Improper eye structure. The principle of the human eye

Eyes are a body with a complex structure, since various working systems are concentrated in them, performing many functions aimed at collecting information and transforming it.

The visual system as a whole, including the eyes and all their biological components, includes more than 2 million components, which include the retina, lens, cornea, nerves, capillaries and blood vessels, the iris, macula and optic nerve occupy an important place.

A person must know how to prevent diseases associated with ophthalmology in order to maintain visual acuity throughout life.

In order to understand what the human eye is, it is best to compare the organ with the camera. The anatomical structure is represented by:

1. Pupil;
2. Cornea (without color, transparent part of the eye);
3. Iris (it determines the visual color of the eyes);
4. The lens (responsible for visual acuity);
5. Ciliary body;
6. The retina.

The structures of the ocular apparatus, such as:

1. Vascular membrane;
2. Optic nerve;
3. Blood supply is carried out using nerves and capillaries;
4. Motor functions are carried out by the eye muscles;
5. Sclera;
6. Vitreous body (primary defense system).

Accordingly, elements such as the cornea, lens and pupil act as a “lens”. Light or sunlight that hits them refracts, then focuses on the retina.

The lens is “autofocus”, since its main function is to change the curvature, due to which visual acuity is maintained at normal rates - the eyes are able to clearly see surrounding objects at different distances.

The retina works as a kind of “film”. It remains the image seen, which is then transmitted in the form of signals through the optic nerve to the brain, where processing and analysis takes place.

To know the general features of the structure of the human eye is necessary for understanding the principles of work, methods of prevention and treatment of diseases. It is no secret that the human body and each of its organs is constantly being improved, which is why the eyes in the evolutionary plan managed to achieve a complex structure.

Due to this, various structures in biology are closely interconnected - vessels, capillaries and nerves, pigment cells, and connective tissue also takes an active part in the structure of the eye. All these elements help the smooth functioning of the organ of vision.

Anatomy of the structure of the eye: basic structures

The eyeball, or directly the human eye, has a round shape. It is located in the deepening of the skull, called the orbit. This is necessary because the eye is a delicate structure that is very easy to damage.

The protective function is performed by the upper and lower eyelids. The visual movement of the eyes is provided by the external muscles, which are called oculomotor.

Eyes need constant hydration - the lacrimal glands perform this function. The film formed by them additionally protects the eyes. The glands also provide the outflow of tears.

Another structure related to the structure of the eyes and providing their direct function is the outer shell - the conjunctiva. It is also located on the inner surface of the upper and lower eyelids, is thin and transparent. Function - gliding during eye movement and blinking.

The anatomical structure of the human eye is such that it has another shell, important for the organ of vision, - sclera. It is located on the front surface, almost in the center of the organ of vision (eyeball). The color of this formation is completely transparent, the structure is convex.

The directly transparent part is called the cornea. It is she who has an increased sensitivity to various kinds of irritants. This happens due to the presence in the cornea of ​​many nerve endings. Lack of pigmentation (transparency) allows light to penetrate.

The next ocular membrane that forms this important organ is the vascular. In addition to providing the eyes with the necessary amount of blood, this element is also responsible for regulating the tone. The structure is located inside the sclera, lining it.

Each person's eyes have a certain color. For this sign, a structure called the iris is responsible. Differences in shades are created due to the pigment content in the very first (outer) layer.

That is why eye color is different for different people. The pupil is a hole in the center of the iris. Through it, light penetrates directly into each eye.

The retina, despite being the thinnest structure, is the most important structure for quality and visual acuity. At its core, the retina is a nervous tissue made up of several layers.

The main optic nerve is formed precisely from this element. That is why visual acuity, the presence of various defects in the form of hyperopia or myopia is determined by the state of the retina.

The vitreous body is called the cavity of the eye. It is transparent, soft, almost jelly-like in sensations. The main function of education is to maintain and fix the retina in the necessary position for its work.

Optical system of the eye

Eyes are one of the most anatomically complex organs. They are the “window” through which a person sees everything that surrounds him. This function allows you to perform an optical system consisting of several complex, interconnected structures. The composition of the "eye optics" includes:

1. The lens;

Accordingly, the visual functions performed by them are the transmission of light, its refraction, and perception. It is important to remember that the degree of transparency depends on the state of all these elements, therefore, for example, when a lens is damaged, a person begins to see the picture indistinctly, as if in a haze.

The main element of refraction is the cornea. The luminous flux first hits it, and only then enters the pupil. It, in turn, is a diaphragm on which light is additionally refracted, focused. As a result, the eye receives an image with high definition and detail.

In addition, the lens also produces a refractive function. After the light flux hits it, the lens processes it, then transfers it further to the retina. Here the image is “imprinted”.

The fluid and vitreous in it contributes slightly to refraction. However, the state of these structures, their transparency, a sufficient number, have a great impact on the quality of human vision.

Normal operation of the ophthalmic optical system leads to the fact that the light incident on it undergoes refraction, processing. As a result, the image on the retina is reduced in size, but completely identical to the real ones.

Also note that it is upside down. A person sees objects correctly, since finally “printed” information is processed in the corresponding parts of the brain. That is why all elements of the eyes, including blood vessels, are closely interconnected. Any minor violation of them leads to a loss of visual acuity and quality.

The principle of the human eye

Based on the functions of each of the anatomical structures, you can compare the principle of the eye with the camera. The light or image first passes through the pupil, then penetrates the lens, and from it to the retina, where it is focused and processed.

