Blood supply and drainage of the eye
The eye is supplied by the ophthalmic artery, which is the first branch of the internal carotid artery, when it has travelled passed the cavernous sinus.
This artery arises from the ophthalmic artery near the optic canal. It runs with the lacrimal nerve to supply the lacrimal gland. The terminal branches of the artery pass through the lacrimal gland and supply the eyelids and conjunctiva as the lateral palpebral arteries, and pass medially to supply the upper and lower eyelids respectively. These arteries then anastomose with the medial palpebral artery and form a complete arterial circle.
The supraorbital artery arises from the ophthalmic artery just as it passes over the optic nerve, and runs forwards, along the medial border of levator palpebrae superioris and superior rectus muscles. It then passes through the supraorbital foramen in order to supply the:
levator palpebrae superioris
part of the scalp
Posterior ethmoidal artery
Once the ophthalmic artery reaches the medial wall of the orbit, it runs forwards and gives off the posterior ethmoidal artery. This artery enters the nasal cavity by passing through the posterior ethmoidal canal.
Anterior ethmoidal artery
This artery branches from the ophthalmic artery within the orbit, and accompanies the nasociliary nerve through the anterior ethmoidal foramen into the middle and anterior air cells as well as the frontal sinus.
Medial palpebral artery
This artery has two branches i.e. the superior and inferior palpebral arteries. They arise opposite the superior oblique muscle. They supply the upper and lower eyelids respectively.