Abstract:  Objective To detect the changes of retinal micro-vessels in patients with diabetic retinopathy (DR) in different disease stages with optical coherence tomography (OCTA), and to analyze its systemic and ocular related influencing factors. Design cross-sectional study. Participants 1096 patients with type 2 diabetes were included in the “Kailuan Eye Disease Study”. Methods All patients underwent systemic health examination and eye examination, DR was diagnosed and graded according to fundus photography, and OCTA was used to measure superficial retinal vascular density (VD), perfusion density (PD) and foveal avascular zone (FAZ) parameters. Differences in ocular and systemic parameters between different DR groups were compared with Kruskal-Wallis rank-sum test, analysis of variance or Chi-Square test. Univariate linear regression and multiple linear regression methods were used to analyze the influencing factors of OCTA measurement parameters in diabetic patients, and to analyze the ocular and systemic variables related to the severity of DR. Main Outcome Measures VD, PD, FAZ area, FAZ perimeter and FAZ morphology index. Results The results of multivariate linear regression analysis showed that in diabetic patients, retinal PD and VD decreased gradually with age (both P<0.001), and increased with the increase of foveal macular thickness (MT) (all P<0.001). Except for the foveal area, PD and VD in the entire macular area and parafovea area were also negatively correlated with the axial length, that is, the longer the axial length, the smaller the PD and VD in these areas (P<0.05). With the increase of age and fasting blood glucose, FAZ area (all P<0.01) and FAZ perimeter (all P<0.01) increased gradually, while FAZ morphological index decreased (P=0.005, 0.003). With the aggravation of DR, macular VD (P=0.003) and perifoveal VD (P=0.001) gradually decreased. The macular VD of eyes without DR, mild NPDR, moderate NPDR, severe NPDR and PDR was 15.7±3.2, 15.7±3.2, 15.4±3.2, 14.3±3.9, 13.4±3.3 (mm/mm2) respectively (χ2=15.9，P=0.003）and perifoveal VD was 16.9±3.4, 16.9±3.3, 16.4±3.3, 15.4±4.1, 14.4±3.3 (mm/mm2) respectively (χ2=18.0，P=0.001). Multivariate linear regression analysis showed that the more severe the DR, the higher the fasting blood glucose, the longer the duration of diabetes, and the smaller the macular VD (P=0.029) and the parafoveal VD (P=0.023), while the DR stage had no significant correlation with PD and FAZ measurement parameters. Conclusion VD in the superficial retina in the macular region gradually decreased with the aggravation of DR, VD may become a quantitative analysis indicator for evaluating the progression of DR. While the PD showed no significant difference after adjustment of blood glucose and disease duration in different stages of DR. OCTA measurement parameters in diabetic patients are related to age, axial length and MT, suggesting that the influence of the above factors on OCTA quantitative analysis parameters should be considered in the process of relevant measurement and follow-up of DR patients. (Ophthalmol CHN, 2022, 31: 253-259)

Key words: diabetic retinopathy, optical coherence tomography angiography, retinal microvascular density, foveal avascular zone