The constituent elements - sticks and cones contribute to sensitivity to penetrating light. Cones, in turn, allow the eyes to perform the function of distinguishing colors and shades.

Violation of their work leads to color blindness. After refraction of the light flux, the retina translates the information printed on it into nerve impulses. They then enter the brain, which processes it and displays the final image that the person sees.

Eye Disease Prevention

Eye health must be constantly maintained at a high level. That is why the issue of prevention is extremely important for any person. Checking visual acuity in a medical office is not the only eye care.

It is important to monitor the health of the circulatory system, as it ensures the functioning of all systems. Many of the identified abnormalities result from a lack of blood or abnormalities in the delivery process.

Nerves are elements that are also important. Their damage leads to a violation of the quality of vision, for example, the inability to distinguish between the details of the object or small elements. That is why you can not strain your eyes.

With prolonged work, it is important to give them rest every 15-30 minutes. Special gymnastics is recommended for those who are associated with work, which is based on a long examination of small objects.

In the process of prevention, special attention should be paid to the illumination of the workspace. Nourishing the body with vitamins and minerals, eating fruits and vegetables helps prevent many eye diseases.

The formation of inflammation should not be allowed, as this can cause suppuration, therefore, proper eye hygiene is a good way to prevent exposure.

Thus, the eyes are a complex object that allows you to see the world around. You need to take care, protect them from diseases, then vision will remain sharp for a long period.

A very detailed and visual structure of the eye is shown in the next video.

Everyone is interested in anatomical issues, because they relate to the human body. Many people are interested in what the organ of vision consists of. After all, it belongs to the senses.

With the help of the eye, a person receives 90% of the information, the remaining 9% goes by ear and 1% to other organs.

The most interesting topic is the structure of the human eye, the article describes in detail what the eyes are made of, what are the diseases and how to cope with them.

What is the human eye?

Millions of years ago, one of the unique devices was created - it human eye. It consists of a thin as well as complex system.

The task of the organ is to convey to the brain the received, then processed information. A person helps everything that happens to see the electromagnetic radiation of visible light, this perception affects every eye cell.

Its functions

The organ of vision has a special task, it consists in the following factors:

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Eye structure

The visual organ is simultaneously covered by several shells that are around the inner core of the eye. It consists of watery moisture, as well as the vitreous and crystalline lens.

The organ of vision has three shells:

1. The first refers to the outside.  The muscles of the eyeball are adjacent to it, and it has a high density. It is equipped with a protective function and is responsible for the formation of the eye. The composition includes the cornea along with the sclera.
2. The middle membrane has another name - vascular.  Its task is in metabolic processes, due to this there is nutrition of the eye. It includes the iris, as well as the ciliary body with the choroid. The central place is the pupil.
3. The inner shell is also called mesh.  It refers to the receptor part of the organ of vision, it is responsible for the perception of light, and also transfers information to the central nervous system.

Eyeball and optic nerve

The spherical body is responsible for visual function - this eyeball. It receives all environmental information.

For the second pair of head nerves is responsible optic nerve. It starts from the lower surface of the brain, then smoothly goes into the cross, to this place the part of the nerve has its own name - tractus opticus, after the cross it has another name - n.opticus.

Eyelids

Around the human organs of vision there are movable folds - the eyelids.

They perform several functions:

Thanks to the eyelids, the cornea and the conjunctiva are equally moistened.

Moving folds consist of two layers:

1. Surface  - It includes the skin along with the subcutaneous muscles.
2. Deep  - it includes cartilage, as well as the conjunctiva.

These two layers are separated by a grayish line, it is located on the edge of the folds, in front of it there are a large number of openings of the meibomian glands.

The task of the lacrimal apparatus is to produce tears and perform the function of drainage.

Its composition:

• lacrimal gland  - is responsible for the secretion of tears, it controls the excretory ducts that push fluid to the surface of the organ of vision;
• lacrimal and nasolacrimal canals, lacrimal sac, they are necessary for drainage of fluid in the nose;

Muscle eyes

The quality and volume of vision is ensured thanks to the movement of the eyeball. The eye muscles in the amount of 6 pieces are responsible for this. 3 cranial nerves control the functioning of the eye muscles.

The external structure of the human eye

The organ of vision consists of several important additional organs.

Cornea

Cornea  - It looks like a watch glass and represents the outer shell of the eye, it is transparent. For the optical system, it is basic. The cornea looks like a convex-concave lens; this is a small fraction of the shell of the organ of vision. She has a transparent appearance, so she easily perceives light rays, reaching the retina itself.

Due to the presence of limbus, the cornea passes into the sclera. The shell has a different thickness, in the very center it is thin, a thickening is observed in the transition to the periphery. The radius of curvature is 7.7 mm; for a horizontal diameter, the radius is 11 mm. And the refractive power is 41 diopters.

The cornea has 5 layers:

Conjunctiva

The eyeball is surrounded by the outer cover - the mucous membrane, it is called conjunctiva.

In addition, the shell is located in the inner surface of the eyelids, due to this, arches form above the eye and below.

Vaults are called blind pockets, due to them the eyeball moves easily. The upper vault is larger than the lower.

The conjunctiva plays a major role - they do not allow external factors to penetrate the organs of vision, while providing comfort. Numerous glands that produce mucin, as well as lacrimal glands, help in this.

A stable tear film is formed after the production of mucin, as well as tear fluid, due to this there is a protection and hydration of the organs of vision. If diseases on the conjunctiva appear, they are accompanied by unpleasant discomfort, the patient feels a burning sensation and the presence of a foreign body or sand in the eyes.

