The structure and functional features of the organs of vision of vertebrates. Age features of the organ of vision

The organ of vision in phylogeny has gone from separate ectodermal origin of light-sensitive cells (in intestinal cavities) to complex paired eyes in mammals. In vertebrates, the eyes develop in a complex way: a light-sensitive membrane, the retina, is formed from the lateral outgrowths of the brain. The middle and outer shells of the eyeball, the vitreous body are formed from the mesoderm (middle germinal layer), the lens - from the ectoderm.

The pigment part (layer) of the retina develops from the thin outer wall of the glass. Visual (photoreceptor, light-sensitive) cells are located in the thicker inner layer of the glass. In fish, the differentiation of visual cells into rod-shaped (rods) and cone-shaped (cones) is weakly expressed, in reptiles there are only cones, in mammals the retina contains mainly rods; in aquatic and nocturnal animals, cones are absent in the retina. As part of the middle (vascular) membrane, already in fish, the ciliary body begins to form, which becomes more complicated in its development in birds and mammals.

The muscle in the iris and in the ciliary body first appears in amphibians. The outer shell of the eyeball in lower vertebrates consists mainly of cartilaginous tissue (in fish, amphibians, most lizards). In mammals, it is built only from fibrous (fibrous) tissue.

The lens of fish and amphibians is rounded. Accommodation is achieved due to the movement of the lens and the contraction of a special muscle that moves the lens. In reptiles and birds, the lens is able not only to mix, but also to change its curvature. In mammals, the lens occupies a permanent place, accommodation is carried out due to a change in the curvature of the lens. The vitreous body, which initially has a fibrous structure, gradually becomes transparent.

Simultaneously with the complication of the structure of the eyeball, auxiliary organs of the eye develop. The first to appear are six oculomotor muscles, which are transformed from the myotomes of three pairs of head somites. Eyelids begin to form in fish in the form of a single annular skin fold. Terrestrial vertebrates develop upper and lower eyelids, and most of them also have a nictitating membrane (third eyelid) at the medial corner of the eye. In monkeys and humans, the remnants of this membrane are preserved in the form of a semilunar fold of the conjunctiva. In terrestrial vertebrates, the lacrimal gland develops, and the lacrimal apparatus is formed.

The human eyeball also develops from several sources. The light-sensitive membrane (retina) comes from the side wall of the brain bladder (the future diencephalon); the main lens of the eye - the lens - directly from the ectoderm; vascular and fibrous membranes - from the mesenchyme. At an early stage of embryonic development (end of the 1st, beginning of the 2nd month of intrauterine life) on the side walls of the primary brain bladder ( prosencephalon) there is a small paired protrusion - eye bubbles. Their terminal sections expand, grow towards the ectoderm, and the legs connecting with the brain narrow and later turn into optic nerves. In the process of development, the wall of the optic vesicle protrudes into it and the vesicle turns into a two-layer ophthalmic cup. The outer wall of the glass further becomes thinner and transforms into the outer pigment part (layer), and the complex light-perceiving (nervous) part of the retina (photosensory layer) is formed from the inner wall. At the stage of formation of the eyecup and differentiation of its walls, at the 2nd month of intrauterine development, the ectoderm adjacent to the eyecup in front thickens at first, and then a lens fossa is formed, which turns into a lens vesicle. Separated from the ectoderm, the vesicle plunges into the eye cup, loses the cavity, and the lens is subsequently formed from it.

At the 2nd month of intrauterine life, mesenchymal cells penetrate into the eye cup through the gap formed on its lower side. These cells form a blood vascular network inside the glass in the vitreous body that is forming here and around the growing lens. From the mesenchymal cells adjacent to the eye cup, the choroid is formed, and from the outer layers, the fibrous membrane. The anterior part of the fibrous membrane becomes transparent and turns into the cornea. In a fetus of 6-8 months, the blood vessels located in the lens capsule and in the vitreous body disappear; the membrane covering the opening of the pupil (pupillary membrane) is resorbed.

The upper and lower eyelids begin to form in the 3rd month of intrauterine life, initially in the form of ectoderm folds. The epithelium of the conjunctiva, including the one that covers the front of the cornea, comes from the ectoderm. The lacrimal gland develops from outgrowths of the conjunctival epithelium that appear on the 3rd month of intrauterine life in the lateral part of the emerging upper eyelid.

