Walsh & Hoyt: Posterior Ischemic Optic Neuropathy

Although the anterior form of ION is far more common than the posterior variety, ischemia of the retrobulbar portions of the optic nerve occurs in many settings, both arteritic and nonarteritic. Ischemia can independently affect the posterior portion of the optic nerve because of the distinct and separate arterial supplies of the anterior and posterior portions of the optic nerve. The anterior optic nerve is supplied by the short posterior ciliary artery and choroidal circulations, while the retrobulbar optic nerve is supplied intraorbitally by a pial plexus arising from the ophthalmic artery, and intracranially by branches of the ipsilateral internal carotid, anterior cerebral, and anterior communicating arteries.