Fig. 19. Arterial supply of the orbit. A. The ophthalmic artery enters the orbit to give off its ocular supply, followed by branches to the extraocular muscles and lacrimal gland, finally ending superomedially as an extraorbital supply to the eyelids and glabella. B. Parasagittal arteriography view shows the ophthalmic artery (OA) branching from the internal carotid artery (ICA) just above the carotid siphon. Note that although the carotid siphon lies within the CS, the ophthalmic artery branches off just above the CS. The kink of the ophthalmic artery within the orbit indicates its course over the optic nerve from medial to lateral. C. Axial CT image. A fortuitous cut shows the ophthalmic artery looping over the optic nerve (large arrows). Small arrows indicate the ethmoidal arteries branching off the ophthalmic arteries to travel through the lamina papyracea. (A modified from Zide BM, Jelks GW: Surgical Anatomy of the Orbit, p 11. New York, Raven Press, 1985)