Kaplan Nursing Entrance Practice Exam

Which part of the eye is responsible for controlling the diameter of the pupil?

1. Cornea

2. Iris

3. Lens

4. Pupil

The correct answer is: Iris

The iris is the part of the eye that plays a crucial role in controlling the diameter of the pupil. It is a thin, circular structure situated between the cornea and the lens, and it contains muscles that can constrict or dilate the pupil in response to varying light levels. When the surrounding light is bright, the iris muscles contract, making the pupil smaller to reduce the amount of light entering the eye and protect the retina. In low light conditions, the iris muscles relax, allowing the pupil to expand and let in more light, enhancing visibility. Other structures in the eye, such as the cornea, lens, and pupil, have different functions. The cornea focuses light as it enters the eye, while the lens further fine-tunes the focus onto the retina. The pupil itself is simply the opening that regulates light entry based on the actions of the iris.