Choroid is thinner in inferior region of optic disks of normal eyes

PURPOSE: To determine the thickness of the choroid across the posterior pole of normal eyes. METHODS: Twenty-eight clinic-based normal eyes (54.1 ± 20.0 years,-3.6 ± 4.1 diopter) were studied. The macula and retina around the optic disk were scanned with a spectral-domain optical coherence tomographic instrument. The retinal mapping program with the enhanced depth imaging technique was used, and the borders of the choroid were drawn manually in each optical coherence tomographic image. A choroidal thickness map was constructed by the built-in program, and the choroidal thickness in the different sectors of the Early Treatment Diabetic Retinopathy Study grid was measured and compared. RESULTS: The choroid inferior to the optic disk was significantly thinner than that in the other sectors of the outer ring of the Early Treatment Diabetic Retinopathy Study grid (superior, 196 ± 62 μm; inferior, 146 ± 47 μm; nasal, 183 ± 80 μm; and temporal, 193 ± 64 μm, P < 0.001). The mean choroidal thickness at the nasal sector of the macular region was significantly thinner than other regions of the Early Treatment Diabetic Retinopathy Study grid (superior, 268 ± 74 μm; inferior, 245 ± 73 μm; nasal, 190 ± 68 μm; temporal, 268 ± 63 μm; and central, 258 ± 88 μm; P < 0.05). Choroidal thickness maps showed that the thinner choroidal area spreads around the optic disk and the inferior part of the posterior pole. CONCLUSION: The thinner choroid inferior to the optic disk may be a natural anatomical architecture of normal eyes, and this area may be more susceptible to hypoxia or to elevated intraocular pressures.