Repeatability and Interobserver Reproducibility of a Swept-Source Optical Coherence Tomography for Measurements of Anterior, Posterior, and Total Corneal Power

INTRODUCTION: The aim of this work is to evaluate the intraobserver repeatability and interobserver reproducibility of corneal power measurements obtained with a swept-source optical coherence tomographer (CASIA 2, Tomey, Japan) in healthy subjects. METHODS: A total of 67 right eyes from 67 healthy subjects were enrolled. Two experienced observers measured each eye three times consecutively with the CASIA 2. Corneal power values were recorded as simulated keratometry, anterior, posterior, and total corneal power. Parameters were flattest keratometry (K(f)), steepest keratometry (K(s)), mean keratometry (K(m)), astigmatism magnitude, astigmatism power vectors J(0) and J(45). Intraobserver repeatability and interobserver reproducibility of the CASIA 2 were assessed by the within-subject standard deviation (S(w)), test–retest repeatability (TRT), coefficients of variation (CoV), and intraclass correlation coefficients (ICCs). Double-angle plots were used for astigmatism vector analysis. RESULTS: The CASIA 2 had high repeatability for all corneal power values, with S(w) values ≤ 0.17 diopters (D), TRT ≤ 0.46 D, and ICCs ranging from 0.866 to 0.998. Interobserver reproducibility was also high, showing all S(w) values ≤ 0.10 D, TRT ≤ 0.27 D, and ICCs ≥ 0.944. The reproducibility of the average of three consecutive measurements (S(w) 0.01–0.10 D, TRT 0.03–0.27 D, ICC 0.944–0.998) was higher than the reproducibility of single measurements (S(w) 0.01–0.17 D, TRT 0.03–0.47 D, ICC 0.867–0.996). CONCLUSIONS: The CASIA 2 showed high intraobserver repeatability and interobserver reproducibility for anterior, posterior, and total corneal power measurements in 6.0-mm diameter area. In addition, we suggest that using the average of three consecutive measurements can improve reproducibility between observers, compared to single measurements only.