Which animal has the best eyesight? Color vision in animals

Vision is one of the five human senses. With its help, a person receives information about the world around him, recognizes objects and their location in space. Importance high level vision cannot be overestimated, because with poor eyesight human life becomes very complicated. It is especially important to have good vision for children, since a decrease in visual acuity can become a serious obstacle to the full development of the child.

Why is verification needed?

Starting from the newborn period, children need regular vision examinations by an ophthalmologist. This must be done in for preventive purposes to prevent future vision impairment or deterioration in the child.

Eye diseases in many cases tend to progress. For example, myopia (or myopia), as a rule, can develop intensively in children in school years when the visual load on the eyes increases. Hypermetropia of the eye is also a common disease in preschool or younger children. school age. Therefore, parents need to take all measures to improve their child’s visual acuity as soon as possible and prevent the development of blindness. As a rule, progressive myopia leads to irreversible changes central departments retina, which significantly reduces visual acuity.

Vision testing for newborns occurs according to the following schedule:

• The baby's eyes are first examined by an ophthalmologist in the first hours after birth. WITH special attention premature babies and children with congenital pathologies or birth injuries, newborns after a difficult birth, since it is in this category of children that hemorrhages or retinal pathologies most often occur.
• The first examination by an ophthalmologist for this category of children is usually scheduled a month after birth, if there are indications.
• A healthy child should be examined for the first time in an ophthalmology office 3 months after birth.
• Next inspection healthy child carried out at 6 months, and then at 12 months.

At 12 months, the child’s visual acuity is determined for the first time. Normally, it is 0.3–0.6 diopters.

A table for checking vision in children was developed by Orlova. This table is used for children preschool age who have not yet learned to count

Existing vision testing charts

IN modern times Many versions of tables have been created to test visual acuity in children.

The first table by which a child’s vision is checked, as a rule, is the Orlova table. This table is used to conduct vision tests for children from the age of 3, when they have not yet learned to read and write. In this table, instead of letters, pictures are used that are familiar to the child and which he can easily name.

To test visual acuity in older children, tables with printed letters are used. In the CIS countries, the Sivtsev or Golovin table is most often used. There is also a foreign analogue - the Snellen table.

In many tables, visual acuity is determined at a distance of at least 5 meters. This distance was chosen by ophthalmologists for the reason that in an eye with normal refraction (the so-called emmetropia), at this distance the point of clear vision is located, as it were, at infinity and on the retina, thus parallel rays are collected, forming a focused, clear image.

Sivtsev table

The Sivtsev table is the most common table in the territory former USSR, which is used to test visual acuity in children.

The table received its name in honor of the Soviet ophthalmologist D.A. Sivtseva. The Sivtsev table is actively used for examining vision in children and adult patients in modern times.

Sivtsev’s vision test table uses 12 lines with printed characters, which can be used to effectively examine the patient’s visual acuity.

7 letters are used as printed characters - Ш, Б, М, Н, К, У, И. The letters have different sizes, but the same width and height. In this case, the size of letters decreases in lines from top to bottom.

Sivtsev’s table also has two additional columns located to the left and right of the rows. The symbols on the left side indicate the distance from which the patient sees the letters of the line with a 100% level of vision. It is expressed in meters and is marked with the symbol “D=...”.

The left column shows the level of refractive error expressed in diopters. Refraction of the eye is the position of the focal point of the eye relative to the retina. With a normal focus position on the retina, refraction is usually zero. This position of the focal point is called emmetropia.

In case of visual impairment, the position of the focal point changes. For example, with myopia, the focal point is in front of the retina, and with farsightedness, the focal point moves behind the retina. Thus, the image is not fixed in the center of the retina and objects appear blurry and indistinct.

As a rule, refractive errors affect visual acuity and require correction. The more the refraction deviates from the norm, the more visual acuity decreases. However, there is no direct relationship between these values. If the refraction is normal, but the patient has poor vision, this may indicate a possible decrease in the transparency of the optical media of the eye. For example, the patient may exhibit symptoms of amblyopia, cataracts with clouding of the lens or cornea.

