Macular vessels density in diabetic retinopathy: quantitative assessment using optical coherence tomography angiography

The aim of this study was to evaluate macular perfusion using OCTA automated software algorithms; vessel area density (VD) and non-flow tool to measure FAZ area in treatment-naïve diabetic eyes with moderate or severe NPDR and having macular edema, and correlate these parameters with LogMAR (logarithm of the minimum angle of resolution) visual acuity. Diabetic eyes without macular edema were included, to detect and define differences within the parameters between diabetic eyes with and without macular edema.

Forty-five diabetic eyes with diabetic macular edema, forty diabetic eyes without macular edema, and forty eyes of healthy controls were examined using OCTA (RTVue-XR Avanti; Optovue, Inc, Fremont, CA). The macular vessel area density (VD) and foveal avascular zone (FAZ) area were assessed and statistically compared between the three groups and also correlated with the foveal thickness and visual acuity. Data were entered and analyzed by SPSS 19. Quantitative data were presented as mean and standard deviation, and qualitative data presented as frequency distribution; independent samples t test, Chi square test and Pearson correlation were done.

Mean whole image VD was 44.4 ± 3.6 in diabetic eyes with DME, 45.6 ± 4.2 in diabetics without DME, and 49 ± 3.9 in control eyes (P = 0.001). Diabetic eyes with DME had significantly lower vessels density values at the level of the deep retinal plexus (in the parafoveal, superior hemi, inferior hemi, temporal, superior, and nasal areas), when compared with diabetic eyes without DME. In diabetic eyes with DME, significant fair negative correlation was found between whole image vessels density at the level of the superficial retinal plexus and LogMAR VA (r = − 0.313, P = 0.036). Also, a significant fair positive correlation was found between FAZ area (at both the superficial and deep retinal plexus) and LogMAR visual acuity, in diabetic eyes with DME, where eyes with larger FAZ area had worse vision (P = 0.005 and P = 0.016, respectively). Diabetic eyes with DME had significantly larger FAZ area at the level of the superficial capillary plexus (mean superficial FAZ ± SD 0.55 ± 0.25) than diabetic eyes without edema (mean superficial FAZ ± SD 0.41 ± 0.12) and control subjects (mean superficial FAZ ± SD 0.35 ± 0.09).

Using OCTA machine with AngioAnalytics parameters (vessel area density and non-flow area) helped in objective quantification of macular perfusion and accurately measuring the FAZ area in diabetic eyes with macular edema. Both parameters were significantly correlated with visual function in treatment-naïve diabetic eyes with edema. These OCTA biomarkers could be used to predict visual function in such eyes, to monitor response to treatment.