The ability of light to enter the eye is controlled by which structure?

The ability of light to enter the eye is controlled by which structure?

• A. Cornea
• B. Lens
• C. Iris
• D. Optic nerve

Answer: (C)

Light entering the eye is regulated at the pupil by the iris. The iris acts like a diaphragm, contracting the sphincter pupillae in bright light to make the pupil smaller and expanding the dilator pupillae in dim light to make it larger. This adjustment controls how much light reaches the retina, protecting photoreceptors and helping optimize vision. The cornea mainly refracts light, the lens helps focus it, and the optic nerve carries visual signals to the brain, but none of these change the amount of light entering the eye.

Light entering the eye is regulated at the pupil by the iris. The iris acts like a diaphragm, contracting the sphincter pupillae in bright light to make the pupil smaller and expanding the dilator pupillae in dim light to make it larger. This adjustment controls how much light reaches the retina, protecting photoreceptors and helping optimize vision. The cornea mainly refracts light, the lens helps focus it, and the optic nerve carries visual signals to the brain, but none of these change the amount of light entering the eye.