The first canine sense that comes to mind is usually their incredible ability to smell. Scientists estimate that depending on their breed, dogs can smell anywhere between 40 and one million times better than we can. What often goes unrecognized, however, is the dog’s amazing sense of sight. Dogs see the world in a very different way than we do, but they see very well.
The canine retina (the layer at the back of the eye that converts light energy into nerve impulses that are sent to the brain to be interpreted) contains the same cells as do ours, just in different proportions. People have excellent color vision and an ability to see fine details. These attributes are the result of the large number of cells called cones in our retinas. The canine retina has fewer cones than does the human retina, meaning dogs have trouble differentiating between greens, yellow-greens, oranges, reds, and greenish-blue colors. Dogs are not color blind, but they do not see color as well as we do.
Because of their relatively low number of cones, dogs also can’t see in fine detail. The standard for vision in people is 20/20. For dogs, it is more like 20/75. To get a feel for what this means, stand 75 feet away from something. For a dog to see the level of detail that you do, he would need to be only 20 feet away.
The canine sense of sight shines under low light conditions and in the detection of movement, however. Dogs have a structure at the back of their eyes called the tapetum lucidum, which reflects light within the eye. This is what makes a dog’s eyes seem to glow at night when light hits them in just the right way. Also, dogs have a greater number of cells called rods in their retinas in comparison to people. Rods detect light under dim conditions and pick up movement, which means dogs can see a moving object and in the dark much better than we can.
What does this mean for owners? Rely on your own eyes for color and fine detail, but if it’s getting dark or your dog seems to be tracking something, take him seriously. Also, if you’re far away from your dog and need to get his attention, don’t just stand still, try waving your arms or moving back and forth. Otherwise, you may just blend into the background.