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Cranial Nerve III, IV and VI
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Testing Procedures – Response to Light

Stand or sit facing the patient in a darkened treatment area. Unilaterally test the pupillary response to light, but do not cover the other eye. Turn on the flashlight and then turn it towards the patient's eye for about 1 to 2 seconds using a quick lateral to medial movement. Repeat the above procedure twice for each eye to observe the direct response in the ipsilateral eye (CN II) and to observe the consensual responses in the contralateral eye (CN III), as pictured to the right. Document normal or abnormal responses.

Special Instructions or Considerations

  • A 20% variation in pupil size is normal
  • Do not startle the patient as this can lead to visual avoidance reactions
  • Light in one eye will produce pupillary constriction in the same eye (direct response) and pupillary constriction in the opposite eye (consensual response)
  • Turn on the light first and then point it in the patient's direction

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Section: Cranial Nerves III, IV and VI
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Page 4 of 15
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