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Y. Li, O. Tan, D. Huang; Corneal Epithelial Thickness Mapping in Normal and Keratoconic Eyes With Fourier-Domain Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5819.
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© ARVO (1962-2015); The Authors (2016-present)
To map corneal epithelial thickness in both normal and keratoconic eyes with optical coherence tomography (OCT).
A Fourier-domain OCT (RTVuv-CAM OCT, Optovue, Inc.) system with 26,000 axial-scans/second scan speed and 5µm axial resolution was used. A pachymetry scan pattern (8 radials, 1024 axial-scans each, 6mm diameter) centered at the pupil center was used to image the cornea. Automatic computer algorithm generated the epithelial thickness (tear film included) map. The map was divided into 3 zones by diameter: central 2mm, superior 2-5mm, and inferior 2-5mm. The average epithelial thickness from each zone was calculated. Each eye was scanned 3 times. Pooled standard deviation was used to evaluate the repeatability of the measurement.
Twenty normal and twenty keratoconic eyes were included in this study. The central, superior, and inferior epithelial thickness averages (± population SD) were 55.6 ± 1.8, 52.9 ± 2.5, 54.1 ± 2.1 µm in normal eyes and 53.7 ± 4.9, 55.2 ± 3.9, 52.7 ± 3.9µm in keratoconic eyes. The central epithelial thickness in normal eyes was thicker than those of keratoconic eyes (mean difference 2.0 µm, t-test p = 0.05). The epithelium was thinner superiorly than inferiorly in normal eyes (mean difference -1.1 ± 0.9 µm, p < 0.001) while thicker superiorly than inferiorly in keratoconic eyes (2.5 ± 4.1 µm, p=0.01). The repeatability of epithelial thickness measurements was better in normal eyes (central 0.5 µm, superior 0.7 µm, inferior 0.6 µm) than those of keratoconus (central 1.0 µm, superior 1.1µm, inferior 1.2 µm).
High-resolution high-speed FD-OCT is able to map the corneal epithelial thickness in normal and keratoconic eyes with excellent reproducibility. The epithelial thickness asymmetry pattern may be useful to identify keratoconic corneas from the normal.
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