ObjectiveTo observe the flow density (FD) of macular and optic disc and area of foveal avascular zone (FAZ) in severe nonproliferative diabetic retinopathy (S-NPDR).MethodsA prospective cross-sectional study. From October 2019 to April 2020, 31 eyes of 25 S-NPDR patients (S-NPDR group) who were diagnosed in the ophthalmological examination of Jiangsu Province Hospital and 30 eyes of 30 age- and sex-matched healthy volunteers (control group) were included in this study. Optical coherence tomography angiography (OCTA) was used to scan the macular area of 6 mm×6 mm and optic disc of 4.5 mm×4.5 mm. The software automatically divides it into three concentric circles centered on the macular fovea, which were foveal area with a diameter of 1 mm, parafoveal area of 1 to 3 mm, and foveal peripheral area of 3 to 6 mm. The area around the optic disc was divided into 8 areas: nasal upper, nasal lower, inferior nasal, inferior temporal, temporal lower, temporal upper, superior temporal and superior nasal. The FD of the optic disc, the superficial capillary layer (SCP) and deep capillary layer (DCP) of the retina and FAZ area were measured. The FD and FAZ area were compared between the two groups by independent sample t test. The correlation between FAZ area and FD was analyzed by Pearson correlation.ResultsIn parafoveal and perifoveal area, compared with the control group, the FD of SCP (t=6.470, 5.220; P＜0.001) and DCP (t=7.270, 7.370; P＜0.001) decreased in S-NPDR group. In foveal area, there was statistically significant difference in the FD of DCP between the two groups (t=2.250, P=0.030), while the difference in FD of SCP between the two groups was not statistically significant (t=0.000, P=0.900). The FAZ area in S-NPDR group was larger than that in control group, and the difference was statistically significant (t=2.390, P=0.030). The FD in the S-NPDR group was lower than that in the control group except the superior nasal, the difference was statistically significant (t=7.520, 5.000, 4.870, 3.120, 2.360, 2.120, 5.410, 5.560, 2.640; P＜0.05). Pearson correlation analysis showed that the FAZ area of S-NPDR was negatively correlated with FD of SCP (r=－0.513, P=0.004), and had no correlation with FD of DCP (r=0.034, P=0.859).ConclusionThe overall FD in macular area and optic disc of patients with S-NPDR decreased and the FAZ area enlarged.