Purpose:To investigate the choroidal structure in keratoconic patients with different severity using the choroidal vascularity index (CVI) derived from image binarization on enhanced depth imaging optical coherence tomography scans (EDI-OCT).Methods:Sixty-eight eyes from 34 keratoconus (KCN) patients and 72 eyes from 36 healthy subjects were recruited in this prospective, noninterventional, comparative cross-sectional study. EDI-OCT was employed to measure choroidal parameters, including choroidal thickness (CT), total choroidal area (TCA), luminal area, stromal area, and CVI.Results:Subfoveal CT was 354.6 ± 66.8 mm in the control group and 371 ± 64.5 mm in the KCN group (P= 0.86). There was no significant difference between control and KCN groups in terms of TCA (0.66 ± 0.14 mm2vs. 0.7 ± 0.12 mm2;P= 0.70), luminal area (0.49 ± 0.10 mm2vs. 0.53 ± 0.08 mm2;P= 0.67), and stromal area (0.16 ± 0.05 mm2vs. 0.17 ± 0.05 mm2;P= 0.84). CVI was also comparable in the control group (75.4% ±3.4%) and the KCN group (75.6% ±4.5%;P= 0.43). There was also no significant correlation between other choroidal parameters and KCN severity indices.Conclusion:It seems that CVI as well as other choroidal biomarkers were not significantly different between patients with KCN and healthy subjects.