Rods are most densely packed at about how many degrees from the fovea?

Rods are most densely packed at about how many degrees from the fovea?

• A. 10
• B. 15
• C. 20
• D. 25

Answer: (C)

Rods provide sensitivity in low light, and their distribution on the retina is arranged so that we gain light-catching power without sacrificing central detail. At the fovea itself, rods are nearly absent, because this area is packed with cones for sharp, color vision. As you move away from the fovea, rod density increases and reaches a maximum in a band roughly 20 degrees from the foveal center. Beyond that zone, the density tapers off toward the far periphery. This peak around 20 degrees lets the visual system achieve high sensitivity in dim conditions while still preserving decent acuity nearby; in dim light, people often shift gaze a bit away from the target to place it on this rod-rich region. So, rods are most densely packed about 20 degrees from the fovea.

Rods provide sensitivity in low light, and their distribution on the retina is arranged so that we gain light-catching power without sacrificing central detail. At the fovea itself, rods are nearly absent, because this area is packed with cones for sharp, color vision. As you move away from the fovea, rod density increases and reaches a maximum in a band roughly 20 degrees from the foveal center. Beyond that zone, the density tapers off toward the far periphery. This peak around 20 degrees lets the visual system achieve high sensitivity in dim conditions while still preserving decent acuity nearby; in dim light, people often shift gaze a bit away from the target to place it on this rod-rich region. So, rods are most densely packed about 20 degrees from the fovea.