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Pentacam pachometry: comparison with non-contact specular microscopy on the central cornea and inter-session repeatability on the peripheral cornea.

Lam AK, Chen D

School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China E-mail: andrew.kc.lam@polyu.edu.hk.

Purpose: Our aim was to compare specular microscopy (SM) and a new corneal topographer with rotating Scheimpflug camera (Pentacam) for non-contact pachometry of the central cornea. The repeatability of Pentacam for topographic pachometry was also studied. Methods: Thirty-nine subjects were recruited and one eye was selected randomly for non-contact pachometry by SM and by Pentacam, in random order. The corneal thickness (CT) was monitored at 30-second intervals for 10 minutes. Baseline CT was defined as the average of all measurements taken over the 10 minutes. Subjects were required to return within one to two weeks for a second corneal evaluation by Pentacam. Comparisons were made on the central CT between the two devices and on the topographic CT from Pentacam between the two visits. Results: The spontaneous variation of central CT was similar for the two instruments. Central CT varied within +/-2.3 microm during the 10 minutes. The 95% limits of agreement between SM and Pentacam were within +/-15 microm for the central CT. The spontaneous variation of peripheral CT was within +/-3.1 microm. There was no significant difference (p > 0.05) between the two visits on CT at different regions. Further analysis found that with Pentacam three measurements should be taken to obtain topographic CT measurement of one per cent precision. Conclusion: Non-contact specular microscopy and Pentacam have good agreement for central CT measurement. Topographic pachometry from Pentacam requires three repeated measurements for one per cent precision.

Published 21 February 2007 in Clin Exp Optom, 90(2): 108-14.
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