Deer eyes only have two photopigment types, giving them dichromatic color vision. Scientists believe that deer can primarily see short-wavelength blue light, and moderate-wavelength light that they probably perceive as something between red and green.

Unlike in humans, the cones in a deer's eye are distributed across the back of the eye on a horizontal plane. The lens in a deer's eye also can't adjust to objects at varying distances. These factors give deer less visual clarity than humans have. An object a deer is looking at straight on is equally in focus as something out to the side. So don't assume that because a deer isn't looking at you that it can't see you.