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Absent Pupillary Light Reflexes



  • 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
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