Repeatability of Corneal Epithelial Thickness Measurements Using Fourier-Domain Optical Coherence Tomography in Normal and Post-LASIK Eyes

Abstract

To evaluate the repeatability of corneal epithelial thickness (ET) and corneal thickness (CT) measurements in normal eyes and laser in situ keratomileusis (LASIK)-treated eyes using optical coherence tomography (RTVue system). In 35 right eyes of 35 normal subjects and 45 right eyes of 45 subjects who underwent a myopic LASIK, corneal ET and CT were evaluated in 17 areas: (1) 1 central zone within a 0- to 2.0-mm diameter, (2) 8 paracentral zones from a 2.0- to 5.0-mm diameter, and (3) 8 peripheral zones from a 5.0- to 6.0-mm diameter. The repeatability was assessed using within-subject standard deviation (SD), coefficient of variation, and intraclass correlation coefficient. At the central and paracentral zones, respectively, the SD values were 0.7 μm and 0.6 to 0.9 μm in normal eyes and 0.7 μm and 0.8 to 1.7 μm in LASIK-treated eyes for ET, and 1.0 μm and 2.8 to 4.6 μm in normal eyes and 1.3 μm and 4.0 to 4.8 μm in LASIK-treated eyes for CT. At the peripheral zones, in normal and LASIK-treated eyes, respectively, the SD values ranged from 0.8 to 1.2 μm and 1.4 to 2.2 μm for ET, and 4.1 to 6.4 μm and 6.0 to 9.1 μm for CT. The coefficient of variation values were low and intraclass correlation coefficient values were high in both groups for both ET and CT measurements. The Optical coherence tomography produced excellent repeatability, especially at the central and paracentral zones up to a 5-mm diameter for both corneal ET and CT measurements.