Effects of Collagen Cross-Linking on the Corneal Optical and Topographic Characteristics in Progressive Keratoconus

Abstract

Aim: To determine the significant changes which occur in the corneal parameters, including pachymetry, after corneal collagen cross linking (CXL) by means of Scheimpflug imaging. Methods: Standard CXL procedure was done for 40 eyes diagnosed as progressive keratoconus (KCN). The following parameters were monitored pre, six months and 1 year post operatively: uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), refractive spherical equivalent (S.E), keratometry1 (K1) and keratometry2 (K2), apex and thinnest point pachymetries, thinnest point coordinates (X,Y) minimum (Min.), maximum (Max.), average (Avg.) pachymetric progression indices, Max. Anterior and posterior elevations. Pentacam (Oculus, Wetzlar, Germany) imaging was used to monitor the corneal parameters of the study. Paired sample T test was used for statistical analysis. Results: Following parameters of the study did not show significant changes after CXL: UCVA: (P= 0.65), BCVA: (P= 0.076), S.E: (P= 0.343), Thinnest point X coordinate: (P=0.545), Thinnest point Y coordinate: (P= 0.144), Max. Anterior elevation (P= 0.508) and the following parameters showed significant changes: K1: (P= 0.001), K2: (P= 0.015), Apex pachymerty: (P <0.001), Thinnest point pachymetry: (P <0.001), Max. Post. Elevation: (P= 0.001) and all (Max., Min., Avg.) pachymetric progression indices: (P <0.001 for all 3). The most significant changes occurred in pachymetric progression indices. Conclusion: We could show six months to 1 year after CXL procedure, the corneal thickness is lower than its baseline and keratometric changes have been settled during this period. UCVA, BCVA have not been changed significantly and the pachymetric progression indices are the most significant parameters to have changes, when evaluating them by Pentacam. Validity of Scheimpflug imaging of the corneas after CXL should be determined in further studies.