Glaucoma is increasingly becoming recognized as a manifestation of both ocular and systemic risk factors. Risk factors in addition to intraocular pressure (IOP) are increasingly being identified and play a critical role in the development and/or progression of glaucoma. Particularly in the lower ranges of IOP, a number of disorders associated with reduced blood flow and ischemia, collectively termed vascular risk factors, such as migraine, Raynaud's phenomenon, atrial fibrillation, and reduced nocturnal blood pressure, lead to decreased ocular perfusion pressure. During sleep, alterations occur in cardiovascular physiology that are balanced by auto-regulatory mechanisms to maintain homeostasis. However, in obstructive sleep apnea (OSA), the normal physiologic balance is upset, leading to hypoxia and sympathetic activation. OSA can range from mild to severe, and, therefore, its associations and their severity may depend on the severity of the sleep apnea. A potentially modifiable systemic risk factor, OSA has recently been increasingly associated with glaucoma, is independent of IOP. Through hypoxia-mediated damage to blood vessels and their compensatory mechanisms, OSA may alter blood flow to the optic nerve head and, in combination with other predisposing factors, lead to decreased ocular perfusion pressure. This in turn may directly affect the optic nerve or it may indirectly increase its susceptibility to other insults. The purpose of this review is to shed light on the association between OSA and glaucoma. © 2012 The Authors. Journal compilation © 2012 Royal Australian and New Zealand College of Ophthalmologists.
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