To describe detailed morphologic and vascular features of the choroid in eyes with high myopia.

Cross-sectional study.

A total of 515 eyes of young men (mean age 21.59 ± 1.15 years) with high myopia (defined as −6.0 diopter [D] or worse, mean spherical equivalent −8.66 ± 2.00 D) and 88 controls with emmetropia in both eyes underwent choroidal imaging using spectral-domain optical coherence tomography with enhanced depth imaging (EDI-OCT). Raw OCT images were loaded on a custom-written application on MATLAB that enabled delineation for detailed morphologic and vascular analyses, including the distance of thickest point from the foveal center, choroidal thickness, choroidal volume, choroidal vascular and stromal areas within the macular (6 mm) and foveal (1.5 mm) regions, and choroidal vascularity, which was determined by dividing vascular area by total choroidal area.

The choroid in high myopic eyes was thickest temporally compared to subfoveal location in emmetropic subjects (thickest point distance from fovea: −1.51 ± 1.42 mm vs −0.53 ± 1.06 mm, P < .001). In eyes with high myopia, after adjusting for age, choroidal vascular and stromal areas were significantly lower (vascular area: β = −0.306, stromal area: β = −0.377, both P < .001) than control eyes with emmetropia at the macular region. Compared to control eyes with emmetropia, choroidal vascularity was greater in eyes with high myopia (β = 0.032, P < .001). Similar results were observed for the subfoveal region.

Our study suggests that choroidal thinning in eyes with high myopia is associated with the reduction in both its stromal and vascular components.