Comparative Study of Central Corneal Thickness Using Fourier-Domain Optical Coherence Tomography Versus Ultrasound Pachymetry in Primary Open-Angle Glaucoma

Abstract

To compare central corneal thickness (CCT) results measured by Fourier-domain optical coherence tomography (FD-OCT) and ultrasound pachymetry (USP) in glaucomatous eyes. In this prospective, observational cross-sectional study, 80 eyes of 80 patients with primary open-angle glaucoma (POAG) and no other ocular abnormality were selected: 28 were treated with 1 drug (subgroup 1), 32 with 2 drugs (subgroup 2), and 20 with 3 drugs (subgroup 3). CCT was measured by FD-OCT (RTVue OCT) and USP (Pachymeter Reichert IOPac). Bland-Altman plots were used to assess the agreement between both instruments. The differences between CCTs measured by USP and FD-OCT were compared among the 3 subgroups. The mean CCT was 537.76 ± 32.24 μm and 520.53 ± 30.44 μm for USP and FD-OCT, respectively. A significant difference was found between the mean values obtained by FD-OCT and USP (17.22 ± 7.96 μm, P < 0.001, paired Student t test). A high correlation was obtained for CCT measured by both methods (Pearson correlation coefficient = 0.969; P < 0.001), and there was good agreement between the 2 pachymetry methods. Similar differences in CCT using USP and FD-OCT were found among the 3 treatment subgroups (P > 0.05 in all pairwise comparisons, analysis of variance). FD-OCT underestimates CCT compared with CCT measured by USP in POAG. Although highly correlated, the difference between these 2 devices can be clinically significant in the context of refractive surgeries in POAG patients but not in intraocular pressure estimation. This difference also seems to be independent of the number of antiglaucoma treatments used.