What is anisocoria and why does it matter?

Anisocoria is characterized by pupils that are not the same size.  This is normal in about 20-percent of the population.  Many do not even realize it, and it is usually harmless.  But sometimes anisocoria is a symptom of a serious condition such as eye trauma, a concussion, bleeding around the brain, a brain tumor, or meningitis.  If you develop blurred or double vision, a severe headache, nausea, or fever, you should seek medical attention right away.