Anisocoria (IPA: /ænˌaɪsəˈkɔriə/) is a condition characterized by an unequal size of the eye’s pupils. Affecting 20% of population, it can be an entirely harmless condition or a symptom of more serious medical problems.
Anisocoria is a common eye condition defined by a difference of 0.4 mm or more between eye’s pupils. About 20% of people have a slight difference in pupil size which is known as physiologic anisocoria. In this condition the difference between pupils is usually less than 1 mm.
The condition can also become present due to a trauma suffered close to or on the eye, leaving one pupil permanently dilated, as seen with singer David Bowie, who got into a school-boy fight in 1962 over a girl resulting in his iconic appearance.