Objective:To analyze the change of macular microcirculation in early diabetic patients and its correlation with visual acuity.Methods:A cross-sectional study was performed.Seventy-five eyes from 75 patients with non-diabetic retinopathy (NDR) and 33 eyes from 33 patients with non-proliferative diabetic retinopathy (NPDR) were included in Subei People's Hospital Affiliated to Yangzhou University from December 2019 to September 2020.The patients were divided into the NDR group and NPDR group according to their condition.Another 35 eyes from 35 healthy subjects served as the control group.Optical coherence tomography angiography (OCTA) images were acquired over 3 mm×3 mm regions centered on the fovea using RTVue XR OCTA device and the data were quantified with Angio Vue software.The area, perimeter and acircularity index (AI) of the macular foveal avascular zone (FAZ), the grading of abnormal superficial and deep FAZ contour, as well as the vessel density of superficial capillary plexuses (SCP), deep capillary plexuses (DCP) and a 300 μm ring area beside FAZ (FD300) were analyzed and compared among the three groups.The correlations between these indexes and visual acuity were analyzed.This study protocol adhered to the Declaration of Helsinki and was approved by an Ethics Committee of Subei People's Hospital affiliated to Yangzhou University (No.2018KY-167). Written informed consent was obtained from each subject prior to any medical examination.Results:No statistically significant differences were found in the FAZ area, FAZ perimeter and AI among the three groups ( F=1.948, P=0.146; F=2.632, P=0.075; H=5.582, P=0.061). The proportions of superficial and deep FAZ contour abnormality were 54.5%(18/33) and 87.9%(29/33) in the NPDR group, 37.3%(28/75) and 70.7%(53/75) in the NDR group, 22.9%(8/35) and 42.9%(15/35) in the control group, respectively, the proportions of superficial and deep FAZ contour abnormality in the NPDR group were significantly higher than those in the control group (both at P<0.05). With the aggravation of the condition, there were more eyes with high grades of abnormal superficial and deep FAZ contours ( χ2=9.827, 9.030; all at P<0.05). The vessel density of parafoveal DCP was (52.50[50.70, 54.80]), (50.40[48.40, 52.60]), (48.30[43.60, 51.55])%, and the vessel density of DCP was (49.90[47.70, 51.80]), (47.30[45.20, 50.10]), (45.80[41.30, 48.60])% in the control group, NDR group and NPDR group respectively, and there were statistically significant differences among the three groups ( H=21.719, 21.652; both at P<0.001), and statistically significant differences were found in pairwise comparisons among the three groups (all at P<0.05). The vessel densities of foveal SCP, foveal DCP and FD300 in the NPDR group were significantly lower than those in the control group (all at P<0.05). There was no statistically significant difference in vessel densities of parafoveal SCP and SCP found in the overall comparison among the three groups ( H=5.290, 5.534; both at P>0.05). In diabetic mellitus patients, there were negative correlations between the vessel density of parafoveal SCP and LogMAR best corrected visual acuity (BCVA), and between the vessel density of SCP and LogMAR BCVA ( rs=-0.305, -0.330; both at P<0.05), and there was a positive correlation between the superficial FAZ contour grading and LogMAR BCVA ( rs=0.353, P<0.05). Conclusions:Abnormal parafoveal DCP and DCP vessel density, as well as FAZ contour, appear in diabetic mellitus patients before the occurrence of visible fundus lesion, and the vessel density of parafoveal SCP and SCP, and superficial FAZ contour grading in diabetic mellitus patients are correlated with visual acuity.OCTA can help monitor disease progression and identify microcirculation parameters that affect visual function.