Presentation on human vision. Presentation - The human organ of vision

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Eye (lat. oculus) - sensory organ(organ of the visual system) of humans and animals, which has the ability to perceive electromagnetic radiation in the light wavelength range and provides the function of vision. The main functions of the eye: 1. an optical system that projects an image; 2. a system that perceives and "encodes" the information received for the brain ;3 "service" life support system.

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The eye consists of: 1. cornea; 2. anterior chamber of the eye; 3. irises; 4. pupil; 5. lens; 6. eyelash band; 7. vitreous body; 8. retina; 9. sclera; 10. choroid;11. optic nerve

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The cornea is the transparent membrane that covers the front of the eye. There are no blood vessels in it, it has a large refractive power. Included in the optical system of the eye. The cornea borders on the opaque outer shell of the eye - the sclera. The human cornea occupies approximately 1/16 of the area outer shell eyes. It has the form of a convex-concave lens with its concave part turned back. The corneal diameter is almost an absolute constant and is 10 ± 0.56 mm, however, the vertical dimension is usually 0.5-1 mm less than the horizontal one. The thickness of the cornea in the central part is 0.52-0.6 mm, along the edges - 1-1.2 mm. The refractive index of the corneal substance is 1.37, the refractive power is 40 diopters. The radius of curvature of the cornea is about 7.8 mm. The structure of the cornea: 1. surface layer; 2. anterior border plate; 3. own substance of the cornea; 4. rear border elastic plate; 5. endothelium.

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The iris is shaped like a circle with a hole inside (the pupil). The iris consists of muscles, with the contraction and relaxation of which the size of the pupil changes. It enters the choroid of the eye. The iris is responsible for the color of the eyes (if it is blue, it means that there are few pigment cells in it, if it is brown, there are many). It performs the same function as the aperture in a camera, adjusting the light output. The pupil is a hole in the iris. Its dimensions usually depend on the level of illumination. The more light, the smaller the pupil.

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The lens is the "natural lens" of the eye. It is transparent, elastic - it can change its shape, "focusing" almost instantly, due to which a person sees well both near and far. It is located in the capsule, held by the ciliary girdle. The lens, like the cornea, is included in the optical system of the eye. The ciliary girdle is a system of fibers coming from the ciliary processes to the lens capsule and attached in the region of its equator; tension R. p. with contraction of the ciliary muscle leads to a decrease in the curvature of the lens. Iridescent-corneal angle (scheme): 1 - conjunctiva; 2 - sclera; 3- venous sinus sclera; 4 - cornea; 5 - iridocorneal angle; 6 - iris; 7 - lens; 8 - ciliary girdle; 9 - ciliary body; 10 - anterior chamber of the eye; 11 - posterior chamber of the eye

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structure of the retina: 1. pigment epithelium 2. rod and cone layer 3. outer glial limiting membrane 4. outer granular layer 5. outer reticular layer 6. inner granular layer 7. inner reticular layer 8. ganglionic layer 9. nerve fiber layer 10. inner glial limiting membrane

The retina is composed of photoreceptors (they are sensitive to light) and nerve cells. Receptor cells located in the retina are divided into two types: cones and rods. In these cells, which produce the enzyme rhodopsin, the energy of light (photons) is converted into electrical energy. nervous tissue, i.e. photochemical reaction. The rods are highly sensitive to light and allow you to see in low light, they are also responsible for peripheral vision. Cones, on the contrary, require more light for their work, but it is they that allow you to see fine details (responsible for central vision) allow color to be distinguished. The greatest concentration of cones is in the fovea (macula), which is responsible for the highest visual acuity. The retina is adjacent to the choroid, but loosely in many areas. This is where it tends to flake off when various diseases retina.

