How the human eye actually sees. Interesting facts about human eyes (15 photos)

22.04.2020 -

Every day a person blinks 11,500 times!

Eye

Eye weight 7-8g, eyeball diameter 2.5cm. Human eye 15 times smaller eyes a giant squid with a diameter of 38 cm, the size of two human heads.

Eyelashes

Eyelashes protect the eyes from dust and ensure that the eyelids close when touched by a foreign object. Since there are 80 eyelashes on each psx, our eyes are protected by a real curtain of 320 eyelashes. Eyelashes fall out and grow back in 100 days. Thus, a man will change his eyelashes 260 times in his life, and a woman – 290. Total number eyelashes in men and women are 83,000 and 93,000, respectively.

Persons suffering poor eyesight, have a fixed gaze and rarely blink. Men usually blink once every 5 seconds. Minus 8 hours of sleep, they blink 11,500 times daily. Over the course of a lifetime, a man blinks 298 million times, and a woman blinks 331 million times.

Tears

Lacrimal fluid (tears) moisturizes the surface of the eye. In the absence of tears, dehydration of such a delicate organ as the eye would occur, and blindness would very quickly occur. The lacrimal glands of both eyes produce three thimbles of tears (0.01 L) daily.

Tears free the body from chemicals related to nervous overstrain, the content of which is reduced by 40%. Not as a reproach to women, it should be noted that due to the secretion of a hormone with the pleasant name “prolactin”, they cry four times more often than men.

Vision

The mechanisms of operation of the eye and the camera are similar. Depending on the aperture, more or less light enters the camera. The role of the diaphragm in the eye is performed by the pupil ( dark spot in the center of the iris). Rays of light reflected by an object pass through the camera lens, and in the eye - through a kind of lens-lens located inside the eyeball. In the camera, these rays of light then converge on the photographic film and capture the inverted image on it. This completes the photography process. In the eye, light rays are captured by the retina (at the back of the eye), which is equipped with 132 million receptor cells - “image receptors”, including 125 million rods that provide light perception and 7 million cones that provide color perception. (The layers of the retina are called “rods” and “cones” because of their shape.) As the image is transmitted to the brain, the image is transferred to the optic nerve.

The eye itself can focus (accommodate) to see near and distant objects. A person with normal vision is able to clearly see objects at a distance of 60 m. The eye can distinguish objects at a distance of less than 5 m. The minimum limit for clear vision in young man 15 cm, but at closer distances objects become blurry. However, this limit changes with age: 7 cm at 10 years old, 15 cm at 20 years old, 25 cm at 40 years old, 40 cm at 50 years old. The increase in the limit with age is explained by farsightedness. In conditions favorable to vision, with good lighting, the eyes can accurately distinguish 10 million shades.

The three-dimensionality of the image arises because we see with two eyes.

Corner full review in humans it is 125 degrees. For comparison, we note that in cats this figure is 187 degrees.

Acuity human vision 500 times lower than that of owls, which are able to distinguish their prey from a distance of 2 m in almost complete darkness. Here are other striking examples: a golden eagle can spot a hare from a height of 3.2 km, and a falcon can spot a pigeon more than 8 km away.

The iris of the eye is a colored diaphragm that can change color in the first years of a person’s life. Both fingerprints and iris patterns are unique to each person.

Blind spot

One area of the retina, the so-called blind spot, does not have photoreceptors and therefore does not perceive light. This is where the optic nerve exits the retina. The blind spot, however, does not prevent us from seeing - the brain for the most part “ignores” it.

Vision defects

Myopia is the inability to see distant objects clearly. In this case, the muscles do not relax the lens enough, so the light rays are focused in front of the retina and the image on it turns out blurry. This shortcoming can be corrected using contact lenses or glasses with concave glass lenses that scatter the light beam.

Farsightedness is the inability to see close objects clearly. In farsighted people, the muscles do not compress the lens tightly enough, so light rays are focused behind the retina and the image also blurs. Glasses with convex lenses that concentrate light help against farsightedness.

Color blindness, or color blindness, is the inability to distinguish certain colors.

