All about the eyesight of animals. Various information about vision Better vision in animals

Do animals distinguish colors? This is an interesting question, but it is not easy to give an accurate and comprehensive answer. It is difficult for us, with color vision, to imagine a universe without colors, and we naturally assume that all living things also perceive the world in the form of multicolor paintings. However, this view is not true.

Color is a rather arbitrary and difficult to define concept. Color perception is not easy to explore and explain; that is why scientists have long experienced difficulties in objectively and accurately interpreting this ability. In fact, no object has color; it simply absorbs white daylight and reflects only one fraction of this light, one or another part of the solar spectrum. So, for example, green trees absorb all parts of the spectrum, except for the green, which is reflected by them; this is what makes them green to our eyes.

Try to explain to a blind person, without resorting to comparisons, what red is. This will be completely impossible. Even among sighted people, varying degrees of color blindness are widespread. People often rate the same color differently; in addition, our color appreciation continues to improve and change. After all, Homer constantly calls the sea wine-red, and some ancient Greek authors mention the green color of a human face.

Ultimately, everything here rests on the peculiarities of the perceiving optical apparatus - a rather small defect or deviation from the norm, for example, the absence in a person of one of the three light-sensitive "wires" leading from the retina to the brain. Each of the mentioned pathways provides the perception of one of the primary colors: red, green or blue. Most color blind people do not have a green "wire"; others have no red "wire" and are blind to red. In the physical sense, the changes in the human body are extremely insignificant; they boil down only to features nervous system... There is every reason to believe that a number of animals with eyes similar to human ones do not have those small details that provide color perception.

WORLD WHITE AND BLACK

From what has been said it is clear enough how difficult it is (considering also that we ourselves can suffer from color blindness to some insignificant extent) to apply to other creatures our limited and not entirely accurate knowledge in the field of color perception. There are many studies devoted to this topic, but many of them are insufficiently evidence-based. It is extremely difficult to establish whether or not a particular animal distinguishes colors. After all, animals themselves are not able to answer this question. Moreover, it is almost always difficult to decide whether an animal is reacting to a color or the degree of brightness and whiteness of an object. Therefore, in order for the experiment to be of value, it is necessary to use colors that are equivalent in brightness and whiteness. Otherwise, the experimental animal, especially if it belongs to higher animals, can distinguish red from green by the relative brightness, as is the case in people suffering from color blindness.

But, despite the obvious limitations, we do know a thing or two in this area. So, it is safe to say that almost all mammals, with the exception of all species, are completely color blind. They live in a world of black and white, with a significant range of intermediate grays. They often distinguish clearly the difference in the intensity of black, in the light saturation of whites and grays. The latter circumstance often leads people to the conclusion that certain animals (for example, dogs) distinguish certain colors.

How often does an admiring owner swear that his dog will recognize a dress by its color, even if it is to a strangerthat she distinguishes a bowl or a pillow solely by their color! It is hard to imagine that you can live in a world devoid of colors! Meanwhile, most mammals in their habits belong to the type of nocturnal or crepuscular animals; they leave their shelters only when the world begins to plunge into darkness and lose its colors, illuminated only by the faint and false light of the moon.

However, all this is not so unusual for people either. After all, we easily watch monochromatic films; many newspapers and magazines are still illustrated with monochrome photographs, and we perceive them as a reflection of true life. A simple drawing made in black pencil often seems extremely natural and lively to us. Despite all the addiction of mankind to paints, we feel their absence much weaker than we sometimes think.

TOREADOR DOESN'T NEED A RED COAT

Along with others, the following simple experiment was carried out. Small squares of gray paper (different shades, but of the same brightness) were staggered; in the center was a blue square. A feeder was installed on each square, and syrup was poured in the feeder located on the blue square, the rest were empty. After a while, the bees were able to train to fly only to the blue square, even if its position relative to others changed.

