Anatomy

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Orbital Apex

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entry portal for all nerves and vessels to the eye and the site of origin of all extraocular muscles except the inferior oblique.

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The superior ophthalmic vein and the lacrimal, frontal, and trochlear nerves pass through the lateral portion of the fissure that lies outside the annulus of Zinn.

The superior and inferior divisions of the oculomotor nerve and the abducens and nasociliary nerves pass through the medial portion of the fissure within the annulus of Zinn.

The optic nerve and ophthalmic artery pass through the optic canal, which also lies within the annulus of Zinn

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Blood Supply

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The principal arterial supply of the orbit : ophthalmic artery( the first major branch of the intracranial portion of the internal carotid artery). This branch passes beneath the optic nerve and accompanies it through the optic canal into the orbit.

The first intraorbital branch is the central retinal artery, which enters the optic nerve . Other branches of the ophthalmic artery include the lacrimal artery, supplying the lacrimal gland and upper eyelid; muscular branches to the various muscles of the orbit; long and short posterior ciliary arteries; medial palpebral arteries to both eyelids; and the supraorbital and supratrochlear arteries.

The short posterior ciliary arteries supply the choroid and parts of the optic ner ve. The two long posterior ciliary arteries supply the ciliary body and anastomose with each other and with the anterior ciliary arteries to form the major arterial circle of the iris.

The anterior ciliary arteries are derived from the muscular branches to the rectus muscles. They supply the anterior sclera, episclera, limbus, and conjunctiva and contribute to the major arterial circle of the iris.

The most anterior branches of the ophthalmic artery contribute to the formation of The most anterior branches of the ophthalmic artery contribute to the formation of the arterial arcades of the eyelids, which make an anastomosis with the external carotid circulation via the facial artery

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