Intrapapillary vessel density using optical coherence tomography angiography in primary open-angle glaucoma and normal eyes

Background: Optical coherence tomography angiography (OCTA) is used to quantify optic nerve blood flow in patients with primary open-angle glaucoma (POAG). Intrapapillary vessel density (iVD) has a high diagnostic accuracy for differentiating healthy from glaucomatous eyes. We compared the iVD of patients with POAG with that of healthy controls in an Egyptian tertiary referral center. Methods: This cross-sectional study consecutively recruited patients with medically controlled POAG and age- and sex-matched healthy individuals. All study participants underwent a detailed medical history evaluation and comprehensive ophthalmic examination, with recording of the cup-to-disc ratio (C/D ratio) and intraocular pressure (IOP). Humphrey visual field evaluation using the standard 24-2 program was performed and global indices, including mean deviation (MD) and pattern standard deviation (PSD), were extracted. OCTA and spectral-domain (SD) OCT images were obtained. Average thickness of the retinal nerve fiber layer (RNFL) and thicknesses in the superior, inferior, nasal, and temporal quadrants were recorded. OCTA imaging was used to measure vessel density, and the automatically processed data for iVD were extracted. Results: We included 86 eyes, 43 in the POAG and 43 in the healthy control group, with male predominance in both groups and mean (standard deviation [SD]) ages of 42.1 (9.4) and 39.3 (9.6) years, respectively. The two groups were comparable in terms of mean age, sex ratio, laterality of the included eyes, and mean IOP (all P > 0.05). The mean (SD) C/D ratio, MD, and PSD were significantly higher in the POAG group than in the control group (all P < 0.01). The mean (SD) average RNFL thickness and RNFL thicknesses in the four quadrants were significantly less in glaucomatous eyes than in healthy control eyes (all P < 0.05). Eyes with POAG had a significantly lower mean (SD) iVD than healthy control eyes (P < 0.01). Linear regression analysis revealed a significant positive correlation between iVD and average RNFL thickness (r = + 0.52; P < 0.001) and a significant negative correlation between iVD and PSD (r = - 0.31; P = 0.042) in eyes with POAG. Conclusions: The structural, vascular, and functional parameters measured in this study deteriorated in eyes with POAG compared to controls. Significant circumpapillary RNFL thinning correlated well with reduced iVD in eyes with POAG. Similarly, a lower iVD detected using OCTA had a significant inverse correlation with PSD in the perimetry of eyes with POAG. Further studies with additional parameters and longer follow-up periods are required to verify our preliminary findings.