What does the iris control in the eye?

The iris plays a crucial role in controlling the size of the pupil, which in turn regulates the amount of light that enters the eye. It is a thin, circular structure located behind the cornea and in front of the lens. The muscle fibers in the iris can contract or relax to adjust the pupil's diameter, allowing for optimal vision under varying lighting conditions. In bright light, the iris constricts the pupil to limit light entry and protect the retina from excessive brightness. Conversely, in low-light conditions, it dilates the pupil to allow more light to reach the retina, enhancing visibility.

Understanding the function of the iris is essential, as it directly impacts visual perception and the eye's ability to adapt to different environments. The other options do not pertain to the iris's function; while clarity of vision is influenced by various structures in the eye, including the lens and cornea, and the production of tears involves lacrimal glands, the strength of eye muscles relates to extraocular muscles controlling eye movement, none of these pertain specifically to the role of the iris in regulating pupil size.