Who has the best eyesight in the world? Which animal has the best vision Animal vision

Not only chameleons, but also seahorses can look in two directions at once. Animals often see much better than humans.

Even those who are considered the closest genetic relatives of humans - apes - see three times better than him. And not only them, of course. An eagle, for example, also has three times more keen vision than a human.

Deep-sea fish, as is known, can see in pitch darkness, and all because the density of rods in their retina reaches 25 million/sq.mm, which is 100 times more than in humans.

Cats also see well in the dark because their pupils can dilate up to 14 millimeters. And dogs see three times better in the dark than we do.

Dogs have an average visibility of 240-250 degrees, which is 60-70 units higher than that of humans.

The pigeon has a viewing angle of 340 degrees. A horse with its head raised also has near-spherical vision. However, as soon as the horse lowers its head, it loses half of its vision. The record holder in panoramic vision is the woodcock bird, which has almost all-round vision!

A fly's image changing speed is 300 frames per second, i.e. it exceeds the similar ability of a person by 5-6 times.

White butterflies (colias) can distinguish image elements of 30 microns, outperforming humans by more than three times.

The vulture distinguishes small rodents from a distance of up to 5 kilometers.

The Falcon is able to see a target 10 cm in size from a distance of 1.5 km, and even at high speed it retains a clear image of objects.

The cockroach notices movement of 0.0002 mm. So, when you are standing in the kitchen and trying to rush at a cockroach to kill it with a slipper, you have practically no chance.

Four-Eyes

These fish live in Mexico and Central America. They are very small, up to 32 cm in length, feed on insects, so they spend most of their time near the surface of the water. Despite their name, these fish only have 2 eyes. However, these eyes are separated by a vein, and each half has its own pupil. This strange adaptation allows the four-eyed fish to see well both above and under water.

Stalk-eyed flies

These small but unusual creatures live in the jungles of southeast Asia and Africa. They got their name from the long protrusions on either side of their heads with eyes and antennae at the end. Males have longer stems. According to observations, females prefer males with longer stems.

Tarsier

It is a small nocturnal primate native to the tropical forests of southeast Asia. This is the only predatory primate in the world; it feeds on lizards, insects and even birds. But its most interesting feature is its huge eyes, disproportionately large in relation to the entire body. If these proportions were applied to a person, then his eyes would be the size of grapefruits. The tarsier has very sharp eyesight. It was even suggested that they could see ultraviolet light. On the other hand, tarsiers have poor color vision, like many other nocturnal predators.

Chameleon

Chameleons are known for their ability to change color, which helps them communicate and express their intentions or moods (only a few species of chameleons use color change as camouflage). These lizards also have very unusual eyes. The eyelids are completely connected, there is only a small slit for the pupil. Each eye moves independently of the other, allowing the chameleon to monitor prey and possible threats at the same time.

Dragonfly

The dragonfly's eyes are so large that they cover almost the entire head, making it look like a helmet and giving it a 360-degree field of vision. These eyes are made up of 30,000 parts, each containing a lens and several light-sensitive cells. Dragonflies have excellent vision. They can detect colors and polarized light, and dragonflies are especially sensitive to movement.

Leaf-tailed gecko

The leaf-tailed gecko has very unusual eyes. He has vertical pupils, which have several “holes”. These openings widen at night, allowing these lizards to see better. A gecko's eyes contain many more light-sensitive cells than human eyes, allowing the animal to detect objects and even distinguish colors at night. While cats and sharks see 6 and 10 times better than humans, geckos see 350 times better.

Colossal squid

It is the largest invertebrate known to science. This squid also has the largest eyes in the animal kingdom. Each eye can be up to 30 cm wide. Such large eyes allow the squid to see in semi-darkness, which is very useful for an animal that spends almost all of its time hunting at a depth of 2000 m underwater.

Opisthoproct

Opisthoproctus is a deep-sea fish with one of the strangest eye structures. A characteristic sign of opisthoproctus is cylindrical eyes directed upward.

