Repeatability of the Sirius imaging system and agreement with the Pentacam HR

To assess measurement repeatability of corneal curvature, minimal corneal thickness, and anterior chamber depth obtained with the Sirius imaging system (Costruzioni Strumenti Oftalmici) and to assess its agreement with the Pentacam HR imaging system (Oculus Optikgeräte GmbH).

Healthy individuals were prospectively recruited. To assess repeatability, eight consecutive measurements were performed in the right eye of healthy individuals with the Sirius. A single measurement was then performed consecutively with both systems. The anterior and posterior corneal radii (antR and posR, respectively), anterior chamber depth, and minimal corneal thickness were evaluated. Repeatability of Sirius was evaluated by calculating coefficients of variation (CoV). Agreement between Sirius and Pentacam was assessed by calculating 95% limits of agreement (LoA) and plotting Bland-Altman graphs.

Forty-five eyes from individuals (21 men, 24 women) aged 20 to 61 years were evaluated. The mean CoV was 0.37% and 1.32% for antR and posR at 3 mm, respectively, and 0.36% and 1.28% for antR and posR at 7 mm, respectively. For anterior chamber depth and minimal corneal thickness, the CoV was 0.56% and 1.69%, respectively. Calculated 95% LoA were -0.1 to 0.12 mm (mean difference: 0.018 mm) and -0.54 to 0.33 mm (mean difference: 0.1 mm) for antR and posR at 3 mm, respectively. For anterior chamber depth, 95% LoA was -0.23 to 0.09 mm (mean difference: 0.068 mm) and -9.61 to 33.44 μm (mean difference: 11.91 μm) for minimal corneal thickness.

The Sirius showed good to excellent repeatability for all measured parameters. Agreement analysis suggests that Sirius and Pentacam should not be used interchangeably.