Ischemic optic neuropathy [Neurosurgery Wiki]

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====== Ischemic optic neuropathy ======

Ischemic [[optic neuropathy]] is the most common cause of the very uncommon [[postoperative visual loss]]. 

Often bilateral. 
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Elevated [[ICP]] transmits pressure to [[retina]] → [[blood flow]] stasis, as well as mechanical trauma to optic chiasm from enlarging [[third ventricle]] (latter more commonly thought to be responsible for [[bitemporal hemianopia]], but could, if unchecked, progress to complete [[visual loss]]). Also, if [[hypotension]] and [[anemia]] were present, consider the possibility of ischemic [[optic neuropathy]], which may be anterior, or posterior (the latter of which carries a poorer prognosis).

If [[hypotension]] and [[anemia]] were present, consider the possibility of ischemic [[optic neuropathy]],

Usually associated with significant blood loss (median: 2 L), and/or prolonged [[operative time]] ( ≥ 6 hrs ). 

All cases had anesthetic time > 5 hrs or blood loss > 1 L. [[Blood loss]] can cause [[hypotension]] (may cause release of endogenous [[vasoconstrictor]]s in addition to reduced blood flow due to low hemodynamic pressure) and increased [[platelet aggregation]]. It is not due to direct pressure on the globe in most cases, and can occur at any [[age]] and even in otherwise healthy patients. No association with age, HTN,[[atherosclerosis]], [[smoking]] or [[DM]].

===== Classification =====

[[Anterior ischemic optic neuropathy]].

[[Posterior ischemic optic neuropathy]] (carries a poorer [[prognosis]]).