Comparative Analysis of Safety and Efficacy of Topography-Guided Customized Cross-linking and Standard Cross-linking in the Treatment of Progressive Keratoconus

Purpose: To compare the safety and efficacy of topography-guided customized corneal cross-linking (PiXL) with standard cross-linking (CXL) for the treatment of progressive keratoconus. Methods: In a prospective interventional analysis, the eyes of patients with progressive keratoconus underwent standard cross-linking (homogenous 9-mm ultraviolet-A irradiation of 9 mW/cm 2 delivering a total fluence of 5.4J/cm 2 ) versus topography-guided customized cross-linking (30 mW/cm 2 pulsed irradiance with a total fluence ranging from 5.4 to 15 J/cm 2 , in concentric circles centered on the posterior float maximum). The following parameters were analyzed at the preoperative, 1-month, 6-month, and 1-year postoperative visits: corrected spectacle distance visual acuity, manifest refraction including sphere, cylinder and mean refractive spherical equivalent, corneal tomography, higher order aberration profile, and endothelial cell count. Anterior segment optical coherence tomography evaluation was performed at the 1-month postoperative visit to assess the depth of the demarcation line. Results: Sixty-four eyes of 45 patients (32 eyes in each group) were included. There was a significant reduction in maximum keratometry and IS asymmetry in the PiXL group at both the 6-month and 1-year postoperative visits ( P = 0.001 and 0.06). Corrected spectacle distance visual acuity improved significantly in the PiXL (0.05 ± 0.08 logarithm of the minimum angle of resolution, P = 0.02) versus the standard CXL (0.01 ± 0.025 logarithm of the minimum angle of resolution, P = 0.26) group. A greater depth of a stromal demarcation line was observed in the customized CXL group ( P = 0.02). No significant complications were noted in either cohort. Conclusions: PiXL demonstrated similar safety with significantly greater keratometry flattening and corneal regularization vis-à-vis standard CXL. This resulted in significant improvement of spectacle corrected visual acuity for eyes with mild-to-moderate keratoconus.