Interesting facts about human eyes and vision. Features of human vision What the eye perceives

In human life it is a window to the world. Everyone knows that we acquire 90% of information through our eyes, so the concept of 100% visual acuity is very significant for a full life. The organ of vision in the human body does not take up much space, but is a unique, very interesting, complex formation that has not yet been fully explored.

What is the structure of our eye? Not everyone knows that we see not with our eyes, but with our brain, where the final image is synthesized.

The visual analyzer is formed from four parts:

1. Peripheral part, including:
   - the eyeball itself;
   - upper and lower eyelids, eye socket;
   - appendages of the eye (lacrimal gland, conjunctiva);
   - extraocular muscles.
2. Pathways in the brain: optic nerve, chiasm, tract.
3. Subcortical centers.
4. Higher visual centers in the occipital lobes of the cerebral cortex.

The following are recognized in the eyeball:

• cornea;
• sclera;
• iris;
• lens;
• ciliary body;
• vitreous body;
• retina;
• choroid.

The sclera is an opaque part of a dense fibrous membrane. Because of its color, it is also called the protein shell, although it has nothing in common with egg whites.

The cornea is a transparent, colorless part of the fibrous membrane. The main responsibility is focusing the light, bringing it to the retina.

The anterior chamber is the area between the cornea and the iris, filled with intraocular fluid.

The iris, which determines the color of the eyes, is located behind the cornea, in front of the lens, divides the eyeball into two sections: anterior and posterior, and controls the amount of light that reaches the retina.

The pupil is a round hole located in the middle of the iris that regulates the amount of light entering

The lens is a colorless formation that performs only one task - focusing rays on the retina (accommodation). Over the years, the lens of the eye thickens and a person's vision deteriorates, which is why most people need reading glasses.

The ciliary or ciliary body is located behind the lens. A watery fluid is produced inside it. There are also muscles that allow the eye to focus on objects at different distances.

Vitreous body– a transparent gel-like mass with a volume of 4.5 ml, which fills the cavity between the lens and the retina.

The retina is made up of nerve cells. It lines the back surface of the eye. The retina, under the influence of light, creates impulses that are transmitted through the optic nerve to the brain. Therefore, we perceive the world not with our eyes, as many people think, but with our brain.

Approximately in the center of the retina there is a small but very sensitive area called the macula or macula. The fovea or fovea is the very center of the macula, where the concentration of visual cells is maximum. The macula is responsible for the clarity of central vision. It is important to know that the main criterion for visual function is central visual acuity. If light rays are focused in front of or behind the macula, a condition called refractive error occurs: farsightedness or nearsightedness, respectively.

The choroid is located between the sclera and the retina. Its vessels nourish the outer layer of the retina.

Extrinsic muscles of the eye- these are the 6 muscles that move the eye in different directions. There are rectus muscles: superior, inferior, lateral (to the temple), medial (to the nose) and obliques: superior and inferior.

The science is called ophthalmology. She studies the anatomy, physiology of the eyeball, diagnosis and prevention of eye diseases. This is where the name of the doctor who treats eye problems comes from - ophthalmologist. And the synonymous word - ophthalmologist - is now used less often. There is another direction - optometry. Specialists in this field diagnose and treat human vision, correct various refractive errors using glasses and contact lenses - myopia, farsightedness, astigmatism, strabismus... These teachings were created in ancient times and are actively developing now.

Eye examination.

At an appointment at the clinic, the doctor can conduct an external examination, special instruments and functional research methods.

External inspection takes place in daylight or artificial light. The condition of the eyelids, orbit, and visible part of the eyeball is assessed. Sometimes palpation, such as palpation of intraocular pressure, may be used.

Instrumental research methods make it possible to find out much more accurately what is wrong with the eyes. Most of them are carried out in a dark room. Direct and indirect ophthalmoscopy, examination with a slit lamp (biomicroscopy), a goniolens, and various devices for measuring intraocular pressure are used.

Thus, thanks to biomicroscopy, you can see the structures of the front part of the eye at very high magnification, as if under a microscope. This allows you to accurately identify conjunctivitis, corneal diseases, and clouding of the lens (cataract).

Ophthalmoscopy helps to obtain a picture of the posterior part of the eye. It is performed using reverse or direct ophthalmoscopy. A mirror ophthalmoscope is used to use the first, ancient method. Here the doctor receives an inverted image, magnified 4 to 6 times. It is better to use a modern electric manual direct ophthalmoscope. The resulting image of the eye when using this device, magnified 14 to 18 times, is direct and corresponds to reality. During the examination, the condition of the optic nerve head, macula, retinal vessels, and peripheral areas of the retina is assessed.

After the age of 40, every person is required to periodically measure intraocular pressure for the timely detection of glaucoma, which in the initial stages proceeds unnoticed and painlessly. For this purpose, the Maklakov tonometer, Goldman tonometry and the recent method of non-contact pneumotonometry are used. In the first two options, you need to drip an anesthetic, the examinee lies down on the couch. With pneumotonometry, ocular pressure is measured painlessly using a stream of air directed at the cornea.

Functional methods examine the photosensitivity of the eyes, central and peripheral vision, color perception, binocular vision.

To test vision, they use the well-known Golovin-Sivtsev table, where letters and broken rings are drawn. Normal vision in a person is considered when he sits at a distance of 5 m from the table, the visual angle is 1 degree and the details of the drawings on the tenth line are visible. Then we can claim 100% vision. To accurately characterize the refraction of the eye, in order to most accurately prescribe glasses or lenses, a refractometer is used - a special electrical device for measuring the strength of the refractive media of the eyeball.

Peripheral vision or visual field is everything that a person perceives around him, provided that the eye is motionless. The most common and accurate study of this function is dynamic and static perimetry using computer programs. Based on the results of the study, it is possible to identify and confirm glaucoma, retinal degeneration, and diseases of the optic nerve.

In 1961, fluorescein angiography appeared, which makes it possible, using pigment in the vessels of the retina, to identify in the smallest detail degenerative diseases of the retina, diabetic retinopathy, vascular and oncological pathologies of the eye.

Recently, the study of the posterior part of the eye and its treatment have made a huge step forward. Optical coherence tomography exceeds the information content of other diagnostic devices. Using a safe, non-contact method, it is possible to see the eye in cross-section or as a map. An OCT scanner is primarily used to monitor changes in the macula and optic nerve.

Modern treatment.

Now everyone is hearing about laser eye correction. Laser can correct poor vision due to myopia, farsightedness, astigmatism, and also successfully treat glaucoma and retinal diseases. People with vision problems forget about their defect forever and stop wearing glasses and contact lenses.

Innovative technologies in the form of phacoemulsification and femtosurgery are successfully and widely in demand in the treatment of cataracts. A person with poor vision in the form of fog before his eyes begins to see as in his youth.

More recently, a method of administering drugs directly into the eye has emerged - intravitreal therapy. Using an injection, the necessary drug is injected into the slopoid body. In this way, age-related macular degeneration, diabetic macular edema, inflammation of the inner membranes of the eye, intraocular hemorrhages, and retinal vascular diseases are treated.

Prevention.

The vision of a modern person is now exposed to such stress as never before. Computerization leads to myopization of humanity, that is, the eyes do not have time to rest, they are overstrained from the screens of various gadgets and, as a result, vision loss, myopia or myopia occurs. Moreover, more and more people suffer from dry eye syndrome, which is also a consequence of prolonged sitting at the computer. Children's vision is especially impaired, because the eye is not yet fully formed until the age of 18.

To prevent the occurrence of threatening diseases, it should be carried out. In order not to joke with your eyesight, you need to have your vision tested in the appropriate medical institutions or, as a last resort, by qualified optometrists in opticians. People with visual impairments should wear appropriate glasses and visit an ophthalmologist regularly to avoid complications.

If you follow the following rules, you can reduce the risk of eye diseases.

