Reply: Reliability of peripheral corneal pachymetry with the Oculus Pentacam

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In our study, we evaluated the mean values and standard deviations as well as the reliability of 3 consecutive examinations of central and peripheral corneal thickness measurements using the Pentacam rotating Scheimpflug camera. The central corneal thickness was measured at the apex and at the pupil center. Peripheral corneal thickness was also examined 3.0 mm superior, inferior, nasal, and temporal to the pupil center as the standard default implemented in the Pentacam settings.

It seems logical that the corneal apex is a more stable reference point than the pupil center. However, in our study, the mean standard deviation of 3 consecutive central pachymetry measurements at the apex (4.41 ± 3.00 μm) were not statistically significantly different than those at the pupil center (4.33 ± 2.96 μm) (Wilcoxon test, P>.05). If the instability of the pupil center were the only explanation for the decreasing reliability in the periphery, we would expect increasing mean standard deviations in the central corneal thickness as well.

Nevertheless, we agree that the reference point is an important factor and needs further investigation. We are very interested in reading the article by Shankar et al. and in reviewing our data in terms of the reliability of repeated peripheral corneal thickness measurements compared with the corneal apex as well as the pupil center.