Repeatability and Agreement in Measuring Adolescents and Children’s Corneal Thickness with Corvis ST and SS-1000 Swept-Source Optical Coherence Tomography

Abstract

Objective: To assess the repeatability of central corneal thickness (CCT) measurements in adolescents and children using the Corvis ST and to examine the agreement between Corvis ST and SS-1000 swept-source optical coherence tomography (SS-1000 OCT). Methods: In this case series study, 44 children who visited the Eye Hospital, Wenzhou Medical University, from January to April of 2015 were enrolled. The age range was between 8 to 14 years old. The subjects were myopic without any other disease. CCT measurements were obtained first with the Corvis ST and then with SS-1000 OCT. The data of the right eyes was analyzed. An intraclass correlation coefficient (ICC), Bland-Altman plots and repeated-measures analysis of variance (ANOVA) were used to assess the repeatability of the Corvis ST. Paired t-tests and Bland-Altman plots were used to compare the agreement between the two devices. Results: The mean ICC of the Corvis ST was 0.987. Bland-Altman plots showed agreement between any two of three measurements (95% limits of agreement was -15.6~16.2 μm, -15.7~13.4 μm, -16.0~13.1 μm, respectively). No statistical significance was found with repeated-measures ANOVA. The mean values of CCT acquired from Corvis ST and SS-1000 OCT were 553±29 μm and 540±28 μm. CCT measured by the Corvis ST was 13 μm thicker than that by SS-1000 OCT (t=-6.037, P<0.001). The 95% limits of agreement were -15.2~41.6 μm for these two devices. Conclusions: The Corvis ST shows excellent repeatability of CCT measurements in healthy children’s eyes. Though there is a good agreement between the two devices for CCT measurements, there are significant differences between them. The measurements acquired by Corvis ST should not be directly interchangeable with SS-1000 OCT measurements in clinical practice. Key words: Corvis ST; central corneal thickness; repeatability; agreement