Most people have to wonder at some point exactly what the differences are between what a pet sees and what we see.
Some have predisposed ideas of what animals see. The reality is, most people don’t know much about what a dog, cat or pet bird sees relative to the vision of humans.
One old saw says that dogs only see in black and white. Not so. They see color, they just don’t see it as vividly as a humans does.
Most know our retina contains photoreceptive structures called rods and cones. Cones are for color, rods are for low levels of light. In humans, we have three sets of cones for red, green and blue vision while it is suspected that dogs only have two for blue and green.
More cones mean more colors seen. More rods mean better night vision.
As a result, dogs can see more shades of grey than humans, and they have remarkably better night vision than we do. When it comes to some colors, dogs actually see them quite vividly, but those colors may be muted to a degree.
Cats, with their vertical pupils, likely only have green and blue cones as well. Cats also have among the most superior night vision in the animal world because they have a high concentration of rods versus cones.
The eyes of cats, as with many other vertebrates, also contain a tissue called tapetum lucidum, which reflects light that reaches the back of the eye. This improves their night vision by an estimated 44 percent.
With eyes on the front of their face, cats also have about a 200-degree field of view. Humans have about 180.
Our normal acuity is 20/20, meaning we see objects clearly at 20 feet. An acuity of 20/100 would mean you would need to be within 20 feet of an object to see it clearly, but a person with normal acuity could see it well at 100 feet.
Welcome to cat vision at 20/100. They can’t see too well at a distance but boy howdy, it works for them in close quarters capturing prey. Colors are mostly greens and blues.
Conversely, if one had 20/10 vision, like that of record-setting pilot Gen. Chuck Yeager, that would mean they could read a line off the eye chart at 20 feet that otherwise normal people could only read at 10 feet. Gen. Yeager’s eyesight was in part what made him a fighter pilot ace and a crack shot with a deer rifle.
Birds, on the other hand, have better vision than cats, dogs and humans. Beyond the three standard cones for red, blue and green, birds have a fourth one that allows them to see the ultraviolet part of the light spectrum. This is thought to help with mating because some bird’s plumage will seemingly glow brightly in color in the UV spectrum because they reflect that light off their feathers.
A special protein in a bird’s eyes also lets it actually see the Earth’s magnetic field. Wrap your mind around that one.
There is a slight indentation in the macula in each of our eyes that helps provide the clearest vision of all. It covers only the middle 40 degrees or so of our visual field. The greatest concentrations of cones only covers about 10 degrees of that field.
Birds of prey have two fovea in each eye giving them vision that is great up close and like a telephoto lens at a distance.
Charlie Powell is the public information officer for the Washington State University College of Veterinary Medicine, which provides this column as a community service. For questions or concerns about animals you’d like to read about, email email@example.com.