Different Topographic Response Between Mild to Moderate and Advanced Keratoconus After Accelerated Collagen Cross-linking

Abstract

To evaluate the clinical and topographic effects after accelerated corneal collagen cross-linking (CXL) in keratoconus. This was a prospective interventional study in 25 eyes of 24 Asian patients with keratoconus, where 10 eyes in group 1 had mild to moderate keratoconus with the steepest keratometry reading (Kmax) < 58 diopters (D), and 15 eyes in group 2 had advanced keratoconus with Kmax ≥ 58.0 D. The patients underwent accelerated CXL with 18 W/cm UV-A light for 5 minutes. Clinical and topographic parameters were obtained before and 1 year after treatment. Overall, spectacle-corrected distance visual acuity, refraction, average keratometry readings, Kmax, anterior elevation at the apex, and corneal endothelial cell density remained stable (P < 0.102). Posterior elevation at the apex increased at 1 year (P = 0.002). The thinnest pachymetry readings also showed significant reduction (P < 0.001). Kmax in group 1 increased by 1.00 ± 1.63 D (range, -2.2 to 5.4 D; P = 0.012), whereas Kmax in group 2 reduced by 1.69 ± 2.61 D (range, -8.4 to 3.2 D; P = 0.013) at 1 year after accelerated CXL. The change in Kmax between the 2 groups was significantly different (P < 0.001). There was no intergroup difference for the change in other parameters. A significant correlation was found between the preoperative Kmax and postoperative change in Kmax at 1 year (r = -0.648; P < 0.001). Accelerated CXL seems to be effective in preventing progression and causing topographic flattening in advanced cases of keratoconus but not as effective in the less progressed counterparts.