<unk>  is a watershed infarction of the optic nerve that may cause either unilateral or, more often, bilateral blindness.<unk>  typically occurs in two categories of people: * People who have undergone non-ocular surgery that is particularly prolonged or is associated with a significant blood loss. * People who have experienced significant bleeding from an accident or ruptured blood vessels. In these cases, the person may develop anemia (too few oxygen-delivering red blood cells in the bloodstream) and often have low blood pressure as well. This combination can produce circulatory shock, and<unk>  has sometimes been called shock-induced optic neuropathy. The combination of anemia and low blood pressure means that the blood is carrying less oxygen to the tissues. The optic nerve can be at very high risk for damage from insufficient blood supply due to swelling (from lack of oxygen) in a confined bony space resulting in a compartment syndrome. Restricted blood flow can lead to permanent damage to the optic nerve and result in blindness (often in both eyes). For technical reasons this occurs more frequently with spinal surgeries. Cardiovascular risk factors Perioperative<unk>  patients have a higher prevalence of cardiovascular risk factors than in the general population. Documented cardiovascular risks in people affected by perioperative<unk>  include high blood pressure, diabetes mellitus, high levels of cholesterol in the blood, tobacco use, abnormal heart rhythms, stroke, and obesity. Men are also noted to be at higher risk, which is in accordance with the trend, as men are at higher risk of cardiovascular disease. These cardiovascular risks all interfere with adequate blood flow, and also may suggest a contributory role of defective vascular autoregulation. Perioperative<unk>  As illustrated by the risk factors above, perioperative hypoxia is a multifactorial problem. Amidst these risk factors it may be difficult to pinpoint the optic nerve's threshold for cell death, and the exact contribution of each factor. Low blood pressure and anemia are cited as perioperative complications in nearly all reports of<unk> , which suggests a causal relationship. However, while low blood pressure and anemia are relatively common in the perioperative setting,<unk>  is exceedingly rare. Spine and cardiac bypass surgeries have the highest estimated incidences of<unk> , 0.028% and 0.018% respectively, and this is still extremely low. This evidence suggests that optic nerve injury in<unk>  patients is caused by more than just anemia and low blood pressure. Evidence suggests that the multifactorial origin of perioperative<unk>  involves the risks discussed above and perhaps other unknown factors. Current review articles of<unk>  propose that vascular autoregulatory dysfunction and anatomic variation are under-investigated subjects that may contribute to patient-specific susceptibility.
Posterior ischemic optic neuropathy
Anterior ischemic optic neuropathy
Ischemic optic neuropathy
Arteritic anterior ischemic optic neuropathy
Optic neuritis
Autoimmune optic neuropathy
Retinal vasculitis
Toxic and nutritional optic neuropathy