The Effect of Short Light Flash on Rods & Cones

The human eye is a complex body organ, with many different tiny cells that combine to provide functioning eyesight. Two particular types of eye cells, rods and cones, work together to help keep a person's vision healthy.

Function

• Rods are cell photoreceptors that function in dim levels of light with no regard to color interpretation. In contrast, the other photoreceptors, called cones, do differentiate color, but only work with bright lighting.

Effects

• When a short light flash is produced across the field of vision, rods respond much slower than cones to the light because rods are geared toward dim light. A bright light flash will be perceived by the cones more quickly due to their faster chemical processes.

Significance

• The slower reaction time of the rods explains why it takes time for a person to acclimate to a dark room visually. As a person enters a dimly-lit room, the rods activate and enhance what little light there is. However, this happens much slower than the activation of the cones if a person suddenly enters a brightly-lit room.