How does the iris control the amount of light entering the eye?

The iris, which is the colored portion of the eye, plays a crucial role in regulating the amount of light entering the eye. It acts like a muscular diaphragm encompassing the pupil, the black circular opening at the center of the eye. The iris has two sets of muscles: the dilator pupillae and the sphincter pupillae. When there is a bright light source, the dilator pupillae contract, expanding the iris and narrowing the pupil, thereby reducing the amount of light entering the eye. Conversely, in dim lighting conditions, the sphincter pupillae muscles contract, causing the iris to constrict, and the pupil dilates to allow more light to enter the eye. This intricate mechanism allows the iris to continuously adjust the size of the pupil, ensuring a balanced and optimal amount of light reaches the retina for clear vision.

This mind map was published on 16 November 2023 and has been viewed 86 times.