Dogs are known to be excellent hunters. And they are perfectly oriented in space. Their senses help them in this. Dogs eyes are not an analyzer of primary necessity, but his abilities are quite high, although they are inferior to human ones.
Eye structure
The anatomically visual analyzer of a dog is very similar to that of a person. The cornea is located in front of the eyeball - this is its outer shell. Normally, it is clean, transparent and shiny. Its purpose is to protect the eyeball from damage. Also, the outer shell is involved in the refraction of light.
Under the cornea is the middle layer of the eye - the iris. In its center is the pupil, and behind it is the lens. In addition, the iris forms a network of blood vessels that feed the eye.
Muscle fibers are attached to the lens. Reducing and relaxing, they change its curvature, providing a vision of objects at different distances.
The pupil and lens take a direct part in the visual perception of the surrounding reality. The light flux, passing and refracting through them, falls on the retina, where it is converted into the corresponding signals.
The retina is the third layer of the eyeball. Its complex design allows you to modify visual impulses and transmit them to the brain. Here the final picture of the world is formed.
In addition to the above-mentioned eye elements that bring together the eyes of an animal and a person, there are others that are strictly specific to dogs.
So, the four-legged eye has an additional outer shell called the third eyelid. This is a thin film enveloping the eye. It protects it from getting specks and dust. And constantly moisturizes, thanks to the lacrimal gland.
The retina deserves special attention. It is its features that provide a specific vision of the outside world with dogs.
As you know, certain cells in the structure of the retina, called rods and cones, are responsible for color perception and orientation at dusk.
Cones are responsible for the color perception of objects during the day, and rods for visual orientation at night. In tetrapods, rods predominate in the reticular structure. They are several times more here than in humans. As for the cones, their number is much smaller.
Also, in caudate there is no yellow spot, which in humans is located in the center of the retina and is a congestion of cones. But there is an additional crystalline layer called tapetum. It plays a special role in the visual adaptation of the animal.
Conventionally, the retina is divided into 2 parts:
- upper - provides the dog with visual orientation in the dark, responsible for visual acuity;
- lower - responsible for daytime vision.
The eyes of our beloved pets are designed in such a way as to help them quickly navigate in space and not miss out on prey. This is laid down by their original nature as a wild predator and a dexterous hunter.
Do colors distinguish?
The statement that the sight of our beloved pets is black and white is a mistake. Dogs see and analyze the world in different colors, although their palette, compared to humans, is rather scarce.
To begin with, retina cones provide color vision to dogs. But their number is negligible.
In humans, these cells have 3 types:
- picks up long waves of the color spectrum and determines red, orange tones;
- reacts to medium waves of yellow, green flowers;
- sensitive to short, blue-violet waves.
In dogs, there are only 2 types of cones.
The perception of the dog is not subject to green and red shades. He perceives them in white or gray colors. But the blue, violet and yellow colors of the dogs are distinguished perfectly. Thus, they show selective color blindness, and their vision can be compared with that of people with color blindness.
How, then, to explain the fact that dogs are guided in traffic signals? There are even special breeds - guide dogs accompanying people with poor eyesight. The fact is that in this case, the dog-conductor does not respond to a color change, but to a change in signal brightness. And this helps them to correctly assess the situation.
Dog breeders have repeatedly noted a change in the behavior of four-legged pets at the sight of a particular color. For example, a dog reacted sharply to people in yellow clothes. This also confirms their color vision.
Such a dog “preference” in colors is advantageously used in their work by trainers. Using toys and color attributes in the practice process, to which their wards are sensitive, they manage to achieve positive results much faster.
How does lighting affect?
The dog’s vision is universal, as this animal is satisfactorily oriented both day and night.
Orientation in the dark
Dogs have a fairly well developed night vision. This is achieved by sticks present in large numbers in the structure of the retina. It is so large that dogs see at night and distinguish objects four times better than people.
It is great to see the already mentioned tapetum helps dogs in complete darkness. This is a retroreflective membrane, which is compared with the glow of headlights or mirror spraying. It is located in the upper part of the retina, responsible for night vision.
Light passing through the retina is reflected on it through the membrane again. Thus, the image is more clear and contrast.
Animals see objects at night in gray. And demarcate, almost, all of its 50 shades.
Daylight
During the day, the four-legged are also well oriented. And I must say that it is given to them easier than people. The human eye is sensitive to too bright light. It's hard for us to look at the sun with our eyes wide, we have to squint.
In dogs, the lower part of the retina contains dark pigment, which allows you to neutralize the excessive flow of bright light. Therefore, they are much less susceptible to harsh light.
Another feature of the animal’s eyes is the glow when a luminous flux hits them. You may have noticed that at certain times your pet's eyes begin to glow yellow or a different color. At the same time, they turn into plain circles, in which even the pupil is not visible.
The reason for this is, again, a reflective membrane, thanks to which the dogs are so well oriented in the dark. The color of the glow can be yellowish, as well as with green and brown-brown hues. Or combine several tones at once: yellow or green above, green-blue below. This is due to the color of the membrane. It is darker in dark-eyed animals than in breeds with a bright iris.
Range and breadth of vision
In addition to the fact that dogs do not perceive a decent range of colors and are well oriented in the dark, their eyesight has other features. This time they are associated with the clarity and breadth of perception.
