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.
The pupil is the opening in the center of the iris of the eye. A chief function of the pupil is to control the amount of light entering the eye. Two muscles, the sphincter and the dilator, control the size of the pupil in response to changes in light. The dilator muscle radiates out from the pupil like a star.