1. Do not read while lying down, because in this position the blood supply to the eyes deteriorates.
2. Do not read in transport - chaotic movements increase eye strain.
3. Use the computer correctly: eliminate glare from the monitor, set its top edge slightly below eye level.
4. Take breaks when working for long periods of time and do eye exercises.
5. Use tear substitutes if necessary.
6. Eat right and lead a healthy lifestyle.

Unusual and interesting facts about the eyes and vision of a person are the most interesting medical facts - with the help of the eyes a person perceives up to 80% information received from outside.

The most unusual and interesting fact about eyes and vision is that a person sees the world around him not with his eye, but with his brain; the function of the eye is exclusively to collect the necessary information about the world around him at a speed of 10 units of information per second. The information collected by the eyes is transmitted upside down(this fact was first established and studied in 1897 by the American psychologist George Malcolm Stratton and is called inversion) through the optic nerve to the brain, where in the visual cortex it is analyzed by the brain and visualized in a completed form.

Blurry or unclear vision is often caused not by eye problems, but by difficulty in the visual cortex of the brain.

Human - the only thing a creature on the planet that has proteins.

The human eye contains two types of cells - and. Cones see in bright light and distinguish colors; the sensitivity of rods is extremely low. In the dark, rods are able to adapt to a new environment, thanks to them a person gains night vision. The individual sensitivity of each person's rods allows them to see in the dark to varying degrees.

One eye contains 107 million cells, all of which are sensitive to light.

Only 16% of the apple is visible in the eye socket.

The eyeball of an adult is ~24 millimeters in diameter and weighs 8 grams. Interesting fact: these parameters are the same for almost all people. Depending on the individual structural features of the body, they can differ by a fraction of a percent. A newborn baby has an apple diameter of ~18 millimeters and a weight of ~3 grams.

Wriggling particles in the eyes are called floaters. Floater opacities are shadows cast on the retina by microscopic filaments of protein.

The iris of the human eye contains 256 unique characteristics(fingerprints - 40) and is repeated in two people with a probability of 0.002%. Using this interesting fact, the customs services of the UK and the USA began to introduce iris identification in passport control services.

When significant loads are placed on vision, general fatigue of the body occurs, tantamount to stress. As a result of overwork, unusually severe (acute) headaches develop and a feeling of fatigue occurs.

Vitamin A (beta-carotene) found in carrots is important for overall health, with a direct link between consumption of the vegetable and improved vision absent. The beginning of the belief in the benefits of carrots for vision was laid by the British in World War II, when the latest aviation radar was invented, which allowed British pilots to effectively detect German aircraft in the dark and at night. In order to hide the existence of this technology, the command of the British Air Force (Royal Air Force, RAF) disseminated misinformation interesting for the enemy that British pilots detect planes at night thanks to the consumption of carrots: the use of a carrot diet improved the vision of pilots.

Tight clothing has a negative impact on a person's vision. Tight clothes impede blood circulation, which affects all organs, including the eyes.

The easiest way to test your vision is to look for the constellation Ursa Major in the sky at night. If you can see a small star in the handle of the constellation bucket next to the middle star, your vision should be considered normal acuity.

Interesting facts about the vision of famous people

Popular people, actors and politicians, despite their wealth and success, do not always have good eyesight. In some cases, having perfect vision, they emphasize that it is not good enough. We have collected for you the most unusual, curious and interesting facts about the vision of famous people.

For example, the third president of Eli Lilly (the world's leading manufacturer of drugs for the ill and ill), under whom the company achieved tremendous success and became one of the ten largest pharmaceutical companies on the planet, was the only ones representative of the Lilly family, who was distinguished by poor eyesight and wore glasses.

Nelson's Eyepatch

An interesting fact from the story about the eyes of the great British admiral Horatio Nelson. Nelson was really wounded into the right eye (during the siege of the Calvi fortress in 1794), and practically stopped seeing with it, but the eye was not damaged externally, and there was no need to wear a bandage. It's interesting that at all lifetime In portraits, Nelson is depicted without the eye patch that appeared in his images and film incarnations. after his death. According to the authors, the eye patch was supposed to confirm to the viewer the fact that Nelson was a strong, strong-willed and courageous person.

Admiral Nelson was first introduced with an eyepatch over his right eye in Alexander Korda's Lady Hamilton (1941), starring Laurence Olivier in the title role.

Fact about Rasputin's look

Well-known historical fact: Grigory Efimovich Rasputin, a favorite of the family of Tsar Nicholas II, trained his eyes, achieving expressiveness in his gaze. According to those around him, the personification of Rasputin’s toughness and strength was precisely his “heavy,” hypnotizing gaze, thanks to which Rasputin asserted his power when communicating with people.

There are a lot of interesting facts about the British-American actress Elizabeth Rosemond Taylor. Elizabeth Taylor was first in history Hollywood woman three times awarded the prestigious Oscar film award, as well as the first actress in the history of cinema to receive a fee for participating in a film in the amount of one million dollars. But the most interesting fact about Taylor's eyes is that the actress had double rows of eyelashes. This interesting anomaly is called distichiasis ( distichiasis). An anomaly in which an additional row of eyelashes appears behind normally growing eyelashes is usually the result of a genetic mutation. In some cases, eyelashes grow directly into the cornea.

The life cycle of an eyelash is no more than five months, after which it dies and falls out. There are 150 eyelashes on the upper and lower eyelids of a human eye.

American actor, director, producer, screenwriter, three-time Oscar nominee Johnny Depp is practically blind in his left eye and nearsighted in his right. The actor reported this interesting fact about his own vision in an interview with Rolling Stone magazine in July 2013. According to Johnny Depp, vision problems have plagued him since late childhood, from about fifteen years old.

It is this interesting fact that explains the reason why most of Depp’s heroes have vision problems and wear glasses.

Fact about Julia Roberts' eyes

In a 2001 interview with Playboy magazine, American film actress Julia Roberts told readers an interesting fact about her eyes: when she is nervous, tears flow from her left eye.

Fact about Tymoshenko's glasses

The famous Ukrainian politician, statesman, former prime minister, and in fact, the leader of Ukraine, Yulia Vladimirovna Tymoshenko, wears glasses. At the same time, Yulia Tymoshenko has excellent vision; she does not suffer from farsightedness or myopia. The fact of wearing glasses in this case is explained by maintaining the image.

An interesting fact about the vision of the President of the Republic of Belarus Alexander Grigorievich Lukashenko. The President of the Republic of Belarus has farsightedness of 2.5 diopters, and there is no none An official photograph in which the Belarusian leader would be depicted wearing glasses (with the exception of sunglasses), this interesting fact about Alexander Lukashenko’s vision is not officially advertised in any way. The Commander-in-Chief of the Armed Forces of the Union State manages well without glasses and is an excellent marksman. The existence of farsightedness in Alexander Lukashenko’s vision can be indirectly assumed from interesting video facts: The President easily reads texts that are quite far from his eyes and handles weapons with complete confidence. It is quite obvious that he absolutely does not need an optical sight when shooting.

Facts about visual impairment and eye diseases

There are a number of unusual interesting facts directly or indirectly related to both eye diseases and other conditions that cause visual impairment.

The Ebers Papyrus, discovered by the German Egyptologist and writer Georg Moritz Ebers in Thebes (Upper Egypt) in the winter of 1872/1873, mentions an interesting medical fact about "opening of vision in the pupils behind the eyes", from which we can assume: ancient Egyptian medicine knew about the possibilities of removing cataracts (clouding of the lens of the eyes).

Cataracts (an ophthalmological disease associated with clouding of the lens) are a consequence of physiological aging of the body. All people are susceptible to cataracts, which develop between the ages of 70 and 80. From the moment the first signs of cataract appear until the moment when it is necessary to begin its treatment, 10 years pass.

Aphakia is a condition characterized by the absence of the lens, in which people see the ultraviolet spectrum of light as a whitish-blue or whitish-violet color.

Herpes of the eye is fixed in 98% people over 60 years of age.

In exceptional cases, due to a defect in the inner ear, its sensitivity is so increased that the person is able to hear sound of eyeballs rotating.

If the photo is with flash only one eye is red- this fact indicates the likelihood of the presence. This pathology is curable.

