Ciliary Ganglion

The ciliary ganglion is a parasympathetic ganglion located in the posterior orbit. It measures 1–2 millimeters in diameter and contains approximately 2,500 neurons. Preganglionic axons from the Edinger-Westphal nucleus travel along the oculomotor nerve and form synapses with these cells. The postganglionic axons run in the short ciliary nerves and innervate two eye muscles:

• the sphincter pupillae constricts the pupil, a movement known as Miosis. The opposite, Mydriasis, is the dilation of the pupil.
• the ciliaris muscle contracts, releasing tension on the Zonular Fibers, making the lens more convex, also known as accommodation.

Both of these muscles are involuntary – they are controlled by the autonomic nervous system.

It is one of four parasympathetic ganglia of the head and neck. (The others are the submandibular ganglion, pterygopalatine ganglion, and otic ganglion).