Repeatability, reproducibility and agreement when measuring central corneal thickness with SS-1000 swept-source optical coherence tomography and ultrasound pachymetry

Abstract

Objective To assess the repeatability of central corneal thickness (CCT) measurements in healthy eyes by comparing measurements obtained with an SS-1000 swept-source optical coherence tomography (SS-1000 OCT) or by ultrasound pachymetry (USP) ; to evaluate the agreement between these two devices. Methods In this prospective study, CCT was recorded after consecutive measurements with SS-1000 OCT and then with USP by a single skilled operator in 62 right eyes of healthy subjects. Intraclass correlation coefficient (ICC) , Bland-Altman plots and repeated-measures analysis of variance (ANOVA) were used to evaluate the repeatability of SS-1000 OCT. Paired t-tests and Bland-Altman plots were used to evaluate the agreement between the two devices. Results The ICC of the SS-1000 OCT measurements was 0.999. Bland-Altman plots showed excellent agreement between any two of the three measurements (95% limits of agreement were -2.4 to 1.8 μm, -2.8 to 2.1 μm, and -2.8 to 2.7 μm). There was no statistical significance found with repeated-measures ANOVA. The mean values of CCT obtained from the SS-1000 OCT and USP were 534.38±24.52 μm and 538.40±25.36 μm, respectively. 95% limits of agreement were -12.6 to 4.5 μm for these two devices. Conclusion The SS-1000 OCT shows excellent repeatability of CCT measurements in healthy eyes. High agreement between CCT measurements suggests that SS-1000 OCT and USP can be used interchangeably in normal subjects. Key words: Tomography, optical coherence; Ultrasonography, A; Central corneal thickness; Reproducibility of result; Agreement