Oblique MusclesThere are two oblique muscles – the superior and inferior obliques. Unlike the recti group of muscles, they do not originate from the common tendinous ring.Superior ObliqueAttachments: Originates from the body of the sphenoid bone. Its tendon passes through a trochlear, and then attaches to the sclera of the eye, posterior to the superior rectus.Actions: Depresses, abducts and medially rotates the eyeball.Innervation: Trochlear nerve (CN IV).Inferior ObliqueAttachments: Originates from the anterior aspect of the orbital floor. Attaches to the sclera of the eye, posterior to the lateral rectusActions: Elevates, abducts and laterally rotates the eyeball.Innervation: Oculomotor nerve (CN III).
Nerves of the Orbit A. Ophthalmic nerve Enters the orbit through the superior orbital fissure and divides into three branches: 1. Lacrimal nerve Enters the orbit through the superior orbital fissure. Enters the lacrimal gland, giving rise to branches to the lacrimal gland, the conjunctiva, and the skin of the upper eyelid. 2. Frontal nerve Enters the orbit through the superior orbital fissure. Runs superior to the levator palpebrae superioris. Divides into the supraorbital nerve , which passes through the supraorbital notch or foramen and supplies the scalp, forehead, frontal sinus, and upper eyelid, and the supratrochlear nerve, which passes through the trochlea and supplies the scalp, forehead, and upper eyelid.
3. Nasociliary nerve Is the sensory nerve for the eye, enters the orbit through the superior orbital fissure. Gives rise to the following: A communicating branch to the ciliary ganglion. Short ciliary nerves , which carry postganglionic parasympathetic and sympathetic fibers to the ciliary body and iris . Long ciliary nerves , which transmit postganglionic sympathetic fibers to the dilator pupillae. The posterior ethmoidal nerve , which passes through the posterior ethmoidal foramen to the sphenoidal and posterior ethmoidal sinuses. The anterior ethmoidal nerve , which passes through the anterior ethmoidal foramen to supply the anterior ethmoidal air cells. It divides into internal nasal branches , which supply the septum and lateral walls of the nasal cavity, and external nasal branches , which supply the skin of the tip of the nose. The infratrochlear nerve , which innervates the eyelids, conjunctiva, skin of the nose, and lacrimal sac.
B. Optic nerve Consists of the axons of the ganglion cells of the retina and leaves the orbit by passing through the optic canal. Carries Special Sensory fibers for vision from the retina to the brain and mediates the afferent limb of the pupillary light reflex. Joins the optic nerve from the corresponding eye to form the optic chiasma. C. Oculomotor nerve Leaves the cranium through the superior orbital fissure. Divides into a superior division , which innervates the superior rectus and levator palpebrae superioris muscles, and an inferior division , which innervates the medial rectus, inferior rectus, and inferior oblique muscles. Its inferior division also carries preganglionic parasympathetic fibers to the ciliary ganglion.
Blood Vessels of the Orbit A. Ophthalmic artery Is a branch of the internal carotid artery and enters the orbit through the optic canal beneath the optic nerve. Gives rise to the ocular and orbital vessels , which include the following: 1. Central artery of the retina Is the most important branch of the ophthalmic artery. Travels in the optic nerve; it divides into superior and inferior branches to the optic disk, Its an end artery that does not anastomose with other arteries, and thus its occlusion results in blindness. 2. Long posterior ciliary arteries Pierce the sclera and supply the ciliary body and the iris. 3. Short posterior ciliary arteries Pierce the sclera and supply the choroid.
4. Lacrimal artery Passes along the superior border of the lateral rectus and supplies the lacrimal gland, conjunctiva, and eyelids. 5. Medial palpebral arteries Contribute to arcades in the upper and lower eyelids. 6. Muscular branches Supply orbital muscles and give off the anterior ciliary arteries, which supply the iris. 7. Supraorbital artery Passes through the supraorbital notch (or foramen) and supplies the forehead and the scalp. 8. Posterior ethmoidal artery Passes through the posterior ethmoidal foramen to the posterior ethmoidal air cells.
9. Anterior ethmoidal artery Passes through the anterior ethmoidal foramen to the anterior and middle ethmoidal air cells, frontal sinus, nasal cavity, and external nose. 10. Supratrochlear artery Passes to the supraorbital margin and supplies the forehead and the scalp. 11. Dorsal nasal artery Supplies the side of the nose and the lacrimal sac.
B. Ophthalmic veins 1. Superior ophthalmic vein Is formed by the union of the supraorbital, supratrochlear, and angular veins. Receives branches corresponding to most of those of the ophthalmic artery and, in addition, receives the inferior ophthalmic vein before draining into the cavernous sinus. 2. Inferior ophthalmic vein Begins by the union of small veins in the floor of the orbit. Communicates with the pterygoid venous plexus and often with the infraorbital vein and terminates directly or indirectly in the cavernous sinus.