Retinal vasculature in glaucoma: a review

Abstract

Despite the critical impact of glaucoma on global blindness, its aetiology is not fully characterised. Elevated intraocular pressure is highly associated with glaucomatous optic neuropathy. However, visual field loss still progresses in some patients with normal or even low intraocular pressure. Vascular factors have been suggested to play a role in glaucoma development, based on numerous studies showing associations of glaucoma with blood pressure, ocular perfusion pressure, vasospasm, cardiovascular disease and ocular blood flow. As the retinal vasculature is the only part of the human circulation that readily allows non-invasive visualisation of the microcirculation, a number of quantitative retinal vascular parameters measured from retinal photographs using computer software (eg, calibre, fractal dimension, tortuosity and branching angle) are currently being explored for any association with glaucoma and its progression. Several population-based and clinical studies have reported that changes in retinal vasculature (eg, retinal arteriolar narrowing and decreased fractal dimension) are associated with optic nerve damage and glaucoma, supporting the vascular theory of glaucoma pathogenesis. This review summarises recent findings on the relationships between quantitatively measured structural retinal vascular changes with glaucoma and other markers of optic nerve head damage, including retinal nerve fibre layer thickness. Clinical implications, recent new advances in retinal vascular imaging (eg, optical coherence tomography angiography) and future research directions are also discussed.

Greater Severity of Glaucomatous Damage in Eyes With Than Without Choroidal Microvasculature Dropout in Open-Angle Glaucoma

“…Numerous studies have suggested that both mechanical and vascular factors may be involved in glaucomatous pathogenesis. [7][8][9] Choroidal layer microvasculature within the peripapillary area is likely closely related to blood flow in ONH as this area mainly receives its blood supply from the short posterior ciliary (SPC) artery, which also provides a vascular network to deep ONH structures, such as prelaminar and laminar tissues. [10][11][12] Since CMvD may represent an area of reduced or absent perfusion within the parapapillary choroidal area next to ONH, 2,5 it could be an important indicator for disease severity when present, considering that glaucoma pathogenesis is closely linked to vascular insufficiency.…”

Elevated Intraocular Pressure Causes Abnormal Reactivity of Mouse Retinal Arterioles

“…Some authors even regard normal tension glaucoma as an ocular manifestation of a systemic vascular dysfunction, as reflected in the so called Flammer syndrome [32,33]. Other research groups found retinal vascular abnormalities in normal-tension and high-tension glaucoma patients, which include narrowing of retinal blood vessels, optic disc hemorrhage, and reduction of blood vessel density [12,34,35]. However, so far none of them has shown that increased IOP induces vascular dysfunction itself possibly triggering further IOP-independent RGC loss by means of vessel dysfunction.…”

Pressure Dependency of Retinal Arterial Pulse Wave Velocity in the Rat

“…These advantageous characteristics make the retina an ideal window to study not only ocular but also vascular related pathogenesis. Prior studies have provided strong evidence for retinal vascular changes in association with different types of disease including stroke [15], dementia [16], Alzheimer's disease [17], hypertension [18], aortic stiffness [19], diabetes [13], glaucoma [20], and sleep apnea [21]. In particular, retinal arteriolar narrowing, widening of retinal veins, and arteriovenous nipping are hypertensive retinopathy signs which have been evidenced to correlate with cardiovascular events [22][23][24].…”