The boy Vovka quickly, deftly wanted to untie the rope. To untie the knot, he began to pry it with an awl. The awl bounced off with force - Volodya’s eye was damaged... You can only handle the awl very carefully. Don’t keep awls, scissors, knives as toys, because it’s very easy to hurt your eyes with a sharp object! Natalia Orlova

Nervous system constantly receives signals from the outside world using special sensors. They are called sense organs. Eyes Light is perceived by the organs of vision - the eyes. From them to the brain the path is very short. The eyes are his outgrowths! Your eyes are like two cameras or two television cameras that are aimed at the world around us. The outer opening of the camera is usually covered...

One summer, a boy named Petya Vorobyov was scaring them in the garden and, forgetting about everything in the world, shot at them with a slingshot. Once! Another! And for the third time! Suddenly he hit his brother in the eye - Almost knocked out his brother’s eye!.. Don’t shoot with slingshots! Natalia Orlova

Tongue The tongue is a muscular organ located in oral cavity. Its length is 9 cm, width 5 cm and weight 50 g. The tongue is formed by muscles connected to the base lower jaw and allowing him to perform many movements, such as folding, rotating (up to 40 times per minute kiss), etc. The functions of language are varied. Due to its mobility (on average up to 80...

There was once a case like this: There was a cartridge lying on the ground, the guys hit it with a stone - and it exploded loudly! The car with Andrey is rushing to the hospital - Get treatment quickly! Hurry!.. Hurry! And in the hospital there is silence. The boy’s bed is long... The boy is crying, very pale - A copper shard got into his eye!.. And early the next morning the Doctor said to the sisters: “Bring the boy to the operating room!” This room is clean, simple, There is a strong smell of medicine, It’s creepy here...

The sense of taste and smell are closely interconnected. A wide variety of taste sensations are created by the combination of taste and smell. Receptor and supporting cells are located in the taste bud, like orange slices. The taste bud recognizes substances dissolved in saliva, which enter the bulb through the taste duct, which opens on the surface of the tongue. The organ of taste is the tongue. On its upper side there are more than 10...

With poor eyesight, guys, living without glasses is torture! You walk along your dear street timidly, like a stranger. Don't you understand - a poster? Poster? Who's coming - Ilyusha? Grisha? It’s hard to recognize people you meet, It’s bad even to play ball... The doctor prescribed glasses for Maya And at the same time he told her: “You wear them without taking them off, So that your eyes don’t get damaged.” Maya began to say: “I won’t wear them, Children at school will often call me...

There are 200 million olfactory cells in the upper posterior part of the nasal cavity! Pleasant and pungent odors floating in the air are captured by the nose and then transmitted to the odor receptor (olfactory mucosa), with a surface area barely equal to the size of a postage stamp (3 cm2). 200 million cells (olfactory receptors), equipped with odor detectors and having nerve endings in the form of hairs, capture the smell...

Suddenly little Slava's eyes began mow, Towards the nose The right one began to shift, What should I do? How can we be here? Doctor Slava examined him and ordered him to wear glasses: “Such a squint so that it doesn’t disgrace you, Here is our conclusion: Glasses are one cure.” They boldly go to the pharmacy, Mom bought glasses, put them on for Glory, and her eyes stood up straight. Natalia Orlova

Let's figure it out together, children: What are eyes for in the world? Why do we all have a pair of eyes on our faces? Varya’s eyes are brown, Vasya and Vera’s are gray, little Alenka’s have green eyes. What are eyes for? So that tears flow from them? Close your eyes with your palm, Sit just a little bit - It immediately became dark: Where...

Our conversation today is about vision. The ability to see is the most faithful and reliable assistant to a person. It allows us to navigate and interact with the world around us.

Approximately A person receives 80% of all information through vision. Let us consider the mechanism of the appearance of a continuously changing visible picture environment.

How a visible image is created

Each of the 6 human sense organs (analyzers) includes three important links: receptors, nerve pathways, and the brain center. Analyzers belonging to various bodies feelings, work in close “commonwealth” with each other. This allows you to get a complete and accurate picture of the world around you.

The function of vision is provided by a pair of eyes.