Mantis crab

These crayfish are known for their aggressiveness and unique weapons (they have a very sharp and powerful claw that can easily cut a human finger in half and break glass in an aquarium). Mantis crabs have the most complex eye in the animal kingdom. They distinguish 12 primary colors - four times more than humans, as well as different types of light polarization, that is, the direction in which the light wave oscillates. The light-sensitive cells of the eye rotate relative to the plane of polarization of light, perceiving almost the entire visible spectrum - from the ultraviolet to the infrared. Now we can only guess what the world looks like for this crustacean.

Ogre Spider

Spiders are known to have many eyes. The ogre spider has 6 of them, but it looks like 2, since the middle pair of eyes is very enlarged. All this serves to improve night vision. Ogre spiders have excellent night vision not only due to the size of their eyes, but also the large number of light-sensitive lenses covering them. This membrane is so sensitive that it breaks down every morning and grows back at night.

We see the world around us and it seems to us that it is exactly like this. It’s hard to even imagine that someone sees it differently, in black and white, or without blue and red. It’s hard to believe that for some people our familiar world is completely different.

But that's exactly how it is.

Let's look at the world around us through the eyes of animals, let's figure out how animals see, in what colors they perceive the world.

So, first, let's look at what vision is and what functional abilities it includes.

What is vision?

Vision is the process of processing images of objects in the surrounding world.

• carried out by the visual system
• allows you to get an idea of ​​the size, shape and color of objects, their relative position and the distance between them

The visual process includes:

• penetration of light flux through the refractive media of the eye
• focusing light on the retina
• transformation of light energy into nerve impulse
• transmission of nerve impulses from the retina to the brain
• processing information with the formation of a seen image

Visual functions:

• light perception
• perception of moving objects
• field of view
• visual acuity
• color perception

Light perception is the ability of the eye to perceive light and determine varying degrees of its brightness.

The process of adapting the eye to different lighting conditions is called adaptation. There are two types of adaptation:

• to darkness - when the light level decreases
• and to light - with increasing light levels

Light perception is the basis of all forms of visual sensation and perception, especially in the dark. The light perception of the eye is also influenced by factors such as:

• distribution of rods and cones (in animals, the central region of the retina at 25° consists predominantly of rods, which improves night vision)
• concentration of light-sensitive visual substances in rods (in dogs, the sensitivity to light of rods is 500-510 nm, in humans 400 nm)
• the presence of a tapetum (tapetum lucidum) - a special layer of the choroid of the eye (the tapetum directs back the photons passed to the retina, causing them to once again act on the receptor cells, increasing the photosensitivity of the eye, which in low light conditions turns out to be very valuable) in cats the eye reflects 130 times more light than a person (Paul E. Miller, DVM, and Christopher J. Murphy DVM, PhD)
• pupil shape - the shape, size and position of the pupil in various animals (the pupil can be round, slit-like, rectangular, vertical, horizontal)
• the shape of the pupil can tell whether an animal is a predator or a prey (in predators the pupil narrows into a vertical stripe, in preys into a horizontal stripe - scientists discovered this pattern by comparing the shapes of the pupils in 214 species of animals)

So, what are the different pupil shapes:

• Slit pupil - (in predatory animals such as domestic cats, crocodiles, gecko lizards, snakes, sharks) allows you to more accurately adjust the eye to the amount of light around, so that you can see in the dark and not go blind in the midday sun

• Round pupil - (in wolves, dogs, big cats - lions, tigers, cheetahs, leopards, jaguars; birds) because they are spared the need to see well in the dark

• The horizontal pupil (herbivores) allows the eye to clearly see what is happening near the ground and covers a fairly wide panorama of the eyes, protected from direct sunlight from above, which could blind the animal

How do animals perceive moving objects?

The perception of movement is vital because... moving objects are signals of either danger or potential food and require quick appropriate action, while stationary objects can be ignored.

For example, dogs can recognize moving objects (due to a large number of rods) at a distance of 810 to 900 m, but stationary objects only at a distance of 585 m.