Leukocoria (cat's eye) is an unusual condition characterized by an abnormally white appearance of the eyes. Leukocoria usually manifests itself in children and indicates a number of diseases: retinoblastoma, toxocariasis, cataracts. Early diagnosis of leukocoria involves photographing the eye. If one eye in the photograph is red (red-eye effect), and the other is white, this combination is a sign of leukocoria.

The fact of schizophrenia in a person is diagnosed with accuracy 98 % with a standard eye movement test.

Glaucoma (blue clouding of the eye, a group of eye diseases characterized by increased intraocular pressure), stroke, and other common diseases lead to the appearance of blind spots in the eyes.

Glaucoma does not lead to serious visual impairment, since the brain and eyes are able to adapt to this environment and contribute to the disappearance of blind spots. The blind spot in the affected eye is suppressed, and the healthy eye compensates for the visual impairment.

Angle-closure glaucoma (increased intraocular pressure as a result of impaired outflow of aqueous humor through the drainage system of the eye) may be accompanied by vomiting, headache, nausea, while the patient does not complain of pain in the eye. Interestingly, an acute attack of angle-closure glaucoma can often be classified as acute gastric disease, migraine, toothache, influenza and meningitis, since the attack is accompanied by symptoms characteristic of these diseases and conditions.

Type 2 diabetes mellitus, which develops asymptomatically throughout life, is primarily diagnosed during an eye examination. In type 2 diabetes mellitus, hemorrhages from blood vessels are detected on the back of the eye.

People suffering from depression really perceive the world around them in dull shades (dark colors). With symptoms of depression, the retina responds less well to stimulation by showing contrasting pictures.

Congenital color blindness incurable and can be inherited. People with color-blind relatives should consult a geneticist at a family planning center before conceiving a child.

Strabismus, a congenital or acquired violation of the parallelism of the visual axes of the eyes, was considered a sign of beauty by the Mayan people. Mayan consciously developed strabismus in children by tying a rubber ball to them in the bridge of the nose at eye level.

A relatively small state in area, Israel, ranks third in the world (after the USA and Germany) in the number of eye surgeries performed. This fact does not mean at all that Israelis have poor eyesight: Israeli medicine is so strong and authoritative that patients from all over the world seek medical help. ~30% of vision correction operations occur in two clinics “” and.

Speaking about eye drops, one cannot fail to mention the interesting history of the development of the ophthalmic drug Okomistin (active ingredient Miramistin). The development of Miramistin began in the USSR in 1973 under the program "Space biotechnologies". Scientists were tasked with developing a universal antiseptic that can be used in the conditions of orbital stations (the closed space of manned space stations, constant temperature and humidity are an ideal environment for the proliferation of pathogenic microorganisms). At that time, there was no universal antimicrobial agent; medicine had a whole range of drugs, each of which acted on a different type of microorganism.

It is interesting that the development of the new drug lasted for 15 years and ended with the victory of Soviet scientists who created the drug BX-14, which later became known as Miramistin. Miramistin has become widespread both in Russia and abroad. Especially in the interests of ophthalmology, an analogue drug based on miramistin was created - Okomistin, which is used today for a number of eye diseases, including. Interestingly, Okomistin is so versatile that it can also be used as ear drops.

Another universal drug, previously produced in the form of an eye gel, and today widely used for varicose veins, including the drug Actovegin, is interesting not because of the history of its creation (although it has been developed for more than five years), but because of its active substance. The basis of Actovegin is deproteinized (freed from protein) hemodialysate obtained from the blood of calves.

Facts about tears and crying

The most interesting fact about human eyes is that when the eyes begin to dry out, they begin to release moisture. The tear secreted by the Harderian or lacrimal glands consists of three components: fat, mucus and water, in certain proportions. If the appropriate proportions are violated, the eyes become dry, the brain gives a command to the gland to secrete tears, and the person begins to cry.

Amazing fact: the eyes of a newborn baby don't produce tears before reaching 6 to 8 weeks of age.

When crying heavily, tears enter the nose through a direct channel. This fact explains the expression "don't make a fuss".

The average woman cries 47 times a year, a man – 7.

Astronauts are not allowed to cry in space. Due to gravity, tears collect in small balls and sting your eyes.

Facts about eyes and weapons

An interesting fact about the eyes related to weapons and optics: the glare of light is greatest in the blue part of the spectrum. For this reason, when shooting firearms, glasses with yellow lenses are used, which reduce the glare from the flash of fire when fired by 30%.

A non-lethal laser weapon (pistol), designed to destroy elements of optical systems and human eyes, was developed by the USSR in 1984 by a group of designers led by Viktor Samsonovich Sulakvelidze. The weapon was intended for use in space for the self-defense of astronauts during the Cold War. A well-known fact: the range of the blinding effect on the eyes is 20 meters.

Misconceptions about eyes and vision

A misconception is the fact that the process of smoking (or rather, tobacco smoke) does not affect vision in any way. The fact is that the eyes require significant blood supply, and the substances present in tobacco smoke help reduce the blood supply to the choroid and retina, which leads to the development of diseases of the optic nerve due to the formation of blockage of blood vessels. As a result, clouding of the lens and macular degeneration of the retina develop, which leads to poor vision and even blindness. Passive smokers suffer no less than smokers themselves: the components of tobacco smoke are powerful allergens and can cause chronic irritation of the conjunctiva of the eye.

The carotenoid pigment lycopene, contained in significant amounts in tomatoes, has a beneficial effect on human health by slowing down the development of cataracts, age-related changes in the retina, protecting the retina from ultraviolet radiation, strengthening it with vitamin A. However, for the vision of smokers, lycopene in capsules is harmful: under the influence of cigarette smoke The antioxidant pigment itself oxidizes and behaves like a free radical.

Another misconception about eyes and vision is the belief that radiation from monitors or televisions impairs vision. In fact, vision deteriorates due to excessive stress on the lens when it focuses on the small details of what is happening on the screen.

There is a misconception that farsightedness is an advantage that does not affect the condition of the body. This fact is relevant only for young people with weak farsightedness (less than 1.5 diopters). Medium (2-4 diopters) and high (4 diopters and above) degrees of farsightedness are often accompanied by headaches, pain in the eyes, pain in the brow ridges, and increased eye fatigue when working close.

Partly It is a misconception that natural childbirth is contraindicated for pregnant women with poor vision. The retina of pregnant women with moderate and high degrees of myopia stretches and thins, and the risk of its detachment and rupture during childbirth increases. This risk necessitates the replacement of natural childbirth with caesarean section. However, the risk of retinal detachment and rupture is prevented by ophthalmic laser coagulation, performed on an outpatient basis for 10 minutes. Preventive laser coagulation is indicated until the 30th week of pregnancy.

At rest, a person blinks 15,000 times a day - once every six seconds. Blinking is half a reflex function. When you blink, foreign objects are removed from the surface of the eye, and the eye becomes covered with tears. Tears help saturate the eye with oxygen and perform antibacterial functions. Interesting fact: the blinking process takes 100-150 milliseconds, a person is able to blink five times per second.

In 12 hours a person blinks for 25 minutes.

Women blink twice as often as men.

Japanese scientists have established an interesting fact: a person often blinks at the end of an event, during a pause during a conversation with an interlocutor, at the end of a sentence when reading, when changing a scene while watching a movie or TV show. Using computed tomography, researchers found an explanation for this fact: when blinking, the activity of the attention neural network sharply drops in the brain, which means the brain goes into standby mode. The process of blinking serves to renew attention as a signal to reboot the corresponding nerve cells.

Facts about reading

Interesting fact: Reading quickly causes your eyes to become tired. less than with slow.

People usually read text from a monitor screen 25% slower than from paper.

Text typed small font, men read easier than women.

Most people between the ages of 43 and 50 should face the fact that sooner or later they will need reading glasses. As we age, the lens of the eye loses its ability to focus. To focus on objects located at a distance of 0.5–2 meters, the lens of the eye must change shape from flat to spherical. The ability to change shape fades with age, and farsightedness develops.

