Quantitative Retinal Optical Coherence Tomography Angiography in Patients With Diabetes Without Diabetic Retinopathy.

Purpose: To compare optical coherence tomography (OCT) angiographic parameters in retina and choriocapillaris between control subjects and diabetic patients without diabetic retinopathy (NDR). Correlations were studied between OCT angiography parameters, retinal structure parameters, and systemic characteristics in all subjects. Methods: Sixty-two patients were included in the study: control subjects (n = 33) and patients with NDR (n = 29). Optical coherence topography angiographic parameters were as follows: vessel density (%) (in superficial, deep retinal vessel plexus and in choriocapillary layer) and foveal avascular zone (FAZ) area (mm2) in superficial and deep retinal vessel plexus of parafovea. Split-spectrum amplitude decorrelation angiography (SSADA) software algorithm was used for evaluation of vessel density and FAZ area (nonflow area tool). Spectral-domain OCT was used to assess full, inner, and outer retinal thickness and volume in parafovea. Results: In superficial and deep retina, vessel densities in NDR (44.35% ± 13.31% and 31.03% ± 16.33%) were decreased as compared to control subjects (51.39% ± 13.05%, P = 0.04; and 41.53% ± 14.08%, P < 0.01). Foveal avascular zone in superficial retina of NDR patients (0.37 ± 0.11 mm2) was greater than in controls (0.31 ± 0.10 mm2, P = 0.02). Superficial vessel density significantly correlated with full retinal thickness and volume in parafovea (r = 0.43, P = 0.01; r = 0.43, P = 0.01) and with outer retinal volume in parafovea (r = 0.35, P < 0.05) of healthy subjects. Systolic blood pressure and ocular perfusion pressure significantly correlated with deep vessel density in NDR (r = -0.45, P = 0.02; r = -0.46, P = 0.01), but not in controls. Conclusions: Superficial and deep retinal vessel density in parafovea of diabetic patients without diabetic retinopathy are both decreased compared to healthy subjects. The associations between vessel density with retinal tissue thickness and with subject's clinical characteristics differ between healthy subjects and patients with NDR.