Conjunctiva structure

The mucous membrane in appearance is thin and transparent represents the conjunctiva. It is located on the back of the eyelids and has a tight connection with cartilage. After the shell, special arches are formed, among them there is an upper and a lower one.

The internal structure of the eyeball

The inner surface is lined with a special retina, otherwise it is called inner shell.

It looks like a plate 2 mm thick.

The retina is the visual part, as well as the blind region.

The visual region is located in most of the eyeball, it is in contact with the choroid and is presented in 2 layers:

• external - the pigment layer belongs to it;
• internal - consists of nerve cells.

Due to the presence of the blind region, the ciliary body is covered, as well as the back of the iris. Its composition includes only the pigment layer. The visual area, along with the mesh portion, borders on the serrated line.

Inspect the fundus and visualize the retina using ophthalmoscopy:

• Where the optic nerve comes out, this place is called the optic disc.  The location of the disc is 4 mm medial than the posterior pole of the organ of vision. Its dimensions do not exceed 2.5 mm.
• There are no photoreceptors in this place, therefore this zone has a special name - blind spot marriott. A yellow spot is located a little further, it looks like a retina with a diameter of 4-5 mm, it has a yellowish color and it consists of a large number of receptor cells. A pit is located in the center, its dimensions do not exceed 0.4-0.5 mm, it contains only cones.
• The central fossa is considered to be the place of best vision; it passes through the entire axis of the organ of vision.  The axis is a straight line that connects the central fossa and the fixation point of the organ of vision. Among the main structural elements, neurons are observed, as well as the pigment epithelium and blood vessels along with neuroglia.

Retinal neurons consist of the following elements:

1. Visual analyzer receptors  presented in the form of sensor cells, as well as rods and cones. The retinal pigment layer is interconnected with photoreceptors.
2. Bipolar cells - maintain a synaptic connection with bipolar neurons. Such cells look like an insertion link, they are on the path of propagation of a signal that passes through the neural chain of the retina.
3. Synaptic connections with bipolar neurons represent ganglion cells.  In conjunction with the optic disk and axons, the optic nerve is formed. Thanks to this, the central nervous system receives important information. The three-membered neural chain consists of photoreceptor, as well as bipolar and ganglion cells. They are interconnected by synapses.
4. Near photoreceptor, as well as bipolar cells, an arrangement of horizontal cells passes.
5. The location of amacrine cells is considered to be the location of bipolar as well as ganglion cells. Horizontal and also amacrine cells are responsible for modeling the process of transmitting the visual signal; the signal is transmitted along the three-membered chain of the retina.
6. The vascular membrane includes the surface of the pigment epithelium, it forms a strong bond.  The inner side of epithelial cells consists of processes, between which the location of the upper parts of the cones, as well as the rods, is visible. These processes have a poor relationship with the elements, therefore, sometimes detachment of receptor cells from the main epithelium is observed, in this case, retinal detachment occurs. Cells die and blindness sets in.
7. Pigmented epithelium is responsible for nutrition, as well as the absorption of light fluxes.  The pigment layer is responsible for the accumulation, as well as the transfer of vitamin A, which is part of the visual pigments.

There are capillaries in the human organs of vision - these are small vessels, with time they lose their original ability.

As a result of this, a yellow spot may appear near the pupil, where there is a sensation of color.

If the spot increases in size, a person will lose vision.

The eyeball receives blood along the main branch of the internal artery, it is called the ophthalmic. Thanks to this branch, the organ of vision is nourished.

A network of capillary vessels creates nutrition for the eye. The main vessels help the retina and the optic nerve.

With age, the small vessels of the organ of vision, the capillaries, wear out, the eyes begin to stay on a starvation diet because they lack nutrients. At this level, blindness does not appear, there is no death of the retina, sensitive parts of the organ of vision undergo a change.

Opposite the pupil there is a yellow spot. Its task is to provide maximum color resolution, as well as greater color. With age, capillary wear occurs, and the stain begins to change, grows old, so a person's vision deteriorates, he does not read well.

The eyeball outside is covered with a special sclera. It represents the fibrous membrane of the eye along with the cornea.

The sclera looks like an opaque tissue, this is due to the random distribution of collagen fibers.

The first function of the sclera is to ensure good vision. It acts as a protective barrier against the penetration of sunlight, if there were no sclera, a person would become blind.

In addition, the shell does not allow penetration of external damage, it serves as a real support for structures, as well as tissues of the organ of vision, which are located outside the eyeball.

These structures include the following bodies:

• oculomotor muscles;
• ligaments;
• blood vessels;
• nerves.

As a dense structure, the sclera maintains intraocular pressure, is involved in the outflow of intraocular fluid.

Sclera structure

The outer dense shell area does not exceed 5/6 part, it has a different thickness, in one place is from 0.3-1.0 mm. In the region of the equator of the ocular organ, the thickness is 0.3-0.5 mm, the same dimensions are at the exit point of the optic nerve.

At this point, the formation of the ethmoid plate occurs, due to this approximately 400 processes of ganglion cells emerge, they are called differently - axons.

The structure of the iris includes 3 leaves, or 3 layers:

• front border;
• stromal;
• it is followed by a posterior muscular pigment.

If you carefully examine the iris, you will notice the location of different parts.

At the highest place are the mesentery, thanks to this the iris is divided into 2 unequal parts:

• internal, it is smaller and pupil;
• external, it is large and ciliary.

The brown border of the epithelium is located between the mesentery, as well as the pupil edge. After this, the location of the sphincter is visible, then the radial branches of the vessels are located. In the outer ciliary region there are outlined gaps, as well as crypts that take place between the vessels, they look like spokes in a wheel.

