<unk>  In both types of<unk> , decreased blood flow leads to the death of optic nerve cells. Ischemic injury to the optic nerve causes inflammation and swelling. Because the<unk>  optic nerve passes through the optic canal, a bony tunnel leading to the brain, swelling in this rigid space causes compression of the optic nerve. This compression worsens ischemia and perpetuates the cycle of injury, and swelling, and compression. A-PION A-PION is caused by an inflammatory disease called giant cell arteritis (GCA). GCA is an inflammatory disease of blood vessels. It is believed to be an autoimmune disease caused by inappropriate T-cell activity. When T-cells damage arteries supplying the optic nerve, a blood clot forms and stops blood flow. When blood flow stops, oxygen delivery stops and optic nerve fibers die. Perioperative<unk>  The exact cause of perioperative<unk>  is unknown. Many risk factors have been identified, all of which contribute to inadequate delivery of oxygen to optic nerve cells. Alone, none of these risk factors is enough to cause<unk> . However, in susceptible individuals, a combination of these risk factors produces devastating blindness. This evidence suggests that<unk>  is a disease of multifactorial origin. Risks of perioperative<unk>  can be divided into two categories, intraoperative ischemic pressures, and cardiovascular risk factors. Intraoperative ischemic pressures Many causes of decreased blood flow during surgery are systemic, i.e. they decrease blood flow throughout the body. Studies have shown that nearly all perioperative<unk>  patients suffered from prolonged periods of low blood pressure during the operation and postoperative anemia. The average perioperative<unk>  patient loses 4 liters of blood during surgery, and the majority receive blood transfusions. Massive blood loss is just one cause of low blood pressure. Medications used for general anesthesia can also lower blood pressure. The average surgery duration in<unk>  cases is 7 to 9 hours, which increases the risk of prolonged low blood pressure. Other intraoperative ischemic pressures are local, i.e. they decrease blood flow to the affected area, the optic nerve. Facial swelling, periorbital swelling, direct orbital compression, facedown position during surgery, and a tilted operating table in feet-above-head position, have all been reported to be associated with perioperative<unk> . All of these factors are believed to increase tissue pressure and venous pressure around the optic nerve, thereby decreasing local blood flow and oxygen delivery. Surgeries with the highest estimated incidence of<unk>  are surgeries with a higher risk of the aforementioned conditions. In spine surgery, patients are susceptible to significant blood loss, and they are positioned face down for long periods of time, which increases venous pressure, decreases arterial perfusion pressure, and often causes facial swelling (increased tissue pressure). Spine surgery is estimated to have the highest incidence of<unk> , 0.028%. Long duration of feet-above-head position in prostate surgery has also been suggested to increase risk of<unk> .
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