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The vitreous body is transparent, colorless, elastic, jelly-like. Located behind the lens. Structure. On the anterior surface of the vitreous body there is a recess - the vitreous fossa, corresponding to the lens. The vitreous body is fixed in the region of the posterior pole of the lens, in the flat part of the ciliary body and near the optic disc. For the rest of its length, it is only adjacent to the inner limiting membrane of the retina. Between the optic disc and the center of the posterior surface of the lens passes a narrow, downwardly curved vitreous canal, the walls of which are formed by a layer of compacted fibers. In embryos, the artery of the vitreous body passes through this canal. Functions: Support function (support for other structures of the eye). Transmission of light rays to the retina. Passively participates in accommodation. Creates favorable conditions for constancy intraocular pressure and stable form eyeball. Protective function- protects the inner membranes of the eye (retina, ciliary body, lens) from displacement during injuries. There are no vessels and nerves in the vitreous body, therefore its vital activity and constancy of the environment are provided by osmosis and diffusion nutrients from intraocular fluid through the vitreous membrane.

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Sclera - an opaque outer shell of the eyeball, passing in front of the eyeball into a transparent cornea. 6 oculomotor muscles are attached to the sclera. It contains not a large number of nerve endings and vessels. The structure of the sclera: 1. Episclera - superficial, looser layer, rich blood vessels. In the episclera, superficial and deep vascular networks are distinguished.2. The proper substance of the sclera contains predominantly collagen and a small amount of elastic fibers.3. Dark scleral plate - loose layer connective tissue between the sclera and the choroid itself, contains pigment cells. Functions of the sclera. 1. The sclera is the site of attachment of the muscles of the eye, which provide free mobility of the eyeballs in various directions. 2. Through the sclera, blood vessels penetrate into the back of the eyeball - short and long posterior ethmoid arteries. From the eye in the region of the equator through the sclera exit 4-6 vorticose (whirlpool) veins, through which venous blood flows from the vascular tract. 3. Sensory nerves off ophthalmic nerve(the first branch of the trigeminal nerve) through the sclera approach the eyeball.

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1. Good Vision Problems Research shows that more than 95% of babies are born with normal vision and no eye defects. But a very small percentage of them reach old age with vision that could be considered in any way normal. A heavy load is placed on people's eyesight. As a result, America is rapidly turning into a country of "bespectacled". The discrepancy between human vision as a whole is one of the most serious defects of modern civilization. Since many imperfections of the eye seem to be created by the load on them and the conditions under which the eyes do their work, the situation can be greatly improved. However, this requires a scientific approach on the part of various groups of people and each person individually. For our part, we must learn how the eye works, what its functions are, what defects there are, and what operating conditions cause overload. First of all, let's start with the study of the eye.

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2. Human visual analyzer The eye is located in the orbit of the skull. From the walls of the orbit to the outer surface of the eyeball, muscles fit, with their help the eye moves. Eyebrows protect the eye, they divert sweat flowing from the forehead to the sides. Eyelids and eyelashes protect the eye from dust. The lacrimal gland, located at the outer corner of the eye, secretes a fluid that moisturizes the surface of the eyeball, warms the eye, washes away foreign particles that fall on it, and then flows from the inner corner of the eye through the lacrimal canal into the nasal cavity.

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The pupil is a hole in the center of the iris. The pupil controls the amount of light entering the eye. In bright light, the pupil constricts reflexively. In low light, the pupil dilates. Behind the pupil is a transparent biconvex lens. It is surrounded by the ciliary muscle. The entire inner part of the eyeball is filled with the vitreous body - a transparent gelatinous substance. The eye transmits light rays in such a way that the images of objects are focused on the inner shell of the eyeball - the retina. The retina contains the receptors of the eye - rods and cones. Rods are twilight light receptors, cones are irritated only by bright light, color vision is associated with them. The middle choroid is permeated with a dense network of blood vessels that supply the eyeball with blood. On the inner surface of this shell is a thin layer of coloring matter - a black pigment that absorbs light rays. The front part of the choroid of the eye is called the iris. Its color (from light blue to dark brown) is determined by the amount and distribution of the pigment. In the retina, light is converted into nerve impulses, which are transmitted along the optic nerve to the brain to the visual zone of the cerebral cortex. In this zone, the final distinction of stimuli occurs - the shape of objects, their color, size, illumination, location and movement.

