Predictive Vascular Changes in OCTA in Diabetic Patients

<b>Background/Objectives</b>: The aim of this study was to investigate quantitative differences in optical coherence tomography angiography (OCTA) between diabetic patients and healthy controls and to identify the early OCTA biomarkers for diabetic macular changes. <b>Methods</b>: Ophthalmological examination and OCTA were performed on two groups of diabetic patients (with and without mild diabetic retinopathy) and healthy controls. Macular, foveal, perifoveal, and parafoveal vessel density (VD) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP), foveal avascular zone (FAZ), and flow area in the choriocapillaris were calculated. <b>Results</b>: A total of 431 eyes of 233 participants were analyzed. The VD in the SCP in the whole macula was the lowest in the DM + DR group and lower than in the DMnoDR group; however, in the fovea, it was the highest in the DM + DR group and higher than in the DMnoDR group. The VD in the SCP in the parafovea was lower in the DM + DR group than in the DMnoDR group, and in the perifovea, it was lower in the DMnoDR group than in the control group. The VD in the DCP in the macula, parafovea, and perifovea was lower in the DM + DR group than in the DMnoDR and control groups. The FAZ and flow areas in the choriocapillaris were smaller in the DM + DR group than in both the DMnoDR and control groups. <b>Conclusions</b>: VD reduction in the SCP and the DCP of the macular and parafoveal regions, as well as in the DCP of the perifoveal region, may indicate progression of diabetic retinopathy from subclinical to clinical stages; however, an increase in the foveal region in the SCP can be a compensatory mechanism. VD reduction in the perifovea and whole macula in the SCP can be a screening factor for subclinical macular changes. FAZ reduction before clinical signs of retinopathy may be an early compensatory vascular mechanism.