Notes

Notes and explanations for the article “Interesting facts about eyes and vision.” To return to a term in the text - click the corresponding number.

• Cones- a type of photoreceptors, peripheral processes of light-sensitive cells in the retina. Cones are highly specialized cells that convert light stimulation into nervous stimulation. The sensitivity of cones to light is explained by the presence of a specific pigment in them - iodopsin.
• Sticks- a type of photoreceptors, peripheral processes of light-sensitive cells in the retina. The human retina contains ~120 million rods, which are 0.06 mm long and 0.002 mm in diameter. The rods are sensitive to light due to the presence of a specific pigment, rhodopsin. The presence of rods and different types of cones gives a person color vision.
• Cornea, the cornea is the anterior most convex transparent part of the eyeball, one of the light-refracting media of the eye. The radius of corneal curvature is ~7.8 mm. The diameter of the cornea from birth to 4 years of age increases very little, as a result of which the eyes of young children appear larger than the eyes of an adult.
Pigmentation of peptide bonds in certain areas of the coiled-coil regions of collagen (releasing the free amino acid hydroxyproline in particular) is collagenase. Amino acids formed as a result of the destruction of collagen fibers (under the influence of collagenase) are involved in the construction of cells and the restoration of collagen.

Collagenase is widely used in medical practice for the treatment of burns in surgery and for the treatment of purulent eye diseases in ophthalmology. In particular, collagenase is part of the polymer draining sorbents “Aseptisorb” (Aseptisorb-DK) produced by the company “Aseptika”, used in the treatment of purulent-necrotic wounds.

• lazy eye(Amblyopia) – functional, reversible decreased vision, in which one of the two eyes is practically (or completely) not involved in the visual process. With amblyopia, the eyes see too different images, and the brain is not able to combine them into one three-dimensional one. The result is suppression of one eye.
• Tumor– swelling in the tissues of the body, a painful neoplasm, a pathological process represented by newly formed tissue, in which changes in the genetic apparatus of cells lead to disruption of the regulation of their differentiation and growth. All tumors are divided into two main groups: benign and malignant (cancerous).
• Clinic (medical center) Hadassah(Hadassah Medical Center, R07, R06, R06, R06,) is one of the largest clinics in Israel, founded by the American women's Zionist organization Hadassah. The clinic's two campuses located in Jerusalem have 22 buildings with 130 departments and departments with 1,100 hospital beds. The Hadassah Clinic provides medical care to more than a million patients every year. Hadassah has 28 medical units, specializing in the treatment of endocrine, urological, oncological, ophthalmological, cardiac and nephrological diseases, among others. The Hadassah Clinic is used as a clinical base by the Hebrew University (No Ratings Yet)
  

The person processes the information received and makes the necessary adjustments. These processes are unconscious in nature and are implemented in multi-level autonomous correction of distortions. This way, spherical and chromatic aberrations, blind spot effects are eliminated, color correction is carried out, a stereoscopic image is formed, etc. In cases where subconscious information processing is insufficient or excessive, optical illusions arise.

Spectral sensitivity of the eye

In the process of evolution, light-sensitive receptors have adapted to solar radiation that reaches the surface of the Earth and spreads well in the water of the seas and oceans. The Earth's atmosphere has a significant transparency window only in the wavelength range 300-1500 nm. In the ultraviolet region, transparency is limited by the absorption of ultraviolet light by the ozone layer and water, in the infrared region - by absorption by water. Therefore, the relatively narrow visible region of the spectrum accounts for more than 40% of the solar radiation energy at the surface.

The human eye is sensitive to electromagnetic radiation in the wavelength range 400-750 nm ( visible radiation) . The retina of the eye is also sensitive to shorter wavelength radiation, but the sensitivity of the eye in this region of the spectrum is limited by the low transparency of the lens, which protects the retina from the destructive effects of ultraviolet radiation.

Physiology of human vision

Color vision

The human eye contains two types of light-sensitive cells (photoreceptors): highly sensitive rods and less sensitive cones. Rods function in relatively low light conditions and are responsible for the night vision mechanism, but they provide only a color-neutral perception of reality, limited to the participation of white, gray and black colors. Cones operate at higher light levels than rods. They are responsible for the mechanism of daytime vision, the distinctive feature of which is the ability to provide color vision.

Light of different wavelengths stimulates different types of cones differently. For example, yellow-green light stimulates L- and M-type cones equally, but less stimulates S-type cones. Red light stimulates L-type cones much more than M-type cones, and does not stimulate S-type cones at all; green-blue light stimulates M-type receptors more than L-type, and S-type receptors a little more; light with this wavelength also stimulates rods most strongly. Violet light stimulates almost exclusively S-type cones. The brain perceives combined information from different receptors, which provides different perceptions of light with different wavelengths.

Genes encoding light-sensitive opsin proteins are responsible for color vision in humans and monkeys. According to proponents of the three-component theory, the presence of three different proteins that respond to different wavelengths is sufficient for color perception. Most mammals have only two of these genes, which is why they have two-color vision. If a person has two proteins encoded by different genes that are too similar or one of the proteins is not synthesized, color blindness develops. N. N. Miklouho-Maclay found that the Papuans of New Guinea, living in the thick of the green jungle, do not have the ability to distinguish the color green.

The red light-sensitive opsin is encoded in humans by the OPN1LW gene.

Other human opsins are encoded by the genes OPN1MW, OPN1MW2 and OPN1SW, the first two of which encode proteins that are sensitive to light at medium wavelengths, and the third is responsible for an opsin that is sensitive to the short-wavelength part of the spectrum.

The need for three types of opsins for color vision was recently proven in experiments on the squirrel monkey (Saimiri), the males of which were cured of congenital color blindness by introducing the human opsin gene OPN1LW into their retina. This work (along with similar experiments in mice) showed that the mature brain is able to adapt to the new sensory capabilities of the eye.

The OPN1LW gene, which encodes the pigment responsible for the perception of red color, is highly polymorphic (recent work by Virrelli and Tishkov found 85 alleles in a sample of 256 people), and about 10% of women who have two different alleles of this gene actually have an additional type color receptors and some degree of four-component color vision. Variations in the OPN1MW gene, which encodes the “yellow-green” pigment, are rare and do not affect the spectral sensitivity of the receptors.

The OPN1LW gene and the genes responsible for the perception of medium-wavelength light are located in tandem on the X chromosome, and non-homologous recombination or gene conversion often occurs between them. In this case, gene fusion may occur or the number of their copies in the chromosome may increase. Defects in the OPN1LW gene are the cause of partial color blindness, protanopia.

The three-component theory of color vision was first expressed in 1756 by M. V. Lomonosov, when he wrote “about the three matters of the bottom of the eye.” A hundred years later, it was developed by the German scientist G. Helmholtz, who does not mention Lomonosov’s famous work “On the Origin of Light,” although it was published and summarized in German.

In parallel, there was an opposing color theory by Ewald Hering. It was developed by David Hubel and Thorsten Wiesel. They received the 1981 Nobel Prize for their discovery.

They suggested that the information that enters the brain is not about red (R), green (G) and blue (B) colors (Jung-Helmholtz color theory). The brain receives information about the difference in brightness - about the difference in brightness of white (Y max) and black (Y min), about the difference between green and red colors (G - R), about the difference between blue and yellow colors (B - yellow), and yellow color ( yellow = R + G) is the sum of red and green colors, where R, G and B are the brightness of the color components - red, R, green, G, and blue, B.

We have a system of equations:

R b − w = ( Y m a x − Y m i n , K g r = G − R , K b r g = B − R − G , (\displaystyle R_(b-w)=(\begin(cases)Y_(max)-Y_(min ),\\K_(gr)=G-R,\\K_(brg)=B-R-G,\end(cases)))

Where R b − w (\displaystyle R_(b-w)), K gr , K brg - functions of white balance coefficients for any lighting. In practice, this is expressed in the fact that people perceive the color of objects the same under different lighting sources (color adaptation). The opposing theory generally better explains the fact that people perceive the color of objects the same under extremely different lighting sources, including different colored light sources in the same scene.

