Comparison and Repeatability of Keratometric and Corneal Power Measurements Obtained by Orbscan II, Pentacam, and Galilei Corneal Tomography Systems

Abstract

To assess the repeatability and comparability of corneal power and central corneal thickness (CCT) measurements obtained using Orbscan II (Bausch & Lomb), Pentacam (Oculus), and Galilei (Ziemer) tomographers. Prospective, comparative study. setting: Departments of Ophthalmology, University of Auckland and Auckland District Health Board, Auckland, New Zealand. study population: Thirty eyes of 30 healthy participants. observations. CCT and corneal power measured using Orbscan II, Pentacam, and Galilei tomography. main outcome measures: Degree of agreement in and repeatability of CCT and corneal power measures. Orbscan II measured significantly lower CCT compared with Pentacam (20μm; P < .0005) and Galilei (18μm; P < .0005). The Orbscan II had wide limits of agreement when compared with both the Galilei (-11 to 47μm) and Pentacam (-88 to 47μm). For each device, the intraclass correlation coefficient for CCT was higher than 0.9. The coefficient of variation ranged from 0.33% to 0.93%. There was no significant difference in mean steep keratometry or mean flat keratometry between instrument pairs. However, there was poor agreement in flat keratometry and steep keratometry obtained by Orbscan II compared with those obtained by the Galilei and Pentacam. The keratometry and pachymetry measurements obtained by Orbscan II, Pentcam, and Galilei tomographers were sufficiently disparate that the 3 devices could not be considered equivalent. All 3devices demonstrated a high level of repeatability, although theGalilei exhibited the best repeatability.