Anisocoria

Specialty: Neurology.

• pupillary asymmetry
• pupillary size difference

Why it occurs

• Physiological or essential anisocoria
• Third cranial nerve palsy (ischemic due to diabetes/hypertension or compressive due to aneurysm)
• Horner syndrome (dysfunction of the ocular sympathetic pathway)
• Adie's tonic pupil (postganglionic parasympathetic hypersensitivity)
• Direct ocular trauma with damage to the iris sphincter
• Exposure to pharmacological or chemical agents with unilateral anticholinergic or sympathomimetic activity

Initial workup

Pupillary examination in light and dark conditions to determine if asymmetry increases in scotopic or photopic conditions; pharmacological test with 0.5% apraclonidine eye drops or 4% cocaine (to confirm Horner syndrome), or diluted 0.1% pilocarpine (to identify Adie's pupil); computed tomography angiography (CT-Angio) or magnetic resonance angiography (MR-Angio) of the skull and neck if structural, aneurysmal pathology or arterial dissection is suspected.

Standard management

• Pilocarpine ophthalmic solution 0.1% or 1% — used in the diagnostic algorithm and therapeutically in selected cases of parasympathetic involvement
• Urgent endovascular or neurosurgical treatment in case of aneurysmal compression of the third cranial nerve.