Can the iris of one eye be larger than the other?

I want to make sure that I answer the question that you are intending to ask. When people refer to the iris they sometimes mean the pupil, and at other times they really mean the cornea, the clear window on the front of the eye that you are looking through when you see the iris. No matter what you are referring to—pupils, irises, or the cornea—one can be larger than the other.

Unequal pupil size may be normal or abnormal. About 20 percent of people have differently sized pupils some of the time. The difference is usually very small and the size difference does not affect their vision. At other times, unequal pupil size can be a sign of a problem. In these cases the size difference is usually greater and there are often other signs present that suggest there is a problem. These other signs can include a droopy upper eye lid, outward deviation of an eye, and double or blurred vision.

A review of old photographs can help determine if the unequal size of the pupil is longstanding or recent. If it is a recent development or is associated with other symptoms, evaluation by an ophthalmologist is important.

The cornea and irises of the eyes can also be of unequal size from birth or acquired due to a disease. In fact, all parts of the eyes can be of unequal size. This generally is present from early childhood and when it is obvious that the eyes are of unequal size, an ophthalmologist should be consulted.