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

PurposeTo assess central corneal thickness (CCT) and corneal haze in keratoconus eyes following corneal cross-linking (CXL).DesignProspective noncomparative case series.MethodsForty patients (44 eyes) with keratoconus that had serial evaluation for CCT, following CXL, using high-definition optical coherence tomography (HD-OCT), ultrasound pachymetry (USP), and dual Scheimpflug tomography. CCT was measured at baseline, then at 2 weeks and 1, 3, 6, and 12 months postoperatively.ResultsThe mean baseline CCT measurements were 470.02 μm, 469.79 μm, and 466.66 μm 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.ConclusionsUSP 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 CCT post-CXL as measured by the latter seems to be correlated with the amount of haze that develops after cross-linking.