These two theories are not entirely consistent with each other. But despite this, it is still assumed that the three-stimulus theory operates at the retinal level, but the information is processed and data is received in the brain that is already consistent with the opponent theory.

Binocular and stereoscopic vision

The maximum changes in the pupil for a healthy person are from 1.8 mm to 7.5 mm, which corresponds to a change in pupil area by 17 times. However, the actual range of changes in retinal illumination is limited to a ratio of 10:1, and not 17:1, as would be expected based on changes in pupil area. In fact, retinal illumination is proportional to the product of the area of ​​the pupil, the brightness of the object and the transmittance of the ocular media.

The contribution of the pupil to the regulation of eye sensitivity is extremely insignificant. The entire range of brightness that our visual mechanism is capable of perceiving is enormous: from 10 −6 cd m −2 for an eye completely adapted to darkness to 10 6 cd m −2 for an eye completely adapted to light. The mechanism for such a wide range of sensitivity lies in the decomposition and restoration of photosensitive pigments in the retinal photoreceptors - cones and rods.

The sensitivity of the eye depends on the completeness of adaptation, on the intensity of the light source, the wavelength and angular dimensions of the source, as well as on the duration of the stimulus. The sensitivity of the eye decreases with age due to the deterioration of the optical properties of the sclera and pupil, as well as the receptor component of perception.

Maximum sensitivity in daylight ( daytime vision) lies at 555-556 nm, and at weak evening/night ( twilight vision/night vision) shifts towards the violet edge of the visible spectrum and is located at 510 nm (during the day it fluctuates between 500-560 nm). This is explained (the dependence of a person’s vision on lighting conditions when he perceives multi-colored objects, the ratio of their apparent brightness - the Purkinje effect) by two types of light-sensitive elements of the eye - in bright light, vision is carried out mainly by cones, and in weak light, preferably only rods are used.

Visual acuity

The ability of different people to see larger or smaller details of an object from the same distance with the same shape of the eyeball and the same refractive power of the dioptric eye system is determined by the difference in the distance between the sensitive elements of the retina and is called visual acuity.

Visual acuity is the eye's ability to perceive apart two points located at some distance from each other ( detail, fine grain, resolution). The measure of visual acuity is the visual angle, that is, the angle formed by rays emanating from the edges of the object in question (or from two points A And B) to the nodal point ( K) eyes. Visual acuity is inversely proportional to the angle of vision, that is, the smaller it is, the higher the visual acuity. Normally, the human eye is capable of apart perceive objects with an angular distance of at least 1′ (1 minute).

Visual acuity is one of the most important functions of vision. A person's visual acuity is limited by his structure. The human eye, unlike the eyes of cephalopods, for example, is an inverted organ, that is, light-sensitive cells are located under a layer of nerves and blood vessels.

Visual acuity depends on the size of the cones located in the area of ​​the macula, the retina, as well as on a number of factors: the refraction of the eye, the width of the pupil, the transparency of the cornea, the lens (and its elasticity), the vitreous body (which makes up the light-refracting apparatus), the state of the retina and optic nerve, age.

The inversely proportional value to visual acuity and/or light sensitivity is called the resolving power of the simple (naked) eye ( resolving power).

line of sight

Peripheral vision (field of view); determine the boundaries of the field of view when projecting them onto a spherical surface (using the perimeter). Field of view is the space perceived by the eye with a fixed gaze. The visual field is a function of the peripheral retina; its condition largely determines a person’s ability to freely navigate in space.

Changes in the visual field are caused by organic and/or functional diseases of the visual analyzer: retina, optic nerve, visual pathway, central nervous system. Violations of the visual field are manifested either by a narrowing of its boundaries (expressed in degrees or linear values), or loss of individual sections of it (Hemianopsia), or the appearance of a scotoma.

Binocularity

Looking at an object with both eyes, we see it only when the axes of vision of the eyes form such an angle of convergence (convergence) at which symmetrical, clear images on the retinas are obtained in certain corresponding places of the sensitive macula ( fovea centralis). Thanks to this binocular vision, we not only judge the relative position and distance of objects, but also perceive relief and volume.

The main characteristics of binocular vision are the presence of elementary binocular, depth and stereoscopic vision, stereo visual acuity and fusional reserves.

The presence of elementary binocular vision is checked by dividing a certain image into fragments, some of which are presented to the left eye, and some to the right eye. An observer has elementary binocular vision if he is able to compose a single original image from fragments.

The presence of depth vision is tested by presenting random dot stereograms, which should evoke in the observer a specific experience of depth, different from the impression of spatiality based on monocular cues.

Stereo visual acuity is the reciprocal of the stereoscopic perception threshold. The stereoscopic threshold is the minimum detectable disparity (angular displacement) between parts of the stereogram. To measure it, the following principle is used. Three pairs of figures are presented separately to the observer's left and right eyes. In one of the pairs the position of the figures coincides, in the other two one of the figures is displaced horizontally by a certain distance. The subject is asked to indicate figures arranged in increasing order of relative distance. If the figures are indicated in the correct sequence, then the test level increases (disparity decreases); if not, the disparity increases.

Fusion reserves are conditions under which motor fusion of the stereogram is possible. Fusion reserves are determined by the maximum disparity between parts of the stereogram, at which it is still perceived as a three-dimensional image. To measure fusion reserves, the principle opposite to that used in the study of stereo visual acuity is used. For example, a subject is asked to combine two vertical stripes into one image, one of which is visible to the left eye and the other to the right eye. At the same time, the experimenter begins to slowly separate the stripes, first with convergent and then with divergent disparity. The image begins to bifurcate at the disparity value, which characterizes the fusion reserve of the observer.

Binocularity may be impaired with strabismus and some other eye diseases. If you are very tired, you may experience temporary strabismus caused by the non-dominant eye switching off.

Contrast sensitivity

Contrast sensitivity is a person’s ability to see objects that differ slightly in brightness from the background. Contrast sensitivity is assessed using sinusoidal gratings. An increase in the contrast sensitivity threshold can be a sign of a number of eye diseases, and therefore its study can be used in diagnosis.

Vision adaptation

The above properties of vision are closely related to the ability of the eye to adapt. Eye adaptation is the adaptation of vision to different lighting conditions. Adaptation occurs to changes in illumination (adaptation to light and darkness is distinguished), color characteristics of lighting (the ability to perceive white objects as white even with a significant change in the spectrum of incident light).

Adaptation to light occurs quickly and ends within 5 minutes, adaptation of the eye to darkness is a slower process. The minimum brightness that causes the sensation of light determines the light sensitivity of the eye. The latter increases rapidly in the first 30 minutes. staying in the dark, its increase practically ends after 50-60 minutes. Adaptation of the eye to darkness is studied using special devices - adaptometers.

Decreased adaptation of the eye to darkness is observed in some eye (retinal pigmentary degeneration, glaucoma) and general (A-vitaminosis) diseases.

Adaptation is also manifested in the ability of vision to partially compensate for defects in the visual apparatus itself (optical defects of the lens, retinal defects, scotomas, etc.)

Processing of visual information

The phenomenon of visual sensations that are not accompanied by the processing of visual information is called the phenomenon of pseudo-blindness.

Visual disturbances

Lens defects

The most common drawback is the discrepancy between the optical power of the eye and its length, leading to a deterioration in the visibility of close or distant objects.

Farsightedness

Farsightedness is a refractive error in which rays of light entering the eye are focused not on the retina, but behind it. In mild forms of the eye with a good reserve of accommodation, it compensates for the visual deficiency by increasing the curvature of the lens with the ciliary muscle.

With more severe farsightedness (3 diopters and above), vision is poor not only near, but also at distance, and the eye is not able to compensate for the defect on its own. Farsightedness is usually congenital and does not progress (usually decreases by school age).

For farsightedness, reading glasses or constant wear are prescribed. For glasses, converging lenses are selected (they move the focus forward to the retina), with the use of which the patient’s vision becomes best.

