Iontophoretic collagen cross-linking versus epithelium-off collagen cross-linking for early stage of progressive keratoconus – 3 years follow-up study

Abstract

Purpose: To compare 3-year iontophoretic corneal collagen cross-linking (I-CXL) outcomes with epithelium-off corneal collagen cross-linking (epi-off CXL) for early stage of progressive keratoconus. Methods: Eighty eyes of 80 patients with early progressive keratoconus treated by I-CXL (n = 40) or epi-off CXL (n = 40) were included in this study. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, corneal topography and pachymetry were assessed at baseline and at 1, 3, 6, 12, 24 and 36 months of follow-up. Results: Visual acuity (VA) showed a significant improvement (p < 0.05) at the end of follow-up in both groups. In the I-CXL group, the UDVA showed a rapid recovery after 3 months (p = 0.04). There was a statistically significant different trend in CDVA between groups with a more favourable outcome for the standard CXL group (p < 0.01). The cylinder improved beginning with 3 months after CXL in both groups. Maximum keratometry showed a significant reduction by 0.9 dioptres (D) in the I-CXL group and by 1.2 D in the epi-off CXL group after 36 months (p = 0.283). Pachymetry values decreased at 3 months while a statistically significant increase occurred in both groups at 24 months. Progression occurred to one patient (2.5%) in I-CXL group. Adverse effects occurred to eight eyes (20%) in the epi-off CXL group. Conclusion: Iontophoretic corneal collagen cross-linking (I-CXL) is non-inferior to epi-off CXL for stopping the progression of keratoconus in its early stages with a higher degree of safety for the patients and a faster recovery of VA.