Anisocoria is the condition where the pupils, or the black part of the eyes, are of different sizes. Normally, pupils are equal in size, but in this condition, they are unequal. This can often develop due to damage to the nerve pathways.

The pupil changes size in response to changes in light. In bright light, the pupils constrict (become smaller), and in low light they dilate (become larger). Pupils naturally vary in size throughout the day. However, if one pupil suddenly becomes significantly larger than the other, you should see an ophthalmologist. This condition can lead to serious complications in the long term.