Purpose: To evaluate the effect of verteporfin photodynamic treatment (PDT) on choroidal thickness in patients with central serous chorioretinopathy (CSC). Methods: Choroidal thickness was measured with enhanced depth imaging- optical coherence tomography (EDI-OCT) before and after verteporfin PDT (full-dose verteporfin, half-light dose) in 16 eyes in 16 patients with serous detachment of the fovea secondary to extrafoveal angiographic fluorescein leakage. Treatment was confined to the area of leakage, whereas choroidal thickness before and after treatment was assessed over a larger area of the fundus using OCT. Results: Complete resolution of the serous detachment was seen in all 16 eyes within 1 month of extrafoveal PDT, while choroidal thickness in the area where PDT was applied decreased from 407 µm [mean; 95% confidence interval (CI(95) ) 356-458 µm] to 349 µm (mean; CI(95) 300-399 µm; p