CDVA) distance visual acuities, corneal topography, and pachymetry were evaluated in all patients. RESULTS The mean patient age was 26.52 ± 3.77 years for the standard CXL group and 28.32 ± 4.91 for the I-CXL group. The mean UCVA and CDVA improved significantly in both groups. At 12 months, the improvement of UCVA was greater in the I-CXL group (P < 0.05). There was a statistically significant different trend in CDVA between groups with a more favorable outcome for the standard CXL group (P < 0.01). The manifest cylinder decreased by a mean of 0.962 ± 0.114 D in the epithelium-off CXL group and by 0.831 ± 0.082 D in the I-CXL group (P < 0.001). At 24 months, the K max values improved by 1.2 ± 0.199 D in the standard group and by 0.908 ± 0.177 D in the I-CXL group (P < 0.001). CONCLUSION All parameters either improved or remained unchanged after the iontophoretic collagen cross-linking intervention. I-CXL was found to be as effective as the standard technique.