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Macular and choroidal perfusion using optical coherence tomography angiography in type-2 diabetic patients without diabetic retinopathy

Purpose The aim of this study was to evaluate the changes in retinal vascular plexuses and choriocapillaris in type-2 diabetes mellitus (DM) patients without clinical diabetic retinopathy (DR) and to compare them with healthy controls and to identify early preclinical biomarkers for DR using optical coherence tomography angiography (OCTA). Patients and methods This is a prospective cross-sectional study that included 68 eyes (34 eyes of type-2 diabetic patients without DR and 34 eyes of healthy controls). Using OCTA, the vessel density (VD) in the superficial and deep capillary plexuses, macular thickness, foveal avascular zone (FAZ) area, and choriocapillaris flow area were measured. The OCTA morphological findings in diabetic patients were noted. In addition, the correlations between OCTA and glycosylated hemoglobin and diabetes duration were evaluated. Results There was a statistically significant decrease in the parafoveal macular thickness in the diabetic group compared with the control group (the superior–hemi parafoveal thickness was 310.94±10.84 vs. 321.71±11.2 μm, respectively, P=0.001, while the inferior–hemi parafoveal thickness was 304.71±11.04 vs. 320.82±11.25 μm, respectively, P=0.001). There was no statistically significant difference in the parafoveal and perifoveal superficial capillary plexus and DCP VD in the diabetic patients compared with the controls. In addition, there was no change in the FAZ area between the two groups, but there was a significant difference regarding the FAZ irregularity (P=0.00). Microaneurysms (100%), capillary nonperfusion (94%), capillary loop (17.6%), enlarged perifoveal intercapillary spaces (17.6%), punched-out FAZ (12%), lost spider web (6%), and capillary blind end (6%) were detected in the diabetic patients. A negative significant correlation was found between the parafoveal thickness and glycosylated hemoglobin in the DM group in the inferior–hemi thickness (r=−0.61, P=0.01), and between DM duration and VD in the DCP in the parafoveal and perifoveal areas (r=−0.55, P=0.06 and r=0.62, P=0.018, respectively). Conclusion OCTA can be used to diagnose preclinical maculopathy/retinopathy in diabetic patients using the parafoveal retinal thickness, DCP VD, FAZ irregularities, quantification of microaneurysms, and choriocapillaris flow area as biomarkers.