The eyeball of a newborn is relatively large, its anteroposterior size is 17.5 mm, its weight is 2.3 g. The visual axis of the eyeball runs laterally than in an adult. The eyeball grows in the first year of a child's life faster than in subsequent years. By the age of 5, the mass of the eyeball increases by 70%, and by the age of 20-25 - 3 times compared with a newborn.

The cornea of a newborn is relatively thick, its curvature almost does not change during life; the lens is almost round, the radii of its anterior and posterior curvature are approximately equal. The lens grows especially rapidly during the first year of life, and then its growth rate decreases. The iris is convex anteriorly, there is little pigment in it, the pupil diameter is 2.5 mm. As the age of the child increases, the thickness of the iris increases, the amount of pigment in it increases, and the diameter of the pupil becomes large. At the age of 40-50 years, the pupil narrows slightly.

The ciliary body in a newborn is poorly developed. The growth and differentiation of the ciliary muscle is carried out quite quickly. The optic nerve in a newborn is thin (0.8 mm), short. By the age of 20, its diameter almost doubles.

The muscles of the eyeball in a newborn are well developed, except for their tendon part. Therefore, eye movement is possible immediately after birth, but the coordination of these movements begins from the 2nd month of a child's life.

The lacrimal gland in a newborn is small, the excretory ducts of the gland are thin. The function of tearing appears on the 2nd month of a child's life. The vagina of the eyeball in a newborn and infants is thin, the fatty body of the orbit is poorly developed. In elderly and senile people, the fat body of the orbit decreases in size, partially atrophies, the eyeball protrudes less from the orbit.

The palpebral fissure in a newborn is narrow, the medial angle of the eye is rounded. In the future, the palpebral fissure rapidly increases. In children under 14-15 years old, it is wide, so the eye seems larger than in an adult.

The human eyeball develops from several sources. The photosensitive membrane (retina) comes from the side wall of the cerebral bladder (the future diencephalon), the lens - from the ectoderm, the vascular and fibrous membranes - from the mesenchyme. At the end of the 1st, beginning of the 2nd month of intrauterine life, a small paired protrusion appears on the side walls of the primary cerebral bladder - eye bubbles. In the process of development, the wall of the optic vesicle protrudes into it and the vesicle turns into a two-layer ophthalmic cup. The outer wall of the glass further becomes thinner and transforms into the outer pigment part (layer). A complex light-perceiving (nervous) part of the retina (photosensory layer) is formed from the inner wall of this bubble. At the 2nd month of intrauterine development, the ectoderm adjacent to the eye cup thickens,
then a lens fossa is formed in it, turning into a crystal bubble. Separated from the ectoderm, the vesicle plunges into the eye cup, loses the cavity, and the lens is subsequently formed from it.
At the 2nd month of intrauterine life, mesenchymal cells penetrate into the eye cup, from which the blood vascular network and the vitreous body are formed inside the glass. From the mesenchymal cells adjacent to the eye cup, the choroid is formed, and from the outer layers, the fibrous membrane. The anterior part of the fibrous membrane becomes transparent and turns into the cornea. In a fetus of 6-8 months, the blood vessels located in the lens capsule and the vitreous body disappear; the membrane covering the opening of the pupil (pupillary membrane) is resorbed.
The upper and lower eyelids begin to form in the 3rd month of intrauterine life, initially in the form of ectoderm folds. The epithelium of the conjunctiva, including the one that covers the front of the cornea, comes from the ectoderm. The lacrimal gland develops from outgrowths of the conjunctival epithelium in the lateral part of the emerging upper eyelid.
The eyeball of a newborn is relatively large, its anteroposterior size is 17.5 mm, weight - 2.3 g. By the age of 5, the mass of the eyeball increases by 70%, and by 20-25 years - 3 times compared to the newborn.
The cornea of a newborn is relatively thick, its curvature almost does not change during life. The lens is almost round. The lens grows especially rapidly during the first year of life, and then its growth rate decreases. The iris is convex anteriorly, there is little pigment in it, the pupil diameter is 2.5 mm. As the age of the child increases, the thickness of the iris increases, the amount of pigment in it increases, and the diameter of the pupil becomes large. At the age of 40-50 years, the pupil narrows slightly.
The ciliary body in a newborn is poorly developed. The growth and differentiation of the ciliary muscle is quite fast.
The muscles of the eyeball in a newborn are well developed, except for their tendon part. Therefore, eye movement is possible immediately after birth, but the coordination of these movements begins from the 2nd month of a child's life.
The lacrimal gland in a newborn is small, the excretory ducts of the gland are thin. The function of tearing appears on the 2nd month of a child's life. The fatty body of the orbit is poorly developed. In elderly and senile people, fatty
the body of the orbit decreases in size, partially atrophies, the eyeball protrudes less from the orbit.
The palpebral fissure in a newborn is narrow, the medial angle of the eye is rounded. In the future, the palpebral fissure rapidly increases. In children under 14-15 years old, it is wide, so the eye seems larger than in an adult.
Anomalies in the development of the eyeball. The complex development of the eyeball leads to birth defects. More often than others, an irregular curvature of the cornea or lens occurs, as a result of which the image on the retina is distorted (astigmatism). When the proportions of the eyeball are disturbed, congenital myopia (the visual axis is elongated) or hyperopia (the visual axis is shortened) appear. A gap in the iris (coloboma) often occurs in its anteromedial segment. The remnants of the branches of the artery of the vitreous body interfere with the passage of light in the vitreous body. Sometimes there is a violation of the transparency of the lens (congenital cataract). Underdevelopment of the venous sinus of the sclera (Schlemm's canal) or spaces of the iridocorneal angle (fountain spaces) causes congenital glaucoma.
Questions for repetition and self-control:

