Autoregulation of optic nerve head blood flow and its role in open-angle glaucoma

Abstract

Ocular blood flow is thought to play an important role in the development of primary open-angle glaucoma (POAG). Whereas there is a large body of evidence evaluating the role of static blood flow in POAG, a growing amount of research focuses on dynamic blood flow and glaucoma, specifically, the autoregulation of blood flow to ocular tissues and its dysfunction in POAG. Autoregulation is defined here as the maintenance of tissue perfusion in light of changes in vascular hemodynamics. This article reviews the clinical evidence of autoregulatory dysfunction in POAG patients and further focuses on the vascular anatomy, physiology and animal and human studies pertinent to the study of autoregulation and POAG.

Keywords::

• anatomy
• autoregulation
• blood flow
• glaucoma
• nocturnal hypotension
• optic nerve
• vasospasm

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Autoregulation is defined as the maintenance of tissue perfusion in light of changes in vascular hemodynamics.

• The association of glaucoma with low blood pressure, nocturnal hypotension and vasospastic entities indicate a potential association between poor autoregulation of blood flow and glaucomatous optic neuropathy.

• Optic nerve head (ONH) blood supply is divided into superficial nerve fiber layer, prelaminar, laminar and retrolaminar contributions. Different modalities of imaging focus on measuring different vascular beds contributing to ONH circulation.

• Vascular autoregulation of the optic nerve is theorized to be due to several potential mechanisms: myogenic, metabolic, endothelial, neurogenic or humoral.

• Evidence from animal and human studies show that autoregulation of blood flow to the optic nerve is impaired with short-term induction of high intraocular pressures.

• Human studies have studied autoregulation of ONH blood flow by using different experimental designs, including changes in posture, isometric exercise and change in intraocular pressure.

• Human studies on patients with glaucoma show impaired autoregulation of the vasculature of the ONH.

• Further studies are needed to determine whether impaired autoregulation is a risk factor for glaucoma development or if it is a result of glaucomatous optic neuropathy.