Objective: To study posterior choroidal thickness in 100 medical students and to determine its correlation with sex and axial length. Materials and Methods: Cross-sectional observational study of 197 eyes in 100 medical students (mean age = 23.1 ± 1.1 years). The macular choroid was imaged using enhanced depth imaging spectral-domain optical coherence tomography (EDI-OCT). Subfoveal choroidal thickness (SFCT) and choroidal thickness were measured by visual inspection and manual fitting of the

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... oroidal borderlines, at 3 mm inferior, superior, nasal, and temporal to the fovea, respectively. Results: The mean SFCT was 202.8 ± 49.0 µm. The choroidal thickness was the biggest (235.9 ± 68.4 µm) at 3 mm superior to the fovea, and was the thinnest (150.5 ± 55.5 µm) at 3 mm nasal to the fovea. No significant difference had been found in the choroidal thickness between male and female volunteer (P > 0.05), either between right and left eyes (P > 0.05). Ocular axial length between 23.23 mm to 27.88 mm, foveal nasal lateral choroidal thickness decreased by 17.46 µm per mm along axial length, the difference between the other four sites of the choroidal thickness was without obvious regularity. Conclusions: The posterior choroidal thickness of 100 medical students has nothing to do with sex, while the foveal nasal lateral choroidal thickness gets thinner with the axial growth.