emDOCs - February 13, 2023 - By Emilie Lothet; Aaron Lacy
Reviewed by: Jessica Pelletier; Marina Boushra
Pearls:
- Anisocoria can be classified into three groups based on pupillary reaction to light: (1) Physiologic anisocoria, ( (2) a pathologically large pupil, or (3) a pathologically small pupil
- Up to 30% of anisocoria is physiologic and asymptomatic, but this must be a diagnosis of exclusion.
- The most concerning cause of the pathologic large pupil is a cranial nerve III palsy, which can be a marker of compressive neoplasm or aneurysm.
- The most concerning cause of the pathologic small pupil is Horner syndrome, most commonly caused by carotid artery pathology.
- Pharmacologic evaluations can help differentiate between etiologies of anisocoria when the physical exam is inconclusive,with limitations in the emergency setting.