How do animals react to flickering light (for example, on TV)?

The response to flickering light provides insight into the function of the rods and cones.

The human eye is capable of detecting vibrations at 55 hertz, while the dog's eye detects vibrations at a frequency of 75 hertz. Therefore, unlike us, dogs most likely see only flickering and most of them do not pay attention to the image on TV. Images of objects in both eyes are projected on the retina and transmitted to the cerebral cortex, where they are merged into one image.

What are the visual fields of animals?

Field of view is the space perceived by the eye with a fixed gaze. There are two main types of vision:

• binocular vision - perception of surrounding objects with both eyes
• monocular vision - perception of surrounding objects with one eye

Binocular vision is not present in all species of animals and depends on the structure and relative position of the eyes on the head. Binocular vision allows you to make fine coordinated movements of the forelimbs, jumping, and move easily.

For predators, binocular perception of hunting objects helps them correctly assess the distance to the intended victim and choose the optimal attack trajectory. In dogs, wolves, coyotes, foxes, jackals, the binocular field angle is 60-75°, in bears it is 80-85°. In cats, 140° (the visual axes of both eyes are almost parallel).

Monocular vision with a large field allows potential victims (marmots, gophers, hares, ungulates, etc.) to notice the danger in time. reaches 360° in rodents, 300-350° in ungulates, and more than 300° in birds. Chameleons and seahorses can look in two directions at once, because... their eyes move independently of each other.

Visual acuity

• the ability of the eye to perceive two points located at a minimum distance from each other as separate
• the minimum distance at which two points will be visible separately depends on the anatomical and physiological properties of the retina

What does visual acuity depend on?

• on the size of the cones, the refraction of the eye, the width of the pupil, the transparency of the cornea, lens and vitreous body (comprising the light refractive apparatus), the condition of the retina and optic nerve, age
• The diameter of the cones determines the value of maximum visual acuity (the smaller the diameter of the cones, the greater the visual acuity)

Visual angle is the universal basis for expressing visual acuity. The normal sensitivity limit of the eye of most people is 1. In humans, to determine visual acuity, the Golovin-Sivtsev table is used, containing letters, numbers or signs of various sizes. In animals, visual acuity is determined using (Ofri., 2012):

• behavioral test
• electroretinography

The visual acuity of dogs is estimated at 20-40% of the visual acuity of humans, i.e. a dog recognizes an object from 6 meters, while a person recognizes an object from 27 meters.

Why doesn't a dog have the visual acuity of a human?

Dogs, like all other mammals except monkeys and humans, lack the central fovea of ​​the retina (the area of ​​maximum visual acuity). Most dogs are slightly farsighted (hyperopia: +0.5 D), i.e. they can distinguish small objects or their parts at a distance of no closer than 50-33 cm; all objects located closer appear blurry, in circles of dispersion. Cats are nearsighted, meaning they cannot see distant objects as well. The ability to see well up close is more suitable for hunting prey. The horse has low visual acuity and is relatively myopic. Ferrets are myopic, which is, no doubt, a reaction to their adaptation to a burrowing lifestyle and searching for prey by smell. Ferrets' nearsighted vision is as sharp as ours and maybe even a little sharper.

Thus, the eagle has the sharpest vision, then in descending order: falcon, man, horse, dove, dog, cat, rabbit, cow, elephant, mouse.

Color vision

Color vision is the perception of the color diversity of the surrounding world. The entire light part of electromagnetic waves creates a color spectrum with a gradual transition from red to violet (color spectrum). Color vision is carried out by cones. There are three types of cones in the human retina:

• the first perceives long-wavelength colors - red and orange
• the second type perceives mid-wave colors better - yellow and green
• the third type of cones is responsible for short-wavelength colors - blue and violet

Trichromasia - the perception of all three colors
Dichromasia - seeing only two colors
Monochromacy - seeing only one color

How do animals perceive color?

