Different Sized Pupils

One in five people has one pupil that is smaller than the other, a condition known as ANISOCORIA. While most people with this sign are born that way, some develop it later in life.

The size of the pupils (the dark openings in the center of the eye through which light travels to the retina) is determined by the iris, which opens and closes to regulate the amount of light entering the eye. Pupils reach their peak size during our teen years ansd start shrinking until we are about 60. After that, they remain pretty much the same size.

Having different-size pupils is usually a normal inherited trait that generally does not cause any problems. But the pupil of one eye can change size as a result of physical trauma, or it can happen for no apparent reason (idiophatic). When such changes occur, they often revert back to normal on their own. Sometimes, however, a sudden change in the size of one pupil can signal a life-threatening condition such as a cerebral hemorrhage, brain tumor, meningitis, encephalitis, or aneurysm.

Seek immediate medical attention if you notice that you have two different-sized pupils in any of the following situations:

• After an eye or head injury
• Accompanied by a headache, nausea, vomiting, blurred vision, or double vision
• Accompanied by fever, light sensitivity, stiff neck, or headache that worsens when you bend forward
• Accompanied by severe eye pain and/or loss of vision