Ophthalmology Book

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MiosisAka: Pupil constriction, Consensual Light Reaction, Near Reaction

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  1. Pupil constriction as a normal response
    1. Parasympathetic stimulation
    2. Near reaction (e.g. Reading)
      1. Pupil constriction mediated by Oculomotor Nerve
      2. Other changes with near reaction
        1. Eye convergence under Oculomotor Nerve control
        2. Accomodation (Lenses become more convex)
    3. Bright light results in bilateral pupil constriction
      1. Direct reaction to light in exposed eye
        1. Light strikes retina of affected eye
        2. Signal passed via Optic Nerve to midbrain
        3. Oculomotor Nerve signals same iris to constrict
      2. Consensual light reaction in opposite eye
        1. Midbrain receives signal from exposed eye
        2. Oculomotor Nerve sinals opposite iris to constrict
  2. Abnormal Causes
    1. Mnemonic: COPS
      1. Cholinergic Toxicity
      2. Clonidine
      3. Opiate overdose
        1. Responds to Naloxone (except synthetic opiates)
      4. Organophosphate Toxicity
      5. Phenothiazines
      6. Pilocarpine
      7. Pontine bleed or lesion
      8. Sedative hypnotics (Benzodiazepine)
    2. Horner's Syndrome

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