<H4>PURPOSE</H4> <p>To characterize the in vivo epithelial thickness profile in a population of normal eyes.</p> <H4>METHODS</H4> <p>An epithelial thickness profile was measured by Artemis 1 (ArcScan Inc) very high-frequency (VHF) digital ultrasound scanning across the central 10-mm diameter of the cornea of 110 eyes of 56 patients who presented for refractive surgery assessment. The average, standard deviation, minimum, maximum, and range of epithelial thickness were calculated for each point in the 10x10-mm Cartesian matrix and plotted. Differences between the epithelial thickness at the corneal vertex and peripheral locations at the 3-mm radius were calculated. The location of the thinnest epithelium was found for each eye and averaged. Correlations of corneal vertex epithelial thickness with age, spherical equivalent refraction, and average keratometry were calculated.</p> <H4>RESULTS</H4> <p>The mean epithelial thickness at the corneal vertex was 53.4±4.6 µm, with no statistically signifi cant difference between right and left eyes, and no significant differences in age, spherical equivalent refraction, or keratometry. The average epithelial thickness map showed that the corneal epithelium was thicker inferiorly than superiorly (5.9 µm at the 3-mm radius, <i>P</i><.001) and thicker nasally than temporally (1.3 µm at the 3-mm radius, <i>P</i><.001). The location of the thinnest epithelium was displaced on average 0.33 mm temporally and 0.90 mm superiorly with reference to the corneal vertex.</p> <H4>CONCLUSIONS</H4> <p>Three-dimensional thickness mapping of the corneal epithelium demonstrated that the epithelial thickness is not evenly distributed across the cornea; the epithelium was significantly thicker inferiorly than superiorly and significantly thicker nasally than temporally with a larger inferosuperior difference than nasotemporal difference. [<cite>J Refract Surg</cite>. 2008;24:571-581.]</p> <h4>ABOUT THE AUTHORS</h4> <p>From London Vision Clinic, London (Reinstein, Archer, Gobbe); the Department of Ophthalmology, St Thomas’ Hospital, Kings College, London, United Kingdom (Reinstein); the Department of Ophthalmology, Weill Cornell Medical College, New York, NY (Reinstein, Silverman, Coleman); Centre Hospitalier National d’Ophtalmologie, Paris, France (Reinstein); and Riverside Research Institute, New York, NY (Silverman).</p> <p>Drs Reinstein, Silverman, and Coleman have a proprietary interest in the Artemis technology (ArcScan Inc, Morrison, Colo) through patents administered by the Cornell Research Foundation, Ithaca, NY. The remaining authors have no proprietary or financial interest in the materials presented herein.</p> <p>Supported in part by National Institutes of Health (NIH), Bethesda, Md, grant EB000238 and the Dyson Foundation, Millbrook, NY.</p> <p>Prepared in part as fulfillment of the requirements for Dr Reinstein’s doctoral thesis, University of Cambridge.</p> <p>Some aspects of this study were presented at the American Academy of Ophthalmology Annual Meeting; November 11-14, 2006; Las Vegas, Nev.</p> <p>Correspondence: Dan Z. Reinstein, MD, MA(Cantab), FRCSC, FRCOphth, London Vision Clinic, 8 Devonshire Pl, London W1G 6HP, United Kingdom. Tel: 44 207 224 1005; Fax: 44 207 224 1055; E-mail: <a href="mailto:dzr@londonvisionclinic.com">dzr@londonvisionclinic.com</a></p> <p>Received: June 21, 2007</p> <p>Accepted: November 20, 2007</p> <p><b>Posted online: April 30, 2008</b></p>