Anisocoria is present when an individual's pupils differ in size. If a person's pupils are symmetric there is said to be isocoria.
Epidemiology
The prevalence of transient physiological anisocoria of >0.4 mm is found in up to 20% population. However persistent anisocoria seems to be rarer, in the same study it was only found in 3% subjects 1.
Pathology
Etiology
Most cases are benign, the two diagnoses of concern are third nerve palsy and Horner syndrome, each of which has multiple causes (see individual articles).
- third nerve palsy
- Horner syndrome
- medication: mydriatics (dilating agents) are more commonly the cause than miotics (constricting agents) 3
- mydriatics
- vasoconstrictors, hyoscine, glycopyrrolate antiperspirant, Jimson weed, angel's trumpet, blue nightshade
- miotics
- opiates, clonidine, organophosphates, pilocarpine, prostaglandins
- mydriatics
- physiological
- local pathology of the iris (rare) e.g. trauma