Superior view of the right orbit with levator palpebrae superioris reflected. The orbital plate of the frontal bone and periorbita have been removed to reveal the contents of the orbit. The eyeball or globe occupies the anterior half of the orbit while the extraocular muscles, fat, and neurovascular elements populate the posterior half. The latter structures enter the apex of the orbit through the optic canal (for the optic nerve and ophthalmic artery) and the superior orbital fissure (for the oculomotor, trochlear, ophthalmic, and abducens nerves, and the superior ophthalmic vein). The optic nerve, developmentally a tract of the brain, is enclosed by meninges as the optic nerve sheath. The probe has reflected the levator palpebrae superioris and superior rectus muscles medially to better visualize the optic nerve, the ophthalmic artery, and the superior ophthalmic vein. The annulus of Zinn or tendinous ring is the whitish connective tissue that the recti muscles attach to at the orbital apex. The optic, oculomotor, abducens, and nasociliary nerves and the ophthalmic artery pass through this ring to enter the orbit. The lacrimal nerve, a branch of the ophthalmic nerve, courses along the lateral wall of the orbit in company with the lacrimal artery, a branch of the ophthalmic artery, and lacrimal vein, a tributary to the superior ophthalmic vein. They follow along the superior border of the lateral rectus muscle to the lacrimal gland. The frontal nerve (also reflected by the probe), a branch of the ophthalmic nerve, courses forward in the orbit superficial to the levator palpebrae superioris and superior rectus muscles. It subsequently divides into the supraorbital (the larger of the two) and supratrochlear branches. The supraorbital artery, a branch of the ophthalmic artery, follows the supraorbital nerve to the supraorbital notch or foramen. The major contents of the orbit are drained by the superior ophthalmic vein which passes posteriorly through the superior orbital fissure to the cavernous sinus. The medial wall of the orbit borders the lateral walls of the ethmoid and sphenoid sinuses. The latter is located beneath the planum sphenoidale. In this image, the floor of the right middle fossa (greater wing of the sphenoid) has been removed to expose the lateral pterygoid muscle and the associated pterygoid venous plexus. (Image courtesy of AL Rhoton, Jr.)