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Yao Nie, Qienyuan Zhou, Kelly Soules, Ben Jang, Multidisciplinary Imaging; Average Corneal Epithelial Thickness Pattern of Normal, Post-LASIK, Post-PRK, KCN, Contact Lens Wearer, and Dry Eyes Using RTVue FD-OCT System. Invest. Ophthalmol. Vis. Sci. 2013;54(15):556.
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To generate the average corneal epithelial thickness pattern and compare the epithelial thickness distribution of normal, post-LASIK, post-PRK, keratoconus (KCN), contact lens (CL) wearer and dry eyes, using RTVue Fourier-domain (FD) optical coherent tomography (OCT) system with Corneal Adaptive Module (CAM) (Optovue, Fremont, CA).
A total of 16 normal, 12 post-LASIK, 8 post-PRK, 39 KCN, 28 CL wearer and 30 dry eye subjects from 4 clinical sites were included, following WIRB-approved study protocols. One eye per subject was selected, each having 3 repeated “Pachymetry+Cpwr” scans with central pupil alignment. Scans with any visible segmentation error were excluded from the following data processing and analysis. To generate the average epithelial thickness pattern, the average epithelial thickness map of repeated scans is calculated for each eye, which is flipped for left eyes to make the temporal(T)/nasal(N) side on the left/right, and then averaged across eyes within each group. The average thicknesses of the central (2mm diameter), superior(S) and inferior(I) (2-5mm) zones, and the variation (assessed by standard deviation SD) of the central 5mm diameter zone were calculated from the epithelial thickness map. The mean and SD for these measurements were generated across eyes within each group.
The average epithelial thickness pattern for each pathology group is shown in Fig. 1. The assessments of the zonal thickness and variation are summarized in Table 1. As shown, the normal, CL wearer and dry eyes are thicker in the I-N region than in the S-T region. The post-LASIK and post-PRK eyes are thicker inferiorly, with the overall thickness noticeably greater than the other groups. The KCN eyes have the greatest zonal variation, with the S-N region thicker than the I-T region. The SD of zonal thickness across eyes is the smallest among normal eyes, and the greatest among post-PRK and KCN eyes.
Epithelial thickness and pattern are affected by corneal pathologies and laser refractive surgery (LRS) as measured with automated epithelial thickness mapping function in RTVue FD-OCT. The results appear consistent with existing knowledge of epithelial change in KCN and post-LRS eyes. Note the sample sizes of the post-LASIK and post-PRK groups are small, which should be considered when interpreting the above study results.
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