Question #517

The ophthalmic nerve is the first branch of the trigeminal nerve. It arises from the trigeminal ganglion and passes through the lateral wall of the cavernous sinus.

It divides into three main branches before entering the orbit through the superior orbital fissure:

1. Frontal nerve (further divides into supraorbital and supratrochlear branches)
2. Lacrimal nerve (communicates with the zygomatic nerve carrying post-ganglionic parasympathetic fibres to the lacrimal gland)
3. Nasociliary nerve (further divides into long and short ciliary branches, posterior and anterior ethmoidal branches and the infratrochlear nerve).

The nasociliary nerve passes through the tendinous ring of the orbit, the other two main branches do not.

The ophthalmic nerve picks up sympathetic fibres from the internal carotid artery sympathetic plexus in the cavernous sinus and carries these fibres via the ciliary ganglion and long ciliary nerves to the dilator pupillae and ciliary muscles.

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