Purpose: To assess the dimensions of hyporeflective choroidal lumina and choroidal thickness in patients with polypoidal choroidal vasculopathy (PCV) without subretinal hemorrhage. Methods: 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. Results: 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 mu m vs. 261 +/- 78 mu m; 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 mu m vs. 137 +/- 48 mu m; 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. Conclusion: 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.