Purpose: To measure the hyporeflective lumen in the choroid of patients with central serous choroidopathy (CSC) and to compare the diameter with that of a control group. Methods: The prospective comparative observational clinical study included patients with unilateral CSC and a control group of normal subjects, matched in age, gender and refractive error with the study group. Subfoveal choroidal thickness (SFCT) and the largest diameter of choroidal hyporeflective lumen as surrogates for the choroidal vessels were measured by enhanced depth imaging optical coherence tomography (OCT). Results: The study group included 15 Chinese patients and the control group 15 control subjects. Mean SFCT was significantly (p=0.04) larger in the affected eyes (455 +/- 73m) than in the contralateral unaffected eyes (387 +/- 94m), in which it was significantly (p=0.005) larger than in the control group (289 +/- 71m). In a parallel manner, the mean diameter of the largest hyporeflective lumen was larger, but not significantly larger (p=0.18) in the affected eyes (305 +/- 101m) than in the in the contralateral unaffected eyes (251 +/- 98m), in which it was significantly (p=0.001) larger than in the control group (140 +/- 40m). Largest vessel diameter was significantly (p<0.001; correlation coefficient: 0.73) correlated with the thickness of the total choroid. Conclusions: In patients with CSC, the affected eyes show larger hyporeflective lumen than the contralateral clinically unaffected eyes and significantly larger than normal control eyes. Assuming these hyporeflective lumens to be choroidal vessels, macular swelling in CSC is markedly associated with vascular engorgement. As also the clinically unaffected eyes showed macular choroidal significant swelling, CSC may have a systemic component with usually asymmetric ocular involvement.