Walsh & Hoyt: Optic Nerve Blood Supply

Most of the optic nerve receives its blood from branches of the ophthalmic artery (OA), which is the first major branch of the internal carotid artery (ICA). The OA arises typically just above the exit of the ICA from the cavernous inus. The OA then passes through the optic canal below the optic nerve, although the artery is separated from the nerve by a dural sheath. Within the orbit, the ophthalmic artery gives rise to two or three posterior ciliary arteries (PCAs) and the CRA, which pierces the optic nerve approximately 12 mm behind the globe and then runs anteriorly within the optic nerve.