Optical and Acoustic Measurements of the Central Corneal and Epithelial Thickness
Thannhäuser C., Wirbelauer C., Pham D. T.
Dept. of Ophthalmology, Vivantes Klinikum Neukölln, Berlin
Purpose: The representation of the cornea is an important part of the ophthalmologic examination and particularly in refractive surgery. The purpose of this study was to investigate the accuracy of optical and acoustic methods to measure the central corneal and epithelial thickness.
Method: In a controlled clinical study 33 patients without corneal pathologies were consecutively studied. The central corneal and epithelial thickness were measured with the noncontact methods of slitlamp-adapted optical coherence tomography (OCT) and optical coherence pachymetry (OCP). Controls were determined with two different ultrasound pachymetric systems (US) with transducer frequencies of 20 MHz and 50 MHz.
Results: The mean central corneal thickness was 537±42 µm (OCT), 535±43 µm (OCP), 552±40 µm (US 20) and 551±34 µm (US 50). The reproducibility was 3.3 µm (OCT), 3.1 µm (OCP), 2.6 µm (US 20) and 1.8 µm (US 50). The mean epithelial thickness was 68±9 µm (OCT) and 54±3 µm (US 50) with a reproducibility of 5.9 µm (OCT) and 1.9 µm (US 50). Although the correlations coefficients for the measurements of the corneal thickness were between 0.97 and 0,99 (P<0,001), the mean difference between optical and acoustic methods was 20 µm (P<0,001). The limits of agreement (±2SD) revealed maximum values of ±41 µm (7.6%).
Conclusions: The measurement of the central corneal and epithelial thic
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