The pupil, the dark center of the eye, determines how much light reaches the light-sensing retina at the back of the eye. Muscles in the iris (the colored part of the eye) can tighten around the ...

The pupil is the opening located in the center of the iris of the eye. It controls the amount of light that enters the eye so that you can see clearly. The pupil size is controlled by muscles of ...

Pupil size is controlled by the brain, which receives signals from each retina and sends a message for your eyes to adjust to the light. Muscles in the colored part of your eye, your iris ...