Correlation of flow density, as measured using optical coherence tomography angiography, with structural and functional parameters in glaucoma patients

To evaluate the correlation between flow density, as measured by optical coherence tomography angiography (OCTA), and structural and functional parameters in patients with open-angle glaucoma. Thirty-four eyes of 34 patients with open-angle glaucoma and 35 eyes of 35 healthy subjects were prospectively included in this study. OCTA was performed using RTVue XR Avanti with AngioVue. The macula was imaged with a 3 x 3 mm scan and the optic nerve head (ONH) with a 4.5 x 4.5 mm scan. Visual field parameters [mean deviation (MD), pattern standard deviation (PSD) and visual field index (VFI)], Bruch's membrane opening minimal rim width (BMO-MRW), retinal nerve fiber layer thickness (RNFLT) and the stereometric parameters rim area, cup/disc area (HRT III, Heidelberg Retina Tomograph, Heidelberg Engineering) were tested for correlation with flow density data. The flow density (whole en face) in the retinal OCT angiograms (superficial: p = 0.01; deep: p = 0.005), in the radial peripapillary capillary network (p < 0.001) and in the OCT angiograms of the optic nerve head (p = 0.004) were significantly lower in the glaucoma group when compared with the control group. The flow density in the RPC network correlated significantly with all functional and structural parameters tested. The strongest correlation was found between the RPC flow density (inside disc) and the BMO-MRW (Spearman's correlation coefficient = 0.912, p < 0.001). Glaucoma patients showed a reduced ONH and macular perfusion when compared with healthy controls. The flow density as measured by OCTA correlated with structural damage and visual field loss in glaucoma patients. Non-invasive quantitative analyses of flow density using OCTA provide a new parameter describing a different aspect of glaucoma, which could be useful in clinical practice.