Fig. 46-8. Reflex pathways. A, the corneal reflex. Touching the cornea lightly results in bilateral blinking. The afferent limb is the ophthalmic nerve. The efferent limb is the facial nerve, which supplies the orbicularis oculi. B, the light reflex. The stimulus provided by light results in miosis (pupillary constriction). The afferent pathway is the optic nerve and tract, from the retina to the pretectal region of the midbrain. The efferent pathway is in the oculomotor nerve: parasympathetic fibers from the accessory oculomotor nucleus, synapsing in the ciliary ganglion, and supplying the sphincter pupillae. Because of contralateral connections, exposure of only one eye to light causes constriction of both pupils (consensual light reflex). E-W, accessory oculomotor nucleus of Edinger-Westphal. C, the accommodation reaction. The afferent pathway extends from the retina to the visual cortex, and then to the pretectal region. The efferent pathway, similar to that of the light reflex, ends in the ciliary muscle (accommodation for focusing on near objects), sphincter pupillae (miosis), and medial rectus (convergence of the eyes). D, the change in the lens (thickening) that occurs during accommodation. The pull of the ciliary muscle relaxes the zonular fibers and allows the lens to become more convex. Small pupils that react poorly to light, although the Accommodation Reaction is Present, may be found in neurosyphilis. The origin of this Argyll Robertson Pupil is unclear, although a lesion in the pretectum has been suggested. Click for high resolution image.