The colored part of the eye surrounding the pupil is called the iris. It automatically regulates the amount of light entering the eyes by regulating the size of the pupil. Light is the primary ...

The black circle in the center of your eye is your pupil. It changes size thousands of times a day. When you're in dim light, it gets bigger to let more light in. When you're in bright light, it ...

The iris is a structure behind the transparent cornea of the eye. It has a circular opening called the pupil that changes size in response to the light level. Your pupils are usually the same size as ...