Agreement In Anterior Segment Measurements Between Swept-Source Optical Coherence And Dual Scheimpflug-Placido Tomography Systems In Keratoconus Eyes

This study aimed to compare the anterior segment parameters measured by a dual Scheimpflug-Placido Analyzer (Galilei G6) and a swept source optical coherence tomography (Casia 2) in keratoconus eyes, evaluating the differences and agreement between the two devices.

A retrospective study was conducted in a tertiary referral hospital in Korea, where patients with keratoconus were scanned randomly with both devices, Galilei G6 and Casia 2.

The parameters analyzed included anterior, posterior, and total keratometry, anterior chamber depth, and thinnest pachymetry. Mean difference and intraclass correlation coefficient (ICC) were calculated to assess the reliability of the parameters measured by each device. ICC values less than 0.5, between 0.5 and 0.75, between 0.75 and 0.9, and greater than 0.90 were indicative of poor, moderate, good, and excellent reliability, respectively.

A total of 68 eyes from 40 patients were enrolled in this study. The results showed significant differences between the two devices in terms of anterior corneal astigmatism, steep and flat keratometry (K), posterior corneal steep and flat K, and anterior chamber depth. The ICC values of anterior, posterior, and total corneal curvature were 0.440, 0.364, and 0.649 for astigmatism, 0.654, 0.869, and 0.909 for steep K, and 0.712, 0.825, and 0.755 for flat K, respectively. The thinnest pachymetry and anterior chamber depth showed high ICC values of 0.917 and 0.940, respectively.

The study findings suggest that the measurements obtained from Casia 2 and Galilei G6 were significantly different and did not show excellent agreement for most parameters related to anterior and posterior corneal curvature in keratoconus eyes. Therefore, these devices cannot be used interchangeably in keratoconus eyes.