Microvasculature of the Optic Nerve Head and Peripapillary Region in Patients With Primary Open-Angle Glaucoma

Abstract

Purpose: To assess optic nerve head (ONH) and peripapillary microvasculature in primary open-angle glaucoma (POAG) of mild to moderate severity using swept-source optical coherence tomography angiography (OCTA). Materials and Methods: In a cross-sectional study, swept-source OCTA images were analyzed for 1 eye from each of 30 POAG patients with glaucomatous Humphrey visual field loss and 16 controls. The anatomic boundary of ONH was manually delineated based on Bruch’s membrane opening and large vessels were removed from en face angiography images to measure vessel density (VD) and the integrated OCTA by ratio analysis signal (IOS), suggestive of flow, in the ONH and peripapillary region. POAG subgroup analysis was performed based on a history of disc hemorrhage (DH) matched by visual field mean deviation (MD). Results: POAG (mean MD ± SD, −3.3 ± 3.0 dB) and control groups had similar demographic characteristics and intraocular pressure on the day of imaging. Groups did not differ in superficial ONH VD or flow indicated by IOS (P ≥ 0.28). POAG eyes showed significantly lower VD (39.4% ± 4.0%) and flow (38.8% ± 5.6%) in deep ONH, peripapillary VD (37.9% ± 2.9%) and flow (43.6% ± 4.0%) compared with control eyes (44.1% ± 5.1%, 44.7% ± 6.9%, 40.7% ± 1.7%, 47.8% ± 2.5%, respectively; P ≤ 0.007 for all). In the subgroup analysis, POAG eyes with (n = 14) and without DH (n = 16) had similar measured OCTA parameters (P > 0.99 for all). Conclusions: The image processing methodology based on the anatomic boundary of ONH demonstrated compromised microvasculature in the deep ONH and peripapillary region in eyes with mild to moderate POAG, regardless of the history of DH.

Signal Strength as an Important Factor in the Analysis of Peripapillary Microvascular Density Using Optical Coherence Tomography Angiography

“…Some investigators also reported that deep retinal layer and parapapillary choroidal microvasculature dropout is associated with RNFL thinning in primary open-angle glaucoma 13,19 . Other studies have reported a reduction in optic disc perfusion in glaucoma 10,12,14–18,30–32 . In addition, Wang et al .…”

Genome-wide meta-analysis identifies 127 open-angle glaucoma loci with consistent effect across ancestries

“…Also, dipyridamole, a 3′,5′-cyclic phosphodiesterase inhibitor, targets PDE7B and current clinical trials are testing therapies based on dipyridamole for diseases such as stroke, coronary heart disease, ischemia reperfusion injury, and internal carotid artery stenosis. Given that our pathway analyses highlighted the involvement of vasculature development and blood vessel morphogenesis in POAG pathogenesis, dipyridamole could be a potential therapy for POAG through modulation of blood flow, which can be defective in POAG 63 , 64 . Further studies to confirm the functionality of these POAG risk genes in vivo and in vitro may support the suitability of repurposing these drugs as alternative treatments for POAG.…”

The Neurovascular Unit in Glaucomatous Neurodegeneration

“…Of particular importance to the health of RGC axons is the microvascular perfusion at the ONH. In glaucoma there is a general compromise of the vasculature in the ONH and surrounding regions (Liu and Neufeld, 2000;Jia et al, 2012;Liu et al, 2015;Scripsema et al, 2016;Akil et al, 2017;Nascimento et al, 2019). Thus glaucoma is often associated with an unmet need for metabolites and O 2 due to insufficient blood flow, or 'ischemia' (Osborne et al, 2004;Kaur et al, 2008;Schmidt et al, 2008).…”

“…Thus glaucoma is often associated with an unmet need for metabolites and O 2 due to insufficient blood flow, or 'ischemia' (Osborne et al, 2004;Kaur et al, 2008;Schmidt et al, 2008). In fact, the posterior lamina is implicated as the primary site of disruption in glaucoma, and emerging studies show a significant decrease in vessel density and blood flow in POAG in the deeper layers of the ONH compared with controls (Nascimento et al, 2019). Microvascular density correlates with RGC axon volume across all areas at the ONH, but the correlation is greater at the posterior lamina cribrosa, further emphasizing the importance of changes in vascular parameters at this site (Kang et al, 2018).…”