ABO NOCE Practice Test 2025 - Free Optician Certification Practice Questions and Study Guide

The iris is the structure that controls the amount of light entering the eye through the pupil. It is a thin, circular structure in the eye that contains muscles which can contract or expand. When the surrounding light conditions change, the iris will adjust the size of the pupil accordingly. In bright light, the iris constricts the pupil to reduce the amount of light that enters, protecting the retina and improving visual acuity. Conversely, in low light conditions, the iris dilates the pupil to allow more light to enter, facilitating better night vision.

Understanding the function of the iris is fundamental in optometry and ophthalmology, as it plays a critical role in regulating the light exposure to the retina, which is essential for clear vision and overall eye health. The other structures mentioned, like the retina, cornea, and lens, have distinct roles in vision, such as focusing light and processing visual information, but they do not control the light entry through the pupil.