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My son was born with a smaller pupil than the other. Why and what is it?
Most children with unequal pupils do not have a serious underlying problem. A difference in pupil size can occur normally in about 20 percent of people, but this size difference is typically very small, on the order of one-half millimeter or so. When the pupils are of unequal size due to a disease process, the normal pupil may be the smaller one or may be the larger one, depending on the condition and the size difference is usually larger than that noted above. In most cases of unequal pupils that are due to a medical condition, there will be other abnormalities present that help to determine the cause of the problem. For example, a child with a small pupil on one side may also have droopy upper eye lid. A child with a large pupil on one side may not be able to move his eye properly. A visit to your pediatrician might help determine if there is a problem.
Answered by: David K. Coats, MD
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