After my recent article on canine color vision, I got a ton of enthusiastic questions from members about what their pets see, and how to measure it.
Dogs have dichromatic color perception. Unlike human eyes, which have three different types of color sensitive cone cells in their retina: - red, green and blue, dogs have only two: - yellow and blue.
As the color bar shows, dogs see colors like a person with red-green color blindness. Red, orange, yellow, and green, they see as yellow. Blue, indigo, and violet, they see as blue.
NOTE: For those interested there is an app for your phone called "Dog Vision" that uses your camera to help you see the difference between what you see and what your dog sees.
Today we will look at another important aspect of canine vision – acuity, that is, sharpness of vision. Visual acuity is the spatial resolution of the visual system that the optometrist measures using an eye chart. Simply put, the visual acuity of the healthy human eye is 20/20. A healthy canine eye, however, can see only about 20/80.
So your pet’s visual acuity is only one-quarter as good as yours. What you can see clearly at 80 feet, your dog can see only at 20 feet. Because acuity varies with breed, measured over a group of different breeds, it turns out to be one-half to one-eighth the visual acuity of humans. Even the best sight hounds have only half the visual acuity of humans.
You can get a reasonable idea of how clearly your dog sees from the bar chart below. The middle bar shows average dog vision. You can see that your dog finds it a lot harder than you to distinguish shapes. If you are using visual signals for training, they have to be extremely clear, and large, and close to the dog.
And you have to wear colors they can see too. Never red, yellow or green against the green background of a field, for example. At 20 feet away the dog can distinguish color, movement, and brightness, but its acuity is only about that of the middle grey stripe below.
Next article on canine vision I will cover brightness and movement. Surprisingly, dogs are better at distinguishing 50 shades of grey than we are. They can see movement better too. Then we will put color, acuity, brightness, and movement together to give you the whole picture of your pet’s visual world.
Miller PE, Murphy CJ. Vision in dogs. J. Am. Vet. Med. Assoc. 1995; 207:1623-34.
Miller PE, Lights F. Vision in animals - What do dogs and cats see? The 25th Annual Waltham/OSU Symposium. Small Animal Ophthalmology. 2001.
For those of us involved in dog agility this information will help us improve our training methods and understand better why our dog might not be understanding our instructions. This is especially relevant in the game of Gamble when our dog might not be seeing the obstacle that is more than 20 ft away, while we can see it quite clearly. Lesley Colgan.