3-D choroidal thickness maps from EDI-OCT in highly myopic eyes

Myopic chorioretinal atrophy is a debilitating condition that causes severe loss of primary vision. However, its mechanisms and pathologic course are not well understood. We performed volumetric measurements of the posterior choroid via three-dimensional analysis of the choroid in patients with high myopia to understand its structure, and we compared the measurements with those of normal subjects.

Twenty-five highly myopic but otherwise normal eyes and 25 nonmyopic eyes were evaluated. Enhanced depth imaging optical coherence tomography (EDI-OCT) was performed using 20 × 20-degree raster scans consisting of 25 high-speed line scans. Three-dimensional retinal and choroidal thickness maps were produced from the EDI-OCT data. For the quantitative analyses, the macula was divided into nine regions, as defined by the Early Treatment Diabetic Retinopathy Study (ETDRS) layout, and the mean retinal and choroidal thicknesses of each region were obtained.

The choroidal thicknesses at all regions in the high-myopia group were significantly smaller than those in the normal refractive group (p < 0.0001). The foveal choroidal thickness was the greatest in the normal group but not in the high-myopia group. In the high-myopia group, the choroidal thickness at the fovea was significantly greater than that at the outer nasal quadrants (p < 0.0001) but significantly smaller than that at the outer superior (p < 0.0001) quadrants.

Three-dimensional choroidal thickness maps obtained via EDI-OCT are useful for quantifying choroid thickness in subjects with high myopia more accurately.