Slightly different from farsightedness is presbyopia, or age-related farsightedness. Presbyopia develops due to the loss of elasticity of the lens (which is a normal result of its development). This process begins at school age, but a person usually notices weakening of near vision after 40 years. (Although at 10 years old, emmetropic children can read at a distance of 7 cm, at 20 years old - already at least 10 cm, and at 30 - 14 cm, and so on.) Senile farsightedness develops gradually, and by the age of 65-70 a person has completely lost ability to accommodate, development of presbyopia is completed.

Myopia

Myopia is a refractive error of the eye, in which the focus moves forward, and an already out-of-focus image falls on the retina. With myopia, the further point of clear vision lies within 5 meters (normally it lies at infinity). Myopia can be false (when, due to overstrain of the ciliary muscle, its spasm occurs, as a result of which the curvature of the lens remains too large in distance vision) and true (when the eyeball increases in the anterior-posterior axis). In mild cases, distant objects are blurred while near objects remain clear (the furthest point of clear vision lies quite far from the eyes). In cases of high myopia, a significant decrease in vision occurs. Starting at approximately −4 diopters, a person needs glasses for both distance and near distance, otherwise the object in question must be brought very close to the eyes. However, precisely because for good image sharpness, a myopic person brings an object close to his eyes, he is able to distinguish finer details of this object than a person with normal vision.

During adolescence, myopia often progresses (the eyes constantly strain to work near, which is why the eye compensatory grows in length). The progression of myopia sometimes takes a malignant form, in which vision drops by 2-3 diopters per year, stretching of the sclera is observed, and degenerative changes in the retina occur. In severe cases, there is a danger of detachment of the overstretched retina due to physical exertion or a sudden blow. Stopping the progression of myopia usually occurs by the age of 25-30, when the body stops growing. With rapid progression, vision by that time drops to −25 diopters and below, severely crippling the eyes and sharply disrupting the quality of vision at distance and near (all that a person sees are cloudy outlines without any detailed vision), and such deviations are very are difficult to fully correct with optics: thick glasses create strong distortions and make objects visually smaller, which is why a person does not see well enough even with glasses. In such cases, a better effect can be achieved using contact correction.

Despite the fact that hundreds of scientific and medical works have been devoted to the issue of stopping the progression of myopia, there is still no evidence of the effectiveness of any method of treating progressive myopia, including surgery (scleroplasty). There is evidence of a small but statistically significant reduction in the rate of increase in myopia in children when using atropine eye drops and pirenzipine eye gel [ ] .

For myopia, laser vision correction is often used (exposure to the cornea using a laser beam to reduce its curvature). This correction method is not completely safe, but in most cases it is possible to achieve a significant improvement in vision after surgery.

Defects of myopia and farsightedness can be overcome with the help of glasses, contact lenses or rehabilitative gymnastics courses.

Astigmatism

Astigmatism is a defect in the optics of the eye caused by the irregular shape of the cornea and (or) lens. In all people, the shape of the cornea and lens differs from the ideal body of rotation (that is, all people have astigmatism of varying degrees). In severe cases, the stretching along one of the axes can be very strong, in addition, the cornea may have curvature defects caused by other reasons (wounds, infectious diseases, etc.). With astigmatism, light rays are refracted with different strengths in different meridians, as a result of which the image turns out to be curved and unclear in places. In severe cases, the distortion is so strong that it significantly reduces the quality of vision.

Astigmatism can be easily diagnosed by looking with one eye at a sheet of paper with dark parallel lines - by rotating such a sheet, the astigmatist will notice that the dark lines either blur or become clearer. Most people have congenital astigmatism up to 0.5 diopters, which does not cause discomfort.

This defect is compensated by glasses with cylindrical lenses having different curvature horizontally and vertically and contact lenses (hard or soft toric), as well as spectacle lenses having different optical powers in different meridians.

Retinal defects

Colorblindness

If the perception of one of the three primary colors in the retina is lost or weakened, then a person does not perceive a certain color. There are “color-blind” ones for red, green and blue-violet. Paired, or even complete color blindness is rare. More often there are people who cannot distinguish red from green. This lack of vision was called color blindness - after the English scientist D. Dalton, who himself suffered from such a color vision disorder and first described it.

Color blindness is incurable and is inherited (linked to the X chromosome). Sometimes it occurs after certain eye and nervous diseases.

Colorblind people are not allowed to work related to driving vehicles on public roads. Good color vision is very important for sailors, pilots, chemists, geologists-mineralogists, artists, therefore, for some professions, color vision is checked using special tables.

Scotoma

Instrumental methods

Correction of visual impairments is usually carried out with the help of glasses.

To expand the capabilities of visual perception, special instruments and methods are also used, for example, microscopes and telescopes.

Surgical correction

It is possible to bring the optical properties of the eye back to normal by changing the curvature of the cornea. To do this, in certain places the cornea is evaporated by a laser beam, which leads to a change in its shape. Basic methods

Vision is the channel through which a person receives approximately 70% of all data about the world that surrounds him. And this is possible only for the reason that human vision is one of the most complex and amazing visual systems on our planet. If there were no vision, we would all most likely simply live in the dark.

The human eye has a perfect structure and provides vision not only in color, but also in three dimensions and with the highest sharpness. It has the ability to instantly change focus to a variety of distances, regulate the volume of incoming light, distinguish between a huge number of colors and an even greater number of shades, correct spherical and chromatic aberrations, etc. The eye brain is connected to six levels of the retina, in which the data goes through a compression stage even before information is sent to the brain.

But how does our vision work? How do we transform color reflected from objects into an image by enhancing color? If you think about this seriously, you can conclude that the structure of the human visual system is “thought out” to the smallest detail by the Nature that created it. If you prefer to believe that the Creator or some Higher Power is responsible for the creation of man, then you can attribute this credit to them. But let's not understand, but continue talking about the structure of vision.

Huge amount of details

The structure of the eye and its physiology can frankly be called truly ideal. Think for yourself: both eyes are located in the bony sockets of the skull, which protect them from all kinds of damage, but they protrude from them in such a way as to ensure the widest possible horizontal vision.

The distance the eyes are from each other provides spatial depth. And the eyeballs themselves, as is known for certain, have a spherical shape, due to which they are able to rotate in four directions: left, right, up and down. But each of us takes all this for granted - few people imagine what would happen if our eyes were square or triangular or their movement was chaotic - this would make vision limited, chaotic and ineffective.

So, the structure of the eye is extremely complex, but this is precisely what makes the work of about four dozen of its different components possible. And even if at least one of these elements were missing, the process of vision would cease to be carried out as it should be carried out.

To see how complex the eye is, we invite you to pay attention to the figure below.

Let's talk about how the process of visual perception is implemented in practice, what elements of the visual system are involved in this, and what each of them is responsible for.

Passage of light

As light approaches the eye, light rays collide with the cornea (otherwise known as the cornea). The transparency of the cornea allows light to pass through it into the inner surface of the eye. Transparency, by the way, is the most important characteristic of the cornea, and it remains transparent due to the fact that a special protein it contains inhibits the development of blood vessels - a process that occurs in almost every tissue of the human body. If the cornea were not transparent, the remaining components of the visual system would have no significance.

Among other things, the cornea prevents debris, dust and any chemical elements from entering the internal cavities of the eye. And the curvature of the cornea allows it to refract light and help the lens focus light rays on the retina.

After light has passed through the cornea, it passes through a small hole located in the middle of the iris. The iris is a round diaphragm that is located in front of the lens just behind the cornea. The iris is also the element that gives the eye color, and the color depends on the predominant pigment in the iris. The central hole in the iris is the pupil familiar to each of us. The size of this hole can be changed to control the amount of light entering the eye.

The size of the pupil will be changed directly by the iris, and this is due to its unique structure, because it consists of two different types of muscle tissue (even there are muscles here!). The first muscle is a circular compressor - it is located in the iris in a circular manner. When the light is bright, it contracts, as a result of which the pupil contracts, as if being pulled inward by a muscle. The second muscle is an extension muscle - it is located radially, i.e. along the radius of the iris, which can be compared to the spokes of a wheel. In dark lighting, this second muscle contracts, and the iris opens the pupil.

