Purpose: Many topography/tomography devices are available, and their interchangeable use is frequently questioned. This study aimed to compare the analogous indices of Orbscan 3 and Pentacam HR to detect whether the interchangeable use of the 2 devices is feasible.
Methods: This retrospective study was conducted at Eye World Hospital, Giza, Egypt. Displays of Orbscan 3 (Bausch & Lomb; Technolas Perfect Vision GmbH) and Pentacam HR (Oculus Optikegrate) for 660 healthy right eyes were explored for various analogous indices. Bland-Altman plots with 95% limits of agreement (LoA) were used for comparisons.
Results: The highest systematic error and lowest agreement existed in the front and back elevations from the best fit sphere (mean differences of 4.7 and 9.2 μm, respectively, and 95% LoA of -2.5 to 12.0 and -10.0 to 28.6, respectively). There was a relatively wide 95% LoA for each pachymetry at the corneal apex (-18 to 22 μm) and at the thinnest location (-22 to 22 μm), anterior chamber depth (-0.88 to 0.95 mm), flattest keratometry (-0.44 to 0.62 D), and steepest keratometry (-0.71 to 0.89 D). By contrast, the lowest systematic error and highest agreement existed for front and back best fit sphere radii of curvature (mean difference of 0.08 mm and 95% LoA of -0.08 to 0.24 and mean difference of 0.03 mm and 95% LoA of -0.17 to 0.23, respectively).
Conclusions: This study negates the accuracy of the use of devices interchangeably regarding most parameters. Therefore, examinations with the 2 devices should not be regarded comparable.