ObjectiveTo observe alterations of macular outer retinal reflectivity (ORR) and the associations with macular vessel density in patients with nonproliferative diabetic retinopathy (NPDR). Methods A retrospective cross-sectional study. From August 2021 to March 2022, a total of 63 NPDR patients with 63 eyes (NPDR group) diagnosed by Department of Ophthalmology of Guangdong Provincial People's Hospital were included in the study. There were 39 males with 39 eyes and 24 females with 24 eyes. Age was 60 (52, 68) years. A total of 66 eyes of 66 healthy volunteers matching age and sex were selected as the control group. Among them, 40 men had 40 eyes and 26 women had 26 eyes. Age was 58 (52, 67) years. Optical coherence tomography (OCT) and OCT angiography (OCTA) were performed in all affected eyes. Image J software was used to calculate ORR, including the optical density of ellipsoid zone (EZ), photoreceptor outer segment (OS), photoreceptor inner segment (IS) and outer nuclear layer (ONL) by OCT examination. The sampling sites were horizontal and vertical scanning of the fovea of the macula on 500 μm (nasal500, temporal500, superior500, inferior500), 1 000 μm (nasal1 000, temporal1 000, superior1 000, inferior1 000) and 2 000 μm (nasal2 000, temporal2 000, superior2 000, inferior2 000). The software automatically divided the retina within 6 mm of the macular fovea into the fovea with a diameter of 1 mm, the parafovea with a diameter of 1-3 mm, and the perifovea with a diameter of 3-6 mm by macular OCTA examination. The blood density of superficial capillary plexus and deep capillary plexus in different zones in the macular area were measured by the built-in software of the device. Spearman correlation analysis was used to analyze the correlation between ORR and blood flow density. ResultsCompared with the control group, retinal reflectivity of EZ in NPDR group was significantly decreased at other sites except the fovea, retinal reflectivity of OS was significantly decreased at nasal2 000, temporal2 000, superior2 000 and superior1 000; retinal reflectivity of IS was significantly decreased at superior1 000, superior500 and inferior500. The retinal reflectivity of ONL in macular fovea was significantly decreased, and the differences were statistically significant (P＜0.05). The ORR was positively correlated with blood flow density, and the correlation coefficient in NPDR group was lower than that in control group. The results of multifactor linear regression analysis showed that the superior and temporal ORR were correlated with blood flow density (P＜0.05). ConclusionsCompared with the control group, ORR is reduced and less correlated with vessel density in NPDR patients. ORR is more affected by retinal blood flow density in temporal and superior parts.