Central Corneal Thickness After Cross-linking Using High-Definition Optical Coherence Tomography, Ultrasound, and Dual Scheimpflug Tomography: A Comparative Study Over One Year

Abstract

To assess central corneal thickness (CCT) and corneal haze in keratoconus eyes following corneal cross-linking (CXL). Prospective noncomparative case series. Forty patients (44 eyes) with keratoconus that had serial evaluation for CCT, following CXL, usinghigh-definition optical coherence tomography (HD-OCT), ultrasound pachymetry (USP), and dual Scheimpflug tomography. CCT was measured at baseline, then at 2weeks and 1, 3, 6, and 12months postoperatively. The mean baseline CCT measurements were 470.02μm, 469.79μm, and 466.66μm using the HD-OCT, the USP, and dual Scheimpflug tomography, respectively (P= .91). Following CXL, the mean CCT measurements by dual Scheimpflug, at all follow-up periods, were lower compared to mean baseline reading (P < .003). The mean CCT measurements by the HD-OCT and USP were similar to baseline readings except for the thicker readings at the 2-week follow-up visit. Overall, the mean CCT obtained by the USP was similar to that obtained by the HD-OCT throughout the 12-month period. However, the mean CCT measurements obtained by dual Scheimpflug tomography were statistically and clinically significantly lower than those obtained by both HD-OCT and USP at all follow-up visits. USP and HD-OCT showed better agreement in CCT readings at all visits, and may better estimate the true CCT following CXL as compared to dual Scheimpflug tomography. The lower mean CCTpost-CXL as measured by the latter seems to be correlated with the amount of haze that develops aftercross-linking.