Kind of animal	Short wavelength, nm	Average wavelength, nm	Source
Dog	454	561	Loop et al. (1987) Guenther & Zrenner (1993)
Cat	429-435	555	Neitz et al. (1989); Jacobs et al. (1993)
Horse	428	539	Carroll et al. (2001); Timney&Macuda (2001)
Pig	439	556	Neitz&Jacobs (1989) Cow 451 555 Jacobsetal. (1998)

Color vision in dogs:

Color vision of cats:

Horse color vision:

Have you ever wondered how you look to your dog? Or even how a bee sees the world? The vision of every species of animal on Earth is unique, and some can see things that are inaccessible to us.

Dogs

Dogs have poor eyesight; their eyes are not sensitive to most colors, and they see the world somewhat faded. On the other hand, they see very well at night. They have a well-developed sense of perspective and depth, and their eyes are more sensitive to movement.

Fish

Your average aquarium-dwelling fish can see in ultraviolet light, and everything in its immediate vicinity is magnified. This is probably why so many fish look surprised all the time.

Birds

Our feathered friends have keen eyesight. Nocturnal birds see very well when there is no light, and during the day they can see shades of colors that humans cannot see, as well as ultraviolet rays.

Snakes

Snakes generally have poor eyesight, but they can see thermal radiation at night ten times better than any modern infrared equipment. During the day, however, they only respond to movement - if their prey doesn't move, they won't catch it.

Mice and rats

Each of the mouse's eyes moves independently, so they see two separate pictures. The world for them is blurry, slow and blue-green.

Cows

For cows, their pastures are not green, but orange and red. They see everything a little magnified.

Horses

The horse's eyes are located on the sides of his head. This helps alert them to any danger. But this also has its drawbacks: these animals never see what is right in front of their noses.

Bees

Bees understand the world three times faster than humans. They also see ultraviolet rays, which we cannot.

flies

Flies have thousands of tiny eyes that create a single image. They can see ultraviolet rays, and the world moves a little slower for them than humans.

Sharks

Underwater predators such as sharks do not see any colors, but their vision underwater is much sharper than ours.

Chameleons

Chameleons are interesting creatures not only because of their appearance, but also because their eyes can move independently of each other. This gives them a 360? view.

Night geckos

These lizards have true night vision. They can see 350 times better than humans.

Butterflies

Butterflies are amazing insects. Their vision is not very sharp, but they can see many more colors and shades than humans, including ultraviolet light.

How do our four-legged friends see?

Until now, we, the owners of our four-legged pets, know practically nothing about their vision. Do our cats and dogs see colors? How do they see the world around them? Are dogs really nearsighted and cats, on the contrary, farsighted? Is it true that animals see into the distance worse than humans? All these interesting and entertaining questions are answered by the Head of the Center for Veterinary Ophthalmology, Associate Professor Alexey Germanovich Shilkin and his colleagues.

I want to say right away that humans and animals see the world around them completely differently and have different eye structures. A person receives more than 90% of information about the world around him through vision. It is not only the most important, but also the dominant one among the other senses. Our vision has excellent sharpness far and near, a wide range of colors, and this is due to the fact that in the human eye there is a functional center of the retina - the macula. The human eye, through the refractive system: cornea, pupil and lens, directs the entire flow of light into the eye to the macula.

Human visual system.

The human optical system focuses the visual image into the macula - the central part of the eye, where the largest amount of light perceiving cone receptors is located. This forms the macular - central vision of a person.

Here are the photoreceptors - cones, with the highest visual activity. The denser their concentration, the higher visual acuity. Moreover, each cone through the fibers of the optic nerve has its own representation in the central nervous system. It looks like a high resolution matrix.

Our optic nerve contains just a huge number of nerve fibers - more than 1 million 200 thousand. All information from the eye passes to the visual area of ​​the cerebral cortex, where the unusually developed higher cortical centers are located. By the way, the old Russian proverb that we see not with our eyes, but with the back of our heads in the light of modern knowledge is not without meaning.

