Repeatability and Reproducibility of Corneal Curvature Measurements Using the Pentacam and Keratron Topography Systems

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To compare the repeatability and reproducibility of corneal curvature measurements using the Pentacam eye scanner (Oculus Optikgeräte GmbH) and Keratron corneal topographer (Optikon 2000 SpA).


Axial topography maps were used to acquire measurements. Twenty-six eyes of 26 healthy patients were measured to determine repeatability and reproducibility. Another 10 eyes of 10 healthy patients were included in a parallel study. Three measurements per eye were performed. Repeatability was assessed via the coefficient of variation. Reproducibility was assessed using Bland-Altman plots. Linear correlations were used to determine the agreement between devices. A P value <.05 was considered statistically significant.


The majority of coefficient of variations for both devices were within 1%. The coefficient of variation of the Pentacam was higher in the superior cornea (P<.01). The mean difference (95% limits of agreement) in the flattest meridian between examiners was −0.03±0.27 diopters (D) (range: −0.56 to +0.49 D) for the Pentacam and −0.08±0.21 D (range: −0.50 to +0.33 D) for the Keratron. The mean difference (95% limits of agreement) in the steepest meridian was −0.10±0.26 D (range: −0.60 to +0.41 D) for the Pentacam and −0.11±0.22 D (range: −0.53 to +0.31 D) for the Keratron. The mean axial power for the central 3.0 mm of the Pentacam was statistically significantly lower than that of the Keratron (P<.01).


Although statistically significant differences were noted, both devices provided repeatable and reproducible corneal measurements centrally. Pentacam repeatability outcomes indicate that superior corneal measurements should be interpreted with caution.

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