Cognitive behavioral therapy (CBT) is a type of psychotherapeutic treatment that helps patients understand the thoughts and feelings that influence behaviors. CBT is commonly used to treat a wide range of disorders, including phobias, addictions, depression, and anxiety.
The iris regulates the amount of light that enters your eye by adjusting the size of the pupil opening. In bright light, the iris closes (or constricts) and makes the pupil opening smaller to restrict the amount of light that enters your eye. The iris in bright light. In dim light, the iris opens (or dilates) and makes the pupil opening larger to increase the amount of light that enters your eye: The iris in dim light. In addition, it is the iris that determines your eye color.
Quick Answer. The primary function of the human pupil is to regulate the amount of light that enters the eye. When the pupil is smaller, less light enters the eye in bright environments. The pupil gets larger as light levels decrease to let more light into the eye. Doctors examine the pupil to ascertain one's neurological function.