Structure of the organ of vision: features

The eye is located in the orbit (orbit). The walls of the orbit are formed by facial and cranial bones. The visual apparatus consists of the eyeball, the optic nerve and a number of auxiliary organs (muscles, tear apparatus, eyelids). Muscles allow the eyeball to move. This is a pair of oblique muscles (upper and lower muscles) and four straight muscles (upper, lower, inner and outer).

Eye as an organ

The human body is a complex structure that includes:

• Peripheral organ of vision (eyeball with appendages);
• Conductive pathways (optic nerve, visual tract);
• Subcortical centers and higher visual centers.

Peripheral organ of vision (eye) is a paired organ, the device of which allows you to perceive light radiation.

Peripheral organ of vision (eye)

Eyelashes and eyelids carry out a protective function. The auxiliary organs include the lacrimal glands. Lacrimal fluid is needed for warming, moisturizing and cleaning the surface of the eyes.

Basic structures

The eyeball is an organ of complex structure.The internal environment of the eye is surrounded by three shells: external (fibrous), medium (vascular) and internal (mesh). The outer shell mostly consists of protein opaque tissue (sclera). In its front, the sclera passes into the cornea: a transparent part of the outer shell of the eye. Through the cornea, the eyeball receives light. The cornea is also necessary for the refraction of light rays.

The cornea and sclera are strong enough. This allows them to maintain the intraocular pressure and maintain the shape of the eye.

The middle shell of the eye is this:

• Iris;
• Vascular membrane;
• Ciliary body.

Iris consists of loose connective tissue and a network of vessels.In its center there is a pupil - an aperture having a diaphragm device.Thus, it can regulate the amount of light entering the eye. The edge of the iris passes into the ciliary body, covered with a sclera. The annular ciliary body consists of the ciliary muscle, vessels, connective tissue and the processes of the ciliary body. Attached to the processes is the crystalline lens. Functions of the ciliary body are the process of accommodation and the production of intraocular fluid. This fluid nourishes certain parts of the eye and maintains a constant intraocular pressure.

The inner shell of the eye is the retina. Here, the light energy is transformed into nerve impulses. In this part of the eye, a primary analysis of the visual information also takes place. The upper layer of the retina absorbs light.

In it, the substances necessary to ensure the process of vision are formed.In the next layer of the retina there are processes, called sticks and cones. By means of the processes, the nervous excitation providing visual perception is transmitted to the optic nerve. The active part of the retina is called the fundus, which contains the vessels, the optic nerve disk and the yellow spot where the majority of the cone-shaped processes responsible for color vision are located.

The shape of rods and cones

Inside the eyeball are:

• Intraocular fluid;
• Lens;
• Vitreous body.

The posterior surface of the eyelids and the anterior part of the eyeball on top of the sclera (up to the cornea) covers the conjunctiva. It is the mucous membrane of the eye, which looks like a thin transparent film.

The anterior structure of the eyeball and tear

Optical system

Depending on the functions performed by different parts of the eyes, it is possible to distinguish the light-conducting and light-sensing parts of the eye. The light-receiving department is the retina.The image of objects perceived by the eye is reproduced on the retina with the help of the optical system of the eye (light-conducting section), which consists of a transparent environment of the eye: the vitreous, the cornea, the moisture of the anterior camera and lens.But mainly refraction of light occurs on the external surface of the eye: the cornea and in the lens.

Optical system of the eye

The rays of light pass through these refractive surfaces. Each of them deflects a light beam. In the focus of the optical system of the eye, the image appears as its inverted copy.

The process of refraction of light in the optical system of the eye is denoted by the term "refraction".The optical axis of the eye is a straight line that passes through the center of all refractive surfaces. The light rays emanating from infinitely distant objects are parallel to this straight line. Refraction in the optical system of the eye collects them in the main focus of the system. That is, the main focus is the place where infinitely distant objects are projected. From objects that are at a finite distance, the rays, refracted, gather in additional tricks. Additional focuses are farther away than the main focus.

In studies of the functioning of the eye, the following parameters are usually taken into account:

• Refractive power in diopters, or refraction;
• The length of the eye;
• Radius of curvature of the cornea;
• The index of refraction of the vitreous body.

It is also the radius of curvature of the retina surface.

