Repeatability of Corneal Epithelial Thickness Map Using Anterior Segment Optical Coherence Tomography in Normal and Corneal Disease Patients.

Abstract

To evaluate the repeatability of corneal epithelial thickness (CET) measurements in normal eyes and eyes diagnosed with corneal disease using the epithelial thickness map (ETM) of anterior segment optical coherence tomography (OCT). In this retrospective study, patients with 3 OCT scans using the ETM mode of Cirrus OCT (Carl Zeiss Meditec AG, Jena, Germany) between October 2021 and January 2024 were reviewed. Two groups of subjects were included: (1) normal subjects with no history of ophthalmic surgery, corneal diseases, and topical antiglaucoma medication uses; and (2) subjects with corneal diseases including dry eye syndrome, recurrent corneal erosion, pterygium, and others. 57 eyes of 57 normal subjects and 106 eyes of 76 patients with corneal disease were included. ETM was analyzed in 25 zones (1 zone within 0-2 mm diameter, 8 zones within 2-5 mm diameter, 8 zones within 5-7 mm diameter, and 8 zones within 7-9 mm diameter). Repeatability was evaluated by calculating intraclass correlation coefficient (ICC), coefficient of variation (CoV), within-subject standard deviation (Sw), and Bland-Altman plot. Among a total of 25 sectors, the normal eyes showed high repeatability (ICC > 0.75, CoV 2.17%-5.29%, and Sw 0.76-1.65 μm) in 23 sectors, and in corneal diseases patients also showed high repeatability (ICC >0.75, CoV 4.17%-9.61%, and Sw 1.29-3.34 μm) in 22 sectors. However, the wide range of 95% limit of agreement (LoA) width of Bland-Altman plot presented in corneal disease group and some peripheral zones in normal eyes indicates some variability of CET measurements. Except for a few peripheral sectors, ETM of Cirrus OCT provides repeatable CET measurements in normal eyes, however in corneal disease group, repeatability was not consistently high. To measure CET accurately, performing multiple measurements is advised especially in patients with corneal disease and patients in whom peripheral CET values.