What is the role of the iris in the eye?

The iris plays a crucial role in regulating the amount of light that enters the eye by controlling the size of the pupil. It is a thin, circular structure located in the front part of the eye and is responsible for adjusting the diameter of the pupil in response to different lighting conditions. In bright light, the iris contracts, reducing the size of the pupil to limit the amount of light that enters, thus protecting the retina from excessive brightness. Conversely, in low light conditions, the iris relaxes, allowing the pupil to enlarge and admit more light, which enhances vision in dim environments. This ability to constrict and dilate is essential for optimizing vision based on the ambient light levels.

The other options, such as reflecting images to the retina, focusing light onto the retina, and producing tears, are functions carried out by different structures in the eye, including the lens and lacrimal glands, making them distinct from the role of the iris.