Age development of the eye and its optical power

After the birth of a person, his vision organs continue to form.In the first six months of life, the area of ​​the macula and the central region of the retina are formed. Functional mobility of the visual pathways also increases. During the first four months there is a morphological and functional development of the cranial nerves. Until the age of two, the cortical visual centers, as well as the visual cellular elements of the cortex, are being improved. In the first years of the child's life, the visual analyzer links with other analyzers are formed and strengthened.The development of the human eye is completed by three years.

Luminous sensitivity in the child appears immediately after birth, but the visual image can not yet appear. Quite quickly (within three weeks) the baby develops conditioned reflex connections, which lead to the improvement of the functions of spatial, objective and color vision.

Central vision develops in humans only in the third month of life.In the future, its improvement takes place.

The visual acuity of the newborn is very low. By the second year of life, it rises to,. By the age of seven, it is developing up to, .

The ability to perceive color appears at the age of two to six months.At five years, color vision in children is quite developed, although it continues to improve. Also, gradually (approximately to school age) reach the normal level of the field of view. Significantly later, other eye functions develop binocular vision.

Adaptation

Adaptation is the process of adapting the organs of vision to the changing level of illumination of the surrounding space and objects in it.Distinguish the process of dark adaptation (changes in sensitivity when going from bright light to total darkness) and light adaptation (in the transition from darkness to light).

The "adaptation" of the eye, which perceived the bright light, develops unevenly to the vision in the dark. Initially, the sensitivity increases rather quickly, and then slows down. Complete the process of dark adaptation can last several hours.

Light adaptation takes a much shorter period of time - about one to three minutes.

Accommodation

Accomodation is the process of "adaptation" of the eye to a clear distinction of those objects that are located in space at different distances from the perceiver.The mechanism of accommodation is associated with the possibility of changing the curvature of the lens surfaces, that is, changes in the focal length of the eye. This occurs when the ciliary body is stretched or relaxed.

With age, the capacity of the organs of vision for accommodation gradually decreases. Presbyopia develops (age-long farsightedness).

Visual acuity

The concept of "visual acuity" means the ability to see separately the points that are located in space at some distance from each other.In order to measure visual acuity, the concept of "angle of view" is used. The smaller the angle of vision, the higher the visual acuity. Visual acuity is considered one of the most important functions of the eye.

The definition of visual acuity is one of the key methods of studying the eye's work.

Tips for the care of eyesight

Hygiene is a part of medicine that develops rules that are important for preventing diseases and promoting the health of various organs and systems of the body.The main rule aimed at preserving the health of the eyes is to prevent overwork of the eyes.It is important to learn how to relieve tension, use methods of vision correction if necessary.

Also, visual hygiene provides for measures that protect the eyes from pollution, injuries, burns.

Hygiene

An important rule that helps maintain eye health is to prevent contamination of the eyes. Eye contact with dust or dirt leads to infection.It is necessary to wash eyes daily in clean water.

Workplace equipment is part of the activities that allow the eyes to function normally. The organs of sight most "work" in the conditions closest to the natural. Unnatural lighting, low mobility of the eyes, dry air in the room can lead to visual impairment.

The health of the eyes is greatly influenced by the quality of nutrition.

Exercises

There is quite a large number of exercises that help maintain good vision.The choice of a complex of gymnastics for the eyes depends on the state of human vision, its capabilities, lifestyle. It is best to get advice from a specialist when choosing these or other kinds of gymnastics.

A simple set of exercises designed for relaxation and exercise:

1. Blink intensively for one minute;
2. "Blink" with closed eyes;
3. To look at a certain point located far from a person. Look into the distance for a minute;
4. Translate the sight to the tip of the nose, look at it for ten seconds. Then, again, look into the distance, close your eyes;
5. Using your fingertips, you can easily pat, perform eyebrow, temples, and infraorbital massage. After that, it is necessary to cover your eyes for one minute with your palm.

Exercise should be done once or twice a day. It is also important to use the complex for rest from intensive visual loads.

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conclusions

The eye is a sensory organ that provides a vision function. Most of the information about the world around us (about 90%) comes to the person by sight. The unique optical system of the eye makes it possible to obtain a clear image, to distinguish colors, distances in space, to adapt to the conditions of changing illumination.

The eyes are a complex and sensitive organ. It is quite easy to damage it not only with trauma, but also creating unnatural conditions of functioning. In order to maintain eye health, hygiene recommendations must be followed. In case of problems with vision or the occurrence of eye diseases, it is necessary to seek consultation with a specialist. This will help a person to preserve visual functions.