Fibrous annulus of Zinn, or common tendinous ring, separates superior orbital fissure into two components.. Portion of orbital apex enclosed by annules is called "oculomotor foramen." Structures traveling outside this foramen are LMSFT (L = lacrimal nerve, M = branch of middle meningeal artery, S = superior ophthalmic vein, F = frontal nerve, T = trochlear nerve). Structures traveling within this foramen are NASO (N = nasociliary nerve, A = abducens nerve, S = sympathetic nerves, 0 = two divisions of oculomotor nerve: superior and inferior),, in addition to optic nerve and ophthalmic artery.