Human fundus

1. The optic disc, consisting of 1 million 120 thousand nerve fibers, provides high visual resolution.
2. Macula( maculae), is the functional center of the human retina, due to the large number of nerve fibers, providing high visual acuity and full color perception.
3. The vessels of the retina are arteries and veins.
4. The periphery of the retina is represented by rods that do not fit tightly to each other. Due to this, a person's vision in the dark is weak.

The yellow spot is characteristic only of humans and a number of higher primates. Other animals do not have it. Several years ago, American scientists compared the vision of humans and monkeys. Studies have shown that monkeys see better. Then similar experiments were carried out between a dog and a wolf. Wolves, as it turns out, see better than our pets. This is probably some kind of retribution for all the benefits of civilization.

How do animals' eyes work?

Our four-legged pets perceive everything a little differently. For dogs and cats, vision is not decisive in the perception of the world around them. They have other well-developed senses: hearing, smell, touch, and use them well. The visual system of animals has some interesting features. Dogs and cats see equally well in the light and in the dark. It should be said that the size of the eyes of animals practically does not correlate with the size of the body. The size of the eye depends on whether the animal is diurnal or nocturnal. Nocturnal animals have larger and protruding eyes, unlike daytime ones.

The size of an animal's eyes does not depend on body size. All nocturnal birds have huge bulging eyes, which help them navigate perfectly in the dark.

For example, an elephant’s eyes are only 2.5 times larger than those of a cat. Animals do not have a macula, the functional center of vision. What does this give them? If a person sees predominantly with the yellow spot and has a central type of vision, then dogs and cats see equally with the entire retina and have a panoramic type of vision.

The visual system of the animal eye.

The optical system of animals uniformly directs the visual image across the entire surface of the retina, thereby creating panoramic vision. Thus, the entire retina of animals sees equally.

The retina of dogs and cats is divided into 2 parts. The upper “tapetal” part shines like mother-of-pearl and is intended for vision in the dark. Its color varies from green to orange and directly depends on the color of the iris. When we see the brilliant green eyes of a cat in the dark, we are precisely observing the green fundus reflex. And the eyes of wolves, glowing at night with an ominous red color, are nothing more than the colored tapetal part of the retina

Fundus of a dog.

1. The optic disc consists of 170 thousand nerve fibers. Due to this, animals have a lower resolution of visual images.
2. The lower part of the retina is pigmented. The pigment protects the retina from burns by ultraviolet radiation (spectrum) of daylight.
3. Retinal vessels.
4. Animals have a reflective shiny membrane (tapetum lucidum). Due to its presence, animals (especially those leading a nocturnal lifestyle) see much better in the dark.

The lower part of the retina is pigmented. It is brown in color and adapted for vision in light. The pigment protects the retina from damage from the ultraviolet part of the solar spectrum. The large bulging eye and the division of the retina into two halves create all the conditions for life in a wide range of illumination. And panoramic vision helps animals hunt better and stay ahead of prey.

What is the visual acuity of animals?

While gaining in panoramic vision and the ability to adapt in a wide range of the spectrum, animals are inferior to humans in visual acuity. According to the literature, dogs see 30%, and cats 10% of human visual acuity. If dogs could read, at a doctor’s appointment they would read the third line from the top (from the table that you all saw), and cats would only read the first. A person with 100% normal vision reads the tenth line. This is due to the absence of a yellow spot in dogs and cats. In addition, light-perceiving photoreceptors are located at a great distance from each other, and the number of nerve fibers in the optic nerve of animals is 160-170 thousand, which is six times less than in humans. The visual image seen by animals is perceived by them less clearly and with low detailed resolutions.

Are dogs really nearsighted and cats farsighted?

This is a widespread misconception, even among veterinarians. We conducted special studies in 40 animals to measure myopia and farsightedness. To do this, dogs and cats were seated in front of an autorefractometer (as at an appointment with a human ophthalmologist) and the refraction of the eye was automatically measured. We have found that dogs and cats do not suffer from myopia and farsightedness, unlike humans.

Why do dogs and cats play with moving objects?

