Comparison of Anterior Segment Measurements With a Dual Scheimpflug Placido Corneal Topographer and a New Partial Coherence Interferometer in Keratoconic Eyes

PURPOSE:To evaluate the repeatability and agreement of the anterior segment measurements obtained using the Galilei dual Scheimpflug analyzer (Galilei DSA; Ziemer) and Nidek AL Scan (Nidek CO, Aichi, Japan) biometry in keratoconic and normal eyes. METHODS:Three consecutive measurements were performed by the same examiner using both devices in 62 healthy and 88 keratoconic eyes. Central corneal thickness (CCT), anterior chamber depth, keratometry readings (K) [in flattest meridian (Kf), in steepest meridian (Ks), and mean (Km)], and white-to-white distance were evaluated. Repeatability was assessed by calculating the within-subject SD and coefficient of variation. The agreement between both devices was assessed using the Bland–Altman method. RESULTS:Both devices achieved excellent repeatability for all parameters in each group. The 95% limits of agreement (LoA) between both devices were also very narrow and acceptable for all parameters in normal corneas. However, the 95% LoA for agreement was large for CCT and measurements related to K (Kf, Ks, and Km) using both 2.4 and 3.3 mm in keratoconic eyes. In addition, compared with the Galilei DSA, K values of the Nidek AL Scan using a diameter of 3.3 mm showed slightly closer 95% LoA than those obtained using a diameter of 2.4 mm. CONCLUSIONS:In normal eyes, the Galilei DSA and Nidek AL Scan can be used interchangeably for anterior segment measurements. In keratoconic eyes, both devices yielded interchangeable anterior chamber depth and white-to-white distance measurements, whereas CCT and keratometry measurements showed clinically significant differences.