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3. The Eye as a Live Camera Obscura The eye is often called a live camera Obscura, but like most analogies this analogy is only partially true. The eye is an infinitely finer and more complex instrument than the best camera, although in principle they are the same. In a camera, there is a simple converging lens or lens system that acts like the converging lens of the eye. The sensitive film in a camera corresponds to the light sensitivity of the retina at the back of the eye; both are inverted, real, reduced images. The aperture controls the amount of light allowed into the camera; The iris regulates the amount of light entering the eye. In the dark, the pupil or opening of the iris can be almost 1 cm in diameter, and in bright light it is the size of a pinhead.

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4. Focusing the Eyes In an instant, a normal eye is able to focus clearly on the retina such a large distant object as a mountain, and in the next fraction of a second it can give an equally clear image of a typed text or a car speedometer, located only at a distance of some tens of centimeters from the eyes. . The lens of the eye simply changes its shape. As the distance of the object increases, resulting in a decrease in the distance of the image, the muscles connected to the outer edges of the eye lens cause the lens to flatten and become thinner. Thus, its focal length is sufficiently increased and the image is sharply focused on the retina. If the object approaches the eye, causing the distance to the image to increase, the lens becomes more convex and thicker. Its focal length is thus reduced so that the distance of the image remains complete and the image does not leave the retina. The image in the eye exists only for 1/16 sec before the next clear image appears. The retina often lacks detail, and one image may overlap and obscure the next image. Afterimage in the eye leads to other interesting phenomena. It causes a blurring of the picture of the spokes of a spinning wheel and creates the appearance of a glowing trail behind a light source moving fast in the dark. In reality, we see in the cinema from 16 to 24 still pictures appearing on the screen every second. After each such picture and before the next, the screen is obscured by the obturator of the film projection apparatus, but the eye retains the impression from one picture to the next and turns individual images into the illusion of continuous movement. The inside of the eye is surrounded by a dark shell that absorbs light. On top of the dark shell of the eye there is a hard white shell that retains the shape of the eyeball and protects the eye from damage.

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5. Far and near points When the eye muscles are completely relaxed, as is the case when looking at a distant object, the lens has a maximum focal length, and then it is said to be adapted to the far point. When an object is so close to the eye that the lens has the smallest possible focal length, the object is said to be at the nearest point.

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6. Presbyopia With age, the ability to accommodate gradually decreases. This is due to a decrease in the elasticity of the lens and the ability of the eye muscles to increase the curvature of the lens. This deficiency is called presbyopia. When such a deficiency occurs, the near point moves away from the eye and the accommodative power decreases. It can be seen from the table that for persons of 65 years of age, the nearest point is at a distance of 200 cm. What will be the approximate nearest distance at which a person of 65 years of age can read this page without the help of glasses? At such a distance (200 cm) it is doubtful that it was possible to make out the words due to the too small size of the image on the retina. There is no ideal distance for reading or other work at close range, but when all factors are taken into account, then 32 - 37 cm can be considered the best distance. But if this distance is less than about one and a half distance of the near point, then the voltage that is required muscles in order to focus the light and get a sharp image on the retina, so great that eye fatigue is likely to occur. At the age of 35, it is easy to follow this rule. After 40 years, this is usually difficult to do. At the age of 45, the minimum distance is 45 cm, which is farther than is necessary for the subject to have the image of the appropriate size and be easily visible. After 40 years, the middle lens of the eye needs an auxiliary device to collect light when viewing close objects. For this purpose, a converging lens of the appropriate optical power is placed in front of the eye. But with such a lens it is impossible to see distant objects. In order to correct this deficiency, you need to either remove glasses or use bifocal lenses. In such lenses, the lower part is used for near vision, and the upper part is used for viewing distant objects. While presbyopia appears to be a natural and irreversible handicap, it appears that stronger illumination of near objects largely replaces reading glasses. Stronger lighting causes pupils to constrict more. This creates a sharper and clearer image on the retina just like in a camera - the smaller the aperture, the sharper the image.

