The optic nerve is responsible for the afferent limb of the pupillary reflex which senses the incoming light. The oculomotor nerve is responsible for the efferent limb of the pupillary reflex which drives the muscles that constrict the pupil.
The pupillary pathway consists of two pathways which are the afferent pupillary light reflex and efferent pupillary light reflex.
AFFERENT:
In afferent pathway, neural fibers that relay visual and pupillary afferent stimulus contain in the retina, optic nerve, optic chiasm and the optic tract. Therefore, any damage would affect both pupillary light reflex and visual function. Afferent pathway goes through the optic nerve, optic chiasm and optic tract. The pupillary fibers follow the optic tract till it reaches the lateral geniculate body. The signals will then enter the midbrain to pretectal nucleus where they synapse. Then pupillary fibers leaves the pretectal nucleus and spilt to the two edinger westphal nuclei. This tract is called tectotegmental tract which carries the pupillary fibers from both pretectal nuclei. Then both pupils will constrict in the consensual light reflex.
EFFERENT:
The efferent pathway begins at the edinger westphal nuclei. Efferent pathway fibers in inferior division will pass through the superior orbital fissure to ciliary ganglion where it synapse.
http://library.med.utah.edu/kw/hyperbrain/anim/reflex.html
