Longitudinal Analysis Of Epithelial Thickness Parameters Measured By Optical Coherence Tomography In Patients With Progressive And Stable Keratoconus

Measurement of epithelial thickness has gained increasing importance in the diagnosis of keratoconus, particularly in the early detection of subclinical forms of the disease. However, it remains unclear if the epithelial parameters are suited to assess disease progression. The aim of this study was to compare the epithelial parameters measured by optical coherence tomography in two consecutive measurements, in eyes of patients with progressive and stable keratoconus.

Faculty of Medicine and University Hospital Carl Gustav Carus, TU Dresden, Department of Ophthalmology, Dresden, Germany

This monocentric longitudinal study included 24 eyes of 24 patients with progressive keratoconus and 25 eyes of 25 patients with stable keratoconus. Epithelial thickness was measured using anterior segment optical coherence tomography (Anterion, Heidelberg Engineering), epithelial thickness maps were divided into 41 zones and inter-zonal epithelial thickness differences were calculated, as well as the standard deviation of mean epithelial thickness across all zones. Two measurements were obtained with a minimum interval of 12 months. Changes of epithelial parameters between the first and second measurements were analyzed using Wilcoxon test; a p-value < 0.05 was considered statistically significant.

The mean (±SD) baseline Kmax was 57.34 D and 50.79 D, mean change in Kmax was 2.04 ± 1.60 D and −0.29 ± 0.41 D,  mean minimum pachymetry at baseline was 452 ± 43.74 μm and 483 ± 38,97 µm with mean changes of −6.58 ± 7.81 μm and −1.64 ± 3.54 μm in the progressive and stable groups, respectively. The standard deviation of mean epithelial thickness at baseline was 5.98 ± 1,53 μm in the progressive group and 4.37 ± 1,82 μm in the stable group, with corresponding mean changes of 1.31 ± 4.09 μm (p<0.01) and 0.17 ± 0.41 μm (p>0.05). No statistically significant differences were observed in inter-zonal epithelial thickness between the first and second measurements in either the progressive or stable groups (p>0.05).

The initial results of this ongoing study indicate increasing standard deviation of mean epithelial thickness in progressive keratoconus, while statistically significant changes were not observed for the other tested epithelial parameters. A larger sample size is required to determine whether epithelial thickness parameters may serve as reliable indicators of keratoconus progression.