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.