What is Depth Perception?
Depth perception is the visual ability to judge distance and the relative size of objects.
The ability to recognize and distinguish between stationary and moving objects is also an important part of depth perception.
Depth perception is over all a complex process that relies on many sources of information.
To better understand depth perception, it helps to gain a deeper understand of binocular vision.
What is Binocular Vision?
Binocular vision, also known as stereoscopic vision, is a form of vision in which two eyes view the same image at the same time.
The brain receives signals from both eyes at the same time, and uses the information in each signal to judge the distances of objects and coordinate eye movements accordingly.
The difference in information between the two signals enables the perception of depth.
Prey Versus Predatory Vision
Vision in animals varies based on their evolutionary history.
Prey animals are blessed with eyes on their side so to allow great peripheral view (width of the visual field) and readily spot predators. This is at the expense of a small, frontal binocular visual field.
Good peripheral view with an almost 360° panoramic vision allow them to easily spot approaching predators.
Predators, on the other hand, have front-facing eyes, which allows a wide binocular visual field and therefore superior depth perception, but they have smaller peripheral fields and some blind spots.
Good depth perception allows predators good judgement for when they are zooming and pouncing over prey as long as their eyes are looking directly ahead.
Depth Perception on Dogs
It can be said that a dog's eyes are set for the main purpose of hunting.
Dogs therefore have predator eyes with binocular vision, which is what humans have too, meaning that the field of vision of both eyes overlap.
This allows a good amount of depth perception, however not to the extent as humans.
Dog Versus Human Depth Perception
Human eyes are for a good part positioned straight forward, while dogs have eyes placed more to the side, typically set at a 20 degree angle.
Basically, humans have a 180 to 190 degree visual field, of which 140 degrees is binocular. Dogs instead have a wider 240 to 270 field of view, of which 30 to 60 degrees is binocular.
As a consequence, this increases the peripheral vision of the dog which off sets their binocular vision, which leads to less depth perception.
On top of this, a dog's nose gets in the way reducing their central visual field.
A dog's depth perception should therefore be best when the dog looks straight, explains board-certified veterinary ophthalmologist Dr. Jeffrey Bowersox.
It's important to point out that, there can be great variance among individual dog breeds when it comes to the visual field of view and depth perception.
Do Puppies Have Good Depth Perception?
Young puppies don’t typically have super great depth perception. This is why you may see some of them them at times struggling with going down a ramp of stairs.
To them, the stairs appear like one long slide versus individual steps, explains Tracie Hotchner in her book: "The Dog Bible: Everything Your Dog Wants You to Know."
Depth Perception For Dog Sports
In dogs involved in dog sports such as a agility, depth perception allows them to successfully navigate through obstacles and adjust their stride length and speed.
Vision problems may be noticed in these dogs first, compared to dogs spending most of their time in the home in familiar surroundings.
Signs of Depth Perception Issues in Dogs
Depth perception allows humans and dog the ability to perceive depth and the relationships between objects. Signs of depth perception issues in dogs will therefore encompass the following:
- Bumping into objects
- Hesitation when about to jump off things
- Reluctance to walk down stairs
- Hesitancy on curbs
- Hesitation to navigate through obstacle courses in performance dogs
Did you know? A dog that suddenly hesitates going downstairs, but does fine climbing up, is likely suffering from some form of impaired vision.
On the other hand, a dog who hesitates going upstairs, but does fine descending, is likely to be suffering from a musculoskeletal issue, points out Cynthia Cook, a board-certified veterinary ophthalmologist.
What Can Cause a Loss of Depth Perception in Dogs?
There are several issues that can cause a loss of depth perception in dogs.
For one, losing vision in an eye can be a culprit. When vision is lost in one eye, dogs may develop decreased depth perception problems, and therefore, you may see them bump into objects on the side that vision is lost, explains the American College of Veterinary Ophthalmologists.
Even dogs suffering from a cataract can lose some of their depth perception, although they can still see well enough to get around without a problem.
If a dog has sustained some type of brain injury, this can too throw off his depth perception some.
As dogs age, their depth perception often starts to deteriorate. This is often due to underlying vision issues such as the onset of nuclear sclerosis.
If you notice any early signs of vision changes in your dog, do not hesitate to have him see the vet.
Dogs are able to compensate very well and often signs show only once issues have progressed, hence the importance of early intervention.
Did you know? Depth perception issues can be a cause of dogs falling off cliffs.
- American College of Veterinary Ophthalmologists: Is My Dog Having Difficulty Seeing?
- Technical Large Animal Emergency Rescue. (2009) Germany: Wiley.
- Hotchner, T. (2005). The Dog Bible: Everything Your Dog Wants You to Know. United States: Penguin Publishing Group.
- Our Canine Connection: The History, Benefits and Future of Human-Dog Interactions (2022) Frontiers Media SA.
- Clear Run, What Do They See & How Do We Know? by Cynthia Cook, board-certified veterinary ophthalmologist.
- DVM360, Vision in Dogs and Cats August 17, 2018 Ron Ofri, DVM, PhD, DECVO
- American College of Veterinary Ophthalmologists, Vision in Pets, Dr. Jeffrey Bowersox, DVM, DACVO