Absent Pupillary Light Reflexes
August 18th, 2017
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
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