Optical system of the human eye

The human eye has a spherical shape with a diameter of about 2.3 cm. The front part of it outer shell transparent and has a name cornea. The back part, the sclera, consists of dense protein tissue. Directly behind the protein is choroid, penetrated by blood vessels. Eye color is determined by the pigment contained in its anterior (iris) part. The iris contains a very important element of the eye - hole (pupil), allowing light to enter the eye. Behind the pupil there is a unique invention of nature - lens It is a biological, completely transparent biconvex lens. Its most important property is accommodation. Those. the ability to reflexively change its refractive power when examining objects at different distances from the observer. The convexity of the lens is controlled by a special group of muscles. Behind the lens is a transparent vitreous.

The cornea, iris, lens and vitreous body form the optical system of the eye.

The coordinated work of this system changes the trajectory of light rays and directs light quanta to the retina. A reduced image of objects appears on it. The retina contains photoreceptors, which are branches of the optic nerve. The light stimulation they receive is sent along the optic nerve to the brain, where it is formed visible image subject.

However, nature has limited the visible part of the electromagnetic scale to a very small range.

Only electromagnetic waves with a length of 0.4 to 0.78 microns pass through the light-conducting system of the eye.

The retina is also sensitive to the ultraviolet part of the spectrum. But the lens does not transmit aggressive ultraviolet quanta and thereby protects this most delicate layer from destruction.

Yellow spot

Opposite the pupil on the retina there is a yellow spot on which The photoreceptor density is particularly high. Therefore, the image of objects falling into this area is especially clear. Whenever a person moves, it is necessary that the image of the object is kept in the area macular spot. This happens automatically: the brain sends commands extraocular muscles, which control eye movement in three planes. In this case, eye movements are always coordinated. Obeying the received commands, the muscles force the eyeballs to turn in the desired direction. This ensures visual acuity.

But even when we look at a moving object, our eyes make very fast movements from side to side, continuously supplying “food for thought” to the brain.

Color and twilight vision

The retina consists of two types of nerve receptors - rods and cones. Rods are responsible for night (black and white) vision, and cones allow you to see the world in all the splendor of colors. The number of rods on the retina can reach 115–120 million, the number of cones is more modest - about 7 million. Rods even react to individual photons. Therefore, even in low light we can distinguish the outlines of objects (twilight vision).

But cones can show their activity only with sufficient lighting. They require more energy to activate because they are less sensitive.

There are three types of light-perceiving receptors corresponding to red, blue and green.

Their combination allows a person to recognize the whole variety of colors and thousands of their shades. And their overlay gives white. By the way, the same principle is used in .

We see the world around us because all objects reflect the light falling on them. Moreover, the wavelengths of reflected light depend on the substance or paint applied to the object. For example, the paint on the surface of a red ball can only reflect wavelengths of 0.78 microns, but green foliage reflects the range from 0.51 - 0.55 microns.

Photons corresponding to these wavelengths, entering the retina, can affect only the cones of the corresponding group. A red rose illuminated by green light turns into a black flower because it is unable to reflect these waves. Thus, The bodies themselves have no color. And the entire huge palette of colors and shades available to our vision is the result amazing properties our brain.

When a light flux corresponding to a certain color falls on a cone, an electrical impulse is formed as a result of a photochemical reaction. The combination of such signals rushes to the visual zone of the cerebral cortex, building an image there. As a result, we see not only the outlines of objects, but also their color.

Visual acuity

One of the most important properties of vision is its acuity. That is, his the ability to perceive two closely located points separately. For normal vision, the angular distance corresponding to these points is 1 minute. Visual acuity depends on the structure of the eye and the proper functioning of its optical system.

Secrets of the eye

At a distance of 3-4 mm from the center of the retina There is a special area devoid of nerve receptors. For this reason it was called a blind spot. Its dimensions are very modest - less than 2 mm. They go to him nerve fibers from all receptors. Uniting in the blind spot area, they form the optic nerve, along which electrical impulses from the retina rush to the visual area of the cerebral cortex.

By the way, the retina somewhat puzzled scientists - physiologists. The layer containing nerve receptors is located on its back wall. Those. light from the outside world must pass through the retinal layer, and then “storm” the rods and cones.

If you look closely at the image, which optical system eyes projects onto the retina, it is clearly visible that it is inverted. This is how babies see it for the first two days after birth. And then the brain learns to flip this image. And the world appears before them in its natural position.

