Which function does the iris perform?

Which function does the iris perform?

• A. The amount of light entering the eye
• B. Focuses light onto the retina
• C. Detects light
• D. Maintains the shape of the eyeball

Answer: (A)

The iris regulates how much light enters the eye. It has smooth muscles that adjust the pupil size—constricting in bright light to let in less light, and dilating in dim light to let in more. This control helps protect the retina and improve vision across lighting conditions. Focusing light onto the retina is done by the cornea and lens, not the iris; detecting light is done by photoreceptors in the retina; and maintaining the eyeball’s shape involves the sclera and other structures, not the iris.

The iris regulates how much light enters the eye. It has smooth muscles that adjust the pupil size—constricting in bright light to let in less light, and dilating in dim light to let in more. This control helps protect the retina and improve vision across lighting conditions. Focusing light onto the retina is done by the cornea and lens, not the iris; detecting light is done by photoreceptors in the retina; and maintaining the eyeball’s shape involves the sclera and other structures, not the iris.