Which photoreceptor mediates the scotopic visual system?

• A. Cones
• B. Ganglion cells
• C. Rods
• D. Both equally

Answer: (C)

Scotopic vision is the low-light, night-time vision, and it is driven by rod photoreceptors. Rods are extremely sensitive to light, able to respond to single photons, which is why they underlie vision when illumination is dim. They provide good light sensitivity but have low spatial resolution and do not convey color information. Cones handle vision in bright light, offering high acuity and color perception, so they’re not the primary mediators of scotopic vision. Ganglion cells aren’t photoreceptors either—they’re the output neurons that carry signals from the retina to the brain after initial processing. Therefore, the photoreceptors responsible for scotopic vision are rods.