We humans see stationary objects better and we owe this to cones. Dogs and cats have predominantly rod vision, and rods are better at perceiving moving objects than stationary ones. So, if animals see a moving object from a distance of 900 meters, then they see the same object in a stationary state only from a distance of 600 meters and closer. As soon as the bow on the string or the ball begins to move, the hunt has begun!

Do our pets see colors?

A person distinguishes colors perfectly due to the cones, which have the greatest density in the area of ​​the macula. Until recently, it was believed that if animals do not have a yellow spot, then they see the world in black and white. Discussions about the ability of animals to distinguish colors have been going on for more than a century. All sorts of experiments were carried out to refute each other. The researchers shone flashlights of different colors into the eyes and tried to understand by the degree of constriction of the pupil which color the reaction was greater.

The end to these disputes was put at the end of the 80s by American researchers. The results of their experiments showed that dogs distinguish colors, but unlike humans, their color palette is much poorer.

The eyes of animals contain significantly fewer cones than those of humans. The human color palette is formed from three types of cones: the first perceives long-wavelength colors - red and orange. The second type perceives mid-wave colors better - yellow and green. The third type of cones is responsible for short-wavelength colors - blue and violet. Dogs do not have the cones responsible for the color red. Thus, dogs generally perceive well the blue-violet and yellow-green range of colors. But animals see up to 40 shades of gray, which gives them undeniable advantages when hunting.

How do animals navigate in the dark?

Dogs are 4 times better and cats are 6 times better at seeing in the dark than humans. This is due to two reasons.

Animals have more rods than humans. They are located along the optical axis of the eye, and have high photosensitivity and are better suited for vision in the dark than human rods.

In addition, animals, unlike humans, have a highly active reflective membrane, tapetum lucidum. It greatly improves the visual abilities of animals into the distance in the dark. Its role can be compared to the silver coating of a mirror or the reflections of a car headlight. The reflective membrane in dogs is represented by guanine crystals located in the upper part behind the retina.

Dog reflective membrane (tapetum lucidum).

The reflective membrane works as follows. In the dark, in dogs, each quantum of light passing through the transparent retina reaches the reflective membrane and, reflected from it, hits the retina again. Thus, a significantly greater light flux reaches the retina, and surrounding objects become more visible in the absence of light.

A gang of cats with glow-in-the-dark eyes. Cats' eyes glow green due to the presence of a reflective membrane. In wolves it is red, and therefore in the dark, wolves' eyes glow “ominous red.”

In cats, reflective crystals also increase the contrast of the image by changing the wavelength of the reflected color to the optimal one for photo receptors.

Width of visual fields of humans and animals

Another important characteristic is the width of the field of view. A person's eye axes are parallel, so he sees best straight ahead.

This is how a person sees the image.

The dog's eyes are positioned so that their optical axes diverge by about 20 degrees.

The human eye has a field of vision in the form of a circle, while the field of vision of a dog is “stretched” to the sides. Due to the divergence of the eye axes and “horizontal stretching,” the dog’s total field of vision increases to 240-250 degrees, which is 60-70 degrees more than that of a person.

A dog's field of vision is much wider than that of a human.

But these are average numbers; the width of the visual field varies among different breeds of dogs. The structure of the skull, the location of the eyes, the shape and size of the nose have an influence. In wide-faced dogs with a short nose (Pekingese, pug, English bulldog), the eyes diverge at a relatively small angle. Therefore, they have limited peripheral vision. In narrow-faced dogs with an elongated nose (greyhounds and other hunting breeds), the axes of the eyes diverge at a large angle. This gives the dog a very wide field of vision. It is clear that this quality is very important for successful hunting.

A horse's field of vision significantly exceeds not only a human's, but also a dog's.

Thus, our pets see the world very differently. Dogs and cats see much better than us in the dark, have a wider field of vision, and perceive moving objects better. All this allows our pets to hunt well and evade pursuit, to see not only in front of them, but also to the sides. At the same time, they are inferior to us in visual acuity and the ability to subtly distinguish colors. But animals don’t need this, they don’t read books until... We’ll see what happens next.