Repeatability and agreement of a Scheimpflug-Placido tomography and a Partial Coherence Interferometer in keratoconus and control eyes.

PURPOSE

To assess the repeatability and agreement of anterior segment measurements obtained using a partial coherence interferometry-based optical biometry device (AL-Scan) and a combined Scheimpflug-Placido disc corneal topography device (Sirius) in keratoconic and control eyes.

METHODS

Central corneal thickness (CCT), anterior chamber depth (ACD), white-to-white distance (WTW), and keratometry values were measured in keratoconic and control eyes using the AL-Scan and Sirius. The agreement, repeatability, and reliability of the measurements were analyzed.

RESULTS

The study included 82 keratoconus patients (82 eyes) and 100 healthy subjects (100 eyes). The mean CCT and ACD values measured by Sirius were significantly higher than those measured by AL-Scan in both groups (p < 0.001). WTW measurements did not differ significantly between devices (p > 0.05). In control eyes, keratometric values showed no significant differences between devices, whereas in keratoconic eyes, almost all keratometric values were significantly different. Reliability was excellent for all parameters in both devices (intra-class correlation coefficient [ICC] > 0.9). Repeatability was excellent for all parameters in both devices (coefficient of variation [CoV] < 1%), except for CCT in keratoconic eyes (CoV < 3%). CONCLUSıONS: Both the AL-Scan and Sirius provide highly repeatable and reliable measurements in both healthy and keratoconic eyes. However, in keratoconic eyes, agreement between the two devices is poor for all parameters except WTW.