Evaluation of the Reliability and Repeatability of Scheimpflug System Measurement in Keratoconus

Purpose: To assess the reliability and repeatability of the parameters obtained using a Scheimpflug system (Pentacam HR-high resolution) for monitoring progression in eyes with keratoconus. Methods: A prospective study was conducted based on measurements taken with the Pentacam HR in 82 eyes with keratoconus. We calculated the intraclass correlation coefficient (ICC) and the repeatability limit for topographic and aberrometric parameters. Results: All the parameters analyzed had excellent ICCs, above 0.95 in all cases, except for the measurement of the anterior best-fit sphere, for which the ICC was 0.873. The key repeatability limits for the parameters analyzed were as follows: 1.54 diopters (D) for the maximum keratometry in the central cornea, 1.08 D for maximum keratometry, 32.6 degrees for the axis of corneal astigmatism, 11.9 degrees for the coma axis, and 14.2 mm for thinnest corneal thickness. Conclusions: The level of repeatability of the measurements obtained with a Pentacam HR confirms the usefulness of this system for the diagnosis of keratoconus. Nevertheless, it has certain limitations for monitoring individual progression of keratoconus and planning intrastromal corneal ring segment insertion.