Investigation of the peripapillary microvasculature in normal tension glaucoma, primary open angle glaucoma, and normal eyes

Purpose: To quantitatively evaluate the peripapillary microvasculature in normal tension glaucoma (NTG), primary open angle glaucoma (POAG) and control eyes using optical coherence tomography angiography (OCTA). Methods: OCTA images of the peripapillary area were acquired using the Zeiss Plex Elite 9000 from 3 groups: POAG (n=30), NTG (n= 30) and normal controls (n=30). Five repeat 3x3mm scans were acquired both nasally and temporally to the optic disc and subsequently averaged. A fully automated machine learning segmentation tool was used to evaluate the superficial and deep retinal vessel density (VD). Additionally, four choriocapillaris flow deficit (FD) measures were calculated using the fuzzy C-means approach: FD density (FDD), mean FD size (MFDS), FD number (FDN), and FD area (FDA). Results: The POAG and NTG eyes exhibited a lower superficial VD than the control eyes (p < 0.01) nasal to the optic disk. The NTG eyes showed a statistically significant increase in FDD (NTG: 5.04 u00b1 2.38 %, Control: 3.79 u00b1 1.26 %), FDN (NTG: 185.90 u00b1 56.66, Control: 156.43 u00b1 38.44), and FDA (NTG: 0.30 u00b1 0.14 mm2, Control: 0.22 u00b1 0.08 mm2) nasal to the optic disc compared to normal controls (p < 0.05). Conclusions: POAG and NTG eyes exhibited a lower superficial VD than the control eyes. While the NTG eyes had significantly higher FDD, FDN and FDA nasal to the optic disc than control eyes. Further studies investigating the influence of the microvasculature on the underlying pathophysiology of NTG subjects are warranted.