List the sense organs, give each of them a functional description.
Describe the structure of the membranes of the eyeball.
Name the structures related to the transparent media of the eye.
List the organs that belong to the auxiliary apparatus of the eye. What are the functions of each of the auxiliary organs of the eye?
Describe the structure and functions of the accommodative apparatus of the eye.
Describe the pathway of the visual analyzer from the receptors that perceive light to the cerebral cortex.
Describe the adaptation of the eye to light and color vision.

In newborns, the size of the eyeball is smaller than in adults (the diameter of the eyeball is 17.3 mm, and in an adult it is 24.3 mm). In this regard, the rays of light coming from distant objects converge behind the retina, that is, the newborn is characterized by natural farsightedness. An early visual reaction of a child can be attributed to an orienting reflex to light irritation, or to a flashing object. The child reacts to light irritation or an approaching object by turning the head and torso. At 3-6 weeks, the baby is able to fix his gaze. Up to 2 years, the eyeball increases by 40%, by 5 years - by 70% of its original volume, and by the age of 12-14 it reaches the size of an adult's eyeball.

The visual analyzer is immature at the time of the birth of the child. The development of the retina ends by 12 months of age. Myelination of the optic nerves and optic nerve pathways begins at the end of the intrauterine period of development and ends at 3-4 months of a child's life. The maturation of the cortical part of the analyzer ends only by the age of 7 years.

Lacrimal fluid has an important protective value, because it moisturizes the anterior surface of the cornea and conjunctiva. At birth, it is secreted in a small amount, and by 1.5-2 months during crying, there is an increase in the formation of lacrimal fluid. In a newborn, the pupils are narrow due to the underdevelopment of the iris muscle.

In the first days of a child's life, there is no coordination of eye movements (the eyes move independently of each other). It appears after 2-3 weeks. Visual concentration - fixation of the gaze on the object appears 3-4 weeks after birth. The duration of this eye reaction is only 1-2 minutes. As the child grows and develops, the coordination of eye movements improves, fixing the gaze becomes longer.

Age features of color perception . A newborn child does not differentiate colors due to the immaturity of the cones in the retina. In addition, there are fewer of them than sticks. Judging by the development of conditioned reflexes in a child, color differentiation begins from 5-6 months. It is by the 6th month of a child's life that the central part of the retina develops, where the cones are concentrated. However, the conscious perception of colors is formed later. Children can correctly name colors at the age of 2.5-3 years. At 3 years old, the child distinguishes the ratio of the brightness of colors (darker, paler colored object). For the development of color differentiation, it is advisable for parents to demonstrate colored toys. By the age of 4, the child perceives all colors . The ability to distinguish colors increases significantly by 10-12 years.