The right column indicates the patient’s visual acuity if he is located at a distance of 5 meters from the table. These values ​​are marked with “V=...”. Visual acuity in the professional terminology of ophthalmologists is the ability of the eye to see and distinguish two distant points with a minimum distance between them.

In ophthalmology, the accepted rule is that an eye with normal visual acuity can distinguish two distant points with an angular distance between them equal to 1 arc minute (1/60 degree).

Normal human visual acuity corresponds to V=1.0, that is, a person with 100% vision should be able to distinguish printed characters of the first 10 lines. However, some subjects may have visual acuity that is greater than normal, for example, 1.2, 1.5, or even 3.0 or more. With refractive errors (myopia, farsightedness), astigmatism, glaucoma, cataracts and other visual impairments, the visual acuity of the subject decreases below normal and acquires values ​​of 0.8, 0.5 and lower.

In Sivtsev’s table, the values ​​of visual acuity in the first ten lines differ in increments of 0.1, the last two lines - in 0.5. In some non-standard versions of the Sivtsev table, additional 3 lines are used with visual acuity values ​​from 3.0 to 5.0.

But these tables, as a rule, are not used in ophthalmology offices of modern clinics.

Visual acuity according to the Sivtsev table is checked according to the following instructions:

• The patient should be at a distance of 5 meters from the table. Studies are carried out for each eye separately.
• The right eye must be tightly covered with the palm of the hand so that it cannot see the letters in the table. Instead of your palm, you can use a piece of dense material (for example, cardboard or plastic). Thus, the visual acuity of the left eye is examined.
• The lines must be read in order, left to right, top to bottom. It takes no more than 2-3 seconds to recognize the sign.

Determining visual acuity using the Sivtsev table is quite simple. The patient, as a rule, has normal visual acuity if he was able to correctly read letters in rows with V = 0.3-0.6. Only one mistake is allowed. In rows below V=0.7, no more than two errors are allowed. The numerical value of visual acuity corresponds to the numerical value of V in the last row, in which no errors were made beyond the norm.

Using this table, only myopia is determined. Farsightedness is not determined according to the Sivtsev table. That is, if the subject sees all 12 lines at a distance of 5 meters, this does not mean that he suffers from farsightedness. This indicates visual acuity above the average.

If the test result is unsatisfactory and a deviation from the norm is detected, then possible reason decreased visual acuity, the child may have a refractive error. In this case, a subsequent determination of refraction is necessary.

Snellen chart

Snellen chart

The Snellen chart is one of the popular tables for testing visual acuity in children. In modern times, this table is especially common in the United States.

The Snellen chart was developed in 1862 by Dutch ophthalmologist Hermann Snellen. The Russian analogue of this table is the Sivtsev table.

The table includes a standard set of rows consisting of Latin letters, which are called optotypes (test types). The size of the letters, just like in Sivtsev’s table, decreases with each line in the downward direction.

The top row of the Snellen chart contains the largest characters that a person with normal visual acuity can read at a distance of 6 meters (or 20 feet). A person with 100% vision is able to distinguish the subsequent lower lines at distances of 36, 24, 18, 12, 9, 6 and 5 meters, respectively. A traditional Snellen chart typically has 11 lines printed. The first line consists of the largest letter, which can be E, H, N, or A.

The subject's vision is checked using the Snellen chart as follows:

• The subject is located at a distance of 6 meters from the table.
• Cover one eye with the palm of your hand or some dense material, and read the letters in the table with the other.

The visual acuity of the subject is usually checked by the indicator of the smallest row, which was read without errors at a distance of 6 meters.

As a rule, if a person with normal visual acuity is able to distinguish one of the lower rows at a distance of 6 meters, then the visual acuity value is 6/6. If the subject is able to distinguish only lines located above the line that a person with normal visual acuity can read at a distance of 12 meters, then the visual acuity of such a patient is 6/12.

