Just How Well Can Dogs See?
It goes without saying that dogs have more acute senses of smell and hearing than humans.
But humans have better eyesight. Don’t they? The answer depends in large part on how you define “better.” Vision is a complicated symphony based on location of the eyes and the anatomy of the eye itself.
Certain animals like rodents, rabbits, and birds have eyes that are placed far on the sides of the head so they can see what’s on both sides of them at the same time, but they are unable to see what’s right in front of them. Human eyes are placed in the center of the face and it’s easy to see what’s right in front of you, but your range of vision isn’t as large.
Dogs Are Somewhere Between
Their eyes are more to the sides of their heads than humans, so they have greater peripheral vision. However, the area of binocular vision in dogs (where both eyes see together, like humans), is only about 50 to 60 percent that of humans.
Another factor to vision is the make-up of the eye itself. The two types of vision receptor cells, cones and rods, exist in both humans and dogs.
Two Cones Mean Less Color
Contrary to popular belief, dogs are not color blind, but their eyes do contain fewer cones than human eyes. In addition, humans have three colors of cones: red, green and blue-violet. Dogs only have two, causing them to see the world in shades of blue, yellow and gray. With fewer cones, dogs not only see fewer colors, but the colors they do see are less vivid.
In addition, humans have a central retina (also called a fovea) area of their eye, which consists of only cones that increase visual acuity. Dogs have no such area. It is estimated a dog’s vision is around 20:80, meaning a dog can see at 20 feet what a human could see at 75 or 80 feet.
More Rods Mean Better Night Vision
However, dogs have a much larger number of rods in their eyes than humans. Rods detect light and dark. In addition, dogs’ pupils are larger than humans, allowing more light into their eyes. Dogs also have a mirror-like structure at the back of their eye called a tapetum. The tapetum allows light to bounce back to the retina a second time. The tapetum is also what causes the yellow or green glow you sometimes see in your dog’s eyes at night. All of these factors combine to allow dogs to see about five times better at night than humans.
Since dogs’ ancestors searched for food in the dark—and were more likely to become food themselves—dogs’ eyes evolved for better night vision. In addition, having more rods in their eyes also makes it easier for dogs to detect motion: another important factor for hunting and surviving.
So who has better sight, you or your dog? You win when it comes to color. You can also see more detail at a distance than your dog. But your dog wins paws down when it comes to night vision. He probably sees motion better, and glimpses things out of the corner of his eye before you see them. In short, you and your dog are stronger as team than either of you is by yourself.