Anisocoria is when your pupils are different sizes. The pupil is the black area at the center of the iris, the colored part of the eye. The pupil allows light to enter the retina, the light-sensitive tissue at the back of the eye.
Anisocoria is usually a condition that has no effect on the overall health of your eyes. This type is called physiologic anisocoria, and is a common condition, with as many as one in five people having some degree of difference in the size of their pupils. However, anisocoria can also be a symptom of a serious eye disorder, including third nerve cranial nerve palsy and Horner’s syndrome. Both are nervous system disorders that can occur when nerves that travel to the eye are damaged by a stroke, tumor or trauma. Anisocoria can also result from a viral infection, syphilis, surgical damage, and or another condition affecting the pupil called Adie’s tonic pupil.
Image courtesy of Steven A. Newman, MD.
Next Page: Anisocoria Symptoms