Repeatability and Reliability of a Combined Dual-Scheimpflug Placido Disc Corneal Topographer in Eyes with Keratoconus

Abstract

Purpose : To investigate the repeatability and reliability of a combined Dual-Scheimpflug Placido disc corneal topographer (Zeimer Galilei G4) with respect to various keratometric indices used to monitor progression of keratoconus (KCN).

Methods : Patients with KCN evaluated at an academic medical center between 9/2017 and 11/2018 were prospectively enrolled in the study. For each eye that lacked a history of corneal surgery, 5 topographic measurements were taken in succession. Only eyes in which 3 high quality measurements could be obtained (as defined by the topographer’s 4 quality metrics) were included in the analysis. The repeatability limit and interclass correlation coefficient (ICC) were calculated for various topographic parameters.

Results : 23 eyes from 17 patients met criteria for inclusion in the data analysis. Repeatability limits for key parameters included: 0.83 diopters (D) for maximum keratometry in the central cornea, 0.32 D for maximum keratometry, 10.66 degrees for corneal astigmatism axis, 0.25 um for vertical coma magnitude, and 3.79 um for thinnest corneal thickness. The ICC for all parameters was excellent (above 0.97) except for spherical aberration (0.71).

Conclusions : The combined Dual-Scheimpflug Placido disc corneal topographer is highly repeatable and reliable in quantifying most parameters typically used in monitoring KCN. More eyes are needed to confirm these results, and analysis of measurement repeatability and reliability in eyes with imperfect image quality may also prove useful.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.