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Pupillary Examination

 
 
 
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Inspection of Pupils

  • Look For

  • The size of the pupils (dilated, normal, constricted) and equality of size bilaterally.
  • Normal Pupillary Size

  • In the dark - 4-8mm
  • Under bright light - 2-4mm
  • Causes of Bilateral Pupillary Dilation

  • Cerebral lesion - herniation, encephalitis, visual cortex infarct, tumour, trauma, MS
  • Drugs - anticholinergics, SSRIs / SNaRIs, stimulants, barbiturates, methanol
  • Brain stem death
  • Causes of Bilateral Pupillary Constriction

  • Drugs - opiates, antipsychotics, acetylcholine, clonidine
  • Intracranial haemorrhage
  • Horner’s syndrome (bilateral) - autonomic failure, amyloidosis, diabetes
  • Causes of Unequal Pupils (Anisocoria)

  • Physiological (20% of the population - compare with an old photo)
  • Migraine
  • Post-ictal
  • Horner’s syndrome (unilateral)
  • Drugs applied to one eye - pilocarpine, tropicamide, cocaine
  • Intraocular conditions - glaucoma, retinal detachment
  • Optic (II) or oculomotor (III) nerve lesion - trauma, compression, optic neuritis, Guillain barré
  • CNS lesion - trauma, tumour, haemorrhage, infarct, MS

Pupillary Light Reflexes

  • How to Elicit

  • Shine a light into each pupil. Watch to see that both the ipsilateral (direct response) and contralateral (consensual response) pupils constrict as a result of the stimulus.
  • Causes of Absent Pupillary Reflexes

  • Intraocular conditions - glaucoma, retinal detachment
  • Optic (II) nerve lesion - trauma, compression, optic neuritis
  • Midbrain lesion - encephalitis, tumour, trauma, haemorrhage, MS, midbrain infarct
  • Oculomotor (III) nerve lesion - trauma, compression, small vessel ischaemia, Guillain barré
  • Medications - sympathomimetic, parasympatholytic (anticholinergics), barbiturates, methanol
  • Interpretation

  • No direct response - absent reflex in the tested eyeIpsilateral oculomotor nerve (III) lesion
  • No consensual response - absent reflex in opposite eyeContralateral oculomotor nerve (III) lesion
  • No afferent response - absent reflex in one eye when testing either eyeIpsilateral optic nerve (II) lesion
  • No response - absent reflex in both eyes when testing either eyeMidbrain lesion, medications

Swinging Light Test

  • How to Perform

  • Shine a light into one eye, swing it into the other eye, and so on back and forth.
  • Interpretation

  • A relative afferent pupillary defect (RAPD) is present if the affected eye dilates, or constricts briefly followed by dilatation.
  • Causes of RAPD

  • Intraocular haemorrhage
  • Retinal detachment
  • Optic or oculomotor nerve lesion
  • Midbrain lesion

Accommodation

  • How to Assess

  • Ask the patient to focus on a distant object, such as the back wall of the room. Place a finger in front of their field of view and ask them to look at it.
  • Causes of Impaired Accommodation

  • Optic (II) nerve lesion - trauma, compression, optic neuritis
  • Thalamic / occipital / midbrain lesion - encephalitis, tumour, trauma, MS, midbrain infarct
  • Oculomotor (III) nerve lesion - trauma, compression, small vessel ischaemia, Guillain barré
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