Certified Paraoptometric (CPO) Practice Exam 2025

Which photoreceptors are primarily responsible for black and white vision?

1. Cones

2. Rods

3. Macula

4. Sclera

The correct answer is: Rods

The correct answer is that rods are primarily responsible for black and white vision. Rods are a type of photoreceptor cell found in the retina of the eye, specialized for low-light conditions. They are highly sensitive to light and allow us to perceive shapes and movements in dark environments but do not provide color information. This makes them essential for night vision and activities in dim lighting, where colors cannot be discerned. In contrast, cones are responsible for color vision and function best in bright light. The macula refers to a specific area of the retina that is rich in cones and crucial for sharp central vision, while the sclera is the white outer coating of the eyeball and does not play a role in photoreception. Therefore, rods are the key players in enabling black and white vision.