Abstract： Objective:To compare the quantitative measurements of the retinal capillary nonperfusion areas in a cohort of proliferative diabetic retinopathy (PDR) patients with fluorescein fundus angiography (FFA) and swept source optical coherence tomography angiography (SS-OCTA), and to determine the intrapersonal variability between examiners.Methods:A cross-sectional study. Eighteen eyes of eleven PDR patients diagnosed in Department of ophthalmology of Henan Provincial People's Hospital from September 2019 to January 2020 were included in this study. FFA was performed using Spectralis HRA+OCT (Germany Heidelberg Company) from and SS-OCTA was performed using VG200D (China Vision Micro Image Corporation). SS-OCTA was used to collect images of retinal layer, superficial capillary plexus (SCP) and deep capillary plexus (DCP). The same observation area was 80°×60° for SS-OCTA and 55° for FFA with both setting centered on the fovea. The forty-nine retinal capillary nonperfusion areas were observed. The area measurement was completed independently by three examiners. Paired sample t test or paired sample Wilcoxon test were used to compare the measured values of retinal capillary nonperfusion areas between the two examination methods and among the three examiners. Results:There was no significant difference in the retinal layer, SCP and DCP nonperfusion area measured by FFA and SS-OCTA among the three examiners ( P>0.05), and the consistency is good (consistency correlation coefficient> 0.9, P<0.05). The nonperfusion area measured by FFA was 0.786 mm 2. The median nonperfusion area of retinal layer and SCP measured by SS-OCTA were 0.787 mm 2 and 0.791 mm 2, respectively, and the average nonperfusion area of DCP was 0.878±0.366 mm 2. The nonperfusion area of retinal layer and SCP measured by FFA and SS-OCTA showed no statistically significant difference ( P=0.054, 0.198). The nonperfusion area of DCP measured by SS-OCTA was significantly larger than that of FFA, and the difference was statistically significant ( P<0.001). The results of repeatability analysis showed that 93.88% (46/49) of the DCP nonperfusion area data measured by SS-OCTA were greater than those measured by FFA. Conclusion:The retinal nonperfusion area of DCP in PDR patients measured by SS-OCTA is larger than that of FFA.