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7. Myopia or nearsightedness In the event that the distance between the retina and the lens is abnormally large or the lens is so rounded and thick that its focal length is abnormally small, the image of a distant object falls in front of the retina. This defect of the eye is very common and is called myopia or myopia. Myopia is an eye defect that is extremely common among schoolchildren and students. According to experts, every 3 out of 100 newborns have this defect; in elementary school, the number of myopic is about 10 out of 100; in high school, the number of myopic reaches 24%, and in college - 31%. Among people who live and work mostly outdoors, myopia is almost unknown. One type of test for myopia is done using the Snellen chart. With normal vision, one can read the seventh line of a well-lit table of standard sizes with each eye separately with a distance of 50 cm. Myopia can be corrected, but not cured, with the help of glasses. In this case, diverging spherical lenses are used. This lens scatters parallel light waves from distant objects sufficiently to project the image on the retina farther than it would be without glasses.

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9. Astigmatism Usually the surface of the cornea - the slightly protruding anterior part of the eyeball - and the surface of the lens are part of an almost perfect sphere. However, often the curvature of one or both of these surfaces is greater in one plane than in any other. This defect, which results in blurry vision, is called astigmatism. The normal eye sees groups of lines depicted in the figure with the same clarity at all distances from the eye. In case the eye has astigmatism (each eye is checked separately), vertical or horizontal lines or some lines between them appear clear and black, while lines at right angles to them appear less dark. Astigmatism can cause headaches and create vagueness, especially when reading for long periods of time. Astigmatism is corrected with a cylindrical lens instead of a spherical one. The direction of the curvature of the lens of the glasses must match the corresponding curvature of the eye lens. Therefore, if an astigmatic lens changes its position relative to the eye, care must be taken to put it back in place, since it is absolutely necessary that the corresponding curvatures coincide

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10. Characteristics of binocular vision If we look at a distant object, then normally the same images will be obtained on the same parts of the retinas of the eye; two images merge into one thanks to the intervention of the brain. This is called binocular vision. If images are focused on mismatched parts of the retinas of the eye, then the brain is unable to merge these images and the result can be a double image. Images cannot merge either if they are markedly asymmetrical or one is larger than the other. First one will predominate, and then the other; they will compete. If the images are not blurred, then soon the image in one eye will be unblurred, then soon the image in one eye will be suppressed, so that only one image will be perceived by the brain. In fact, one eye ceases to function. If the eye with the predominant image is closed, or if that eye ceases to function, then in many cases the other eye will take over its role. As a result, it turns out that such a person normally sees only with one eye, but is not aware of this. Cross-eyed people, if their defect is not corrected, see with only one eye.

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11. Three-dimensional cinema and binocular vision Three-dimensional cinema is a development of the principles of binocular vision and methods of stereoscopic photography. Instead of one image of each scene, as is the case in conventional cinematography, two photographs are taken with two different cameras located a few centimeters apart from each other. Both photos are projected simultaneously on the screen by two different projectors. Both projectors polarize light so that the plane of polarization of one projector is perpendicular to the plane of polarization of the other. Therefore, if you look at the screen through polaroid glasses, as shown in Fig. 11, then one eye sees one image on the screen, and the other eye sees another. As a result, both images merge in the brain into one that has not only width and height, but also depth.

• All about human vision

• To control the functioning of the body, nervous system you need to know a lot about the world around you.

• Who do you think plays the role of informers?

• 1. nose

• 2. eyes

• 3. language

• 4. skin

• 5. ears

• ! Vision gives a person 70% of information about the world around him.

• Eyes- the organ of vision.

• If you shoot on film everything that a person sees during the day, then it will take 20 kilometers of film.

• Why do you think vision is necessary for a person?

• Responsible for the functioning of the organs of vision occipital lobe brain.

• Look at the object, what do you see?
• What do you think vision is?

• VISION- sensation, the ability to perceive light, spatial arrangement and color of objects in the form of an image (image).

• What can we learn from sight?

• - about the shape and size of the object,
• - its color
• - an object is moving or at rest
• How far is it from us

• Through vision, we
• we can find out:

• The structure of the organs of vision:

• The inner part of the eye - the eyeball - is a spherical dark chamber.

• Behind the pupil is a lens-like lens. The eye muscles can change the shape of the lens so that a clear image of near or distant objects is obtained on the retina. The retina contains nerve fibers responsible for black and white and color vision.

