Thickness Mapping of the Cornea and Epithelium Using Optical Coherence Tomography

Purpose. To measure corneal and epithelial thickness across four meridians using Optical Coherence Tomography (OCT) and to compare these measurements between normal non-lens wearers (NLW), rigid gas permeable (RGP) lens wearers, and RCP-wearing keratoconics (KC). Methods. Both eyes of 60 Subjects were measured (20 NLW, nine female:11 male, 27.6 +/- 5.9 years; 20 RGP, 20 female, 23.9 +/- 7.6 years; and 20 KC, seven female:13 male, 32.4 +/- 8.1 years). A customized fixation target employing LEDs in eight directions of gaze was attached to the OCT and corneal images obtained. Raw OCT scans were analyzed to yield values for cornea) and epithelial thickness and color-coded maps were compiled. Results. Central corneal thickness (CCT) was thinnest in KC (447 +/- 68 mu m) and similar between RGP (518 +/- 32 mu m; P-KC < 0.001) and NLW (517 +/- 21 mu m) (P-KC < 0.001 NLW > 0.05). Peripheral corneal thickness in NLW was thickest in the superior temporal and thinnest in the interior (1) regions (superior temporal(thickest) vs. l(thinnest) p < 0.001). Central epithelial thickness was thinnest in KC (44 +/- 7 mu m), followed by RGP (50 +/- 4 mu m), then NLW (54 +/- 2 mu m) (P-KC < 0.001 NLW p(RGP) < 0.05). Central epithelial thickness in the KC group was significantly thinner than in the RGP group (p < 0.001). In the NLW group, peripheral epithelial thickness was thicker (63 +/- 5 mu m) than central (p < 0.001) and was thickest in the superior (S) region and thinnest in the interior (1) region (S-thickest vs. I-thinnest p < 0.001). KC epithelium was thinnest in the interior temporal meridian (42 +/- 5 mu m). Conclusions. Thickness of the normal cornea and epithelium was greatest in (lie Superior region. In all groups, the inferior cornea and epithelium was thinnest, and to a greater extent in the KC group. (Optom Vis Sci 2008;85:963-976)