The pupillary light reflex is assessed by shining a light into each eye and observing the pupils' reaction. Here's how to do it:
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Darken the Room: Reduce ambient lighting to allow for better pupil dilation.
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Instruct the Patient: Ask the patient to look straight ahead at a distant object. This helps prevent accommodation, which can affect pupil size.
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Shine the Light: Bring a penlight in from the side of the patient's face, shining it directly into one eye.
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Observe Direct Response: Observe the pupil of the eye you're shining the light into (the direct response). It should constrict (get smaller).
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Observe Consensual Response: Observe the pupil of the other eye (the consensual response or indirect response). It should also constrict.
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Repeat on the Other Eye: Repeat steps 3-5 for the other eye.
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Note the Dilation: After shining the light, observe that both pupils dilate again once the light is removed.
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Assess Equality and Size: Note whether the pupils are equal in size (anisocoria is the term for unequal pupils) and their approximate size in millimeters.
Key Observations:
- Direct Response: Pupil constriction in the eye the light is shone into.
- Consensual Response: Pupil constriction in the opposite eye.
- Pupil Size: Normal pupil size varies, but generally ranges from 2-4 mm in bright light and 4-8 mm in dim light.
- Equality: Pupils should be approximately equal in size.
- Speed of Response: Pupils should constrict and dilate briskly. Sluggish or absent responses can indicate neurological issues.
If either pupil fails to constrict appropriately or if there is a significant difference in pupil size, this may indicate a neurological problem and warrants further investigation.