These organs are random in nature, the clearer their arrangement, the more uniformly the vessels are arranged. On the iris are not only crypts, but also grooves that concentrate the limbus. These organs are able to affect the size of the pupil, due to them, the pupil dilates.

Ciliary body

To the middle thickened part of the vascular tract is the ciliary or in a different way, ciliary body. She is responsible for the production of intraocular fluid. The lens receives support thanks to the ciliary body, due to this there is a process of accommodation, this is called the thermal collector of the organ of vision.

The ciliary body is located under the sclera, in the very middle, where the iris and choroid are located, it is difficult to consider in normal conditions. On the sclera, the ciliary body is located in the form of rings, in which the width is 6-7 mm, it takes place around the cornea. The ring has a large width on the outside, and on the bow it is smaller.

The ciliary body has a complex structure:

Retina

The visual analyzer has a peripheral section called the inner lining of the eye or the retina.

The organ contains a large number of photoreceptor cells, due to this, perception is easy, as well as the conversion of radiation, where the visible part of the spectrum is located, this is converted into nerve impulses.

The anatomical mesh looks like a thin shell, which is located near the inner side of the vitreous, on the outside is located near the choroid of the organ of vision.

It consists of two different parts:

1. Visual  - she is the largest, she reaches the ciliary body.
2. Front  - she is called blind because she does not have photosensitive cells. In this part, the main ciliary as well as the iris region of the retina is considered.

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Light-refracting apparatus - how does it work?

The human organ of vision consists of a complex optical system of lenses; the image of the external world is perceived by the retina in an inverted and also reduced form.

The structure of the dioptic apparatus includes several organs:

• transparent cornea;
• besides it there are front and rear chambers in which there is a watery wave;
• as well as the iris, it is located around the eye, as well as the lens and vitreous.

The radius of curvature of the cornea, as well as the location of the anterior and posterior surfaces of the lens, affects the refractive power of the organ of vision.

Chamber moisture

The processes of the ciliary body of the organ of vision produce a clear liquid - chamber moisture. It fills the eyes, and is located near the perivascular space. It consists of elements that are in the cerebrospinal fluid.

Lens

The structure of this body includes the nucleus along with the cortex.

There is a transparent membrane around the lens, it is 15 microns thick. Near it is attached ciliary belt.

The organ has a fixing device, the main components are oriented fibers having different lengths.

They originate from the lens capsule, and then smoothly pass into the ciliary body.

Through the surface, which is delimited by 2 media with different optical density, light rays pass, this is all accompanied by a special refraction.

For example, the passage of rays through the cornea is noticeable as they are refracted, this is due to the fact that the optical density of air differs from the structure of the cornea. After that, the light rays penetrate the biconvex lens, it is called the lens.

When refraction ends, the rays occupy one place behind the lens and are located in focus. Refraction is influenced by the angle of incidence of light rays reflecting on the surface of the lens. The rays are more refracted from the angle of incidence.

Greater refraction is observed in the rays that are scattered at the edges of the lens, in contrast to the central ones, which are perpendicular to the lens. They do not have the ability to refract. Because of this, a blurred spot appears on the retina, which has a negative effect on the organ of vision.

Due to good visual acuity, clear images on the retina appear due to the reflectivity of the optical system of the organ of vision.

Accommodation unit - how does it work?

When the direction of clear vision at a certain point away, when the voltage returns, the organ of vision returns to the near point. Thus, it turns out the distance that is observed between these points and is called the area of ​​accommodation.

People with normal vision have a high degree of accommodation, this phenomenon is expressed in long-sighted people.

When a person is in a dark room, a slight tension is expressed in the ciliary body, this is expressed due to the state of readiness.

Ciliary muscle

In the organ of view there is an internal steam muscle, it is called ciliary muscle.

Thanks to her work, accommodation is provided. She has another name, you can often hear the ciliary muscle talking to this muscle.

It consists of several smooth muscle fibers that differ in type.

The blood supply of the ciliary muscle is carried out using the 4 front ciliary arteries - these are branches of the arteries of the organ of vision. In front are the ciliary veins, they receive venous outflow.

Pupil

In the center of the iris of the human organ of vision there is a round hole, and it is called pupil.

It often changes in diameter and is responsible for regulating the flow of light rays that enter the eye and remain on the retina.

Constriction of the pupil is due to the fact that the sphincter begins to strain. Expansion of the organ begins after exposure to the dilator, it helps to influence the degree of illumination of the retina.

Such work is carried out as a camera diaphragm, since the aperture is reduced in size after exposure to bright light, as well as strong illumination. Due to this, a clear image appears, the blinding rays are cut off. The aperture expands if the illumination is dim.

This function is called diaphragm, it carries out its activities due to the pupillary reflex.

Receptor apparatus - how does it work?

The human eye has a visual retina, it represents the receptor apparatus. The outer pigment layer as well as the inner photosensitive nerve layer are part of the inner lining of the eyeball and retina.

Retina and blind spot

From the wall of the eye cup begins the development of the retina. It is the inner shell of the organ of vision, it consists of leaflets of light-sensitive, as well as pigment.

Its division was found for 5 weeks, at this time the retina is divided into two identical layers:

Yellow spot

In the retina of the organ of vision there is a special place where the greatest visual acuity is collected - this yellow spot. It is an oval and is located opposite the pupil, above it is the optic nerve. The yellow pigment is in the cells of the stain, so it has this name.

