Anteriorly the superior orbital fissure is related to the annulus of Zinn (common tendinous ring) on which the four rectus muscles attach. The annulus splits the superior orbital fissure into three sectors: lateral, central (oculomotor foramen) and inferior.

It transmits the: infra-orbital nerve (from the maxillary division of trigeminal nerve) zygomatic nerve (from the maxillary division of trigeminal nerve) a branch of the inferior ophthalmic vein and several emissary veins connecting it to the pterygoid venous plexus.

This fissure, which separates the greater and lesser wings of the sphenoid and lies between the optic foramen and the foramen rotundum, provides passage to the three motor nerves to the extraocular muscles of the orbit: oculomotor nerve (CN III), trochlear nerve (CN IV), and abducens nerve (CN VI).

The order of the nerves passing through the superior orbital fissure from superior to inferior:

• L: lacrimal nerve (branch of CN V1)
• F: frontal nerve (branch of CN V1)
• T: trochlear nerve (CN IV)
• S: superior division of the oculomotor nerve (CN III)
• N: nasociliary nerve (branch of CN V1)

The inferior orbital fissure (IOF) lies in the floor of the orbit inferior to the superior orbital fissure and it is bounded superiorly by the greater wing of sphenoid, inferiorly by maxilla and orbital process of palatine bone and laterally by the zygomatic bone.

Important differentials to distinguish from superior orbital fissure syndrome are as follow (see Table 1 ): Orbital apex syndrome: where the main differentiator is optic nerve involvement , since both syndromes involve CN III, IV, VI, and the ophthalmic division of CN V (CNV-1) .

Inferior orbital fissure. The skull from the front. (Label for inferior orbital fissure is at center right.) The medial wall and the floor of the orbit are separated posteriorly by the inferior orbital fissure which transmits the zygomatic branch of the maxillary nerve and the ascending branches from the pterygopalatine ganglion.