What is the role of the iris in the eye?

The iris plays a crucial role in controlling the size of the pupil, which directly impacts the amount of light entering the eye. By changing the size of the pupil through the contraction and relaxation of the muscles in the iris, the eye can adjust to different lighting conditions. In bright light, the iris constricts the pupil to reduce the amount of light entering the eye, helping to protect the retina and improve visual acuity. Conversely, in dim lighting, the iris dilates the pupil to allow more light to enter, enhancing visibility. This regulatory function is essential for maintaining optimal vision under varying external brightness conditions. Understanding the iris's role in pupil control is fundamental in the study of ocular anatomy and physiology.