HD-OCT Angiography and SD-OCT in Patients with Mild or No Clinically Apparent Diabetic Retinopathy

<b>Purpose:</b> To analyze the retinal and choriocapillaris changes in diabetic patients with no or with early signs of diabetic retinopathy using high-definition (HD) angio optical coherence tomography angiography (OCTA) software and spectral-domain (SD) OCT. <b>Methods:</b> A total of 112 eyes (54 eyes from 27 diabetic patients and 58 eyes from 29 control subjects) were included in this retrospective cross-sectional study of healthy and diabetic adults. Retinal microvascular changes were assessed by using HD-OCTA software to calculate vascular density (VD) and foveal avascular zone (FAZ). SD-OCT was used to assess retinal thickness and volume in parafovea as well as ganglion cell complex (GCC) parameters. <b>Results:</b> The VD-whole image was significantly higher in the healthy control group (MW z = 1109.5, <i>p</i> = 0.012; <i>t</i> = 2.611, <i>p</i> = 0.010). Also, VD-parafovea was significantly higher in the healthy subjects (MW z = 1053.5, <i>p</i> = 0.004; <i>t</i> = 3.207, <i>p</i> = 0.002). GCC focal loss volume (FLV) was significantly decreased in diabetic patients (<i>p</i> = 0.051). Non-flow FAZ did not show a statistically significant difference between groups, although the FAZ was larger in the diabetic patients. <b>Conclusions:</b> Diabetic patients with no or early signs of diabetic retinopathy have decreased VD compared to healthy individuals. They also present retinal changes at the GCC that are correlated with initial neurodegeneration. HD-OCTA and SD-OCT can detect vascular changes and structural signs of retinal neurodegeneration before clinically apparent diabetic retinopathy. Potentially, these methods may offer new biomarkers for monitoring disease progression and visual prognosis.