Deer do not have good visual acuity because their eyes lack foveae (no sharp central vision). The fovea centralis is a small pit or depression at the back of the retina forming the point of sharpest vision. It allows primates and humans, which are basically hunters, to focus intently and see very clearly when they look directly ahead at an object.
That being said, deer are much more aware of movement around them. Their eyes are located on the sides of their skull as opposed to ours which are in front. As is the case with many flight animals, their eyes bulge out a bit from the side of their face and are curved a bit more. As a result, they are able to see more than 270 degrees around them without moving their head.
This allows them to be more aware of their surroundings and movement in a wider range than humans.
For a variety of reasons, deer cannot see colors in the same way humans do. In a paper by Karl Miller, et. al., entitled “Photopigments of Whitetailed Deer”, the full range of the ability of a whitetail deer to see color was explored under research conditions.
Vision is the result of light being absorbed by photoreceptors in the retina which is the light absorbing tissue in the back of the eye. Vision is limited by the size of the eye, the size of the pupil and the refractive power of the eye’s optical elements. There are also filters the light passes through before it reaches the retina that vary by animal. In addition there is a difference in the light absorption qualities of the photoreceptors, and, the reflective tissue that lies behind the photoreceptors.
Under lab conditions, nine deer were anesthetized to measure the sensitivity of the deer’s eyes to wavelengths of light across the spectrum. The researchers came to several conclusions that help us as hunters to understand deer better.