Many still experience some difficulties when they try to explain how the formation of the above-mentioned elements of the human visual system occurs, because in any other intermediate form, i.e. at any evolutionary stage they simply would not be able to work, but man sees from the very beginning of his existence. Mystery…

Focusing

Bypassing the above stages, light begins to pass through the lens located behind the iris. The lens is an optical element shaped like a convex oblong ball. The lens is absolutely smooth and transparent, there are no blood vessels in it, and it itself is located in an elastic sac.

Passing through the lens, light is refracted, after which it is focused on the fovea of ​​the retina - the most sensitive place containing the maximum number of photoreceptors.

It is important to note that the unique structure and composition provide the cornea and lens with a high refractive power, guaranteeing a short focal length. And how amazing it is that such a complex system fits in just one eyeball (just think what a person could look like if, for example, a meter was required to focus light rays coming from objects!).

No less interesting is the fact that the combined refractive power of these two elements (cornea and lens) is in excellent correlation with the eyeball, and this can be safely called another proof that the visual system is created simply unsurpassed, because the process of focusing is too complex to talk about it as something that happened only through step-by-step mutations - evolutionary stages.

If we are talking about objects located close to the eye (as a rule, a distance of less than 6 meters is considered close), then everything is even more curious, because in this situation the refraction of light rays turns out to be even stronger. This is ensured by an increase in the curvature of the lens. The lens is connected through ciliary bands to the ciliary muscle, which, when contracted, allows the lens to take on a more convex shape, thereby increasing its refractive power.

And here again we cannot fail to mention the complex structure of the lens: it consists of many threads, which consist of cells connected to each other, and thin belts connect it with the ciliary body. Focusing is carried out under the control of the brain extremely quickly and completely “automatically” - it is impossible for a person to carry out such a process consciously.

Meaning of "camera film"

Focusing results in focusing the image on the retina, which is a multi-layered light-sensitive tissue covering the back of the eyeball. The retina contains approximately 137,000,000 photoreceptors (for comparison, we can cite modern digital cameras, which have no more than 10,000,000 such sensory elements). Such a huge number of photoreceptors is due to the fact that they are located extremely densely - approximately 400,000 per 1 mm².

It would not be out of place here to cite the words of microbiologist Alan L. Gillen, who speaks in his book “The Body by Design” about the retina of the eye as a masterpiece of engineering design. He believes that the retina is the most amazing element of the eye, comparable to photographic film. The light-sensitive retina, located on the back of the eyeball, is much thinner than cellophane (its thickness is no more than 0.2 mm) and much more sensitive than any human-made photographic film. The cells of this unique layer are capable of processing up to 10 billion photons, while the most sensitive camera can process only a few thousand. But what’s even more amazing is that the human eye can detect a few photons even in the dark.

In total, the retina consists of 10 layers of photoreceptor cells, 6 layers of which are layers of light-sensitive cells. 2 types of photoreceptors have a special shape, which is why they are called cones and rods. Rods are extremely sensitive to light and provide the eye with black-and-white perception and night vision. Cones, in turn, are not so sensitive to light, but are able to distinguish colors - optimal operation of the cones is noted in the daytime.

Thanks to the work of photoreceptors, light rays are transformed into complexes of electrical impulses and sent to the brain at incredibly high speed, and these impulses themselves travel over a million nerve fibers in a fraction of a second.

The communication of photoreceptor cells in the retina is very complex. Cones and rods are not directly connected to the brain. Having received the signal, they redirect it to bipolar cells, and they redirect the signals they have already processed to ganglion cells, more than a million axons (neurites along which nerve impulses are transmitted) which form a single optic nerve, through which data enters the brain.

Two layers of interneurons, before visual data is sent to the brain, facilitate parallel processing of this information by six layers of perception located in the retina. This is necessary so that images are recognized as quickly as possible.

Brain perception

After the processed visual information enters the brain, it begins to sort, process and analyze it, and also forms a complete image from individual data. Of course, there is still a lot that is unknown about the workings of the human brain, but even what the scientific world can provide today is enough to be amazed.

With the help of two eyes, two “pictures” of the world that surrounds a person are formed - one for each retina. Both “pictures” are transmitted to the brain, and in reality the person sees two images at the same time. But how?

But the point is this: the retinal point of one eye exactly corresponds to the retinal point of the other, and this suggests that both images, entering the brain, can overlap each other and be combined together to obtain a single image. The information received by the photoreceptors in each eye converges in the visual cortex, where a single image appears.

Due to the fact that the two eyes may have different projections, some inconsistencies may be observed, but the brain compares and connects the images in such a way that a person does not perceive any inconsistencies. Moreover, these inconsistencies can be used to obtain a sense of spatial depth.

As you know, due to the refraction of light, visual images entering the brain are initially very small and upside down, but “at the output” we get the image that we are used to seeing.

In addition, in the retina, the image is divided by the brain in two vertically - through a line that passes through the retinal fossa. The left parts of the images received by both eyes are redirected to , and the right parts are redirected to the left. Thus, each of the hemispheres of the viewing person receives data from only one part of what he sees. And again - “at the output” we get a solid image without any traces of connection.

The separation of images and extremely complex optical pathways make it so that the brain sees separately from each of its hemispheres using each of the eyes. This allows you to speed up the processing of the flow of incoming information, and also provides vision with one eye if suddenly a person for some reason stops seeing with the other.

We can conclude that the brain, in the process of processing visual information, removes “blind” spots, distortions due to micro-movements of the eyes, blinks, angle of view, etc., offering its owner an adequate holistic image of what is being observed.

Another important element of the visual system is. There is no way to downplay the importance of this issue, because... In order to be able to use our vision properly at all, we must be able to turn our eyes, raise them, lower them, in short, move our eyes.

In total, there are 6 external muscles that connect to the outer surface of the eyeball. These muscles include 4 rectus muscles (inferior, superior, lateral and middle) and 2 obliques (inferior and superior).

At the moment when any of the muscles contracts, the muscle that is opposite to it relaxes - this ensures smooth eye movement (otherwise all eye movements would be jerky).

When you turn both eyes, the movement of all 12 muscles (6 muscles in each eye) automatically changes. And it is noteworthy that this process is continuous and very well coordinated.

According to the famous ophthalmologist Peter Janey, the control and coordination of the communication of organs and tissues with the central nervous system through the nerves (this is called innervation) of all 12 eye muscles is one of the very complex processes occurring in the brain. If we add to this the accuracy of gaze redirection, the smoothness and evenness of movements, the speed with which the eye can rotate (and it amounts to a total of up to 700° per second), and combine all this, we will actually get a mobile eye that is phenomenal in terms of performance. system. And the fact that a person has two eyes makes it even more complex - with synchronous eye movements, the same muscular innervation is necessary.

The muscles that rotate the eyes are different from the skeletal muscles because... they are made up of many different fibers, and they are controlled by an even larger number of neurons, otherwise the accuracy of movements would become impossible. These muscles can also be called unique because they are able to contract quickly and practically do not get tired.

Considering that the eye is one of the most important organs of the human body, it needs continuous care. It is precisely for this purpose that an “integrated cleaning system,” so to speak, is provided, which consists of eyebrows, eyelids, eyelashes and tear glands.

The lacrimal glands regularly produce a sticky fluid that moves slowly down the outer surface of the eyeball. This liquid washes away various debris (dust, etc.) from the cornea, after which it enters the internal lacrimal canal and then flows down the nasal canal, being eliminated from the body.

Tears contain a very strong antibacterial substance that destroys viruses and bacteria. The eyelids act as windshield wipers - they clean and moisturize the eyes through involuntary blinking at intervals of 10-15 seconds. Along with the eyelids, eyelashes also work, preventing any debris, dirt, germs, etc. from entering the eye.