When the blue paper was replaced with red (of the same brightness), the bees were disoriented - they could not distinguish the red square from the gray ones. Bees are not only blind to red; they live, as it were, in a world of blue, violet and yellow shades; at the same time, they (like a number of other insects) are able to penetrate further than humans into the ultraviolet part of the spectrum. Of course, pollen-carrying insects fly to flowers, guided not only by color, but also by smell; this is evidenced, in particular, by how easily bees find flowers of willow, ivy, linden.

MOSCOWS PREFER BLACK

As a rule, only insects with well-developed, faceted eyes have color perception. Dragonflies have the best color perception among insects; the second place, apparently, is occupied by wasp flies, as well as some species of moths. Common flies are blue; they probably do not like him, since they avoid blue-washed windows, blue walls and curtains. Mosquitoes, distinguishing between yellow, white and black, seem to prefer the latter. In one of the areas where these insects abound in Oregon (USA), an experiment was carried out in which seven people participated, dressed in dresses of different colors. It was found that the largest number of mosquitoes were attracted by black clothing (1499 in half a minute); in second place, with a significant lag, was the white one (520 insects in the same period of time).

The eyes are a special organ that is endowed with all living things on the planet. We know in what colors we see the world, but how do animals see it? What colors do cats see and which ones do not? Is vision black and white in dogs? Knowledge about the eyesight of animals will help us take a broader look at the world around us and understand the peculiarities of the behavior of our pets.

Features of vision

And yet, how do animals see? According to some indicators, animals have more perfect vision than humans, but it is inferior in the ability to distinguish between colors. Most animals see only in a specific palette for 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 shown that animals see different wavelengths, unlike humans.

Thanks to sight, we receive more than 90% of information about the world that surrounds us. The eyes are for us the predominant sense organ. It is interesting that the vision of animals in its acuity significantly exceeds human. It's no secret that predators can see 10 times better. The eagle is able to detect prey in flight from a distance of several hundred meters, and the peregrine falcon tracks the pigeon from a height of a kilometer.

The difference is also that most animals can see perfectly in the dark. The photoreceptor cells of the retina in their eyes focus the light, and this allows nocturnal animals to pick up streams of light in several photons. And the fact that the eyes of many animals glow in the dark is due to the fact that under the retina there is a unique reflective layer called tapetum. Now let's take a look at certain types of animals.

Horses

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

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. Also, this animal has peripheral vision and sees excellently at dusk.

Let's add some anatomy. In the retina of any living being, there are two types of receptors: cones and rods. Depends on the number of cones color vision, and the rods are responsible for the peripheral. In horses, the number of rods prevails over that in humans, but cone receptors are comparable. This suggests that horses also have color vision.

Cats

Many houses keep animals, and the most common of course are 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. It reacts sharply to large amounts of bright light by narrowing down to a small slit. This indicator says that in the retina of animals there are a large number of receptor rods, 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 research has shown that it distinguishes well between gray, green and blue colors. In addition, he 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, then in the eyes of a person there are three types of cone receptors:

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

The eyes of animals are distinguished by the presence of two types of cones, so dogs cannot 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.

Sight is practically not the main organ in 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 color-blind people, they see blue and purple, yellow and green, but the mixture of colors may seem to them just white. But best of all, dogs, like cats, distinguish gray colors, and up to 40 shades.

Cows

Many believe, and we are often presented, that domestic artiodactyls react sharply to red. In reality, the eyes of these animals perceive the color palette in very blurry fuzzy tones. Therefore, bulls and cows react more to movement than to how your clothes are colored or what color they wave in front of their face. Interestingly, who will like it if they start waving a rag in front of his nose, sticking, in addition, a spear into the scruff of the 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' vision is similar to a magnifying glass, and for this reason they are often frightened when they see people unexpectedly approaching them.

Nocturnal animals

Many nocturnal animals have tarsier, for example. This is a little monkey that goes hunting at night. Its size does not exceed 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 turn in their sockets. But at the same time, the tarsier has a very flexible neck that allows him to rotate his head 180 degrees. He also has extraordinary peripheral vision, allowing him to see even ultraviolet light. But 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 sight, but fly only thanks to echolocation. But recent studies have shown that they have excellent night vision, and what's more, bats are able to choose whether to fly to sound or turn on night vision.

