Reginal Anatomy of the Orbit and Superior Orbital Fissure. A, The lesser wing of the sphenoid bone forming the roof of the superior orbital fissure has been removed to expose the contents of the fissure. The trochlear nerve and the frontal nerve, a branch of the ophthalmic division of the trigeminal nerve, enter the orbit through superior orbital fissure above the annular tendon. B, The orbital roof of the right orbit has been removed to expose the periorbita. At the superior orbital fissure, dura covering the middle fossa and cavernous sinus blends into the periorbita of the orbital apex and into the annular tendon from which the rectus muscle arises. The dura lining the superior orbital fissure and optic sheath blends into the periorbita. C, The periorbita has been opened and retracted laterally to expose the orbital fat, in which the trochlear, frontal, and lacrimal nerves course. D, The orbital fat has been removed. The ophthalmic nerve divides into the lacrimal, frontal, and nasociliary nerves. The trochlear nerve passes medially above the levator muscle to reach the superior oblique muscle. The tendon of the superior oblique muscle passes through the trochlea and below the superior rectus muscle to insert on the globe between the attachment of the superior rectus and lateral rectus muscles. The lacrimal nerve passes above the lateral rectus muscle to innervate the lacrimal gland. E, Enlarged view of the superior orbital fissure from above. The dura lining the right superior orbital fissure has been removed to expose the course of the trochlear nerve from the cavernous sinus to the orbit. (Images courtesy of AL Rhoton, Jr.)