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 advanced 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 animal 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 take a look individual species 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. Depends on the number of cones color vision, and the rods are responsible for the peripheral. 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 a large number of bright light narrowing to a small slit. 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 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, then in the human eye there are three types of cone receptors:
- 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, distinguish gray colors best, 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 their nose, sticking spears into the back of their 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 scared 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 - the 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 thermal sensors, but they still distinguish infrared radiation and 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 of birds of prey are able to see ultraviolet light, which allows them to find the nearest 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.
Most animals have visual organs. Some people have eyes that are close together, improving depth perception. Others have eyes far apart, creating a larger field of vision and receiving advance warning 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 a lightning-fast reaction to movement.
Only humans have the whites of their eyes, which show their mood and emotional background.
Peculiarities of eye function in animals and insects
The chameleon controls its 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 an ostrich's eyes is larger than the volume of this bird's brain!
The owl's eyeballs occupy the entire space of the skull; they rotate with difficulty. The owl compensates for this by turning its neck half a circle in any direction.
Some scorpions have up to six pairs of eyes. Many of the spiders have 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 bodies. These marine animals can only distinguish between light and dark lighting.
A whale's eye weighs about a kilogram. But the whale can only see at a distance of 1 meter.
The eyes of the mantis shrimp are a complex system. She can see in polarized light, in the optical, IR and UV ranges.
A person will obtain such accuracy only by using equipment weighing a hundredweight.
Among marine animals, cuttlefish, squid and octopuses have the most perfect vision.
How animals and insects see colors
Cats cannot distinguish the color red. Their colors are dim. A person has only 4 rods for each cone, while a cat has 25. That's why cats see the world as gray.
Dogs clearly see blue and purple tones, but cannot recognize warm shades, such as yellow, orange and red.
Bulls and cows do not emit red. The bullfighter irritates the animal not with the red color of his cloak, but with sudden movements.
The bee does not distinguish red; it confuses it with green, gray or black. The bee accurately sees yellow, blue, blue-green, indigo, violet and purple. Excellently highlights ultraviolet tones and the corresponding radiation.
How animals and insects see near, far and to the sides
Dogs see well in the distance, but poorly up close. A dog's visual acuity is approximately 60% weaker than a human's. But dogs can easily determine the distance by eye.
An eagle's visual acuity is twice as strong as a human's.
A 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 made up of 30 thousand individual biological chambers. Each camera captures one point, then the array of images in the brain is combined into a single object. The dragonfly's eye captures up to 300 images per second.
Frogs see only moving objects, considering them as possible prey.
Thanks to horizontal and rectangular pupils, goats and bison see 240°. The horse's field of vision is 350%.
The viewing angle for cats is 190°, while for dogs it is only 40°.
Each person has a unique iris pattern. Along with fingerprints, the iris pattern is used to identify a specific person.
Ordinary human eye with all the richness of its functions, it weighs less than a bullet for the 7.62x54 cartridge. The bullet weighs 9 grams, the eyes are only 8.
Diameter eyeball for most adults it is approximately 24 mm.
The least common eye color in humans is green. Occurs in 2% of cases.
At birth, a person has an indeterminate 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. A 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 is only found in albinos.
The primary colors perceived by humans are red, blue and green. Their different saturations allow 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 detected in 8% of men and only 1% of women.
Europe has the most light eyes among the Swedes, Finns, Poles and residents of the Baltic states. The most dark eyes- among 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 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 to avoid damaging 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 blink taking from one to three seconds. During the day, men blink for about an hour.
Women blink approximately twice as often as men.
Women cry about 40 times a year, men about 6.
The eyes adapt to the dark in about an hour. During this time, the sensitivity of the eyes to light increases 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 received information allows you to respond to sudden changes.
The inner surface of the eye is lined with retinal tissue. Its function is reminiscent of the film in a camera or the digital matrix of a mobile phone.
The cornea is an element of the eye that changes 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 compensated by information from the other eye.
Eye transplantation is not possible. Upon separation optic nerve the first one dies immediately from the brain. However, the cornea of the eye is successfully transplanted.
Tears in a newborn appear in the second month of life.
Ordinary people recognize thousands of color shades, but artists recognize millions.
Circles under the eyes indicate dehydration, and bags indicate kidney problems.
In the first days, babies can see only 25 cm into the distance.
At fast reading the eyes get tired less than with a slow one.
Illuminating the eyes with red light increases sensitivity to darkness for half an hour.
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 sharp vision. 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.
The meaning of vision
It is well known that acute vision is very important for most living beings, be it humans, animals or insects. For wild animals, blindness is certain death, because a blind predator will not be able to catch prey, and a blind herbivore will not see the approaching hunter. Not to mention the danger of falling off a cliff or bumping into an obstacle. For a person, poor vision does not pose such a danger, because in modern world There are many means for vision correction (glasses, lenses, vision restoration operations).
Completely blind people have the opportunity to use the help of loved ones or the services of a guide dog. Pets are in a similar position: veterinary clinics can help pets see again, and although, of course, the animal cannot wear glasses, there are already special lenses for pets. But the representatives wildlife you won't envy.
Well, which of the inhabitants of the globe has the most poor eyesight? It is not easy to answer this question, since several “leaders” can be identified here. Among mammals this is undoubtedly mole. In those few species of moles that have retained eyes, the ability to see is limited to the ability to distinguish light from darkness - the undeveloped eyes of moles are unable to see even the outlines of objects.
Alternative to vision in snakes
Few better vision in blue whales and some other aquatic animals. Among reptiles, a very original type of blindness is found snakes: They are only able to see a moving object. But this disadvantage is compensated by good thermal vision, so snakes are able to locate creatures that emit heat. True, the thermal image is quite vague.
Longhorn beetles
Among insects, those with the longest antennae (and therefore the best sense of touch) have the poorest eyesight. Thus, those with the poorest vision are longhorned beetles(antennae can reach a length 4 times greater than the length of the insect’s body) and tropical grasshoppers, whose antennae are 6 (!) times longer than the body. By the way, longhorned beetles are included in the list of the largest beetles in the world.
Most creatures with poor vision have eyes either reduced as unnecessary, or poor vision is compensated by good sense of smell and touch. It is much worse for animals whose poor vision is caused by a genetic error and is not compensated for by anything.
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 vision a person’s life becomes very difficult. 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 for preventive purposes in order 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 during 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 sees poorly, this may indicate possible reduction 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 more 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 most capital letters, 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.
Causes and symptoms of retinal detachment, what kind of disease it is and what effective methods You will learn about the treatment in the article.
Treatment of eye blepharitis, its symptoms and common pathogens are described here.
Glasses to protect your eyes from the computer: http://eyesdocs.ru/ochki/kompyuternye/ochki-dlya-raboty-s-kompyuterom.html
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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 the normal development of the child. Nowadays, various eye tables have been created for testing vision, which are used to determine the quality of peripheral vision, and sharpness, and other indicators. Especially considering that a disease such as farsightedness in children is now actively gaining momentum.
