Which is the black spot in the middle of the iris that dilates or constricts to adjust for light?

• A. Iris
• B. Lens
• C. Retina
• D. Pupil

Answer: (D)

The opening in the center of the eye that changes size to control light is the pupil. The iris—the colored ring around it—has muscles that dilate or constrict this opening. In bright light, the pupil constricts to limit light; in dim light, it dilates to allow more light in. The lens sits behind the pupil to focus light onto the retina, which detects light and sends signals to the brain. The pupil appears black because it is an opening through which light passes, and most of that light is absorbed by the eye’s deeper structures.