Nasociliary nerve

The nasociliary nerve is the intermediate branch of the ophthalmic division of the trigeminal nerve.

Gross anatomy

The nasociliary nerve divides off the ophthalmic division just before entering the orbit through the superior orbital fissure and through the tendinous ring between the inferior and superior divisions of the oculomotor nerve. It courses from lateral to medial in the intraconal space superior to the optic nerve and between the superior oblique and medial rectus muscles giving off branches to the globe:

• small communicating branch to the ciliary ganglion
• short ciliary nerves
• long ciliary nerves

It then pierces the myofascial cone and in the extraconal space gives off three branches along the medial wall of the orbit:

• infratrochlear nerve
• posterior ethmoidal nerve
• anterior ethmoidal nerve (some authors describe this as the terminal branch or a continuation of the nasociliary nerve once it passes through the anterior ethmoidal foramen)