Orlova table

Orlova's vision test table is used to determine visual acuity in preschool children. This table contains rows with special pictures, the size of which becomes smaller with each row from top to bottom.

Orlova table

On the left side of the table, next to each line, the distance from which a child with normal visual acuity is able to distinguish symbols is indicated.

Variation of Orlova's table

The distance is marked with the symbol “D=...”. IN right side The table indicates visual acuity if the child recognizes them at a distance of 5 meters.

Vision is considered normal if a child is able to recognize pictures of the tenth line with each eye from a distance of 5 meters.

If the child’s visual acuity is reduced and he is not able to recognize the signs on the tenth line, then he is brought closer to the table at a distance of 0.5 meters and asked to name the characters in the top row. The child’s visual acuity is determined by the line in which the child can correctly name all the symbols.

Before the examination, it is advisable to show the child pictures so that he understands what is required of him and ask him to say the names of the pictures out loud.

Golovin table

The Golovin table is also a fairly common table for checking visual acuity in children. Like Sivtsev’s table, it is used mainly in the CIS countries. The table got its name in honor of the famous ophthalmologist S.S. Golovin, who lived in the USSR.

Unlike Sivtsev’s table, this table uses symbols – Landolt rings – instead of printed letters. There are also twelve rows in Golovin's table and the rings printed in these rows decrease in size with each row in the downward direction. These rings are of equal and equal width in each row.

Golovin's vision table

Visual acuity indicators are indicated on the right side of the table and are marked with the symbol “V=...”.

In the traditional Golovin table, it is possible to determine visual acuity in the range of 0.1-2.0. The first 10 lines, as in Sivtsev’s table, differ in increments of 0.1, the remaining two - in 0.5. In some versions of the tables, three extra rows are additionally used to determine visual acuity above the average. These lines differ in increments of 1.0.

The left side of the table indicates the distance in meters from which a person with normal visual acuity is able to recognize the symbol in a given line. It is marked with the symbol “D=...”.

Visual acuity is determined at a distance of 5 meters separately for each eye.

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Conclusions

IN childhood should never be ignored ophthalmological examinations, since it is at this age that serious eye diseases, which over time can lead to a noticeable deterioration in vision and even blindness, which can greatly impede normal development child. Nowadays, various eye tables have been created for testing vision, which are used to determine the quality of peripheral vision, acuity, and other indicators. Especially considering that a disease such as farsightedness in children is now actively gaining momentum.

Man is the highest intelligent being on Earth, but some of our organs are significantly inferior to our smaller brothers, one of which is vision. At all times, people have been interested in how the world around us Birds, animals, insects see, because outwardly everyone’s eyes are so different, and today’s technologies allow us to look through their eyes, and believe me, the vision of animals is very interesting.

Animal eyes

The first thing everyone is interested in is - how do our closest friends cats and dogs see?

Cats see perfectly in pitch darkness, as their pupil can expand up to 14 mm, thereby capturing the slightest light waves. In addition, they have a reflective membrane behind the retina, which acts as a mirror, collecting all the particles of light.

Cat pupils

Due to this, a cat sees in the dark six times better than a human.

In dogs, the eye is structured in approximately the same way, but the pupil is unable to expand as much, thereby giving it a fourfold advantage over humans to see in the dark.

What about color vision? Until recently, people were sure that dogs see everything in shades of gray, not distinguishing a single color. Recent research has proven this to be a mistake.

Dog color spectrum

But you have to pay for the quality of night vision:

1. Dogs, like cats, are dichromats; they see the world in faded blue-violet and yellow-green colors.
2. Visual acuity is poor. In dogs it is about 4 times weaker than ours, and in cats it is 6 times weaker. Look at the Moon - do you see spots? Not a single cat in the world sees them; for her they are just a gray spot in the sky.

It is also worth noting the location of the eyes in animals and in us, due to which pets see with peripheral vision no worse than with central vision.

