Optical coherence tomography angiography of the peripapillary capillaries in primary open-angle and normal-tension glaucoma

Objectives To evaluate the vascular architecture of the radial peripapillary capillaries (RPCs) and its relation with visual function in patients with open-angle glaucoma (OAG) and normal-tension glaucoma using spectral-domain optical coherence tomography (SD-OCT) angiography. Subjects and methods Clear OCT angiography images of blood vessels in the optic disc and peripapillary retina were obtained from 52 patients (52 eyes) aged 55.42 +/- 10.64 (range 28-72) years with primary OAG. The mean spherical equivalent was -3.19 +/- 2.31 diopters, and the mean deviation (MD) of the central 24/30-2 threshold test using the Humphrey Field Analyzer (HFA) was -10.47 +/- 7.99 dB. The correlations between the disappearance angle of the RPCs on OTC images, flow density (FD) and the circumpapillary retinal nerve fiber layer (cpRNFL) thickness, the angle of retinal nerve fiber layer (RNFL) defect, the MD and pattern standard deviation (PSD) values of the HFA central 24/30-2 threshold test using the Swedish interactive thresholding algorithm, the sensitivity threshold, age, corneal thickness, and refractive value were analyzed. In addition, the correlation between FD and the cpRNFL thickness was analyzed at FD measurement points. Results FD was significantly correlated with cpRNFL thickness, PSD value, MD value, and sensitivity threshold, whereas the disappearance angle of the RPCs was significantly correlated with the angle of the RNFL defect (P < 0.001), MD value (P < 0.01), and sensitivity threshold (P < 0.01). There was a negative correlation between FD and age (P < 0.05). The Pearson correlation coefficient of FD and cpRNFL thickness in the area surrounding the optic disc revealed the most significant correlation in the inferior visual field (r = 0.851, P < 0.001), followed by the superior visual field (r = 0.803, P < 0.001) and then the temporal visual field (r = 0.653, P < 0.001). Conclusion SD-OCT angiography enabled thorough observation of the RPCs. FD and the disappearance angle of the RPCs were significantly and independently correlated with glaucomarelated functional and morphological changes in the optic nerve, suggesting that these two factors are novel functional and morphological indicators of visual defects due to glaucoma.