Retinal and Choroidal Vascularization Parameters in Patients with Type 2 Diabetes Without Diabetic Retinopathy

The purpose of this study was to evaluate retinal and choroidal vascularization parameters in patients with type 2 diabetes mellitus (DM), without diabetic retinopathy (DR), and to compare them to healthy controls.

Seventy-four eyes from 74 patients (40 eyes in the DM group and 34 eyes in the control group) were included in the study. Optical coherence tomography angiography RTVue XR Avanti was used to obtain 3×3mm scans of the macula. The choroidal vascularity index (CVI), superficial and deep capillary plexus vascular densities (SCP and DCP, respectively), and choroidal thickness (CT) were measured.

In the diabetic group, SCP was lower in the superior and nasal segments (48.68 vs 50.62, p=0.02; 45.50 vs 48.82, p=0.02, respectively). The DCP did not differ between the groups. CVI was significantly lower in the study group in all measured segments, including central and parafoveal (31.73 vs 48.86 and 50.32 vs 59.58, p<0.001, respectively). CT was larger in the study group only at the center of the macula (281.89µm vs 268.37µm p<0.001) and in the inferior segment (337.47µm vs 329.40µm, p<0.001). In the multivariate regression, clinical and vascularization parameters affecting CVI and CT were analyzed after adjusting for age and sex. Decreased central CVI was associated with the presence of DM, lower central SCP, and bigger foveal avascular zone area (b=-0.68, b=0.47, b=-0.21). Parafoveal CVI was also negatively affected by DM (b= -0.46) and positively by parafoveal SCP (b= 0.44). Increased central CT was found to be positively associated with higher central SCP (b=0.48) and male sex (b=0.20).

The results of our study confirmed a reduction of SCP and CVI in diabetic patients without DR. DM and SCP are age and sex independent parameters affecting CVI. Central CT is affected by SCP and sex, rather than the presence of diabetes.