Repeatability and agreement between novel SS-OCT VG2 and CASIA2 in anterior segment parameters

To evaluate the repeatability of anterior segment parameters measured with a novel swept-source optical coherence tomography (SS-OCT) instrument, and to compare these anterior segment parameters with those measured with the CASIA2.

This prospective case series study included 119 eyes from 119 participants. Anterior segment parameters, including steep keratometry (SimK), total corneal power (TCP), maximum keratometry (Kmax), thinnest corneal thickness (TCT), central corneal thickness (CCT), and corneal epithelial thickness within the 0-2 mm, 0-5 mm, 2-5 mm, and 5-7 mm zones were measured using VG2 and CASIA2. Repeatability was evaluated using the coefficient of variation (CoV) and intraclass correlation coefficient (ICC). Agreement between devices was evaluated using Pearson correlation coefficients, Bland-Altman plots.

All ICCs for anterior segment parameters measured by VG2 were greater than 0.9. The ICC values for SimK, TCP, Kmax, and TCT were greater than 0.99. Except for epithelial thickness parameters, all anterior segment parameters showed CoV values below 0.5%. Strong correlations (r > 0.9) were observed between VG2 and CASIA2 for steep SimK, flat SimK, steep TCP, flat TCP, Kmax, CCT, and TCT. Bland-Altman plots analysis revealed narrow 95% LoA for steep SimK, flat SimK, and Kmax, whereas wider LoA were observed for TCP, TCT, CCT, and epithelial thickness measurements.

VG2 demonstrates good repeatability in measuring anterior segment parameters. The steep SimK, flat SimK, and Kmax measurements obtained with VG2 show good agreement with those from CASIA2, VG2 and CASIA2 can only be used interchangeably in measuring anterior corneal curvature, other parameters cannot be interchanged in clinical practice.