USA Biology Olympiad (USABO) Practice Exam

What is the primary role of vitamin A in relation to vision?

1. Aids in the absorption of light

2. Prevents night blindness

3. Enhances color vision

4. Improves visual acuity

The correct answer is: Prevents night blindness

Vitamin A plays a crucial role in vision, particularly in enabling the proper functioning of the retina, which is essential for night vision. One of the main forms of vitamin A, retinal, is a vital component of rhodopsin, the pigment found in rod cells of the retina. Rod cells are responsible for detecting light in low-light conditions. When light hits rhodopsin, it undergoes a chemical change that eventually leads to a signal being sent to the brain, allowing us to see in dim light. A deficiency in vitamin A can lead to a diminished production of rhodopsin, which directly impacts the ability to see in low-light environments, resulting in night blindness. This condition illustrates how vitamin A is not just important for overall vision but is specifically critical for adapting to darker settings and functioning effectively in those conditions. While other choices mention aspects related to vision, they do not address the primary function of vitamin A in preventing night blindness, making prevention of this condition the most accurate representation of its essential role in vision.