What is the primary function of the rods in the human retina?

The primary function of rods in the human retina is night vision. Rods are photoreceptor cells that are highly sensitive to light, making them essential for vision in low-light conditions. They do not detect color; instead, they respond to shades of gray and are particularly adept at detecting movement and providing peripheral vision in dim environments.

In contrast, cones, which are the other type of photoreceptor cells in the retina, are responsible for color perception and sharp vision during daylight. While cones require brighter light to function effectively, rods become more active as light diminishes, allowing humans to see in dark or poorly lit situations. This distinction highlights why rods are fundamentally crucial for night vision specifically, rather than the other functions listed.