Anisocoria

Background

• Pupils of different sizes
• Usual pathophysiology includes imbalance of efferent autonomic nerves
  • Parasympathetic causes miosis/constriction and sympathetic causes mydriasis/dilatation
• Other cause is mechanical

Etiologies

• Greater difference in dim light
  • Horner syndrome, with ipsilateral miosis, ptosis, anhidrosis, enopthalmos, and lack of ciliospinal reflex
  • Cholinergic medications, such as pilocarpine to treat glaucoma
  • Posterior synechiae
• Greater difference in bright light
  • Cranial nerve III palsy, typically from compression of the third nerve inhibiting parasympathic fibres, and typically with ptosis, possibly "down and out" eye
    • May be caused by uncal brain herniation, usually with decreased level of consciousness
  • Migraine
  • Cycloplegic medications, such as atropine, cyclopentolate, and tropicamide
  • Sympathomimetics
  • Tonic pupil (Adie pupil), more common in young women and is benign
  • Traumatic mydriasis
• Equal difference in bright and dim light
  • Physiologic anisocoria