×
MedSchool: Ace Your OSCEsThe Medical Company
 
 
 
 
 
GET - On the App Store
View
Cranial Nerves
 
 

Pupillary Light Reflexes

 
 
 
Bookmark

Overview

The pupillary light reflexes rely on a reflex pathway with the optic nerve as the sensory nerve, the oculomotor nerve as the motor nerve and the midbrain as the processing centre.
  • 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
  • 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
Next Page
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Want more info like this?
  • Your electronic clinical medicine handbook
  • Guides to help pass your exams
  • Tools every medical student needs
  • Quick diagrams to have the answers, fast
  • Quizzes to test your knowledge
Sign Up Now
   
 
 

Snapshot: Initialising...