Current Protocols of Corneal Collagen Cross-Linking: Visual, Refractive, and Tomographic Outcomes

PURPOSE: To study the effect of different protocols of collagen cross-linking on visual, refractive, and tomographic parameters in patients with progressive keratoconus. DESIGN: Prospective randomized interventional study. METHODS: In this study, 138 eyes of 138 patients with progressive keratoconus underwent corneal collagen cross-linking (CXL). Following detailed preoperative examination, Group I underwent conventional crosslinking (36 patients, 3 mW/cm(2) for 30 min); Group II (36 patients, 9 mW/cm(2) for 10 min), Group III (33 patients, 18 mW/cm(2) for 5 min), and Group IV (33 patients, 30 mW/cm(2) for 3 min) underwent accelerated cross-linking. Changes in corrected distance visual acuity (CDVA), spherical equivalent (SE), flat keratometry, steep keratometry, thinnest pachymetry, specular microscopy, and demarcation line were studied at 6 and 12 months. RESULTS: Improvement in the mean CDVA and SE were statistically significant in all groups except Group IV (P = .15 at 6 months, P = .17 at 12 months), with Group III (P = .01 at 6 and 12 months) showing the best results. Flattening of steep and flat keratometry was significant in Groups I (P = .01) and II (P = .01) as compared to the other groups. There was no significant difference in the pachymetry or specular microscopy in any of the groups. Groups I and II demonstrated a good demarcation line when compared to other groups. CONCLUSION: Conventional CXL (Group I) and accelerated CXL with irradiations of 9 mW/cm(2) (Group II) and 18 mW/cm(2) (Group III) showed better visual, refractive, and tomographic improvements at the end of 12 months.