By the way, why did nature provide us with two eyes? Both eyes project images of the same object onto the retina that are slightly different from each other (since the object in question is located slightly differently for the left and right eyes). But nerve impulses from both eyes fall on the same neurons of the brain, and form a single, but volumetric image.

Eyes are extremely vulnerable. Nature took care of their safety through subsidiary bodies. For example, eyebrows protect the eyes from droplets of sweat and rain moisture flowing from the forehead, eyelashes and eyelids protect the eyes from dust. And special lacrimal glands protect the eyes from drying out, facilitate the movement of the eyelids, and disinfect the surface of the eyeball...

So, we got acquainted with the structure of the eyes, the main stages visual perception, revealed some of the secrets of our visual apparatus.

As in any optical device, various failures are possible here. And how a person copes with visual defects, and what other properties nature has endowed his visual apparatus with - we will tell you at the next meeting.

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We can say with confidence that vision is the most important sense of a person, since it is the eyes that provide us with up to 80% of all the information that people receive from the environment. Structure and functioning visual analyzer very complex, and some nuances still remain a mystery to scientists. However, there are many interesting facts about the eyes that will certainly not leave you indifferent.

1.Retina (light-receiving inner shell eyes) perceives images of surrounding objects inverted, that is, a person, in fact, sees everything “upside down”, as well as in a reduced version. But in this situation, the brain comes to the rescue and “puts” the picture in its place. To see the world as our retina does, we can wear glasses with prismatic lenses.

The human eye perceives everything around in an inverted state, but the brain makes its own adjustments to this process

2. A person actually sees with his brain. The human eye, in fact, is only a means of collecting information, and we see solely thanks to the brain. The light leaves a reduced and inverted image on the retina, which is transformed from light rays into nerve impulse. The latter, through the optic nerve, reaches the visual part of the cerebral cortex (occipital region), where the received information is deciphered, analyzed, processed, corrected, and the person perceives the image correctly.

3. All blue-eyed people have the same ancestor. The fact is that blue eye color appeared as a mutation approximately 6,000 (maximum 10,000) years ago. Until this moment, blue eyes simply did not exist in humans. Changes occurred in the OCA2 gene, which is responsible for the process of melanin synthesis (the pigment on which the color of human eyes depends). Researchers, after conducting several experiments and studies, came to the conclusion that the first person who received blue eyes as a gift from nature lived on the Black Sea coast. Exactly how the mutation spread throughout the world remains a mystery, but today approximately 40% of Caucasians are blue-eyed.

Interesting fact: all people with blue eyes come from the same ancestor

4. There are people with different eye colors. This situation is not considered a disease, but is a deviation in normal development and occurs in approximately 1% of people, called heterochromia. Heterochromia develops due to a violation of melanin synthesis in the iris of the eye. Most often it is hereditary, but can occur due to previous injuries and certain ailments. There is also a partial form of heterochromia, in which case part of the iris has, for example, a brown color, and at the same time islands are present gray.

Variant of complete and partial heterochromia of eye color

5. Eyebrows serve a protective function.. Many people don’t even know why a person needs eyebrows. However, they do important role. They protect the eyes from possible sweat that flows from the forehead. Sweat contains large number salt, which can harm the delicate structures of the eye. The thicker the eyebrows, the better the eyes are protected.

6. Everyone's eyeball size is the same. Regardless of status, age, race, physique, the size of the eye in all people is almost equal and corresponds to 24 mm. It is also interesting that in small children it is almost the same, so the eyes of children seem large and expressive.

The size of the eyeball is the same in almost all people

7. The fastest reflex in the body is blinking. The muscle that is responsible for eyelid movements is the fastest. To implement the blink reflex, our body needs only 10-30 ms, which is an absolute record.

8. The lens is many times superior to even the fastest and highest quality photographic lens in the world. To understand this, it is enough to realize how many objects a person immediately focuses his gaze on. The change of focus occurs before you even move your gaze to the next object. No camera is capable of this, not even yourself. the best lens it takes seconds to change focus.

