2020–2021 BCSC Basic and Clinical Science Course™
7 Oculofacial Plastic and Orbital Surgery
Part I: Orbit
Chapter 1: Orbital Anatomy
Inferior Orbital Fissure
The inferior orbital fissure is bounded by the sphenoid, maxillary, and palatine bones and lies between the lateral orbital wall and the orbital floor. It transmits the second (maxillary) division of CN V, including the zygomatic nerve, and branches of the inferior ophthalmic vein leading to the pterygoid plexus. The maxillary nerve (V2) exits the skull through the foramen rotundum and travels through the pterygopalatine fossa to enter the orbit at the infraorbital groove. After giving off the zygomatic branch, the nerve becomes the infraorbital nerve and travels anteriorly in the floor of the orbit through the infraorbital canal, emerging on the face of the maxillary bone 1 cm below the inferior orbital rim. The infraorbital nerve carries sensation from the lower eyelid, cheek, upper lip, upper teeth, and gingiva.
Figure 1-4 View of orbital apex, right orbit. The ophthalmic artery enters the orbit through the optic canal, whereas the superior and inferior divisions of cranial nerve (CN) III, CN VI, and the nasociliary nerve enter the muscle cone through the oculomotor foramen. CN IV, the frontal and lacrimal nerves, and the ophthalmic vein enter through the superior orbital fissure and thus lie within the periorbita but outside the muscle cone. Note that the presence of many nerves and arteries along the lateral side of the optic nerve mandates a superonasal surgical approach to the optic nerve in the orbital apex.
(Illustration by Cyndie C. H. Wooley.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.