Corneal changes following collagen cross linking and simultaneous topography guided photoablation with collagen cross linking for keratoconus

Purpose: To compare the outcome of Collagen cross-linking (CXL) with that following topography-guided customized ablation treatment (T-CAT) with simultaneous CXL in eyes with progressive keratoconus. Materials and Methods: This was a prospective, non-randomized single centre study of 66 eyes with progressive keratoconus. Of these, 40 eyes underwent CXL and 26 eyes underwent T-CAT + CXL. The refractive, topographic, tomographic and aberrometric changes measured at baseline, 1, 3 and 6 months post-operatively were compared between both groups. Results: After a mean follow-up of 7.7 +/- 1.3 months, the mean retinoscopic cylinder decreased by 1.02 +/- 3.16 D in the CXL group (P = 0.1) and 2.87 +/- 3.22 D in the T-CAT + CXL group (P = 0.04). The Best corrected visual acuity increased by 2 lines or more in 10% of eyes in the CXL group and in 23.3% of eyes in the T-CAT + CXL group. The mean steepest-K reduced by 0.40 +/- 3.71 D (P = 0.77) in the CXL group and by 2.91 +/- 2.01D (P = 0.03) in the T-CAT + CXL group. The sag factor and surface asymmetry index showed no significant change in the CXL group but reduced by 3.59 +/- 5.94 D (P = 0.01) and 0.72 +/- 1.18 (P = 0.02) respectively in the T-CAT + CXL group. There was a significant increase in the highest posterior corneal elevation in both groups (9.57 +/- 14.93 mu in the CXL group and 7.85 +/- 9.25 mu in the T-CAT + CXL group, P <= 0.001 for both). There was significantly greater reduction of mean coma (P < 0.001) and mean higher-order aberrations (P = 0.01) following T-CAT + CXL compared to CXL. Conclusions: CAT + CXL is an effective approach to confer biomechanical stability and to improve the corneal contour in eyes with keratoconus and results in better refractive, topographic and aberrometric outcomes than CXL