The dog cannot boast of visual acuity. The reason for this is the lack of a yellow spot on his retina, characteristic of the human eye. It is here that a large number of cones are concentrated. Thanks to the yellow spot, we are able to see objects both near and far (if we are talking about a healthy person).
The retina of dogs is devoid of a yellow spot, and therefore their visual acuity is useless.
In order for the dog to clearly see any object, it must be at least 30 cm from it. From which it was concluded that the visibility of these animals is akin to people with a slight degree of farsightedness. However, despite the difficulty of focusing on nearby objects, dogs cleverly estimate the distance to the target.
Another property of the canine eye is the perception of a moving object. He identifies his dog at a distance of 900 m. Excellent property for hunting breeds. But if the same target is immobilized, then the tailed one will be able to see it no further than 600 m. The visibility of objects in the dynamics is provided by a large number of sticks in the dog's retina.
They also determine the panoramic vision of tetrapods. That is, they perceive the image of the entire retina due to the lack of a yellow spot.
As for latitude or field of view, in dogs it is on average 250 °. This is significantly more than a person. And it depends on the location of the visual axis of both eyes. In animals, they diverge at an angle of 20 °, while in humans they are parallel. A large degree affects the shape of the visual field. It is not round, like a human, but has an oval shape, which becomes a significant advantage during the hunt - allows you to view more space.
But the field of view is not the same for all breeds. This indicator varies based on the structure of the canine skull. The narrower the muzzle and the longer the nose, the higher the degree of visual latitude.
How do dogs see people and the world around them?
If for a person eyes are 90% of information, then for four-legged eyesight is not at first in the first place. Much more important for them is hearing and scent.
Nonetheless Dogs adapt visually well in space. They distinguish individual colors, perceive distant static objects. However, their vision provides certain goals. Its main task is fixing on dynamic objects, that is, moving in space.
By the way, it is not for nothing that they say that when an angry, grinning dog rushes at you, first of all, stop. Thus, you will be less attractive to her.
Dogs living in the wild, and domesticated individuals perceive the world around them in the same way. And even their beloved pet owners near are perceived by them as a blurred outline. A faithful dog recognizes its owner from a thousand not by facial features, eye color or nose shape, but by completely different criteria.
Interestingly, in 1 second the dog’s eye perceives 80 frames. Compared to human, this is 56 frames more. Therefore, four-legged friends are completely uninterested in television, because the frame rate in it is 60 Hz. The picture on the screen pussies get in the form of a blurry spot.
Although some modern TVs have a frequency of 100 Hz and are available for viewing for dogs. Currently, developments are underway to create "dog" programs. They will help pass the four-legged leisure, when their owners are busy.
The main differences from human vision
The structure of the organ of vision of a person and a dog are very similar. And coincide in all major indicators. But small differences make the canine and human vision of the surrounding world fundamentally different.
- Their main difference is the difference in the color spectrum. In humans, it is much more extensive, due to the wide variety of cones.
- The predominance of shaggy sticks helps them to navigate several times better in the darkness of night than to humans, while distinguishing objects in fairly clear outlines.
- Hairy visual acuity is much lower than in humans.
- But dogs can boast a breadth of field of view, 70 ° higher than the human figure.
- Human vision is perfect. It allows you to see near and far, to separate the sea of colors and shades, to perceive objects of any size and configuration. The dog eye does not see well near. And instantly perceives moving objects.
These are the main criteria that distinguish our eyesight from canine. Such differences are caused, first of all, by the purpose of the organ of vision, which for us and for them has different meanings.
How to check your eyesight
The eyes in caudate, as in humans, undergo changes that can cause destructive processes and decreased vision. There may be several reasons for this: age, injuries, certain diseases, including infections.
You are able to recognize a visual problem in a pet even at home. To understand that your dog’s eyes are out of order will help, first of all, the appearance of visible changes in the organ itself. It can be abundant discharge from the eyes, lacrimation, hanging of the upper eyelid, redness or blurred eyes. Such phenomena almost always affect the ability of visual perception.
It is possible to understand that an animal has become poorly seen by its behavior. Elementary, watch how the dog moves. With vision problems, her movements will become timid and insecure. The pet will begin to stumble on the corners, it will be difficult for him to fit into the doorway.
To dispel all doubts about the dog’s ability to see, there are special tests.
The easiest is to move your hand in front of the dog's face. If there is no response from the animal, and the pupil does not react to the change in light intensity from the held hand, it is worth considering.
Another test involves creating an obstacle course from individual objects. One person lets the animal go at the beginning of the distance, and the other, being at the end of the strip, calls him. How accurately, avoiding all obstacles, the pet will go this distance, it will indicate the presence or absence of eye changes.
It is worth noting that home experiments will only allow you to suspect your dog has vision problems. After this, you should seek the help of a specialist. Using special equipment, he will determine the nature of the violation, establish a possible cause and suggest solutions to the problem.
It is probably wrong to say that dogs see the world around them worse or better than us. Their vision is fundamentally different from our vision. Nevertheless, it gives them the opportunity to adapt perfectly and exist in the world around them, to be on guard of order and master some “professions”.
Interesting dog vision facts await you in the video below.
