Overview
Look For
- The size of the pupils (dilated, normal, constricted) and equality of size bilaterally.
Normal Pupillary Size
- In the dark: 4-8mm
- Under bright light: 2-4mm
Miosis
Miosis refers to pupillary constriction that is out of keeping with the level of light.
If not bilateral, miosis will present as anisocoria.
Causes of Bilateral Miosis
- Drugs - opiates, antipsychotics, acetylcholine, clonidine
- Intracranial haemorrhage
- Bilateral Horner's syndrome - autonomic dysfunction, amyloidosis, diabetes
Mydriasis
Look For
- Mydriasis refers to pupillary enlargement that is out of keeping with the level of light.
If not bilateral, mydriasis will present as anisocoria.
Causes of Bilateral Mydriasis
- Cerebral lesion - cerebral herniation, encephalitis, visual cortex infarct, tumour, trauma, multiple sclerosis
- Drugs - anticholinergics, SSRIs, SNaRIs, stimulants, barbiturates, methanol
- Brain stem death
Anisocoria
Look For
- Unequal pupils.
Ask about whether the patient has had unequal pupils in the past, or if they have an old ID photo to compare to.
Causes of Anisocoria
- Physiological (20% of the population)
- Migraine
- Post-ictal
- Horner's syndrome (unilateral)
- Drugs applied to one eye - pilocarpine, tropicamide, cocaine
- Intraocular conditions - glaucoma, retinal detachment
- Oculomotor (III) nerve lesion - nerve trauma, nerve compression, optic neuritis, Guillain barré
- Adie's tonic pupil
- CNS lesion - head trauma, intracranial tumour, subarachnoid haemorrhage, ischaemic stroke, multiple sclerosis
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