What is the function of an iris?

The iris is the colored part of the eye that controls the size of the pupil, regulating the amount of light that enters the eye. It consists of muscle fibers that constrict or dilate the pupil in response to changing light conditions. Additionally, the iris plays a role in enhancing visual acuity by helping to focus light onto the retina. Overall, it contributes to both vision and the protection of the inner eye structures.