Central and peripheral vision

Another interesting fact- dogs see 70 frames per second. When we watch TV, 25 frames per second for us merge into a single video stream, but for dogs it’s a quick series of pictures, which is probably why they don’t really like watching TV.

Except dogs and cats

A chameleon and a seahorse can look in different directions at the same time, each of its eyes is processed separately by the brain. Before throwing out its tongue and grabbing the victim, the chameleon still closes its eyes to determine the distance to the victim.

But an ordinary pigeon has a viewing angle of 340 degrees, which allows you to see almost everything around, which makes hunting difficult for cats.

A few dry facts:

• Deep-sea fish have a super-dense retina, with 25 million rods concentrated on every millimeter. This exceeds ours a hundred times;
• A falcon sees a mouse in a field from a distance of one and a half kilometers. Despite its flight speed, clarity is completely preserved;
• The scallop has about 100 eyes on the edge of its shell;
• The octopus has a square pupil.

The reptiles outdid everyone a bit. Pythons and boas are able to see infrared waves, that is, heat! In a sense, we also “see” it with our skin, but snakes see it with their eyes, like the predator in the film of the same name.

Mantis shrimp

But the mantis shrimp have the most unsurpassed eyes. These are not even eyes, and an organ stuffed with wave sensors. Moreover, each eye actually consists of three - two hemispheres separated by a stripe. Visible light is perceived only by the middle zone, but the hemispheres are sensitive to ultraviolet and infrared ranges.

Shrimp sees 10 colors!

This does not take into account the fact that the shrimp has trinocular vision, in contrast to the most common on the planet (and in our country) binocular vision.

Insect eyes

Insects can also surprise us a lot:

• It is not so easy to kill an ordinary fly with a newspaper, since it sees 300 frames per second, which is 6 times faster than us. Hence the instant reaction;
• A domestic cockroach will see movement if the object has moved only 0.0002 millimeters. This is 250 times thinner than a hair!
• The spider has eight eyes, but in fact they are practically blind insects, capable of distinguishing only a spot, their eyes practically do not work;
• A bee's eye consists of 5,500 microscopic lenses that do not see red;
• The earthworm also has eyes, but atrophied ones. He can distinguish day from night, nothing more.

Bee eyes

The most sharp vision among insects, dragonflies have it, but it is still about 10 times worse than ours.

How sharp of vision do humans have compared to animals?

Scientists from Duke University asked this question and conducted a study in which they compared visual acuity in humans and in various animals. At the same time, with the help of a special program, images were even created demonstrating how blurry or clear the world can be seen by some animals.

In the animal kingdom, most species "see the world in much less detail than we do," notes Eleanor Caves, co-author new job. Of course, scientists can't ask animals to read the letters on an optometric chart; instead, experts study the anatomy of the eyes and conduct behavioral tests to determine the visual acuity of particular animals.

This time, the researchers used a method that measures cycles per degree to determine visual acuity. This information was then processed into special program, in which images were then created to demonstrate how clear or blurry the world was seen by the animal being studied.

Humans distinguish approximately 60 cycles per degree—that is, 60 pairs of black and white parallel lines per degree of visual angle. At the same time, as researchers discovered, chimpanzees and other primates have approximately the same indicator as ours. Some birds are even superior to humans: for example, the wedge-tailed eagle is able to see 140 cycles/degree - such acute vision apparently helps it notice prey on the ground at an altitude of thousands of meters.

Most other animals have much less acute vision than humans, researchers have found. Thus, many fish and birds see about 30 cycles/degree, but elephants see only 10 cycles/degree. The last indicator is already the level of blindness for humans, but in many animals and insects it is even lower.

Cats are typical nocturnal predators. For a fruitful hunt, they need to make maximum use of all their senses. " Business card What is unique to all cats without exception is their night vision. A cat's pupil can dilate up to 14 mm, allowing a huge beam of light into the eye. This allows them to see perfectly in the dark. In addition, the cat's eye, like the Moon, reflects light: this explains the glow cat eyes in the dark.