The lower part of the organ is filled with blood capillaries. The thinning of the retina is noticeable in the middle of the spot; a fossa forms there, which consists of photoreceptors.

Eye diseases

The organs of human vision repeatedly undergo various changes, because of this, a number of diseases develop that can change a person's vision.

Cataract

The clouding of the lens of the eye is called a cataract. The lens is located between the iris, as well as the vitreous body.

The lens has a transparent color, it is, in fact, speaking of a natural lens, which is refracted with the help of light rays, and then passes them to the retina.

If the lens has lost transparency, the light does not pass, the vision becomes worse, and over time the person becomes blind.

Glaucoma

Refers to a progressive sight of the disease affecting the visual organ.

The cells of the retina are gradually destroyed by increased pressure, which is formed in the eye, as a result, the optic nerve atrophies, visual signals do not enter the brain.

In humans, the ability of normal vision decreases, peripheral vision disappears, visibility decreases and becomes much smaller.

Myopia

A complete change of focus is myopia, while the person is poorly seeing objects located far away. The disease has another name - myopia, if a person has myopia, he sees objects that are close.

Myopia is a common disease associated with visual impairment. More than 1 billion people living on the planet suffer from myopia. One of the varieties of ametropia is myopia, these are pathological changes, found in the refractive function of the eye.

Retinal detachment

Severe and common diseases include retinal detachment, in which case it is observed as the retina moves away from the choroid; it is called the choroid. The retina of the healthy organ of vision is connected by the choroid, thanks to which it feeds.

This phenomenon is considered the most difficult among the pathological changes, it is not amenable to surgical correction.

Retinopathy

Disease of retinal vessels appears retinopathy. It leads to the fact that the blood supply of the retina is disturbed.

It undergoes changes, eventually the optic nerve atrophies, and then blindness occurs. During retinopathy, the patient does not feel painful symptoms, but before his eyes a person sees floating spots, as well as a veil, vision decreases.

Retinopathy can be identified by diagnosing a specialist. The doctor will conduct a study of acuity and visual fields, using ophthalmoscopy, biomicroscopy is done.

The fundus of the eye is checked for fluorescent angiography, it is necessary to do electrophysiological studies, in addition, it is necessary to do an ultrasound of the organ of vision.

Color blindness

The disease color blindness bears its name - color blindness. The peculiarity of the view is in the violation of differences between several different colors or shades. Color blindness is characterized by symptoms that occur by inheritance or due to violations.

Sometimes color blindness appears as a sign of a serious disease, it can be a cataract or a brain disease, or a disturbance of the central nervous system.

Keratitis

Due to various injuries or infections, as well as an allergic reaction, inflammation of the cornea of ​​the organ of vision occurs and eventually a disease called keratitis is formed. The disease is accompanied by blurred vision, and then a strong decline.

Strabismus

In some cases, there is a violation of the proper functioning of the muscles of the eye and as a result, strabismus appears.

One eye in this case deviates from the common point of fiction, the organs of vision are directed in different directions, one eye is directed at a specific object, and the second deviates from the normal level.

When strabismus appears, binocular vision is impaired.

The disease is divided into 2 types:

• friendly,
• paralytic.

Astigmatism

The disease while concentrating on some object has a partial or completely blurred image. The problem is that the cornea or lens of the organ of vision becomes irregular.

When astigmatism is detected, the light rays are distorted, there are several points on the retina, if the organ of vision is healthy, one point is located on the retina of the eye.

Conjunctivitis

Due to inflammatory damage to the conjunctiva, a manifestation of the disease is observed - conjunctivitis.

The mucous membrane that covers the eyelids and the sclera undergoes changes:

• hyperemia forms on it,
• also puffiness
• folds along with eyelids suffer,
• purulent fluid is released from the eyes,
• there is a burning sensation
• tears begin to flow copiously
• there is a desire to scratch the eye.

Eyeball prolapse

When the eyeball begins to bulge out of the eye socket, it appears proptosis. The disease is accompanied by swelling of the eye shell, the pupil begins to narrow, the surface of the organ of vision begins to dry.

Dislocation of the lens

Among serious and dangerous diseases in ophthalmology stands out lens dislocation.

The disease appears after birth or is formed after an injury.

One of the most important parts of the human organ of vision is the lens.

Thanks to this organ light refraction is carried out, it is considered a biological lens.

The crystalline lens takes its permanent place if it is in a healthy state; a strong connection is observed in this place.

Eye burn

After penetration of physical and chemical factors on the organ of vision appears damage, which is called - eye burn. This may occur due to low or high temperature or exposure to radiation. Among the chemical factors are chemicals of high concentration.

Prevention of eye diseases

Measures for the prevention and treatment of organs of vision:

Vision - the pledge and wealth of the human organ of vision, therefore, it should be protected from an early age.

Good vision depends on proper nutrition, in the diet of the daily menu should be foods containing lutein. This substance is in the composition of green leaves, for example, it is in the cabbage, as well as in a salad or spinach, still found in green beans.

Human eye  - It is a paired organ that provides the function of vision. Eye properties are divided into physiological  and opticaltherefore, they are studied by physiological optics, a science located at the junction of biology and physics.

The eye is shaped like a ball, so it is called eyeball.

There is a skull eye socket  - the location of the eyeball. Its significant surface is protected there from damage.

Oculomotor muscles  provide the mobility of the eyeball. Constant moistening of the eye, creating a thin protective film, is provided by the lacrimal glands.

The structure of the human eye - a scheme

Structural parts of the eye

The information that the eye receives is shinereflected from objects. The final stage is the information entering the brain, which, in fact, “sees” the object. Between them is eye  - an incomprehensible miracle, created by nature.

