A Dog's Vision: Seeing Through a Dog's Eyes
Sight is one of the most important senses, as it’s usually our first source of information about our surroundings. There has always been speculation about how animals perceive the world. In this context, specialists already have the answer to how the eyes of virtually any animal function. In this article, we’ll be seeing the world through a dog’s eyes as we look at how a dog’s vision works.
Some people think that dogs, and other animals such as cats, don’t perceive colors and that their vision is entirely in black and white, but how true is this? In this article, we’ll clarify all the questions related to the sense of sight in our beloved pets.
A dog’s vision
Although we could think that dogs’ eyes resemble ours, this isn’t so. There are certain differences that change the way they perceive the world. Vision itself results from a combination of factors, such as field of vision or width, depth, focus or sharpness, perception of movement, and color.
All these aspects are processed in the main organ, the brain, and give rise to the sense of sight. Let’s look at some details of how these factors act to generate a dog’s vision.
The position of an animal’s eyes determines their field or width of vision. In the case of dogs, this aspect is 240°, larger than in humans, which barely reaches 200°. This gives them a wider range of vision.
Focus or acuity
When we mention the terms focus or visual acuity, we’re talking about the clarity of vision. Although it’s a difficult factor to measure, a dog’s vision is said to be poorer than that of the human being. So, to give you a clearer idea, when we can distinguish something at 75 feet away, they can visualize it at only 20 feet, an incredible difference.
Just like with the visual field, the position of the eyes on the head determines the way they perceive distances, that is, the binocular vision of a dog. Some experiments on puppies have shown that perception with one eye and with both eyes are excellent in canines, and so, in adults, it would be even better.
Other research on some ocular cells affirms that the area of depth perception in these pets may be less quality. Thus, three-dimensional vision would be impaired. However, more studies are needed to clarify this,
What about movement?
In the case of movement, a dog’s eyes are very good at detecting it, even at a distance. In addition, they have the ability to distinguish more images per second than we can, an aspect that stands out in dog vision.
How do dogs perceive color?
Color differentiation in animals is determined by the structure of the eye. In particular, by the presence of photoreceptors (of the cone type) in the retina. These are the pigments that are sensitive to the wavelengths of each color. In humans, there are three types of cones. Dogs, on the other hand, have two, so it’s said that their color vision is dichromatic.
It’s from the mixture or superposition of the pigments present in the cones that the whole range of visible colors arises.
So, thanks to the presence of photoreceptors in the retina of the dog’s eye, we can affirm that they do have color vision and that it isn’t only black and white, as was thought at the beginning. However, since there are only two types of cones, they find it difficult to visualize the whole chromatic spectrum. In particular, green and red tones, which they see as yellow or gray.
In addition, the number of these receptors is also very low. In fact, while in humans the central retina is made up entirely of cones, in dogs, it barely reaches 20%.
Other aspects of a dog’s vision
In addition to all the perceptual capabilities, a dog’s vision has the ability to discriminate between objects, sizes and even quantities. Particularly when the differences are quite large. They also have the ability to discriminate between familiar and unfamiliar faces (in 2D tests) of both dogs and humans.
Dog night vision
The ability to see in dim light is also present in dogs. This is based on the modifications they have undergone that are typical of night hunters. They possess a special element, the tapetum lucidum, which functions as a reflective membrane and contributes to their vision in low light conditions, an adaptation that humans don’t have.
Similarly, variation has been observed in the tapetal area based on dog breeds and their sizes. In general, smaller dogs have smaller areas, while larger dogs have a more complete tapetum lucidum.
Thanks to the presence of this tapetum, dogs have brightened eyes in the presence of a car light, a camera flash or any flash towards their eyes when they’re in darkness.
In addition, the rod photoreceptor cells and the pigment (rhodopsin) found in the retina of the dog’s eye, both function in low light conditions. Although they’re present in humans, they possess greater sensitivity in canines. In fact, the retina is dominated by them. Thus, their efficiency and quantity, together with the presence of the tapetum lucidum, allow for better vision in the dark or in dim light than those possessed by humans.
As we have seen, the anatomy and even the position of the dog’s eyes on the head provide clues as to how these animals perceive the world. However, further studies are needed to investigate whether morphological differences between breeds represent discrepancies in the vision of each type of dog.
Although the vision of dogs is worse than that of humans in many respects, in others it’s clearly superior. In particular, they’re experts in low-light conditions. So, canine eyes see the world in a different way than ours, but certainly with adaptations according to their needs.It might interest you...