• The iris gives color to the eyes. In its center is a hole - the pupil.

• The eyes are located in the sockets of the skull - eye sockets.

• Eyebrows block the way for drops of rain and sweat.
• Lashed eyelids protect eyes from wind, dust, and bright light.

• The blinking of the eyelids protects the eyes from drying out. A person blinks an average of 20 times per minute, while shedding tears. Tears wash away specks and germs.

• ● Women blink about 2 times more often than men
• ● It is not possible to sneeze with open eyes.
• ●best of all a person sees up to 12 years
• ● The eye can distinguish between 130-250 pure color tones and 5-10 million mixed shades.
• ● there is a disease of the organs of vision - micropsia or "Syndrome of Alice in Wonderland". With this disease, a person perceives objects much less than they actually are.

• Often our vision deteriorates, which means that we have to wear glasses or lenses.

• * Bad light
• * lying down reading
• * clogged eyes
• * Watching TV for many hours.
• * long work at the computer

• What can damage our eyesight?

• ● Don't stare wide-eyed at the sun
• ● Do not take sharp, piercing objects in your hands during outdoor games
• ● Books or a notebook should be at a distance of 25-30 centimeters from the eyes. The light should illuminate them from the left.
• ● Not three eyes dirty hands. If the eyes are inflamed, wash them with tea leaves or chamomile decoction.
• ● If a mote gets into the eye, do not reach it with your hands, just move the eyelid away from the eye. A tear that appears will wash away the mote.

• How to take care of your eyesight?

• In order for our vision not to deteriorate, it is necessary to regularly perform gymnastics for the eyes.

• A set of exercises number 1
• 1. Horizontal eye movements: right - left. (6 times)
• 2. Movement of the eyeballs vertically up and down. (6 times)
• 3. Circular eye movements: clockwise and in the opposite direction. (6 times)
• 4. Intense squeezing and unclenching the eyes at a fast pace. (6 times)
• 5. Frequent blinking of the eyes. (6 times)

• ● Now intensively squeeze and unclench your eyes at a fast pace. (6 times)
• ● Blink your eyes often. (6 times)

• Follow your eyes

• A set of exercises number 2
• ● Take a deep breath, close your eyes as much as possible. Tighten the muscles of the neck, face, head. Hold your breath for 2-3 seconds, then exhale quickly, opening your eyes wide as you exhale. Repeat 5 times.
• ● Close your eyes, massage the brow ridges and the lower parts of the eye sockets in a circular motion from the temples to the nose.

• ● Close your eyes, relax your eyebrows.
• Roll your eyeballs from left to right and right to left. Repeat 10 times.
• ● Place your fingertips on your temples, squeezing them slightly. Blink quickly 10 times. Close your eyes and do 2-3 deep breaths. Repeat 3 times.

• What is vision?
• Why does a person need vision?
• How to take care of your eyesight?

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Presentation - The human organ of vision

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human organ of vision
Completed by Kopyrina Vera Vladimirovna, teacher of biology, MBOU gymnasium No. 2 "Kvantor", Kolomna

I chose the topic “Human Vision Organ”, because this problem is very relevant today, since a large number of people and especially schoolchildren now suffer from various eye diseases caused by visual overload, namely: radiation from a computer, TV, reading loads and letter at school, and of course, non-compliance simple rules to keep your eyes healthy.

Light was an irritant that led to the emergence in the animal world of a special organ of vision, organum visus, main part which in all animals are specific sensitive cells derived from the ectoderm, perceiving irritation from light rays. They are mostly surrounded by pigment, the purpose of which is to transmit light in a certain direction and absorb excess light rays.
Evolution

Perception of visual stimuli: Light enters the eyeball through the pupil. The lens and vitreous body serve to conduct and focus light rays onto the retina. The oculomotor muscles - there are six of them - ensure that the position of the eyeball is such that the image of the object would fall exactly on the retina, on its yellow spot. In the receptors of the retina, light is converted into nerve impulses, which are transmitted along the optic nerve to the brain - to the visual zone of the cerebral cortex. The analysis of the color, shape, illumination of an object, its details, which began in the retina, ends in the visual cortex. All information is collected here, it is decoded and summarized. As a result, an idea about the subject is formed.
Brief information about the work of the eye