Photos with description

The first surface on which the light falls is -. This is a “lens” that refracts incident light. Similar to this natural masterpiece, parts of various optical devices, such as cameras, were constructed. The cornea, which has a spherical surface, focuses all the rays at one point.

But before the final stage, the light rays have to go a long way:

1. Light passes first front camera  with colorless liquid.
2. Rays fall on, defining eye color.
3. The rays then pass through - the hole located in the center of the iris. The lateral muscles are able to dilate or constrict the pupil depending on external circumstances. Too bright light can harm the eye, so the pupil narrows. In the dark - expands. The diameter of the pupil responds not only to the degree of illumination, but also to various emotions. For example, in a person experiencing fear or pain, the pupils become larger. This feature is called by adaptation.
4. The following miracle is located in the rear camera - lens . This is a biological lenticular lens, whose task is to focus the rays on the retina, which acts as a screen. But, if the glass lens has a constant size, then the radii of the lens have the ability to change with compression and relaxation of the surrounding muscles. This feature is called accommodation. It consists in the ability to see sharply, both remote and close objects, changing the radii of the lens.
5. Space between the lens and the retina vitreous body . The rays pass through it calmly, thanks to its transparency. Vitreous helps to maintain the shape of the eye.
6. Item image is displayed on retina but upside down. So it turns out because of the structure of the “optical scheme” of the passage of light rays. In the retina, this information is encoded into electromagnetic pulses, after which they are processed by the brain, which flips the image.

This is the internal structure of the eye and the path of the light flux inside it.

Video:

Eye shell

The eyeball has three shells:

1. Fibrous  - is outdoor. Protects, gives shape to the eye. The muscles are attached to it.

Composition:

•   - front end. Being transparent, it lets in the rays of the eye.
• Sclera of white color - posterior surface.

2. Vascular  eye shell - its structure and functions can be seen in the figure above. Is the middle "layer". The blood vessels present in it provide blood supply and nutrition.

The composition of the choroid:

• The iris is a department located in front, with a pupil in the center of it. Eye color depends on the content of melanin in the iris. The more melanin, the darker the color. The smooth muscles contained in the iris change the size of the pupil;
• Ciliary body. Due to the muscles it changes the curvature of the surfaces of the lens;
• The choroid itself is in the back. Infused with many small blood vessels.

1. Retina  - is the inner shell. The structure of the human retina is very specific.

It has several layers providing different functions, the main of which is   light perception.

Contains sticks  and cones  - photosensitive receptors. The receptors function differently depending on the time of day or the lighting in the room. Night is the time of the chopsticks, daytime cones are activated.

Eyelid

Although the eyelids are not part of the visual organ, it makes sense to consider them only as a whole.

Purpose and structure of the century eyes:

1. External view

The eyelid consists of muscles covered with skin, with eyelashes on the edge.

1. Purpose

The main goal is to protect the eye from an aggressive external environment, as well as constant moistening.

1. Functioning

Due to the presence of muscles, the eyelid can move easily. With regular closure of the upper and lower eyelids, the eyeball is moistened.

The eyelid consists of several elements:

• outer skin and muscle tissue;
• cartilage serving to maintain the century;
• conjunctiva, which is a mucous tissue and has tear glands.

Alternative medicine

One of the methods of alternative medicine, based on the structure of the eye, is iridology.  The scheme of the iris helps the doctor to diagnose with various diseases in the body:

This analysis is based on the assumption that different organs and parts of the human body correspond to specific areas on the iris. If the body is ill, then it is reflected in the relevant area. By these changes, you can find out the diagnosis.

The value of vision in our lives is difficult to overestimate. In order for it to continue to serve us, it is necessary to help him: wear glasses for correcting eyesight, if necessary, and sunglasses in bright sun. It is important to understand that over time there are age-related changes that can be delayed only.

Vision is the channel through which a person receives about 70% of all data about the world that surrounds him. And this is possible only for the reason that it is human vision that is one of the most complex and amazing visual systems on our planet. If there were no vision, we all, most likely, would 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. He has the ability to instantly change the focus at various distances, regulate the amount of incoming light, distinguish between a huge number of colors and even more shades, make correction of spherical and chromatic aberrations, etc. Six levels of the retina are associated with the brain of the eyes, in which even before the information is sent to the brain, the data goes through a compression stage.

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

A huge number of parts

The structure of the eye and its physiology can easily be called truly ideal. Think for yourself: both eyes are located in the bony depressions of the skull, which protect them from all kinds of damage, but they protrude from them precisely so as to ensure the widest possible horizontal visibility.

The distance at which the eyes are apart 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 of this as a matter of course - very few people come to imagine what it would be like if our eyes were square or triangular or their movement was chaotic - this would make vision limited, confused and ineffective.

So, the device of the eye is extremely difficult, but this is exactly what makes possible the work of about four dozen of its various components. And even if there were not even one of these elements, the process of vision would cease to be carried out in the way it should be carried out.

To make sure how complicated the eye is, we suggest you turn your attention to the figure below.

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

Passage of light

As the light approaches the eye, the light rays collide with the cornea (otherwise it is called 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 the specific protein contained in it inhibits the development of blood vessels - a process that occurs in almost every tissue of the human body. In the event that the cornea was not transparent, the remaining components of the visual system would have no meaning.

Among other things, the cornea does not allow dust, dust and any chemical elements to fall into the internal cavities of the eye. And the curvature of the cornea allows it to refract light and help the lens focus the light rays on the retina.

