Final answer:
The parasympathetic ganglion that serves the eye is the ciliary ganglion. It is located in the posterior orbit and controls pupillary size.
Step-by-step explanation:
The parasympathetic ganglion that serves the eye is the ciliary ganglion. This ganglion is one of the terminal ganglia of the parasympathetic system, located in the posterior orbit. The preganglionic parasympathetic fibers within cranial nerve III terminate in the ciliary ganglion, and the postganglionic parasympathetic fibers from the ganglion project to the iris to control pupillary size.