Change in size or shape of pupil

Many conditions and diseases can cause a change in the size or shape of your pupils. It may be one of the first symptoms or a later problem of the disease.

If you have any health risks, be sure to watch for any pupil change.

When you check the pupils, look for changes in the pupil reaction, such as changes in the size of the pupils or the way they react to light. These changes may be signs of a head injury and need to be reported to your health professional.

• Look carefully at both eyes to compare the pupils' size and shape.
  • Look at the pupils in low light. The pupils will be naturally slightly larger (dilated) in low light.
  • Make sure the light is shining evenly in both eyes.
• Use a flashlight or penlight to shine a beam of light in one eye at a time.
  • Each pupil should get smaller (constrict) when you shine the light in it.
  • The reaction should be the same on both sides (symmetric).
• Note whether the pupils' reaction has changed since the last time they were checked.

A change in your pupils with eye pain or vision loss is an emergency and you should call 911 immediately.