Reptiles

Telling how animals see, one cannot remain silent about how snakes see. The tale of Mowgli, where a boa constrictor mesmerizes monkeys with its gaze, is awe-inspiring. But is it true? Let's figure it out.

Snakes have very poor eyesight, this is affected by the protective shell that covers the reptile's eye. Because of this, the named organs seem cloudy and take on that terrifying appearance, about which they make legends. But vision for snakes is not the main thing, basically, they attack moving objects. Therefore, the tale says that the monkeys sat as if in a daze - they instinctively knew how to escape.

Not all snakes have some kind of heat sensors, but they still distinguish between infrared radiation and colors. The snake has binocular vision, which means it sees two pictures. And the brain, quickly processing the information received, gives it an idea of \u200b\u200bthe size, distance and outlines of a potential victim.

Birds

Birds are striking in a variety of species. It is interesting that the eyesight of this category of living beings is also very different. It all depends on what kind of lifestyle the bird leads.

So, everyone knows that predators have extremely sharp eyesight. Some types of eagles can spot their prey from a height of more than a kilometer and fall down like a stone to catch it. Did you know that certain species of 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 house has excellent eyesight and is able to see everything in color. Studies have shown that these individuals distinguish each other with bright plumage.

Of course, this topic is very broad, but we hope that these facts will be useful for you to understand how animals see.

Most animals have organs of vision. In some, the eyes are close together, improving depth perception. In others, the eyes are far from each other, forming a larger field of vision and receiving a signal in advance of a possible attack.

There are many types of eyes in the animal kingdom. The human eye is not anatomically similar to the eye of a fly, designed for lightning-fast response to movement.

Only humans have the whites of the eyes that indicate mood and emotional background.

Features of the eyes of animals and insects

The chameleon controls his eyes independently of each other. They can look in different directions at the same time.

Goats, mongooses, sheep, and octopuses have eyes with rectangular pupils.

The volume of the ostrich's eyes is greater than the volume of the brain of this bird!

The eyeballs of an owl occupy the entire space of the cranium, they rotate with difficulty. The owl compensates for this by turning the neck half a circle to either side.

Some scorpions have up to six pairs of eyes. Many of the spiders are four pairs. The Tuatara lizard has three eyes!

Jumping spiders have two main eyes and six auxiliary eyes.

Starfish have eyes at the end of each ray and receptors throughout their body. These marine animals can only distinguish between light and dark lighting.

A whale's eye weighs about a kilogram. But the whale sees only at a distance of 1 meter.

A complex system is the eyes of the praying mantis shrimp. She can see in polarized light, in the optical, infrared and UV ranges.

A person will receive such accuracy only by using equipment weighing a centner.

Among marine animals, cuttlefish, squid and octopus have the most perfect vision.

How animals and insects see colors

Cats do not distinguish between red. Their color scheme is not bright. A person has only 4 rods for each cone, and a cat has 25. Therefore, cats see the world as gray.

Dogs can see blues and purples clearly, but they cannot recognize warm hues such as yellow, orange and red.

Bulls and cows do not emit red. Torero annoys the animal not with the red color of his cloak, but with sharp movements.

The bee does not distinguish between red, it confuses it with green, gray or black. The bee clearly sees yellow, blue, blue-green, blue, violet and purple. It perfectly emits ultraviolet tones and the corresponding radiation.

How animals and insects see near, far and around

Dogs see well into the distance, but poorly up close. A dog's visual acuity is about 60% weaker than a human's. But dogs can easily determine the distance "by eye".

Eagle's visual acuity is twice as strong as human.

The falcon can see an object 10 cm in size from a height of 1500 m.

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

The dragonfly is one of the most vigilant insects. She sees a match head a meter away. The dragonfly's eye is composed of 30,000 separate biological chambers. Each camera captures one point, then the array of images in the brain is added to a single object. The dragonfly eye captures up to 300 images per second.

Frogs only see moving objects, considering them as possible prey.

