Pupil Response to Bright Light: How Your Eyes Adapt

The pupil is the black circular opening in the center of the iris of the eye that allows light to enter the eye. The size of the pupil is controlled by the iris, which is a muscular structure that surrounds the pupil. When you go from a dark room into bright light, the pupil constricts, or gets smaller, in order to reduce the amount of light that enters the eye. This helps to protect the retina, which is the light-sensitive tissue at the back of the eye, from being damaged by too much light.

The pupil also constricts when you focus on something up close. This is because the ciliary muscles in the eye contract, which causes the lens to change shape and become more rounded. This allows the eye to focus on objects that are close to the eye.

The pupil dilates, or gets bigger, when you go from a bright room into a dark room. This is because the ciliary muscles relax, which causes the lens to become less rounded. This allows the eye to focus on objects that are far away from the eye.