All seeing dove

Pigeons have an amazing feature in visual perception the surrounding world. Their viewing angle is 340°. These birds see objects located at a much greater distance than humans see them. That is why, at the end of the 20th century, the US Coast Guard used pigeons in search and rescue operations. Acute pigeon vision allows these birds to perfectly distinguish objects at a distance of 3 km. Since impeccable vision is the prerogative of mainly predators, pigeons are one of the most vigilant peaceful birds on the planet.

Falcon vision is the most vigilant in the world!

The falcon bird of prey is recognized as the most vigilant animal in the world. These feathered creatures can track small mammals (voles, mice, gophers) from great heights and at the same time see everything that happens on their sides and in front. According to experts, the most vigilant bird in the world is the peregrine falcon, which can spot a small vole from a height of up to 8 km!

Pisces are no slouch either!

Among the fish with excellent vision, the inhabitants of the deep are especially distinguished. These include sharks, moray eels, and monkfish. They are able to see in pitch darkness. This happens because the density of rods in the retina of such fish reaches 25 million/sq.mm. And this is 100 times more than in humans.

Horse vision

Horses see the world around them using peripheral vision because their eyes are located on the sides of their heads. However, this does not at all prevent horses from having a viewing angle of 350°. If a horse raises its head up, its vision will be closer to spherical.

High speed flies

It has been proven that flies have the fastest visual reaction in the world. In addition, flies see five times faster than humans: their frame rate is 300 images per minute, while humans have only 24 frames per minute. Scientists from Cambridge claim that photoreceptors on the retina of flies' eyes can physically shrink.

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 it even high speed preserves the clarity of images 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.

Eyes are a special organ that is endowed with all living beings on the planet. We know in what colors we see the world, but how do animals see it? What colors do cats see and what colors do they not? Do dogs have black and white vision? Knowledge about animal vision will help us take a broader look at the world around us and understand the behavior of our pets.

Features of vision

And yet, how do animals see? According to certain indicators, animals have more perfect vision than humans, but it is inferior in the ability to distinguish colors. Most animals see only in a palette specific to their species. For example, for a long time it was believed that dogs see only in black and white. And snakes are generally blind. But recent research has proven that animals see different wavelengths, unlike humans.

Thanks to vision, we receive more than 90% of the information about the world that surrounds us. The eyes are our predominant sensory organ. It is interesting that the sharpness of animals’ vision is significantly higher than that of humans. It's no secret that feathered predators see 10 times better. An eagle is able to detect prey in flight from a distance of several hundred meters, and a peregrine falcon tracks a pigeon from a height of a kilometer.

Another difference is that most animals have excellent vision in the dark. Photoreceptor cells in the retina of their eyes focus light, and this allows nocturnal animals to capture streams of light of several photons. And the fact that the eyes of many animals glow in the dark is explained by the fact that under the retina there is a unique reflective layer called tapetum. Now let's look at individual types of animals.

Horses

The gracefulness of the horse and its expressive eyes are unlikely to leave anyone indifferent. But often those who learn to ride are told that approaching a horse from behind is dangerous. But why? How do animals see what is happening behind them? No way - it’s behind the horse’s back and therefore it can easily get scared and buck.

The horse's eyes are positioned so that it can see from two angles. Her vision is, as it were, divided in two - each eye sees its own picture, due to the fact that the eyes are located on the sides of the head. But if the horse looks along the nose, then it sees one image. This animal also has peripheral vision and sees excellently at dusk.

Let's add a little anatomy. The retina of any living creature contains two types of receptors: cones and rods. Color vision depends on the number of cones, and rods are responsible for peripheral vision. In horses, the number of rods exceeds that in humans, but the cone receptors are comparable. This suggests that horses also have color vision.

Cats

Many people have animals at home, and the most common are, of course, cats. The vision of animals, and especially of the cat family, differs significantly from that of humans. A cat's pupil is not round, like most animals, but elongated. He reacts sharply to large number bright light narrowing to a small gap. This indicator says that in the retina of the animal’s eye there is a large number of rod receptors, due to which they see perfectly in the dark.

