In the orbit the ophthalmic artery gives off numerous branches as follows: the lacrimal artery, which arises from the ophthalmic artery on the lateral side of the optic nerve, and passes anteriorly on the lateral side of the orbit, supplying the lacrimal gland, muscles, the anterior ciliary branch to the eyeball, and the lateral sides of the eyelid; the central retinal artery, which enters the optic nerve, proceeds down the center of the nerve to the retina, and is clearly seen when viewing the retina with an ophthalmoscope—occlusion of this vessel or of the parent artery leads to blindness; the long and short posterior ciliary arteries, which are branches that enter the eyeball posteriorly, piercing the sclera, and supplying structures inside the eyeball; the muscular arteries, which are branches supplying the intrinsic muscles of the eyeball; the supra-orbital artery, which usually arises from the ophthalmic artery immediately after it has crossed the optic nerve, proceeds anteriorly, and exits the orbit through the supra-orbital foramen with the supra-orbital nerve—it supplies the forehead and scalp as it passes across these areas to the vertex of the skull; the posterior ethmoidal artery, which exits the orbit through the posterior ethmoidal foramen to supply the ethmoidal cells and nasal cavity; the anterior ethmoidal artery, which exits the orbit through the anterior ethmoidal foramen, enters the cranial cavity giving off the anterior meningeal branch, and continues into the nasal cavity supplying the septum and lateral wall, and ending as the dorsal nasal artery; the medial palpebral arteries, which are small branches supplying the medial area of the upper and lower eyelids; the dorsal nasal artery, which is one of the two terminal branches of the ophthalmic artery, leaves the orbit to supply the upper surface of the nose; and the supratrochlear artery, which is the other terminal branch of the ophthalmic artery and leaves the orbit with the supratrochlear nerve, supplying the forehead as it passes across it in a superior direction.
There are two venous channels in the orbit, the superior and inferior ophthalmic veins (Fig. 8.100).
The superior ophthalmic vein begins in the anterior area of the orbit as connecting veins from the supra-orbital vein and the angular vein join together. It passes across the superior part of the orbit, receiving tributaries from the companion veins to the branches of the ophthalmic artery and veins draining the posterior part of the eyeball. Posteriorly, it leaves the orbit through the superior orbital fissure and enters the cavernous sinus.
The inferior ophthalmic vein is smaller than the superior ophthalmic vein, begins anteriorly, and passes across the inferior part of the orbit. It receives various tributaries from muscles and the posterior part of the eyeball as it crosses the orbit.
The inferior ophthalmic vein leaves the orbit posteriorly by: joining with the superior ophthalmic vein, passing through the superior orbital fissure on its own to join the cavernous sinus, or passing through the inferior orbital fissure to join with the pterygoid plexus of veins in the infratemporal fossa.
Because the ophthalmic veins communicate with the cavernous sinus, they act as a route by which infections can spread from outside to inside the cranial cavity.
Numerous nerves pass into the orbit and innervate structures within its bony walls. They include the optic nerve [II], the oculomotor nerve [III], the trochlear nerve [IV], the abducent nerve [VI], and autonomic nerves. Other nerves such as the ophthalmic nerve [V1] innervate orbital structures and then travel out of the orbit to innervate other regions.