• 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
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

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