Nerves

Sensory innervation to the periorbital area is provided by the ophthalmic and maxillary divisions of CN V (Fig 1-10). After branching off at the trigeminal ganglion, the ophthalmic division of CN V travels in the lateral wall of the cavernous sinus, where it divides into 3 main branches: frontal, lacrimal, and nasociliary. The frontal nerve and lacrimal nerve enter the orbit through the superior orbital fissure above the annulus of Zinn (see Fig 1-6) and travel anteriorly in the extraconal fat to innervate the medial canthus (supratrochlear branch), upper eyelid (lacrimal and supratrochlear branches), and forehead (supraorbital branch). The nasociliary branch enters the orbit through the superior orbital fissure within the annulus of Zinn, entering the intraconal space and traveling anteriorly to innervate the eye via the ciliary branches. The short ciliary nerves penetrate the sclera after passing through the ciliary ganglion without synapse. The long ciliary nerves pass by the ciliary ganglion and enter the sclera, where they extend anteriorly to supply the iris, cornea, and ciliary muscle.

Figure 1-7 Side view of left orbit. AZ, annulus of Zinn; CG, ciliary ganglion; CS, cavernous sinus; ICA, internal carotid artery; IOM, inferior oblique muscle; IOV, inferior ophthalmic vein; IRM, inferior rectus muscle; LA, levator aponeurosis; LCT, lateral canthal tendon; LG, lacrimal gland; LM, levator muscle; LRM, lateral rectus muscle; Man., mandibular nerve; Max., maxillary nerve; MRM, medial rectus muscle; ON, optic nerve; Oph., ophthalmic nerve; PTM, pretarsal muscle; SG, sphenopalatine ganglion; SOM, superior oblique muscle; SOT, superior oblique tendon; SOV, superior ophthalmic vein; SRM, superior rectus muscle; STL, superior transverse ligament; T, trochlea; TG, trigeminal (Gasserian) ganglion; VV, vortex veins; 1, infratrochlear nerve; 2, supraorbital nerve and artery; 3, supratrochlear nerve; 4, anterior ethmoid nerve and artery; 5, lacrimal nerve and artery; 6, posterior ethmoid artery; 7, frontal nerve; 8, long ciliary nerves; 9, branch of CN III to medial rectus muscle; 10, nasociliary nerve; 11, CN IV; 12, ophthalmic (orbital) artery; 13, superior ramus of CN III; 14, CN VI; 15, ophthalmic artery, origin; 16, anterior ciliary artery; 17, vidian nerve; 18, inferior ramus of CN III; 19, central retinal artery; 20, sensory branches from ciliary ganglion to nasociliary nerve; 21, motor (parasympathetic) nerve to ciliary ganglion from nerve to inferior oblique muscle; 22, branch of CN III to inferior rectus muscle; 23, short ciliary nerves; 24, zygomatic nerve; 25, posterior ciliary arteries; 26, zygomaticofacial nerve; 27, nerve to inferior oblique muscle; 28, zygomaticotemporal nerve; 29, lacrimal secretory nerve; 30, lacrimal gland–palpebral lobe; 31, lateral horn of levator aponeurosis; 32, lacrimal artery and nerve terminal branches.

(Reproduced from Stewart WB, ed. Ophthalmic Plastic and Reconstructive Surgery. 4th ed. San Francisco: American Academy of Ophthalmology Manuals Program; 1984.)

Figure 1-8 Top view of left orbit. AZ, annulus of Zinn; CG, ciliary ganglion; CS, cavernous sinus; ICA, internal carotid artery; IRM, inferior rectus muscle; LA, levator aponeurosis; LG, lacrimal gland; LM, levator muscle; LRM, lateral rectus muscle; Man., mandibular nerve; Max., maxillary nerve; MRM, medial rectus muscle; ON, optic nerve; Oph., ophthalmic nerve; SG, sphenopalatine ganglion; SOM, superior oblique muscle; SOT, superior oblique tendon; SOV, superior ophthalmic vein; SRM, superior rectus muscle; STL, superior transverse ligament; T, trochlea; TG, trigeminal (Gasserian) ganglion; VV, vortex veins; 1, infratrochlear nerve; 2, supraorbital nerve and artery; 3, supratrochlear nerve; 4, anterior ethmoid nerve and artery; 5, lacrimal nerve and artery; 6, posterior ethmoid artery; 7, frontal nerve; 8, long ciliary nerves; 9, branch of CN III to medial rectus muscle; 10, nasociliary nerve; 11, CN IV; 12, ophthalmic (orbital) artery; 13, superior ramus of CN III; 14, CN VI; 15, ophthalmic artery, origin; 16, anterior ciliary artery; 17, vidian nerve; 18, inferior ramus of CN III; 19, sensory branches from ciliary ganglion to nasociliary nerve; 20, motor (parasympathetic) nerve to ciliary ganglion from nerve to inferior oblique muscle; 21, branch of CN III to inferior rectus muscle; 22, short ciliary nerves; 23, zygomatic nerve; 24, posterior ciliary arteries; 25, zygomaticofacial nerve; 26, nerve to inferior oblique muscle; 27, zygomaticotemporal nerve; 28, lacrimal secretory nerve; 29, lacrimal artery and nerve terminal branches.

(Reproduced from Stewart WB, ed. Ophthalmic Plastic and Reconstructive Surgery. 4th ed. San Francisco: American Academy of Ophthalmology Manuals Program; 1984.)

Figure 1-9 Periorbital and eyelid arteries, frontal view.

(Reproduced with permission from Dutton JJ. Atlas of Clinical and Surgical Orbital Anatomy. Philadelphia: Saunders; 1994.)

The muscles of facial expression, including the orbicularis oculi, procerus, corrugator supercilii, and frontalis muscles, receive their motor supply by way of branches of CN VII (the facial nerve) that enter on the undersurface of each muscle.

The parasympathetic innervation, which controls accommodation, pupillary constriction, and lacrimal gland stimulation, follows a complicated course. Parasympathetic innervation enters the eye as the short posterior ciliary nerves after synapsing within the ciliary ganglion. Parasympathetic innervation to the lacrimal gland originates in the lacrimal nucleus of the pons and eventually joins the lacrimal nerve to enter the lacrimal gland.

Sympathetic activity originates in the hypothalamus, with sympathetic fibers descending through the brainstem to the spinal cord, where they continue. Fibers destined for the orbit synapse in the ciliospinal center of Budge-Waller and then travel with branches of the carotid artery to enter the orbit. The sympathetic nerves carry innervation for pupillary dilation, vasoconstriction, smooth muscle function of the eyelids and orbit, and hidrosis. The nerve fibers follow the arterial supply to the pupil, eyelids, and orbit and travel anteriorly in association with the long ciliary nerves. Interruption of this innervation results in the familiar signs of Horner syndrome: ptosis of the upper eyelid, elevation of the lower eyelid, miosis, anhidrosis, and vasodilation. See Chapter 1 in BCSC Section 5, Neuro-Ophthalmology, for detailed discussion of neuro-ophthalmic anatomy.

Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.