Here are some of the most common ones: Medications There's a wide variety of things that can cause dilated pupils. Anisocoria is benign and affects about 20 percent of the population. But typically, dilated pupils don’t respond normally to light.Ī large pupil that is completely unresponsive to light is called a 'fixed' dilated pupil.ĭilated pupils aren't the same as anisocoria, which is a common condition in which both pupils react normally to light but differ in size by about a half millimeter or more. To some degree, pupil size tends to get smaller with age.Ī dilated pupil sometimes can still react to light - that is, get smaller in bright light or when a light is shined at the eye.
Generally, normal pupils range in size from 2.0 to 4.0 millimeters (mm) in bright light, and 4.0 to 8.0 mm in the dark. In dim lighting, your pupils dilate (get larger) to allow more light in. In bright light, your pupils constrict (get smaller) to prevent too much light from entering your eyes.
The size of your pupils is controlled by muscles in the colored part of your eye (iris) and the amount of light reaching your eyes. Dilated pupils are pupils that are larger than normal in size.