If the eyelids did not fulfill their function, a person's eyes would gradually dry out and become covered with scars. If there were no tear ducts, the eyes would constantly be filled with tear fluid. If a person did not blink, debris would get into his eyes and he could even go blind. The entire “cleaning system” must include the work of all elements without exception, otherwise it would simply cease to function.

Eyes as an indicator of condition

A person’s eyes are capable of transmitting a lot of information during his interaction with other people and the world around him. The eyes can radiate love, burn with anger, reflect joy, fear or anxiety, or fatigue. The eyes show where a person is looking, whether he is interested in something or not.

For example, when people roll their eyes while talking to someone, this can be interpreted very differently from a normal upward gaze. Big eyes in children evoke delight and tenderness among those around them. And the state of the pupils reflects the state of consciousness in which a person is at a given moment in time. Eyes are an indicator of life and death, if we speak in a global sense. This is probably why they are called the “mirror” of the soul.

Instead of a conclusion

In this lesson we looked at the structure of the human visual system. Naturally, we missed a lot of details (this topic itself is very voluminous and it is problematic to fit it into the framework of one lesson), but we still tried to convey the material so that you have a clear idea of ​​HOW a person sees.

You couldn't help but notice that both the complexity and capabilities of the eye allow this organ to surpass even the most modern technologies and scientific developments many times over. The eye is a clear demonstration of the complexity of engineering in a huge number of nuances.

But knowing about the structure of vision is, of course, good and useful, but the most important thing is to know how vision can be restored. The fact is that a person’s lifestyle, the conditions in which he lives, and some other factors (stress, genetics, bad habits, diseases and much more) - all this often contributes to the fact that vision can deteriorate over the years, i.e. .e. the visual system begins to malfunction.

But deterioration of vision in most cases is not an irreversible process - knowing certain techniques, this process can be reversed, and vision can be made, if not the same as that of a baby (although this is sometimes possible), then as good as possible for each individual person. Therefore, the next lesson in our course on vision development will be devoted to methods of vision restoration.

Look at the root!

Test your knowledge

If you want to test your knowledge on the topic of this lesson, you can take a short test consisting of several questions. For each question, only 1 option can be correct. After you select one of the options, the system automatically moves on to the next question. The points you receive are affected by the correctness of your answers and the time spent on completion. Please note that the questions are different each time and the options are mixed.

Vision is one of the most important senses for perceiving the world around us. With its help, we see objects and objects around us, we can evaluate their size and shape. According to research, through vision we receive at least 90% of information about the surrounding reality. Several visual components are responsible for color vision, which allows for more accurate and correct transmission of images of objects to the brain for further processing of information. There are several pathologies of color transmission disorders that significantly impair interaction with the world and reduce the quality of life in general.

How does the organ of vision work?

The eye is a complex optical system that consists of many interconnected elements. The perception of various parameters of surrounding objects (size, distance, shape, etc.) is provided by the peripheral part of the visual analyzer, represented by the eyeball. This is a spherical organ with three shells, which has two poles - internal and external. The eyeball is located in a bony cavity protected on three sides - the orbit or orbit, where it is surrounded by a thin layer of fat. In front are the eyelids, which are necessary to protect the mucous membrane of the organ and clean it. It is in their thickness that there are glands necessary for constant moistening of the eyes and the unhindered operation of closing and opening the eyelids themselves. The movement of the eyeball is provided by 6 muscles of different functions, which allows for the cooperative actions of this paired organ. In addition, the eye is connected to the circulatory system by numerous blood vessels of different sizes, and to the nervous system by several nerve endings.

The peculiarity of vision is that we do not see the object directly, but only the rays reflected from it. Further processing of information occurs in the brain, more precisely in the back of the head. Light rays initially enter the cornea and then pass to the lens, vitreous body and retina. The human natural lens, the crystalline lens, is responsible for the perception of light rays, and the light-sensitive membrane, the retina, is responsible for its perception. It has a complex structure, in which 10 different layers of cells are distinguished. Among them, especially important are the cones and rods, which are unevenly distributed throughout the layer. It is the cones that are the necessary element responsible for human color vision.

The highest concentration of cones is found in the fovea, the image-receiving area in the macula. Within its limits, the density of cones reaches 147 thousand per 1 mm 2.

Color perception

The human eye is the most complex and advanced visual system of all mammals. It is capable of perceiving more than 150 thousand different colors and their shades. Color perception is possible thanks to cones - specialized photoreceptors located in the macula. An auxiliary role is played by rods - cells responsible for twilight and night vision. It is possible to perceive the entire color spectrum with the help of only three types of cones, each of which is sensitive to a specific part of the color gamut (green, blue and red) due to the content of iodopsin. A person with full vision has 6-7 million cones, and if their number is less or there are pathologies in their composition, various color vision disorders occur.

Structure of the eye

The vision of men and women is significantly different. It has been proven that women are able to recognize more different shades of colors, while representatives of the stronger sex have a better ability to recognize moving objects and maintain concentration on a specific object longer.

Color vision deviations

Color vision anomalies are a rare group of ophthalmological disorders that are characterized by distorted color perception. Almost always, these diseases are inherited in a recessive manner. From a physiological point of view, all people are trichromats - to fully distinguish colors, they use three parts of the spectrum (blue, green and red), but with pathology, the proportion of colors is disrupted or one of them is completely or partially lost. Color blindness is only a special case of pathology in which there is complete or partial blindness to any color.

There are three groups of color vision anomalies:

• Dichromatism or dichromasia. The pathology lies in the fact that only two parts of the spectrum are used to obtain any color. Exists, depending on the drop-down section of the color palette. The most common is deuteranopia - the inability to perceive the color green;
• Complete color blindness. Occurs in only 0.01% of all people. There are two types of pathology: achromatopsia (achromasia), in which there is a complete absence of pigment in the cones on the retina, and any colors are perceived as shades of gray, and cone monochromasia– different colors are perceived equally. The anomaly is genetic and is associated with the fact that color photoreceptors contain rhodopsin instead of iodopsin;

Any color deviations cause many restrictions, for example, for driving vehicles or serving in the army. In some cases, color vision anomalies lead to visual impairment.

Definition and types of color blindness

One of the most common pathologies of color perception, which is of a genetic nature or develops against a background. There is a complete (achromasia) or partial inability (dichromasia and monochromasia) to perceive colors; the pathologies are described in more detail above.

Traditionally, several types of color blindness are distinguished in the form of dichromasia, depending on the loss of part of the color spectrum.

• Protanopia. Color blindness occurs in the red part of the spectrum, occurring in 1% of men and less than 0.1% of women;
• Deuteranopia. The green part of the spectrum falls out of the perceived range of colors and is most common;
• Tritanopia. The inability to distinguish shades of blue-violet colors, plus the absence of twilight vision is often observed due to disruption of the rods.

Separately, trichromasia is distinguished. This is a rare type of color blindness in which a person distinguishes all colors, but due to a violation of the concentration of iodopsin, color perception is distorted. People with this anomaly have particular difficulty interpreting shades. In addition, the effect of overcompensation is often observed in this pathology, for example, if it is impossible to distinguish between green and red, improved discrimination of khaki shades occurs.

Types of color blindness

The anomaly is named after J. Dalton, who described the disease back in the 18th century. Great interest in the disease is due to the fact that the researcher himself and his brothers suffered from protanopia.

Color blindness test

In recent years, to determine color vision anomalies are used, which are images of numbers and figures, applied to a selected background using circles of different diameters. A total of 27 pictures were developed, each of which has a specific purpose. Plus, the stimulus material contains special images to identify feigning a disease, since the test is important when passing some professional medical commissions and when registering for military service. The interpretation of the test should only be carried out by a specialist, since analyzing the results is a rather complex and time-consuming process.

It is believed that only printed cards can be used, as color distortion may occur on the monitor or screen.

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conclusions

Human vision is a complex and multifaceted process for which many elements are responsible. Any anomalies in the perception of the surrounding world not only reduce the quality of life, but can be a threat to life in some situations. Most visual pathologies are congenital, so when diagnosing a child with a deviation, you need not only to undergo the necessary treatment and correctly select corrective optics, but also to teach him to live with this problem.