Artikel
Pentacam vs. Keratograph: comparison of keratometry of normal eyes and eyes with corneal pathology
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Autoren
Veröffentlicht: | 22. September 2004 |
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Gliederung
Text
Objective
The Pentacam, a new measurement tool, can also be used for keratometry. In contrast to the common used Keratograph (based on Placido rings), measurements are based on Scheimpflug imaging. Up to now there is no generally accepted way how to interprete the results of the Pentacam. Therefore we investigated the correlation of keratometry data between both tools (Oculus Optikgeräte GmbH, Wetzlar, Germany).
Methods
First the horizontal and vertical K-readings (Khoriz bzw. Kvertic) [D] were measured by Keratograph (version: 2,50) und Pentacam (version: 2,57) in 101 normal eyes and 63 eyes with corneal pathology. The mean differences of the results of both tools were calculated and statistically analysed. Second, different measuring modes available for the Pentacam were compared (50 eyes): 12 vs. 25 pictures per eye. Analysis was performed as described.
Results
The mean difference between Khoriz(Keratograph) and Khoriz(Pentacam) in the group of normal eyes was 0,83± 0,42 D and for Kvertic 0,95± 0,52 D, which was statistically significant (p<0,005; Mann-Whitney Rang Sum Test). Concerning the eyes with corneal pathologies the differences were 0,99± 0,98 D (Khoriz) and 1,38± 1,76 D (Kvertic) resp. (no statistically significance). The Keratograph reveal higher K-readings compared to the Pentacam in 87,1% of the normal eyes (Khoriz aswell as Kvertic), and in 76,2% (Khoriz) and 81,0% (Kvertic) of pathological corneas. The mean difference between the two measurement modes of the Pentacam was 0,44± 0,41 D (Khoriz) resp. 0,52± 0,68 D (Kvertic) (no statistically significance: paired t-test, p=0,7792 resp. p=0,8954). Using 25 pictures per eye the K-readings were higher than in the 12 picture mode in 60,0% of the eyes.
Conclusions
In this first published comparison of keratometry data between Keratograph and Pentacam lower K-readings were obtained by the latter method. We assume that this difference is due to the fact that the posterior curvature of the cornea is considered in the algorithm of the Pentacam but not in the one of the Keratograph. Additionally the possible differences in K-readings in varying measurement modes need further investigations.