Thanks to the horizontal and rectangular pupils, goats and bison see at 240 °. The horse's field of view is 350%.

The viewing angle is 190 ° for cats and only 40 ° for dogs.

Each person has an individual pattern of the iris. Along with fingerprints, the iris pattern is used to identify a specific person.

An ordinary human eye, with all the richness of its functions, weighs less than a bullet for a cartridge 7.62x54. The bullet weighs 9 grams, with only 8 eyes.

Diameter eyeball for most adults, it is about 24 mm.

The least common eye color in humans is green. It occurs in 2% of cases.

At birth, a person has an undefined eye color. The eyes acquire a permanent color after two to three years.

The human eye distinguishes up to 5 million different shades of color, having a huge number of light-sensitive cells (over 130 million).

Eye color is determined by melanin, the pigment in the iris. Low concentration of pigment contributes to the acquisition of light cold tones - blue, gray, green. With a high concentration of melanin, the iris turns black or brown. The absence of melanin in the iris only in albinos.

The main colors perceived by humans are red, blue and green. Their different saturation allows you to get all the color options visible to the eye.

For every hundredth person, the colors of the iris of the left and right eyes are different.

Color blindness is diagnosed in 8% of men and only 1% of women.

In Europe, Swedes, Finns, Poles and Baltics have the brightest eyes. The darkest eyes are for the Yugoslavs, Turks and Portuguese.

About night vision

Of the birds, owls see best in the dark. Owls can accurately see mice or squirrels even without the moon. During the day, owls see poorly, so they hide in secluded places.

Cats see in the dark better than people... At dusk and at night, the pupils of cats dilate up to 14 mm. In humans, the diameter of the pupil, even at night, is no more than 8 mm. In bright light, cats instinctively close their eyes so as not to instinctively damage the retina.

The human eye has 150 eyelashes on each eyelid.

Sneezing is always accompanied by closing the eyes, as this develops a speed of 170 km / h and pressure on the nasal sinuses.

The man blinks every 10 seconds, each blinking takes from one to three seconds. For a day, the length of the blinking of men takes about an hour.

Women blink about twice as often as men.

Women cry about 40 times a year, men about 6.

The eyes adjust to darkness in about an hour. During this time, the sensitivity of the eyes to light grows thousands of times. The sudden transition from darkness to bright light causes discomfort.

The human eye is a complex biological organ that receives visual information from the outside and transmits it further to the brain. The high speed of processing the received information allows you to respond to sudden changes.

The inner surface of the eye is lined with retinal tissues. Its function resembles a photographic film in a camera or a digital matrix of a mobile phone.

The cornea is an element of the eye that changes its shape and focuses on objects at different distances. The cornea is transparent; it is covered by the iris, which is a colored film. In the center of the iris is the pupil, through which a stream of light passes to the retina. The pupil regulates the amount of incoming light.

In the human eye, where the optic nerve passes through the retina, there is a small blind spot. This feature is offset by information from the other eye.

Eye transplantation is not possible. When separating optic nerve the first one immediately dies from the brain. However, the cornea of \u200b\u200bthe eye is successfully transplanted.

Tears in a newborn appear in the second month of life.

Ordinary people recognize thousands of color shades, while artists recognize millions.

Circles under the eyes indicate dehydration, and bags indicate kidney problems.

During the first days, babies can see only 25 cm in the distance.

The eyes get tired less with fast reading than with slow reading.

Illuminating the eyes in red increases the sensitivity to darkness by half an hour.

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 a person's 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 a child.

Why check?

From the very beginning of the neonatal period, children need to have regular eye examinations by an ophthalmologist. This must be done for prophylactic purposes in order to prevent further visual 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 during school years, when the visual load on the eyes increases. Also, hyperopia of the eye in children of preschool or primary school age is a common disease. 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.

Eyesight examination in newborns takes place according to the following schedule:

• For the first time, a child's eyes are examined by an ophthalmologist in the first hours after birth. Premature babies, babies with congenital abnormalities or birth trauma, newborns after a difficult birth are checked with special attention, since it is in this category of children that hemorrhages or retinal pathologies are most often manifested.
• The first checkup with an ophthalmologist in this category of children is usually scheduled one month after birth, if indicated.
• A healthy child should be examined for the first time in an ophthalmological office 3 months after birth.
• Next inspection at 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 equal to 0.3-0.6 diopters.

