Systemic and Ocular Hemodynamic Risk Factors in Glaucoma

Abstract

Primary open angle glaucoma (POAG) is a multifactorial disease characterized by progressive retinal ganglion cell death and visual field loss. It is known that alterations in intraocular pressure (IOP), blood pressure (BP), and ocular perfusion pressure (OPP) can play a significant role in the pathogenesis of the disease. Impaired autoregulatory capacity of ocular blood vessels may render tissues vulnerable to OPP changes and potentially harmful tissue ischemia-reperfusion damage. Vascular risk factors should be considered more important in a subgroup of patients with POAG, and especially in patients with normal tension glaucoma (NTG) with evidence of unphysiological BP response. For example, reduction of BP during the nighttime has an influence on OPP, and increased circadian OPP fluctuation, which might stand for unstable ocular blood flow, has been found to be the consistent risk factor for NTG development and progression. Central visual field may be affected more severely than peripheral visual field in NTG patients with higher 24-hour fluctuation of OPP. This review will discuss the current understanding of allegedly major systemic and ocular hemodynamic risk factors for glaucoma including systemic hypertension, arterial stiffness, antihypertensive medication, exaggerated nocturnal hypotension, OPP, and autonomic dysregulation.

Figure 1

Circadian mean ocular perfusion pressure (MOPP) fluctuation (CMF) in patients with normal tension glaucoma (NTG), classified by different blood pressure pattern (nondippers, dippers, and overdippers). Overdippers had a significantly larger CMF than did the other groups on post hoc comparison test (Dunnett's test; P = 0.007 between nondippers and overdippers, and P = 0.035 between dippers and overdippers). Error bars, 95% confidence interval (adapted from [72]).

Figure 2

Different vascular support system between macula and peripapillary area. (1) Macula is only supplied only by the single-layered perifoveal capillary arcade. (2) Peripapillary area had double-layered vascular support system which connects between radial peripapillary capillaries (RPC) in retinal nerve fiber layer and capillaries in ganglion cell layer. MOPP, mean ocular perfusion pressure (adapted from [73]).

Figure 3

Schematic representation on the complex relationships among various glaucoma risk factors. BP, blood pressure; IOP, intraocular pressure; OBF, ocular blood flow; HTN, hypertension; PVD, primary vascular dysregulation.