After furnishing a small twig to the dura mater, the ophthalmic division travels forwards in the lateral wall of the cavernous sinus, and enters the orbit through the medium of the sphenoidal (superior orbital) fissure. In the fissure it splits into three branches, namely the frontal, nasal (naso-ciliary), and lacrimal. The frontal and lacrimal nerves enter the orbit above the muscles, but the nasal nerve passes between the two heads of the lateral rectus.
In the Avail of the cavernous sinus, the ophthalmic division communicates with the sympathetic, oculo-motor, trochlear, and abducens nerves.
The Lacrimal Nerve passes along the outer part of the orbit to supply the lacrimal gland, conjunctiva, and skin of the upper eyelid.
The Frontal Nerve divides into the supra-orbital and supratrochlear which lie beneath the roof of the orbit. The former is the larger and is situated laterally to the supra-trochlear. It reaches the scalp by means of the supra-orbital notch, divides into medial and lateral, and communicates with the temporal branches of the facial nerve. The supra-trochlear runs above the pulley of the superior oblique muscle; it communicates with the infra-trochlear branch of the nasal. The frontal nerve is distributed to the mucous membrane of the frontal air sinus, and to the integument of the upper eyelid, forehead, and scalp.
The Nasal (Naso-Ciliary) Nerve crosses the optic nerve obliquely from the lateral to the medial side, lying under cover of the superior rectus and superior oblique muscles. After leaving the orbit by the anterior ethmoidal foramen, the nerve passes over the cribriform plate of the ethmoid and enters the nose through the nasal slit. In the nose the nerve gives off a medial branch to the nasal septum, and a lateral branch which reaches the face between the nasal bone and alar cartilage. It supplies the skin on the lower part of the side of the nose, communicating with the zygomatic branches of the facial.
Three branches arise from the nasal nerve in the orbit:-(a) a twig to the ciliary ganglion;(b) two long ciliary nerves to the eyeball; and (c) the infra-trochlear. which passes beneath the pulley of the superior oblique muscle to supply the skin of the medial parts of the eyelids and upper part of the nose. It communicates with the zygomatic branches of the facial nerve.