Optical coherence tomographic enhanced depth imaging of polypoidal choroidal vasculopathy

To assess the dimensions of hyporeflective choroidal lumina and choroidal thickness in patients with polypoidal choroidal vasculopathy (PCV) without subretinal hemorrhage.

Chinese patients with PCV and without subretinal hemorrhage and subjects of a control group underwent enhanced depth imaging by optical coherence tomography. Choroidal thickness and the largest diameter of choroidal hyporeflective lumina as surrogates for choroidal vessels were measured.

The study included 18 eyes of Chinese patients with PCV and 19 subjects of a control group, with no significant difference in age (P = 0.10) or refractive error (P = 0.89) between the groups. Mean subfoveal choroidal thickness was significantly higher in the study group than in the control group (338 ± 107 μm vs. 261 ± 78 μm; P = 0.017), and mean largest diameter of the choroidal vessels was significantly larger in the study group than in the control group (236 ± 63 μm vs. 137 ± 48 μm; P < 0.001). Choroidal thickness was significantly (P < 0.001) correlated with the largest choroidal vessel diameter. In the area of the branching choroidal vascular networks in PCV eyes, a "double-layer sign" with two highly reflective layers was noted with an undulating retinal pigment epithelial line, a hyperreflective straight line representing Bruch membrane, and a moderate hyperreflectivity between these two lines. Bruch membrane appeared to be intact. In 4 eyes (22%), a dome-shaped retinal pigment epithelial elevation was detected. It correlated spatially with the polypoidal lesions.

Polypoidal choroidal vasculopathy is characterized by a thickened subfoveal choroid with dilated choroidal vessels, a double-layer sign at the level of the retinal pigment epithelium-Bruch membrane-choriocapillaris complex, and hyperreflectivity between the retinal pigment epithelium and Bruch membrane. Choroidal macular swelling in PCV is mainly associated with vascular engorgement and dilatation.