Orbital apex

The orbital apex refers to the posterior confluence of the orbit at the craniofacial junction, where nerves and vessels are transmitted from the intracranial compartment into the orbit via several bony apertures. It is also the point where the extra-ocular muscles derive their origins.

Contents

There are three bony apertures that permit the entry of neurovasculature in to the orbit:

• optic canal
• superior orbital fissure
• inferior orbital fissure

The four recti extra-ocular muscles originate from the orbital apex at the tendinous ring, surrounding the optic canal.

The key structures of the orbital apex have complex anatomical relations:

• the tendinous ring encircles the optic canal and medial portion of superior orbital fissure 
• the optic canal lies superomedial to the superior orbital fissure and is separated from it by the inferior root of the lesser wing of the sphenoid; it forms a 45° angle to the head in the sagittal plane and transmits the optic nerve and ophthalmic artery, passing through the tendinous ring
• the medial part of the superior orbital fissure transmits CN III, VI and nasociliary nerve through the tendinous ring; the superolateral part transmits the frontal and lacrimal nerve, CN IV and superior ophthalmic vein
• the inferior orbital fissure is located between the lateral wall and floor of the orbit, its long axis forming a 45° angle to the head in the sagittal plane; transmits the infra-orbital nerve, zygomatic nerve, infra-orbital artery and vein and the inferior ophthalmic vein.

Related pathology

• orbital apex syndrome
• orbital apex fracture