9. Visual acuity is more than 100% (or 1.0). Anyone who has ever been to an ophthalmologist is familiar with the procedure for checking vision using special tables. Typically they have 10 lines of letters or images. If a person sees the last line from a distance of 5 m, then his vision is considered ideal and equals 1.0 (100%). But in fact, there are individuals whose eyes can be even more keen and see, for example, 120%.

Visual acuity of one is far from the limit for a person

10. Colorblindness predominantly affects males., and every 12 men may not distinguish one or more colors, and most of them are not even aware of their peculiarity. Color blindness is a genetic defect that is passed on the X chromosome from a carrier mother to her son. This is why men have an increased risk factor for color blindness, since they do not have a “spare” healthy X chromosome, unlike women.

11. Peripheral vision in women is much better developed than in men. This is due to the peculiarities of human evolution. Since ancient times, a woman’s main task was caring for children, preparing food and other household chores (often it was necessary to take care of everything at the same time). The men were focused on hunting and looked only at the center. By the way, such an interesting fact about the vision of men and women was described quite recently. A woman, looking straight, sees much more with her peripheral vision than the stronger sex.

Women see much better with peripheral vision than men

12. Newborn children see very poorly only at a distance of 30-40 cm. This is exactly the distance at which the mother's face is when breastfeeding. That is why the first person a baby begins to recognize is his mother.

13. Eye muscles– the most “hard-working” in the body. These small muscle fibers are more active than any other muscle in the body. They almost never rest, because even in their sleep a person moves eyeballs.

14. Ommatophobia – fear of eyes. There are a lot of strange and little-studied phobias in the world, and ommatophobia is considered one of these. An ommatophobic person cannot look another person in the eye due to fear. Such people never look others in the eye, wear deep hoods, and wear dark glasses. Fortunately, this phobia is rare and most often manifests itself in an erased form. Patients are treated by a psychotherapist. As soon as it becomes clear what exact reasons became the basis for ommatophobia, getting rid of it becomes easy.

People suffering from ommatophobia are afraid of the eyes

15. Brown eyes are actually blue, but underneath a layer of pigment.. Everyone knows that children are born with the same eye color - dirty blue, and at about 3-5 months of life the iris acquires its final color - brown, green, blue, black, etc. The fact is that pigment cells begin to synthesize that amount melanin, which is embedded in the genetic code, and the eyes change color. But if your iris is brown, then you can easily change its color to blue. For this there is a special laser surgery, which reduces the amount of pigment and the originally blue tint appears.

16. The pattern of a person's iris is as unique as a fingerprint.. There are no two identical individuals in this parameter. Therefore, it can be used for identification, for example, when going through passport control.

The iris pattern, like fingerprints, is unique to each person.

17. It's impossible to sneeze with with open eyes . Scientists explain this as a reflex response - when sneezing, the facial muscles of the face contract, including the orbicularis oculi muscle. This action is associated with protective function– closing the eyelids when sneezing prevents microorganisms from entering the eyes that fly out of the mouth.

18. The most rare color the eye in nature is green. According to statistics, green Only 2% of the planet's population have irises of various shades (from gray-green to emerald). It is also interesting that the medieval Inquisition considered red-haired women with green eyes to be witches and burned them at the stake. This also influenced the low prevalence of such a beautiful color in our time.

So there are many amazing facts about human eyes and this is only a small part of them. It is not for nothing that they say that the eyes are the mirror of the human soul, and the soul is the greatest secret of our world.

The eyes are a unique organ in structure, thanks to which a person receives about 80% of information about the world around him: about the shape, color, size, movement and other parameters of objects and phenomena. But how much do we know about our most valuable sense organ, which, according to the scientist Sechenov, provides us with about a thousand different sensations per minute? Let's look at 10 of the most surprising facts about eyes and vision.

Source: depositphotos.com

Fact 1. The average eye diameter is 2.5 cm, weight is about 8 g, and these parameters, with a difference of a fraction of a percent, are similar in all people over 7 years of age. The diameter of the eye of a newborn child is 1.8 cm, weight is 3 g. Only 1/6 of the organ of vision is visible to humans. Interior the eyes are connected to the body optic nerve transporting information to the brain.