After the light has passed through the cornea, it passes through a small hole located in the middle of the iris of the eye. The iris is a circular diaphragm, which is located in front of the lens immediately behind the cornea. The iris is also the element that gives the eye a color, and the color depends on the pigment prevailing in the iris. The central hole in the iris is the pupil that is familiar to each of us. The size of this hole has the ability to change to control the amount of light entering the eye.

The size of the pupil will change directly with the iris, and this is due to its unique structure, because it consists of two different types of muscle tissue (even here there are muscles!). The first muscle is a circular contraction - it is arranged in a circle in the iris. When the light is bright, its contraction occurs, as a result of which the pupil contracts, as if drawn in by the muscle. The second muscle is expanding - it is located radially, i.e. on the radius of the iris, which can be compared with the spokes in the wheel. In dark light, this second muscle contraction occurs, and the iris opens the pupil.

Many still have some difficulties when they try to explain how the formation of the above-mentioned elements of the human visual system takes place, because in any other intermediate form, i.e. they simply could not work at any evolutionary stage, but man sees from the very beginning of his existence. Riddle ...

Focusing

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

Passing through the lens, the light is refracted, after which it focuses on the fossa of the retina, the most sensitive spot containing the maximum number of photoreceptors.

It is important to note that the unique structure and composition provide the cornea and lens a great refractive power, which guarantees a short focal length. And how surprising it is that such a complex system fits in just one eyeball (think only how a person could look like if, for example, a meter would be needed to focus the light rays coming from objects!).

No less interesting is the fact that the joint refractive power of these two elements (the cornea and the crystalline lens) is in an excellent relationship with the eyeball, and this can be safely called another proof that the visual system was created simply unmatched, because the process of focusing is too complex to talk about it, as about something that happened only due to step-by-step mutations - the 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 here it is still more curious, because in this situation the refraction of light rays turns out to be even stronger. This is provided by an increase in the curvature of the lens. The lens is connected by means of the ciliary belts with the ciliary muscle, which, by contracting, allows the lens to assume a more convex shape, thereby increasing its refractive power.

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

The value of "film"

The result of focusing is the concentration of the image on the retina, which is a multi-layered tissue that is sensitive to light, covering the back of the eyeball. The retina contains approximately 137,000,000 photoreceptors (for comparison, modern digital cameras can be cited, in which no more than 10,000,000 like sensor elements exist). Such a huge number of photoreceptors is due to the fact that they are located extremely densely - about 400,000 per 1 mm².

Here it will not be superfluous to cite the words of microbiology specialist Alan L. Gillen, who speaks in his book “The Body According to the Plan” about the retina, as a masterpiece of engineering design. He believes that the retina is the most amazing element of the eye, comparable with film. The photosensitive retina, located on the back of the eyeball, is much thinner than cellophane (its thickness is no more than 0.2 mm) and is 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 of them. But even more surprising is that the human eye can pick up photons even in the dark.

Total retina consists of 10 layers of photoreceptor cells, 6 layers of which are layers of photosensitive cells. Two types of photoreceptors have a special form, for which reason they are called cones and chopsticks. The rods are extremely susceptible to light and provide the eye with black and white perception and night vision. Cones, in turn, are not so susceptible to light, but they are able to distinguish colors - optimum cone work is observed in the daytime.

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

Communication of photoreceptor cells in the retina is very complex. Cones and sticks are not directly connected with the brain. Having received the signal, they redirect it to bipolar cells, and they redirect the signals already processed by the ganglion cells, more than a million axons (neurites along which nerve impulses are transmitted) of which make up a single optic nerve, through which the data enter the brain.

Two layers of intermediate neurons, before the visual data is sent to the brain, contribute to the parallel processing of this information by the six levels of perception located in the retina. It is necessary for the images to be recognized as quickly as possible.

Brain perception

After the processed visual information enters the brain, it begins its sorting, processing and analysis, and also forms a complete image of the individual data. Of course, a lot of things are still unknown about the work of the human brain, but even the fact that the scientific world can provide today is quite 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 a person sees two images at the same time. But how?

And the thing is: the point of the retina of one eye exactly corresponds to the point of the retina of the other, and this means that both images, getting into the brain, can be superimposed on each other and combined together to produce a single image. Information obtained by the photoreceptors of each of the eyes converges in the visual cortex, where a single image appears.

Due to the fact that the two eyes may have a different projection, there may be some inconsistencies, but the brain compares and connects the images in such a way that a person does not feel any inconsistencies. Not only that - these inconsistencies can be used to gain a sense of spatial depth.

As it is known, due to the refraction of light, the visual images that enter the brain are initially very small and inverted, but “at the exit” we get the image we are used to seeing.

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

Separation of images and extremely complex optical paths make the brain see each of its hemispheres separately using each of its 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 ceases to see the other.

It can be concluded that the brain in the process of processing visual information removes "blind" spots, distortions due to micro-movements of eyes, blinks, angle of view, etc., offering its owner an adequate holistic image of the observed.

Another important element of the visual system is. To diminish the value of this question is impossible, because in order to be able to use vision properly, we must be able to turn our eyes, raise them, lower them, in short - move our eyes.

In total, 6 external muscles can be distinguished, which connect to the outer surface of the eyeball. These muscles include 4 straight (lower, upper, lateral and middle) and 2 oblique (lower and upper).

At that moment, when any of the muscles contract, the muscle, which is opposite to it, relaxes - this ensures an even eye movement (otherwise all eye movements would be carried out by jerks).