Orlova developed the table for checking eyesight in children. This table applies to children preschool agewho have not yet learned to count

Existing vision test tables

In modern times, many variants of tables have been created for testing visual acuity in children.

The first table by which a child's eyesight is checked, as a rule, becomes Orlova's table. According to this table, a study of vision is carried out for children from 3 years old, when they have not yet learned to read and write. In this table, instead of letters, pictures are used that are well known to the child and which he can easily name.

To test visual acuity in older children, tables with block letters are already used. On the territory of the CIS countries, the Sivtsev or Golovin table is most often used. There is also their foreign counterpart - the Snellen table.

In many tables, visual acuity is determined at a distance of at least 5 meters. This distance is 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, as it were, at infinity and on the retina, thus, parallel rays are collected, forming a focused, clear image.

Sivtsev table

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

The table got its name in honor of the Soviet ophthalmologist D.A. Sivtseva. Sivtsev's table is actively used to examine vision in children and adult patients in modern times.

In the Sivtsev table, 12 lines with printed signs are used to test vision, with the help of which you can effectively examine the patient's visual acuity.

7 letters are used as printed characters - W, B, M, H, K, Y, I. The letters have different sizes, but the same width and height. This reduces the size of the letters 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 100% vision. It is expressed in meters and marked with the symbol "D \u003d ...".

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 the normal focus 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, in myopia, the focal point is in front of the retina, and in hyperopia, the focal point is shifted 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 refraction is normal, but the patient sees poorly, this may indicate a possible decrease in the transparency of the optical media of the eye. For example, a patient may show symptoms of amblyopia, cataracts with clouding of the lens or cornea.

The right column shows the patient's visual acuity if he is at a distance of 5 meters from the table. These values \u200b\u200bare marked with "V \u003d ...". 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 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).

The normal visual acuity of a person corresponds to the indicator V \u003d 1.0, that is, a person with 100% vision should be able to distinguish between the printed characters of the first 10 lines. However, some subjects may have visual acuity that over normal, for example, 1.2, 1.5, or even 3.0 or more. With refractive errors (myopia, hyperopia), astigmatism, glaucoma, cataracts and other visual impairments, the visual acuity of the subject decreases below normal and acquires values \u200b\u200bof 0.8, 0.5 and below.

In Sivtsev's table, the visual acuity values \u200b\u200bin 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 tables, there are also 3 additional lines with visual acuity values \u200b\u200bfrom 3.0 to 5.0.

But these tables, as a rule, are not used in ophthalmological 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 firmly closed with a palm so that it cannot see the letters in the table. Instead of a palm, you can use a piece of dense material (such as cardboard or plastic). Thus, the visual acuity of the left eye is examined.
• The lines must be read in order, from left to right, from top to bottom. It takes no more than 2-3 seconds to recognize the sign.

Determination of visual acuity according to the Sivtsev table is quite simple. The patient, as a rule, has normal visual acuity if he could correctly read the letters in the rows with V \u003d 0.3-0.6. Only one mistake is allowed. In rows below V \u003d 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 over-normal errors were made.

With this table, only myopia is determined. Farsightedness according to the Sivtsev table is not determined. 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 a visual acuity above the average norm.

If the test result is unsatisfactory and an abnormality is detected, then possible reason a decrease in visual acuity in a child may have a refractive error. In this case, a subsequent determination of refraction is necessary.

Snellen table

snellen table

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

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

The table contains a standard set of lines consisting of Latin letters, which are called test types. The size of the letters, as well as in the Sivtsev 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 following, lower lines at a distance 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 according to the Snellen table is checked as follows:

• The subject is located at a distance of 6 meters from the table.
• Closes one eye with a palm or some dense material, reads the letters in the table with the other.