Anatomy of the organ of vision
AND - auxiliary apparatus, eye muscles B - diagram of the structure of the visual analyzer C - structure of the retina D - diagram of the structure of the eyeball E - color discrimination by eye receptors

Human visual analyzer in n.a. provides binocular vision, i.e. vision with two eyes with one visual perception. Main reflex mechanism binocular vision is the image fusion reflex - the fusion reflex (fusion), which occurs with simultaneous stimulation of functionally dissimilar nerve elements of the retina of both eyes. As a result, there is a physiological doubling of objects that are closer or further than the fixed point (binocular focusing). Physiological doubling (focus) helps to assess the distance of an object from the eyes and creates a feeling of relief, or stereoscopic vision.
Binocular and stereoscopic vision

The main part of the eye is the eyeball. It includes several skins. The transparent cornea, the uppermost of the membranes, is followed by the vascular, supplied with blood vessels and pigment cells. In front of the eye, it is represented by the iris, which is responsible for the color of the eye. The iris in one of its deep layers contains special cells - chromatophores containing the pigment melanin, which shines through the cornea. All people are born light-eyed, and the final eye color is formed in a child by 2-3 years, when the melanin enzyme appears. The more it is present in the cells, the darker the eye. Blue-eyed nations tend to live far from the equator, brown-eyed nations tend to live in temperate regions, and black eyes indicate proximity to the equator.
What determines eye color?

Light sensitivity of the human eye
The ability of the eye to perceive light and recognize, distinguish between the degrees of its brightness is called light perception, and the ability to adapt to different brightness of illumination is called adaptation of the eye; Light sensitivity is estimated by the value of the threshold of light stimulus.

Ability various 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 diopter eye system is due to the difference in the distance between the sensitive elements of the retina and is called visual acuity.
Visual acuity

Consider various violations of the refraction of light rays in optical system eyes, leading to defocusing of the image on the retina.
Violations in the optical system.

lens defects lens defects
Hyperopia Mostly a hereditary disease, when during a period of intense visual load due to weakness of the ciliary muscle, circulatory disorders in the eye, the dense shell of the eyeball (sclera) is stretched in the anteroposterior direction.
Nearsightedness Another vision defect is nearsightedness (myopia). Myopia develops from prolonged visual strain associated with a lack of lighting.
Astigmatism This defect of vision is associated with a violation of the shape of the lens or cornea, as a result of which a person loses the ability to see equally well horizontally and vertically, begins to see objects distorted, in which some lines are clear, others are blurry.
retinal defects retinal defects
Color blindness If the perception of one of the three primary colors falls out or is weakened in the retina, then the person does not perceive any color.
Scotoma Scotoma (Greek skotos - darkness) is a spot-like defect in the visual field of the eye, caused by a disease in the retina, diseases of the optic nerve, glaucoma.

Do eye exercises regularly; Periodically do compresses; Let your eyes rest (close your eyes for 3-4 minutes); AT sunny day wear Sunglasses; Avoid reading books, newspapers, magazines, etc. for yourself. in a moving vehicle; When writing, reading, doing needlework, it is necessary to ensure workplace good lighting. The light should fall from the left side (if you are right-handed), from the right side (if you are left-handed) and a little from above; Do not wear sunglasses on cloudy days and in the evening; If you already have vision problems (nearsightedness, farsightedness), you must wear glasses appropriate for your visual impairment (according to the prescription for glasses); It is necessary to provide your diet with the following vitamins, minerals and other substances - vitamins A, C, E, anthocyanins (blueberry extract), lutein, selenium.
How to keep your eyesight

So we see that our visual analyzer, our eyes are an exceptionally complex and amazing gift of nature. In a very simplistic way, we can say that the human eye is, ultimately, a device for receiving and processing light information, and its closest technical analogue is a digital video camera. Treat your eyes carefully and carefully!
Conclusion

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