Accelerated versus Standard Corneal Cross-linking for Progressive Keratoconus in Syria

Abstract

Purpose: To compare the outcomes of accelerated versus standard corneal cross-linking for the treatment of progressive keratoconus. Methods: In this retrospective comparative study, 63 eyes of 40 patients with progressive keratoconus were divided into two groups; 27 eyes in group one were treated with an accelerated protocol (10 mW/cm2, 9 min) and 36 eyes in group two were treated with the standard method (3 mW/cm2, 30 min). Visual acuity, refraction, corneal topography, corneal tomography, and anterior and posterior corneal higher-order aberrations (HOAs) were assessed preoperatively and 18–30 months postoperatively. Results: The LogMAR uncorrected and corrected distance visual acuity values were improved in both groups postoperatively. However, the improvement was significantly higher in group one (P < 0.05, all). The flattening in the anterior keratometry readings, flat K, steep K, and average K were significantly higher in group two (P < 0.001, all). The maximum anterior keratometry (AKf) values significantly decreased in both groups, whereas the maximum posterior keratometry (AKb) values increased. The reduction in the minimum corneal thickness (ThKmin) was significantly greater (36.49um) in group two, compared to 10.85um in group one. There was a significant increase in the posterior average keratometry, and a significant decrease in the posterior astigmatism, along 3 mm meridian in S-CXL (P = 0.03, P = 0.008, respectively), while the corresponding values showed no statistical significance in group one (P > 0.05). The anterior corneal trefoil was significantly reduced in group one (P = 0.002), whereas anterior total HOAs and coma were significantly improved in group two (P < 0.0014, all). The posterior corneal spherical aberration decreased significantly in group one (P = 0.02), while group two revealed significant reduction in the posterior trefoil values (P = 0.011). The change in the anterior maximum keratometry was significantly and positively correlated to the preoperative maximum keratometry in group two (P = 0.53, P = 0.003). Conclusion: An accelerated cross-linking protocol using 10 mW/cm2 for 9 min showed more visual improvement and less pachymetric reduction when compared to the standard protocol, however, anterior corneal flattening, posterior corneal steepening, and the change in the posterior astigmatism were significantly higher in the standard protocol; while corneal HOAs were improved in both protocols.