Age features of the optical system of the eye. The lens in children is very elastic, so it has a greater ability to change its curvature than in adults. However, starting from the age of 10, the elasticity of the lens decreases and decreases. accommodation volume- the adoption by the lens of the most convex shape after the maximum flattening, or vice versa, the adoption of the lens of the maximum flattening after the most convex shape. In this regard, the position of the nearest point of clear vision changes. Closest point of clear vision(the smallest distance from the eye at which the object is clearly visible) moves away with age: at 10 years old it is at a distance of 7 cm, at 15 years old - 8 cm, 20 - 9 cm, at 22 years old -10 cm, at 25 years old - 12 cm, at 30 years old - 14 cm, etc. Thus, with age, in order to see better, the object must be removed from the eyes.

At the age of 6-7 years, binocular vision is formed. During this period, the boundaries of the field of view expand significantly.

Visual acuity in children of different ages

In newborns, visual acuity is very low. By 6 months it increases and is 0.1, at 12 months - 0.2, and at the age of 5-6 years it is 0.8-1.0. In adolescents, visual acuity rises to 0.9-1.0. In the first months of a child's life, visual acuity is very low, at the age of three, only 5% of children have it normal, in seven-year-olds - in 55%, in nine-year-olds - in 66%, in 12-13-year-olds - 90%, in adolescents 14 - 16 years old - visual acuity, as in an adult.

The field of view in children is narrower than in adults, but by the age of 6-8 it expands rapidly and this process continues up to 20 years. The perception of space (spatial vision) in a child is formed from the age of 3 months due to the maturation of the retina and the cortical part of the visual analyzer. The perception of the shape of an object (volumetric vision) begins to form from the age of 5 months. The child determines the shape of the object by eye at the age of 5-6 years.

At an early age, between 6-9 months, the child begins to develop a stereoscopic perception of space (he perceives the depth, remoteness of the location of objects).

Most six-year-old children have developed visual acuity and all parts of the visual analyzer are completely differentiated. By the age of 6, visual acuity approaches normal.

In blind children, the peripheral, conductive, or central structures of the visual system are morphologically and functionally not differentiated.

The eyes of young children are characterized by slight farsightedness (1-3 diopters), due to the spherical shape of the eyeball and the shortened anterior-posterior axis of the eye (table 7). By the age of 7-12, farsightedness (hypermetropia) disappears and the eyes become emmetropic, as a result of an increase in the anterior-posterior axis of the eye. However, in 30-40% of children, due to a significant increase in the anterior-posterior size of the eyeballs and, accordingly, the removal of the retina from the refractive media of the eye (lens), myopia develops.

Age patterns of skeletal development. Prevention of disorders of the musculoskeletal system

Prevention of disorders of the musculoskeletal system in children. Hygienic requirements for the equipment of schools or preschool institutions (4 hours)

1. Functions of the musculoskeletal system. Composition and growth of children's bones.

2. Features of the formation of the bones of the hand, spinal column, chest, pelvis, bones of the brain and facial skull.

3. Curves of the spine, their formation and timing of fixation.

4. Heterochronism of muscle development. Development of motor skills in children. The formation of mass, muscle strength. Resilience in children and adolescents. motor mode.

5. Features of the reaction to physical activity at different ages.

6. Correct posture in a sitting position standing, walking. Postural disorders (scoliosis, increased natural curves of the spine - lordosis and kyphosis), causes, prevention. Flat feet.

7. School furniture. Hygienic requirements for school furniture (distance and differentiation). Selection, arrangement of furniture and seating of students in the classroom.

Functions, classification, structure, connection and growth of bones

Skeleton - a set of hard tissues in the human body - bone and cartilage.

Skeleton Functions: supporting (muscles are attached to the bones); motor (separate parts of the skeleton form levers, which are set in motion by muscles attached to the bones); protective (bones form cavities in which vital organs are located); mineral metabolism; formation of blood cells.

The chemical composition of the bone: organic matter - ossein protein, which is part of the intercellular substance of bone tissue, is only 1/3 of the bone mass; 2/3 of its mass is represented by inorganic substances, mainly calcium, magnesium, and phosphorus salts.

The skeleton consists of about 210 bones.

The structure of the bones:

periosteum, consisting of connective tissue containing blood vessels that feed the bone; actual bone, consisting of compact And spongy substances. Features of its structure: body - diaphysis and two thickenings at the ends - upper and lower epiphyses. On the border between the epiphysis and the diaphysis is a cartilaginous plate - epiphyseal cartilage, due to cell division of which the bone grows in length. A dense connective tissue membrane - the periosteum, in addition to blood vessels and nerves, contains dividing cells, osteoblasts. Thanks to osteoblasts, bone thickening occurs, as well as the healing of bone fractures.

