The World Through the Dogs Eyes
The first question we must ask ourselves is – How does the dog see and how does it compare to humans? I know I have mentioned before the importance of remembering that a dog is not a human and once again this rings true for our partners eyesight (as compared to ours). I have tried to summarize the difference to put it in layman’s terms so we all (including me) can understand it better.
Our eye and the eye of the dog are made of the same basic design. However, there are specific differences that have evolved in each species to accommodate environments and lifestyles. We have evolved as a diurnal (daytime) species and our dogs have evolved as a nocturnal (night time) species. This obviously means that we see better during the day and our dogs see better at night. The basic reason for this has to do with the cones and rods inside our eye. Cones are for color and rods are for nighttime and movement. Dogs have many more rods then we do and we have many more cones (hence we see color much better). If you think about it, this makes sense that canines over the years evolved from a nocturnal environment where the need for distinguishing color was not as important. However, the need to focus on movements in this same environment was paramount. This is still true today for our domestic canines cousin the wolf.
Another difference has to do with near and far sightedness. Dogs are myopic; that is to say they suffer from nearsightedness (difficulty in focusing at distant objects). Humans with degrading eyesight often suffer from hyperopia, referred to as farsightedness (difficulty in focusing on close objects). Generally dogs do not suffer from this condition. As a dog ages the condition of myopia (nearsightedness) can worsen. As far back as 1901 test were done that showed differences in breeds. It was shown that domestic breeds suffered from myopia, contrasted with wolves, jackals and dingos who suffered slightly from hyperopia.
To make a comparison here, think of yourself doing basic obedience work with your dog. If you are at a distance and you are recalling your dog. He may not initially recognize you. In fact if another person was in the general area during your recall he may respond to the other person. Depending on lighting and the environment the dog may not correct himself until he hears a verbal command, which would allow the dog to redirect himself to the right person. The dog is responding to the figure that is in his standard position, which he has been conditioned to do from numerous past experiences. When working your dog you should recognize this fact and with this knowledge adjust accordingly. The bottom line is that often a dog’s perceived confusion and sometimes-perceived disobedience may be because of his myopic condition. This is the same reason why dog trainers often use sweeping hand movements when recalling with visual signals. These sweeping movements are easily recognizable to the dog.
The subject of canine eyesight always sparks the question of color blindness. The rumor of a dog being colorblind is false. Their range of colors is of course less then ours but they do indeed see color. Without getting to technical, dogs can basically pick out two colors, blue-violet and yellow, and can see differences in shades of gray. They are color blind to red and green. Another misnomer is the thought that a dog can see blood and react to it, this would have to do with its smell and the totality of the given environment rather then the color of blood itself.
As far as vision comparison to a human goes, a human with good eyesight sees 20/20 as compared to a dog who sees 20/75. That is to say a dog a must be about 20 feet away from something to see it as well as a human who is 75 feet away. Once again I mention this for application when handlers are working their dogs. Just because we see it clear does not mean our dogs do. This is why we have to make more effort to direct a dog on a given task that may not be clear to him visually. An example would be a directed deployment at a distance with other like objects.
To summarize dogs are much better adapted to working in nocturnal (night) environments then us. Though they do not see details like us, they can see movement very well and much better then us at night. They are not color blind, seeing blue-violet and yellow with shades of gray. As stated they have about a 20/75 vision as compared to a human’s good eyesight of 20/20. Knowing these differences and reminding ourselves of them will help in maintaining and correcting problems with our canines.
Sergeant Doug Roller