Repeatability and reproducibility of corneal deformation response parameters of dynamic ultra-high-speed Scheimpflug imaging in keratoconus.

Abstract

To assess the repeatability and reproducibility of dynamic corneal response (DCR) parameters obtained by ultra-high-speed Scheimpflug imaging (Corvis ST); in keratoconic patients. Clinics in Germany, Italy, and Brazil. Prospective, observational study. Patients were examined 3 times using 2 different dynamic Scheimpflug analyzers (Corvis ST) to obtain repeatability and reproducibility. The reliability of intraocular pressure (IOP), biomechanically corrected IOP (bIOP), pachymetry, and DCR parameters were assessed by the coefficient of repeatability, coefficient of variation (CoV), intraclass correlation coefficient (ICC), and within-subject standard deviation (sw). Ninety-eight eyes from 98 KC patients were included. The sw of the IOP and bIOP did not exceed 1.1 mm Hg. A CoV less than 10% was found in all DCR parameters and had a good to excellent accordance regarding the ICC. The Corvis Biomechanical Index showed an excellent repeatability and interdevice reproducibility of 0.918 and 0.827, respectively. Also, the tomographic biomechanical index showed an excellent repeatability of 3 Corvis ST and Pentacam measurements (ICC = 0.997). With regard to keratoconic severity, a significant increase in the CoV was found between mild and moderate stages compared with the advanced stage. Nevertheless, it did not exceed 10% of the CoV in severe keratoconic eyes. Corvis ST measurements in keratoconic eyes were highly repeatable and reproducible.