What about color vision? What colors do cats see? Until recently, it was believed that cats see in black and white. But studies have shown that it distinguishes between gray, green and blue colors. In addition, it sees many shades of gray - up to 25 tones.

Dogs

Dogs' vision is different from what we are used to. If we return to anatomy again, there are three types of cone receptors in the human eye:

• The first perceives long-wave radiation, which distinguishes orange and red colors.
• The second is medium wave. It is on these waves that we see yellow and green.
• The third, accordingly, perceives short waves at which blue and violet are distinguishable.

Animals' eyes are distinguished by the presence of two types of cones, so dogs do not see orange and red colors.

This difference is not the only one - dogs are farsighted and see moving objects best. The distance from which they see a stationary object is up to 600 meters, but dogs notice a moving object from 900 meters. It is for this reason that it is best not to run away from the four-legged guards.

Vision is practically not the main organ of a dog; for the most part, they follow smell and hearing.

Now let's summarize - what colors do dogs see? In this they are similar to colorblind people; they see blue and violet, yellow and green, but a mixture of colors may seem simply white to them. But dogs, like cats, are best at distinguishing gray colors, and up to 40 shades.

Cows

Many believe, and we are often told, that domestic artiodactyls react strongly to the color red. In reality, the eyes of these animals perceive the color palette in very blurry, fuzzy tones. That's why bulls and cows respond more to movement than to how your clothes are colored or what color is waved in front of their face. I wonder, who will like it if they start waving some kind of rag in front of his nose, sticking spears into the back of his neck?

And yet, how do animals see? Cows, judging by the structure of their eyes, are able to distinguish all colors: white and black, yellow and green, red and orange. But only weakly and blurry. Interestingly, cows have vision like a magnifying glass, and it is for this reason that they are often frightened when they see people unexpectedly approaching them.

Nocturnal animals

Many nocturnal animals have, for example, tarsier. This is a small monkey that comes out to hunt at night. It is no larger than a squirrel, but it is the only primate in the world that feeds on insects and lizards.

The eyes of this animal are huge and do not rotate in their sockets. But at the same time, the tarsier has a very flexible neck, allowing it to rotate its head a full 180 degrees. He also has extraordinary peripheral vision, allowing him to see even ultraviolet radiation. But the tarsier distinguishes colors very poorly, like everyone else

I would also like to say about the most common inhabitants of cities at night - bats. For a long time it was assumed that they do not use vision, but fly only thanks to echolocation. But recent studies have shown that they have excellent night vision, and what's more - bats able to choose whether to fly towards the sound or turn on night vision.

Reptiles

While talking about how animals see, one cannot remain silent about how snakes see. The fairy tale about Mowgli, where a boa constrictor bewitches the monkeys with his gaze, leaves you in awe. But is this true? Let's figure it out.

Snakes have very poor vision, which is affected by the protective membrane covering the reptile's eye. This makes the named organs appear cloudy and take on that terrifying appearance about which legends are made. But vision is not the main thing for snakes; they mainly attack moving objects. That's why the fairy tale says that the monkeys sat in a daze - they instinctively knew how to escape.

Not all snakes have unique heat sensors, but still infrared radiation and they distinguish colors. The snake has binocular vision, which means she sees two pictures. And the brain, quickly processing the information received, gives it an idea of ​​the size, distance and outline of the potential victim.

Birds

Birds are amazing in their diversity of species. It is interesting that the vision of this category of living beings also varies greatly. It all depends on what kind of life the bird leads.

So, everyone knows that predators have extremely acute vision. Some species of eagles can spot their prey from a height of more than a kilometer and drop like a stone to catch it. Did you know that certain species birds of prey are able to see ultraviolet light, which allows them to find nearby burrows in the dark

And the budgie living in your home has excellent eyesight and is able to see everything in color. Studies have proven that these individuals distinguish each other using bright plumage.

Of course, this topic is very broad, but we hope that the facts presented will be useful to you in understanding how animals see.