To investigate the corneal epithelial thickness distribution profile in patients with ametropia and its relationship with corneal thickness.

In this cross-sectional study, a total of 159 ametropia subjects (318 eyes) were enrolled at Peking University Shougang Hospital from May 2020 to February 2021 and were divided into three groups according to corneal thickness: 60 eyes with a thin cornea (＜500 μm), 171 eyes with a normal cornea (500-550 μm), and 87 eyes with a thick cornea (＞550 μm). The central (2 mm diameter), para-central (2-5 mm diameter), and peripheral (5-6 mm diameter) corneal thicknesses and epithelial thickness were measured by RTVue Fourier domain optical coherence tomography (FD-OCT), and their correlation was analyzed.

The corneal epithelial thickness in the central 2 mm diameter zone was (53.6±3.8) μm, the minimum epithelial thickness was (50.4±3.7) μm, and the lower part was significantly thicker than the upper part [(54.1±3.6) μm vs (51.5±3.8) μm, P＜0.05] in the 318 eyes. There was a positive correlation between the total thickness of the cornea and the thickness of the epithelium in the lower part of the nose of the 2-5 mm area (r=0.167, P＜0.05) in the normal thickness group. There was a positive correlation between the total thickness of the cornea and the thickness of the epithelium in the central 2 mm area (r=0.232, P＜0.05), the nasal side (r=0.255, P＜0.05), the lower part of the nose (r=0.216, P＜0.05), and the inferior part (r=0.249, P＜0.05) of the 2-5 mm area, and the nasal side (r=0.264, P＜0.05) and the inferior part (r=0.256, P＜0.05) of the 5-6 mm area in the thick group. There was a positive correlation between the total thickness of the cornea and the thickness of epithelium in the inferior part (r=0.267, P＜0.05) of the 2-5 mm area in the thin group.

The thickness of the corneal epithelium is not evenly distributed, and the epithelial thickness and corneal thickness show a positive correlation. This requires a close observation by the surgeons during corneal refractive surgery.