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Mydriasis

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Mydriasis, Pupil Dilation, Pupil Dilitation, Unilateral Dilated Pupil, Blown Pupil

  • See Also
  1. Pupil Disorder
  2. Pupil Constriction (Miosis)
  3. Anisocoria
  • Physiology
  • Normal Response
  1. Sympathetic stimulation
  2. Dark lighting conditions
  3. Images
    1. EyePupillaryReactionNeuroPath.png
    2. EyePupillaryReaction.png
  • Causes
  • Bilateral Dilated Pupil
  1. Carbon Monoxide Poisoning
  2. Hallucinogens (Ketamine, PCP)
  3. Medications and toxins (Mnemonic: AAAS)
    1. Affects may be asymmetric (see unilateral causes below)
    2. Atropine
    3. Anticholinergic Toxicity (e.g. Antihistamines)
    4. Antidepressants (and Serotonin Syndrome)
    5. Sympathomimetics (Cocaine, Amphetamines)
  • Causes
  • Unilateral Dilated Pupil
  1. See Also Anisocoria
  2. Comatose patient with non-reactive dilated pupil (Blown Pupil)
    1. Indicative of Brainstem Herniation
  3. Alert patient
    1. Not due to Increased Intracranial Pressure
    2. Acute Glaucoma
    3. Cranial Nerve III compression or paralysis
      1. Posterior Communicating Artery aneurysm
      2. Compression of third nerve (parasympathetic fibers) along its course (e.g. Cavernous Sinus)
    4. Mydriatic drug (e.g. Atropine)
      1. See Bilateral dilated pupil causes above
      2. Cyclopentolate (Cyclogyl)
        1. Commonly used for dilated Eye Exam (duration 6 to 24 hours, up to 2 days in some cases)
      3. Scopolamine
        1. Often used for perioperative Nausea (may result in Mydriasis in first postoperative 1-2 days)
        2. Consider returning travelers who used Motion Sickness patch
          1. Touching patch and then eye may result in Mydriasis
      4. Phenylephrine nasal spray
        1. May traverse lacrimal duct with unilateral effects
      5. Nebulized Ipratropium Bromide (Duoneb)
        1. Ill fitting nebulizer mask result in Mydriasis (typically unilateral)
  • Causes
  • Dilated pupil does not constrict with Pilocarpine
  1. Local Eye Trauma
  2. Topical Anticholinergic Agent present in eye