Repeatability and reliability of ectasia display and topometric indices with the Scheimpflug system in normal and keratoconic eyes

Purpose To evaluate the repeatability and reliability of Belin-Ambrósio Enhanced Ectasia Display-III indices and topometric indices with a Scheimpflug system (Pentacam HR) in normal eyes and keratoconic eyes. Setting Ulucanlar Eye Research and Training Hospital, Ankara, Turkey. Design Prospective case series. Methods The same operator performed 3 consecutive successive measurements with the Scheimpflug device in the eyes of patients with keratoconus (keratoconus group) and healthy volunteers (normal group). The keratoconus group was further classified into the following 3 subgroups according to the topographic keratoconus classification: early, moderate, and severe. One eye of each volunteer was assigned randomly to a repeatability test. The maximum keratometry (K), 6-parameter topometric indices, and 9 parameter ectasia display indices were recorded. The within-subject standard deviation, precision, repeatability indices, coefficient of variation, and intraclass correlation coefficient (ICC) values were calculated for repeatability and reliability assessments. Results There were 100 patients in the keratoconus group and 100 healthy volunteers in the normal group. The maximum K, topometric indices except for index of height asymmetry, ectasia display indices except for deviation of normality of the front elevation, and deviation of normality of the back elevation were repeatable in normal eyes and keratoconic eyes. The repeatability indices of all parameters increased as the severity of keratoconus increased. The maximum K value and all indices showed good to excellent reliability in both groups (ICC values between 0.750 and 1.0 for all values). Conclusion The maximum K value, most topometric indices, and ectasia display indices were repeatable and reliable in normal eyes and keratoconic eyes.