It is interesting to consider what your dog surveys when he looks out on the world. A toy dogs eyes are about 8 inches above the ground. A Pomeranian walking through tall grass might feel he is in the midst of a jungle. A medium sized dog like a Beagle would probably be able to peer above the grass. My Irish Wolfhound would have no difficulty orienting himself visually. Think about it. We are head and shoulders above our four-legged friends when we look about, and they are unable to see the world as we do. Keep this in mind when you take your dog for a walk.
Height is not the only challenge that dogs face. You may have heard the old wife's tale that dogs can only see in black and white. Dogs can see colors, but not as many as we perceive. Vision depends on special photoreceptor cells in the retina. Rods are most sensitive to light and dark changes, shapes, and movement. They are not good for color vision but are excellent in dim light conditions. Cones can detect either red, green, or blue light, and work only in bright light.
Most humans have all three types of cones and see the world in a wide range of color. Dogs have only cones that detect yellow and blue light. Other colors that we can distinguish appear as various shades of gray to a dog. A dog's color vision is much like that of a human who is red-green color blind.
You have no doubt seen C.M. Coolidge's famous painting of dogs playing poker. Pups would no doubt do poorly at the game, because they can't see red. They can distinguish shapes, but hearts and diamonds would still be a challenge. Your dog probably has no plans to play poker, but remember to be patient if you throw a red ball onto a green lawn, and it takes him some time to find it. Red and green are basically the same color to him.
It is interesting that many companies that produce dog toys and food use red and green to color their products. Obviously, the colors are attractive to human owners who can see them, and who pay the bills. Red and green toys and kibble make no difference to dogs. You may want to consider color when you choose new toys for your friend.
Like people, most dogs do not have 20/20 vision. In 2008, a group from the Department of Surgical Sciences in the School of Veterinary Medicine at the University of Wisconsin found that refractive states of canine eyes varied widely and were influenced by breed and age. For example, Rottweilers, Collies, Miniature Schnauzers, and Toy Poodles tended to be myopic or nearsighted while Australian Shepherds, Alaskan Malamutes, and Bouvier des Flandres dogs were generally hyperopic or farsighted. Nearsightedness seemed to increase with age in all breeds.
Interestingly, there was a prevalence of astigmatism among German Shepherd Dogs. Many dogs are challenged with nearsightedness, farsightedness, and other visual problems that plague people, but dogs seem to manage quite well without glasses.
Some folks believe that human eyesight is superior to that of dogs. That really isn't the case. Eyesight developed to suit the needs of each. Dogs were nocturnal until we domesticated them. They made their living by hunting at dawn or dusk. Their prey was often similar in color to its surroundings so well developed color vision was not a big plus. Canine vison had the qualities that gave a dog in the wild a distinct advantage when hunting fast moving prey in dim light.
Early man, on the other hand, did his hunting and gathering of food in the bright light of day. Cones that detect color were and still are important to diurnal critters including man who do most of their business in the daytime.
Dogs have a different field of vision than us because they are much shorter. In human terms, many would need glasses, and all are red-green color blind. Their eyesight was adapted to serve them well as nocturnal beings. They actually have adjusted quite well to the diurnal lifestyle that we require them to share.
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With a Ph.D. in Biological sciences from the University of Texas in Austin and a masters in Zoology from Southern Illinois University, Dr. Sue is devoted to the care and massaging of pets. Read her articles here.