Comparison of central corneal thickness measured by ultrasound pachymetry, corneal topography, spectral domain- optical coherence tomography, and non-contact specular microscopy

Background: This study aims to investigate the compatibility of central corneal thickness (CCT) measurements obtained with spectral-domain optical coherence tomography (SD-OCT), Scheimpflug-Placido-based corneal topography (CT), non-contact specular microscopy (NCSM), and ultrasonic pachymetry (UP). These four corneal measurement techniques have not been compared in a single study on these many subjects. Methods: CCT was measured in 185 eyes of 185 volunteers with each of the four devices by a single observer. CCTs from Optovue (R) iVue SD-OCT, Sirius corneal topography, NonconRobo NCSM, and Accutom UP devices were recorded. Compatibility between devices was evaluated with intraclass correlation coefficient (ICC) and Bland-Altman plots. Pairwise comparisons were performed using the Bonferroni test. Measurement differences between devices were analyzed with the Pearson correlation coefficient. Results: Of the 185 volunteers, 103 were men, and 82 were women. Their mean age was 48.55 +/- 16.6 (18-70) years. Mean CCT values measured by UP, CT, OCT, and NCSM were 546.77 +/- 39.2, 535.29 +/- 39.2, 526.49 +/- 39.05, 505.15 +/- 46.1 mu m, respectively. Statistically significant differences were found between the mean CCT values obtained from the paired devices (p <0.001). The highest difference between pairs was found between UP and NCSM (43.63 +/- 1.8 mu m; CI 38.74 to 48.5 mu m; p <0.001), while the lowest difference was found between OCT and CT (7.3 +/- 1.5 mu m; 95%CI 3.1 to 11.6 mu m; p <0.001). In pairwise comparisons of four devices, the highest ICC value was between UP and CT (ICC: 0.899, 95%CI 0.759-0.947; p <0.001). Conclusion: Despite the high correlation between measurements obtained from different methods, notable differences in CCT values exist, rendering devices non-interchangeable. Therefore, alternative brands of the same device may yield different outcomes.