Corneal Epithelial Thickness Profile in the Diagnosis of Keratoconus

Abstract

PURPOSE: To illustrate the hypothesis that epithelial thickness profi le maps could be used as an adjunctive tool to improve the sensitivity and specifi city of keratoconus screening by presenting a case series of examples. METHODS:The Artemis very high-frequency digital ultrasound arc-scanner was used to obtain epithelial thickness profi les in addition to a comprehensive ophthalmic examination to screen for keratoconus. Five case examples are presented; a normal eye, an eye with advanced keratoconus, and three cases where a diagnosis of keratoconus was uncertain based only on the ophthalmic examination.

Comparison of front-surface corneal topography and Bowman membrane specular topography in keratoconus

“…They found that changes in the epithelial thickness profile induced by myopic laser in situ keratomileusis (LASIK) result in a myopic shift, a so-called epithelial regression; the mean epithelial thickening at the corneal vertex was 7.41 G 1.09 mm, 9.29 G 1.22 mm, and 12.33 G 1.05 mm for low, moderate, and high myopia, respectively. 20 In eyes with keratoconus, Reinstein et al 19,22,23 found that the mean corneal vertex epithelial thickness was 45.7 G 5.9 mm, with an "epithelial doughnut pattern" of epithelial thinning over the cone surrounded by an annulus of epithelial thickening, except in normal eyes, in which the mean corneal vertex epithelial thickness was 53.1 G 4.5 mm and the epithelial pattern was slightly thinner superiorly. Similarly, Haque et al 24 found with optical coherence tomography measurements that the central keratoconic epithelium was 4.7 mm thinner than in the normal cornea.…”

“…17 Based on the knowledge that the epithelium thins above the apex of the cone (Reinstein et al's work 22,23 ), the transepithelial laser (plano photoablation) approach was preferred to the simple manual epithelial removal using the epithelium as a physiologic ablation mask. 4 Nevertheless, because of the very high amount of refractive aberrations in keratoconus cases, a custom PRK profile must be applied to obtain significant refractive improvement.…”

Age-related differences in corneal epithelial thickness measurements with anterior segment optical coherence tomography

“…Corneal epithelial thickness (CET) has recently drawn increasing attention because it not only plays an active role in determining total corneal power but also manifests structural or functional changes under various conditions, such as keratoconus, contact lens use, dry eye, and limbal stem cell deficiency [1][2][3][4][5][6][7][8][9]. The recent availability of corneal epithelial imaging by optical coherence tomography (OCT) presents a practical tool for clinical in vivo epithelial mapping, with good repeatability in normal and post-LASIK eyes [2,5,10].…”

Corneal cross-linking

“…The Athens protocol utilized PTK for removal of epithelium, followed by partial topography-guided PRK with mitomycin C, then the cross-linking procedure. 69 Regional epithelial thickness is highly variable in ectatic corneas, 116,125 and the epithelium undergoes remodeling following cross-linking. 124 117 These anatomic findings may explain the benefits of PTK for cross-linking, and direct epithelial measurements may ultimately prove useful for planning combined treatments.…”