Fact 2. The human eye is capable of perceiving only three parts of the spectrum - green, blue and red. The remaining distinguishable shades (there are more than 100 thousand of them) are derived from these three colors. Only 2% of women have an additional section of the retina that allows them to recognize up to 100 million shades. All children are born farsighted and colorblind, unable to perceive colors, but 8% of males remain colorblind into adulthood.

Fact 3. All people are blue-eyed. The difference in shades of the iris depends on the amount of melanin concentrated in it. It is highest among those with brown eyes, and lowest among those with light eyes. So, all children are born with gray-blue eyes, which after 1.5-2 years acquire their genetic color. Thanks to this, it became widespread laser procedure color correction, clearing the iris of melanin. It allows you to change your brown eye color to blue in a minute; but it is impossible to return the previous shade.

Fact 4. About 1% of people on the planet have different eye colors - a genetic disorder called heterochromia. This can be a consequence of injuries, diseases, genetic mutations and is explained by an excess of melanin in one organ of vision and its deficiency in the other. With partial (sector) heterochromia there are areas of different colors on one iris, with absolute heterochromia there are two entire eyes different colors. More often than in humans, heterochromia occurs in animals - cats, dogs, horses and buffaloes. In ancient times, people with heterochromia were considered sorcerers and witches.

Fact 5. One of the most rare shades irises - green. This beautiful color is obtained due to the presence of the yellow pigment lipofuscin in the outer layer of the iris, combined with a blue or cyan tint in the stroma. It occurs in only 1.6% of the world's population and is eradicated in families with a dominant brown-eyed gene.

Fact 6. The structure and collagen structure of the human cornea is similar to that of a shark, which is often used as a substitute for eye surgery. Today, transplanting the cornea of a sea predator to a human (an achievement in zoo-ophthalmology) is a highly effective treatment method serious illnesses organ and restoration of vision.

Fact 7. The retina of the eye is unique: it has 256 unique characteristics(probability of repetition in two different people is 0.002%). Therefore, iris scanning, along with fingerprinting, can be used for personal identification purposes. Already today, the procedure for recognizing a person by the iris of the eye is used in the customs services of the USA and Great Britain.

Source: depositphotos.com

Fact 1. The average eye diameter is 2.5 cm, weight is about 8 g, and these parameters, with a difference of a fraction of a percent, are similar in all people over 7 years of age. The diameter of the eye of a newborn child is 1.8 cm, weight is 3 g. Only 1/6 of the organ of vision is visible to humans. The inside of the eye is connected to the body by the optic nerve, which transports information to the brain.

Fact 3. All people are blue-eyed. The difference in shades of the iris depends on the amount of melanin concentrated in it. It is highest among those with brown eyes, and lowest among those with light eyes. So, all children are born with blue-gray eyes, which after 1.5-2 years acquire their genetic color. Thanks to this, laser color correction procedures, which cleanse the iris of melanin, have become widespread. It allows you to change your brown eye color to blue in a minute; but it is impossible to return the previous shade.

Fact 4. About 1% of people on the planet have different eye colors - a genetic disorder called heterochromia. This can be a consequence of injuries, diseases, genetic mutations and is explained by an excess of melanin in one organ of vision and its deficiency in the other. With partial (sector) heterochromia there are areas of different colors on one iris, with absolute heterochromia there are entire eyes of two different colors. More often than in humans, heterochromia occurs in animals - cats, dogs, horses and buffaloes. In ancient times, people with heterochromia were considered sorcerers and witches.

Fact 5. One of the rarest shades of the iris is green. This beautiful color is obtained due to the presence of the yellow pigment lipofuscin in the outer layer of the iris, combined with a blue or cyan tint in the stroma. It occurs in only 1.6% of the world's population and is eradicated in families with a dominant brown-eyed gene.

Fact 6. The structure and collagen structure of the human cornea is similar to that of a shark, which is often used as a substitute for eye surgery. Today, transplanting the cornea of a marine predator to a person (an achievement in zoo-ophthalmology) is a highly effective method of treating severe diseases of the organ and restoring vision.

Fact 7. The retina of the eye is unique: it has 256 unique characteristics (the probability of repetition in two different people is 0.002%). Therefore, iris scanning, along with fingerprinting, can be used for personal identification purposes. Already today, the procedure for recognizing a person by the iris of the eye is used in the customs services of the USA and Great Britain.