Repeatability and agreement of corneal thickness measurement with Pentacam Scheimpflug photography and Visante optical coherence tomography

Abstract

To evaluate the repeatability and agreement of central and peripheral corneal thickness (CT) measurements by high resolution Pentacam rotating Scheimpflug photography and Visante optical coherence tomography (OCT) in unoperated myopic eyes and eyes after Laser In Situ Keratomileusis (LASIK). CT at central, thinnest, 1.0 mm and 2.5 mm superior, inferior, nasal and temporal periphery locations, and the location of the corneal thinnest thickness were measured using Pentacam and Visante OCT in 60 myopia patients (60 eyes) and 60 patients (60 eyes) after LASIK. The results were analyzed by paired-t test, Pearson correlation analysis and Bland-Altman method. Both Pentacam and Visante OCT demonstrated high intraobserver repeatability, with all intraclass correlation coefficients and Cronbach's alphas were more than 0.9, and coefficient of variation were less than 0.9%. Significantly higher CoV was measured with Pentacam than by Visante OCT in at central (0.46 ± 0.30), thinnest (0.43 ± 0.28) and 1.0 mm locations in both groups (t = 2.465, 2.226, P < 0.05), but no statistically significant difference were found at 2.5 mm locations in healthy subjects and all locations in post-LASIK eyes (t = -0.518, 1.542, -0.876, 0.756, P > 0.05). The thickness of central corneal with Pentacam was (543.01 ± 22.89) µm, the thinnest point was (540.61 ± 22.84) µm, they were greater than the value of Visante OCT (t = 17.946, 23.071, P < 0.05). The Pearson correlation coefficients were all more than 0.9 (all r > 0.9, P < 0.01). The Bland-Altman plots showed the 95% LoA between both devices were lower than 22 µm at central, thinnest and 1.0 mm locations. However, the 95% LoA were 24 µm to 44 µm at 2.5 mm locations. Pentacam and Visante OCT demonstrate high repeatability for central and peripheral CT measurements in young myopia and post-LASIK eyes. However, both devices can't be used interchangeably for measurements of peripheral CT.