Accuracy of Cirrus HD-OCT and Topcon SP-3000P for measuring central corneal thickness

PURPOSE: To compare and analyze the interchangeability of three measuring systems, each based on a different technique, for central corneal thickness (CCT) analysis. METHODS: CCT measurements were measured using optical coherence tomography (OCT), non-contact specular microscopy (NCSM), and ultrasonic pachymetry (USP) in 60 eyes of 60 healthy patients with a mean age of 66.5 ± 15.0 years and a mean spherical equivalent of 0.43 ± 1.14 D. Analysis of variations in measurement concordance and correlation among the three different methods were performed. Comparison of CCT measurements were done using Bland–Altman plots (with bias and 95% confidence intervals), intraclass correlation coefficient (ICC), and paired t-student analysis. RESULTS: Mean CCT values were: 549.20 ± 26.91 μm for USP (range 503–618 μm), 514.20 ± 27.49 μm for NCSM (range 456–586 μm) and 542.80 ± 25.56 μm for OCT (range 486–605 μm). CCT values obtained with NCMS were significantly lower than those obtained with OCT and USP methods. NCMS CCT value was 36.08 ± 10.72 μm lower than USP value (p < 0.05), and NCMS CCT value was 7.88 ± 8.86 μm lower than OCT value (p < 0.05). ICC between USP–NCSM pair was 0.488 and 0.909 between USP–OCT pair. CONCLUSION: OCT and UPS offered highly comparable results, whereas NCSM offered lower mean CCT values compared to the other two methods. Therefore, NCSM should not be considered a reliable method for measuring CCT and should rather be considered for assessing longitudinal changes in the same patient.