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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 extraocular muscles derive their origins.
There are three bony apertures that permit the entry of neurovasculature into the orbit:
Five of the six extraocular muscles originate at the orbital apex:
- superior rectus, inferior rectus, medial rectus, and lateral rectus from the annulus of Zinn, the common tendinous ring
- superior oblique from the lesser wing of the sphenoid bone just superior and medial to the common tendinous ring
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.
- 1. David L. Daniels, Peter Pech, Marilyn C. Kay, Kathleen Pojunas, Alan L. Williams, Victor M. Haughton. Orbital Apex: Correlative Anatomic and CT Study. AJNR Am J Neuroradiol. 1985;6(5):705-10. - Pubmed
- 2. D L Daniels, L P Mark, M F Mafee et al. Osseous Anatomy of the Orbital Apex. AJNR Am J Neuroradiol. 1995;16(9):1929-35. - Pubmed