Overview Introduction Basic principle the parasympathetic and sympathetic nervous system control the pupil parasympathetic fibers lead to pupillary constriction (miosis) sympathetic fibers lead to pupillary dilation (mydriasis) as well as controlling the superior tarsal muscle elevates the upper lid smooth muscle orbitalis prevents eye sinking into the orbit facial and neck cutaneous arteries and sweat glands Miosis light enters the eye which activates retinal ganglion cells that will project axons into the optic nerve → optic chiasm → optic tract and then reach the pretectal nucleus fibers from the pretectal nucleus project to the Edinger-Westphal nucleus pre-ganglionic parasympathetic fibers exit the Edinger-Westphal nucleus and synapse in the ciliary ganglion post-ganglionic parasympathetic fibers from the ciliary ganglion innervate the pupillary constrictor muscles causing uniform bilateral miosis Mydriasis sympathetic fibers from many hypothalamic nuclei descend and reach T1 and T2 spinal cord levels pre-ganglionic sympathetic fibers exit the T1 and T2 spinal cord level to join the paravertebral sympathetic chain (via the white ramus) and synapse to the superior cervical ganglion post-ganglionic sympathetic fibers ascend via the carotid plexus of the internal carotid artery, goes through the cavernous sinus, and synapses to the pupillary dilator muscle Select Pupillary Defects Pupillary Defect Comments Horner syndrome Pathogenesis inolves impairment in sympathetic pathways to the eye and face which results in ptosis secondary to impaired innervation into the upper lid smooth muscles miosis secondary to impaired innervation into the pupillary dilator muscles anhidrosis Marcus Gunn pupil Describes an afferent pupillary defect resulting in the affected eye is not sensitive to the light there is minimal or absent pupillary constriction of the affected eye to light A lesion may affect eye retina optic nerve Afferent pupillary defects can be detected with swinging flashlight test which will show the affected pupil dilate when exposed to the penlight Argyll Robertson pupil A type of light-near dissociation where the eye does not constrict in response to light as much as it does with accomodation Associated with neurosyphilis Adie's myotonic pupil A type of light-near dissociation where the eye does not constrict in response to light as much as it does with accomodation Secondary to degeneration of the ciliary ganglion postganglionic parasympathetic neurons