© 2019 Gazi Eye Foundation. All rights reserved.Purpose: To evaluate the changes in choroidal vascular index (CVI) after low fluence photodynamic therapy (PDT) in central serous chorioretinopathy (CSC). Materials and Methods: Patients with complaints of longer than 6 months who were diagnosed as CSC and underwent low fluence PDT was reviewed retrospectively. Patients with enhanced depth imaging (EDI) - optical coherence tomography (OCT) images before and after treatment were included in the study. Subfoveal area of1500 μm was evaluated after segmentation. CVI was defined as ratio of lumen area (LA) to total choroidal area (TCA) as measured on EDI-OCT images. Results: Twenty-three eyes of 19 patients were included to the study. The mean age was 43.21 ± 7.4, and 10 (52.6%) of the patients were male. Choroidal vascularity index was 65.4% before treatment, 64.82% on week 1, 62.42% at month 6, and 62.97% at month 6 after treatment. A significant decrease in choroidal vascular indecency was detected at months 1 and 6 after treatment when compared with those obtained before treatment (p<0.05). The subfoveal choroidal thickness was 457.65 ± 108.15 μm before treatment whereas 443.30 ± 108.38 μm on week 1, 416.60 ± 89.71 μm at month 1 and 411.47 ± 101.29 μm at month 6. The choroidal thickness measurements at all time points after treatment were significantly lower than those obtained before treatment (p <0.05). Conclusion: There was a significant decrease in choroidal vascular index after PDT in CSC. The choroidal vascular index may be a useful biomarker to monitor treatment response in CSC.