Comprehensive anterior segment normal values generated by rotating Scheimpflug tomography

Purpose To identify normal values for tomographic parameters that are considered useful in screening patients for refractive surgery. Setting Private center, Albany, New York, USA. Design Database study. Methods A Pentacam HR Scheimpflug system was used to examine 1 randomly selected eye of patients to determine normal values of 21 parameters considered the most clinically applicable for surgical screening. Normality of data was evaluated using the Kolmogorov-Smirnov test. Statistical analyses were performed using the Student t test to compare means and the 2-paired sample Wilcoxon signed-rank test. Results are displayed in 95.0% and 97.5% confidence intervals (CIs). Results The study evaluated 341 adults. High-end outliers at the 97.5% CI were 46.1 diopters (D) for flat keratometry (K), 47.4 D for steep K, 3.4 D for astigmatism, 3.8 μm for anterior chamber depth, 4 μm for front apical elevation, 5 μm for front elevation at the thinnest point, and 12 μm for front elevation in the central 4.0 mm. Respective posterior elevation values were 7 μm, 13 μm, and 25 μm, with a progression index maximum of 1.53 and mean of 1.19, difference between apical and thinnest pachymetric reading of 7 μm, a maximum K of 48.2 D, and an inferior-superior ratio of 1.44 D. Low-end outliers were a maximum Ambrósio relational thickness of 335 and a mean of 425, minimum pachymetry of 479 μm, thickness at the apex of 481 μm, and central 4.0 mm corneal volume of 6.31 mm³. Conclusion Scheimpflug-derived corneal tomography identified key refractive surgery parameters that may be useful in screening refractive surgical patients. Financial Disclosure Drs. Ambrósio and Belin are consultants to Oculus Optikgeräte GmbH. No other author has a financial or proprietary interest in any material or method mentioned.