Orbital fissures and foramina

The orbital fissures and foramina are the round and longitudinal (cleft-like) openings found in the bony structure of the human eye orbit (socket). The different blood vessels and nerves run through these small clefts and round orifices in order to supply, innervate, and drain the eyeball and lacrimal gland. The human orbit, or eye socket, has two important fissures and three foramina, which are described as canals.

Fissures

The superior orbital fissure– It is located between the greater and lesser wings of the sphenoid bone, just lateral to the optic canal. This small cleft in the orbit allows the branches of the oculomotor nerve (CN-III), the trochlear nerve (CN-IV), the abducent nerve (CN-VI), nasociliary, frontal and lacrimal branches of the ophthalmic nerve (CN-V), and the superior ophthalmic vein to go through.

The inferior orbital fissure– It is a cleft that lies between the sphenoid bone and the maxillary bone, keeping apart the lateral wall of the orbit and the floor of the orbit. It lets the maxillary nerve and its zygomatic branch, and the infra-orbital vessels go through.

Foramina

Optic canal– It is a round opening lying at the apex of the pyramidal-shaped orbit. It is surrounded by the body and the lesser wing of the sphenoid bone. The optic canal allows the passage of the optic nerve and the ophthalmic artery which supplies the eye.

Infraorbital canal– It is an opening in the maxillary bone in the floor of the orbit which opens onto the face (anterior surface of the body of the maxillary bone) as the infraorbital foramen, right below the orbit. A branch of the maxillary nerve and blood vessels go through it.

Nasolacrimal canal– It lies between the maxilla, lacrimal bone, and the inferior nasal concha. It allows the passage of the nasolacrimal duct, through which the tears run from the lacrimal sac into the nasal cavity.

An schematic image of the eye socket, showing its orbital fissures and foramina. The nasolacrimal canal is not labeled. It lies on the medial side of socket between the lacrimal bone and inferior nasal concha.