Orbital Blood Vessels

Ophthalmic artery and its branches

• Orbital contents are mainly supplied by the ophthalmic artery and its branches

• Ophthalmic artery is the first branch from the internal carotid after it leaves the roof of the cavernous sinus

• Travels below the optic nerve in the optic canal, within dural sheath

• The central retinal artery (first branch) leaves while the ophthalmic lies inferolateral to the nerve

• The CRA continues below the nerve
• Pierces the dura 12mm behind the globe
• Gives off some small pial branches
• Then wraps around and passes above the optic nerve after entering the orbit

• The next branch is usually the lacrimal arising after the ophthalmic enters the orbit
• As above, this passes along the top of lateral rectus

• Supplies the lacrimal gland and gives rise to the lateral palpebral vessels (superior and inferior)

• The next are the posterior ciliary branches. These typically form as two initial branches which then divide into the long and short ciliary branches

• Long: paired long ciliary vessels pierce the sclera outside the circle of Zinn and travel in the suprachoroidal space to the ciliary body

• Contribute to major arterial arcade of the iris
• Supply the choroid anterior to the equator

• Short: short posterior ciliaries pierce the sclera around the optic nerve and form the anastomotic circle of Zinn supplying the intraocular part of the optic nerve

• Divide into 10-20 branches and the anterior branches supply the choroid posterior to the equator

• Subsequent branches are the muscular arteries

• Two arteries accompany each rectus muscles except the lateral rectus which receives just one

• These give rise to the anterior ciliary branches which supply the sclera and conjunctiva and contribute to the major arterial circle of the iris

• The supraorbital artery and posterior ethmoidal arteries arise after the ophthalmic artery passes over the optic nerve

• Supraorbital: muscles and skin of forehead
• Posterior ethmoidal: posterior ethmoidal sinuses and some intracranial meninges

• More anteriorly the anterior ethmoidal artery arises
• Supplies the anterior and middle ethmoidal and frontal sinuses

• Overall, the artery travels forward above medial rectus and below superior oblique
• At the trochlea, the medial palpebral arteries (superior and inferior) emerge
• Terminates in the dorsal nasal and supratrochlear (aka frontal) branches

Vortex veins

• On average, there are 6 vortex veins in each eye
• They drain the venous system of the choroid
• They emerge from the sclera posterior to the equator
• There are no anastomoses with the vortex veins

Inferior ophthalmic vein

• Receives drainage from the facial and angular veins
• Has fewer tributaries than the superior ophthalmic vein
• Travels above inferior rectus

• May join the superior ophthalmic but more usually drains directly into the cavernous sinus

• Communicates with the pterygoid plexus