The visual acuity of the subject is usually checked according to 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 the lines located above the line that a person with normal visual acuity is able to read at a distance of 12 meters, then the visual acuity of such a patient is 6/12.

Orlova's 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's 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 characters is indicated.

Variation of Orlova's table

The distance is marked with the symbol “D \u003d…”. The visual acuity is indicated on the right side of the table if the child recognizes them at a distance of 5 meters.

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

If a child's visual acuity is reduced, and he is not able to recognize the signs of the tenth line, then he is brought closer to the table at a distance of 0.5 meters and asked to name the symbols of the upper row. A 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 for the child to show the pictures so that he understands what is required of him and ask him to pronounce the names of the pictures aloud.

Golovin's table

Golovin's table is also a fairly common table for checking visual acuity in children. Like the Sivtsev 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's rings - instead of printed letters. There are also twelve lines in Golovin's table and the rings printed in these lines decrease in size with each line in the downward direction. These rings are equal and the same width on each line.

golovin's table of view

Visual acuity indices are indicated on the right side of the table and are marked with the symbol "V \u003d ...".

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 the Sivtsev table, differ in increments of 0.1, the remaining two - in 0.5. In some variants of the tables, three extra rows are additionally used to determine visual acuity above the average norm. These lines differ in increments of 1.0.

The left side of the table shows the distance in meters from which a person with normal visual acuity is able to recognize a character in this line. It is marked with the symbol "D \u003d ...".

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

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findings

IN childhood ophthalmological examinations should never be ignored, 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 hinder the normal development of the child. Nowadays, various eye charts have been created to test vision, which determine the quality of peripheral vision, and acuity, and other indicators. Especially taking into account that a disease such as hyperopia in children is now actively gaining momentum.

Vision allows us to navigate the world around us, to enjoy its beauty. For animals, vision primarily helps to find food and defend against attack.

It would seem that dogs, cats and people have 2 eyes, which means that their vision is no different, but this is not so. In cats and dogs, the field of view is wider because the eyes are located on the sides of the head. Human eyes cover a 150-degree angle, and canine or feline eyes reach 250. In addition, cats and dogs see much better in the dark than humans. The reason for this is the special device of the eyes: in the dark, the pupil expands as much as possible to let in as much light as possible. Plus, animals have a special layer under the retina that reflects and enhances the light flux, for this reason we can observe glowing eyes in the dark.

One of the most popular claims is that cats and dogs see the world in black and white. However, in reality this is not entirely true. A study of the eyesight of dogs showed that they are good at distinguishing between red and blue, but they confuse green and red. This fact proves that they have color vision, but not as well developed as that of humans. In dogs, the retina contains approximately 20% of all photoreceptors, and in humans, the central region of the retina is 100% covered with them, this is approximately 127 million photoreceptors. For comparison, the giant squid has 1 billion photoreceptors, but its eyes are not small either, their diameter reaches 25 centimeters. The octopus has 20 billion photoreceptors in its eyes, and the pupil has a bizarre square shape.

Animals also break records in the number of eyes. The scallop has about a hundred eyes. The four-eyed aquarium fish uses its eyes for different purposes, two for seeing on land and the other two for seeing underwater. Some species of scorpions have 12 eyes, while spiders have 8.

The eyes of animals are adapted to the conditions of their habitat. For example, penguins have flat corneas, so they can see in water without any distortion. Camels' eyes do not miss any specks: eyelashes are automatically intertwined and completely protect the eye, which is simply necessary, because there are dust storms in the desert, and bones along the edges of the eye sockets protect from the scorching sun.

In terms of visual acuity, a person also loses to representatives of the animal world. Hawkeye has the ability to examine a victim from a distance of 1.5 kilometers, even if its size does not exceed 10 centimeters. Even the visual acuity of monkeys is approximately three times that of humans. But people do not need such supervision, they simply do not need it, we are not predators.

Man has always dreamed of possessing super vision, which is reflected in fairy tales and fantastic literature. However, nature decreed otherwise and endowed us with only those abilities that we need for a comfortable everyday life. Take care and take care of your 100% vision!