When two eyes are rotated, the movement of all 12 muscles automatically changes (6 muscles per eye). And it is noteworthy that this process is continuous and very well coordinated.

According to the famous ophthalmologist Peter Jeni, monitoring and coordinating the connection 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 the redirection of the gaze, the smoothness and evenness of the movements, the speed with which the eye can rotate (and it totals up to 700 ° per second), and combining all this, we will actually get phenomenal in terms of performance the system. And the fact that a person has two eyes makes it even more complex - with the simultaneous movement of the eyes, the same muscular innervation is necessary.

The muscles that rotate the eyes are different from the muscles of the skeleton, because They are made up of many different fibers, and they are controlled by an even greater number of neurons, otherwise the accuracy of movements would become impossible. These muscles can be called unique also because they are able to contract quickly and almost never get tired.

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

With the help of the lacrimal glands, a sticky fluid is regularly produced, moving at a slow rate down the external surface of the eyeball. This fluid 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 removed from the body.

Tears contain a very strong antibacterial substance that destroys viruses and bacteria. Eyelids perform the function of wipers - they clean and moisturize the eyes due to involuntary blinking at intervals of 10-15 seconds. Along with the centuries, eyelashes also work, preventing any litter, dirt, germs, etc. from getting into the eye.

If the eyelids did not fulfill their function, the eyes of the person would gradually dry up and become scarred. If there were no tear duct, the eyes would be constantly flooded with tear fluid. If the person did not blink, garbage would fall into his eyes, and he could even go blind. The whole "cleaning system" should include the work of all elements without exception, otherwise it would simply cease to function.

Eyes as an indicator of condition

Human eyes are able to transmit a lot of information in the process of its interaction with other people and the world. 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, talking to someone, this can be seen in a completely different way than an ordinary upward glance. Big eyes in children cause excitement and affection in others. And the state of the pupils reflects the state of consciousness in which the person is at a given time. The eyes are an indicator of life and death, if we speak in a global sense. Probably for this reason they are called the “mirror” of the soul.

Instead of conclusion

In this lesson we have examined 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 still tried to bring the material so that you have a clear idea of ​​HOW a person sees.

You could not help noticing that both the complexity and the capabilities of the eye allow this body to repeatedly exceed even the most modern technologies and scientific developments. The eye is a clear demonstration of the complexity of engineering in a huge amount of nuances.

But to know about the vision device 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, addictions, diseases, and much more) - all this often contributes to the fact that over the years, vision can deteriorate, t . the visual system begins to falter.

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

See the root!

Test your knowledge

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

Eyesight and hearing are much better developed in humans than smell. Photosensitive cells and cells that capture sounds, are collected from us, like all highly developed animals, in special organs - eyes and ears.

Like the camera, our eye has a “lens window” (cornea), aperture ”(iris), an“ adjustable lens ”(lens) and a photosensitive layer” (retina lying in the depth of the eye). Retinal cells send signals through the optic nerve to the cerebral cortex.

In the human eye, there are two types of photosensitive cells: rods and cones. Sticks distinguish between dark and light. Cones perceive color. Cells of both types are located on the retina - a thin inner blood vessel penetrated by blood vessels of the eyeball. In general, the eyeball consists of several dense layers of connective tissue that give it shape.

Thanks to the lens, everything that we see is reflected on the retina upside down. However, the brain corrects a distorted picture. In general, he adapts to everything easily. Have someone think about standing on his head for weeks on end; soon, instead of inverted images, he will again see normal, “put on his feet” images.

1. Optic nerve; 2. Muscle; 3. The frontal bone; 4. Cornea; 5. Muscle

The front part of the eyeball - the cornea - is transparent, like glass: it transmits light to the inside of the eye. Then the light is captured by the "diaphragm" of the eye - the iris - and collected in a beam. The pigment cells of the iris give the eyes a certain color. If there is a lot of pigment, the eyes are brown, if there is little or no at all - in greenish-gray and blue tones. Then the light penetrates the pupil - a hole in the iris, surrounded by two small muscles. In bright light, one muscle narrows the pupil, the other expands it if it is dark. Passing the pupil, the light rays fall directly on the lens - an elastic organ, which all the time trying to take the form of a ball. It prevents the ring from the muscles: they are constantly stretched and reduce the convexity of the lens. So, the lens easily changes its curvature. Therefore, the rays of light fall on the retina layer dotted with sticks and cones, and we clearly see objects. When we look at closely spaced objects, the lens becomes convex and refracts rays more strongly, and when objects that are far from us, it becomes flatter and refracts rays more weakly. With age, the lens loses its elasticity. In order to somehow fix the misfortune, we have to help our natural lens - the lens - and use glasses.

Like the camera, the eye is provided with a “lens window”, “diaphragm”, “adjustable lens” and “photosensitive layer”, resembling photographic film. Only this layer is a part of the eye itself, its retina. And yet, a person sees more than a camera. After all, he looks at the world with two eyes. Both left and right eyes see objects in their own way. Our brain compares the two images obtained and by them judges the form of what they saw. Therefore, people have spatial vision. But, for example, a chicken's eyes are planted on the sides of the head, and it is not endowed with volumetric vision.

Myopia and hyperopia

Almost one in three suffer from visual impairment. Myopia and hyperopia are most common, but are very well corrected with glasses or contact lenses. Myopia results from the pathology of the eye. A nearsighted person can clearly see up close, but when looking into the distance the image becomes very blurry. Farsightedness - a consequence of normal aging of the eye. From the age of 40, we see near less and less clear, since over the years the lens loses its flexibility.