As a veterinary ophthalmologist, I am frequently asked questions about the specifics of vision in dogs, especially performance dogs. Vision depends on a number of factors, but there are some important concepts common to all dogs. These concepts are often most easily understood in a comparative fashion to our vision.
Field of vision: Dogs have a wider field of vision based on the more lateral position of the eyes. Compared to humans who have about 180-200 degrees, a dog’s vision field is 240-270 degrees, meaning that their peripheral vision is much better than ours. This allows our dogs to run ahead of us and yet still be able to detect our pace, body position, and arm motions when we are behind and lateral to them. This also gives them much more in the way of obstacle options from which to choose compared to what we are focusing on, so our body position needs to assist in accurately directing them.
Detail vision: The advantage of the wider field of view in dogs results in a compromise in binocular vision. This results in decreased depth perception and a decrease in focusing/accommodation or detail vision. In comparison to the average human with 20/20 vision, the average dog has 20/75 vision (the detail that we see at 75 ft, they see at 20 ft). This means that from a distance they cannot see facial expressions or an object at rest. So frowning at your dog is not perceived! This loss of detail is outweighed by their ability to see much better in dim light and to detect motion.
Color: Dogs are NOT color blind. They are similar to a human with red-green color blindness in that they do see SOME color. Specifically the canine retina contains 2 cones (versus 3 in humans): one at 429 nm (blue) and the other at 555nm (yellow). They can easily differentiate colors in these wavelengths similar to humans. They lack a red type cone, so red/orange/green are seen as shades of yellow. From an agility equipment standpoint, blue and yellow are easily distinguished which is why most contact equipment in competition involves these contrasts. The dark green and yellow are contrasted well enough to be distinguishable.
Night vision: The dog’s retina is rod-dominated, and rods are responsible for dim light vision. They also have a reflective structure within the retina that reflects light (tapetum). Because of this, dogs (and cats) can see much better than humans in dim light. Training at night is much harder for us than for them!
Motion: Rods are also responsible for motion detection. With a rod dominated retina and a wider field of view, dogs are MUCH more sensitive to subtle motion changes than humans are. This is why a flick of the hand can be so distracting and can cause a knocked bar or a sudden pull out of a tunnel. A subtle change in our pace (acceleration/deceleration) is very notable to them as well.
I hope that this improves some understanding of how your agility dog visualizes the equipment and the handler. Even with this abundant knowledge, I still flick my hand or adjust my sunglasses while my dog is weaving.
Anne Cook and Hunley