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Superior Exposure of the Right Orbit

Surgical Correlation

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Superior exposure of the right orbit. The right orbital plate of the frontal bone and underlying periorbita have been removed as well as orbital fat in this dissection. In addition, superficially, the frontal nerve, a branch of the ophthalmic nerve, has been reflected laterally and a large section of the levator palpebrae superioris and superior rectus muscles have been resected. The muscle insertions into the upper eyelid and sclera, respectively, can be seen however. The frontal nerve divides into a larger supraorbital branch and a smaller supratrochlear branch. The optic nerve emerges from the back of the eyeball and courses posteromedially into the optic canals. The nerve is crossed by several structures, including the nasociliary branch of the ophthalmic nerve and the ophthalmic artery. The thin-walled larger diameter superior ophthalmic vein crosses more superficially and receives the lacrimal vein before exiting the superior orbital fissure to empty into the cavernous sinus. The ophthalmic artery supplies the eyeball and contents of the orbit. Branches shown here include the posterior ciliary to the eyeball and the lacrimal artery, which courses along the superior border of the lateral rectus muscle to the lacrimal gland in company with the vein and lacrimal nerve, also a branch of the ophthalmic nerve. The medial wall of the orbit is paper thin (lamina papyracea) and is made up principally by the orbital plate of the ethmoid bone. Medial to this plate are the ethmoid air cells or sinuses. Along the frontoethmoidal suture are foramina that transmit anterior and posterior ethmoidal neurovasculature to the ethmoid air cells and nasal cavity. In the midline is the crista galli that divides the cribriform plate into two fossae for the olfactory bulbs. Each bulb receives axons of olfactory neurofilaments from nasal olfactory epithelium. This sensory information is directed to the olfactory cortex via the olfactory tracts. The extraocular muscles that move the eyeball include the superior, inferior, medial, and lateral recti muscles, and the superior and inferior oblique muscles. The trochlear nerve supplies the superior oblique. It enters the apex of the orbit outside the annular tendinous ring medial to the frontal nerve and quickly enters the superior border of the muscle. The lateral rectus is supplied by the abducens nerve that passes through the ring and enters the medial surface of the muscle. The remaining muscles are supplied by the oculomotor nerve which also traverses the annular ring. It gives rise to two divisions: the superior division supplies the levator palpebrae superioris and superior rectus, the inferior division supplies the inferior and medial recti and the inferior oblique. (Image courtesy of PA Rubino)

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