Distinguish axial skeleton and additional.

Axial skeleton includes head skeleton (skull) and torso skeleton.

Scoliosis- lateral curvature of the spine, in which the so-called. "scoliotic posture". Signs of scoliosis: sitting at the table, the child stoops, leans on his side. With severe lateral curvature of the spinal column, the shoulders, shoulder blades and pelvis are asymmetrical. scoliosis there are congenital And acquired. Congenital scoliosis occurs in 23% of cases. They are based on various deformations of the vertebrae: underdevelopment, their wedge-shaped form, additional vertebrae, etc.

Acquired scoliosis includes:

1) rachitic, manifested by various deformations of the musculoskeletal system due to a deficiency in the body of calcium. They are caused by soft bones and weak muscles;

2) paralytic, arising after childhood paralysis, with unilateral muscle damage;

3) habitual (school), the cause of which may be an incorrectly selected table or desk, seating students without taking into account their height and desk numbers, carrying briefcases, bags, and not knapsacks, sitting at a table or desk for a long time, etc.

Acquired scoliosis accounts for about 80%. With scoliosis, asymmetry of the shoulder girdle and shoulder blades is noted. With jointly expressed lordosis and kyphosis - a protruding head, a round or flat back, a protruding abdomen. There are the following types of scoliosis: thoracic right-sided and left-sided, thoracolumbar.

After birth, human organs of vision undergo significant morphofunctional changes. For example, the length of the eyeball in a newborn is 16 mm, and its weight is 3.0 g, by the age of 20 these figures increase to 23 mm and 8.0 g. In the process of development, the color of the eyes also changes. In newborns in the first years of life, the iris contains few pigments and has a bluish-grayish tint. The final color of the iris is formed only by 10-12 years.

The development of the visual sensory system also proceeds from the periphery to the center. Myelination of the optic nerve pathways ends by 3-4 months of age. Moreover, the development of sensory and motor functions of vision is synchronous. In the first days after birth, eye movements are independent of each other, and, accordingly, the mechanisms of coordination and the ability to fix an object with a glance are imperfect and form at the age of 5 days to 3-5 months. The functional maturation of the visual zones of the cerebral cortex, according to some data, occurs already by the birth of a child, according to others - somewhat later.

The optical system of the eye also changes in the process of ontogenetic development. The child in the first months after birth confuses the up and down of the object. The fact that we see objects not in their inverted image, but in their natural form is explained by life experience and the interaction of sensory systems.

Accommodation in children is more pronounced than in adults. The elasticity of the lens decreases with age, and accommodation decreases accordingly. As a result, some disorders of accommodation occur in children. So, in preschoolers, due to the flatter shape of the lens, farsightedness is very common. At 3 years, farsightedness is observed in 82% of children, and myopia - in 2.5%. With age, this ratio changes and the number of myopic people increases significantly, reaching 11% by the age of 14-16. An important factor contributing to the appearance of myopia is a violation of visual hygiene: reading while lying down, doing homework in a poorly lit room, increased eye strain, and much more.

In the process of development, the color perception of the child changes significantly. In a newborn, only rods function in the retina, cones are still immature and their number is small. Elementary functions of color perception in newborns, apparently, are, but the full inclusion of cones in the work occurs only by the end of the 3rd year. However, at this age level it is still inferior. The sensation of color reaches its maximum development by the age of 30 and then gradually decreases. Training is of great importance for the formation of color perception. Interestingly, the fastest way a child begins to recognize yellow and green colors, and later - blue. Recognition of the shape of an object appears earlier than recognition of color. When getting acquainted with the object in preschoolers, the first reaction is its shape, then the size and, last but not least, the color.

With age, visual acuity increases and stereoscopy improves. The most intensive stereoscopic vision changes up to 9-10 years old and reaches its optimal level by 17-22 years old. From the age of 6, girls have higher stereoscopic visual acuity than boys. The eye in girls and boys of 7-8 years is much better than in preschoolers, and has no gender differences, but approximately 7 times worse than in adults. In subsequent years of development in boys, the linear eye becomes better than in girls.

The visual field develops especially intensively at preschool age, and by the age of 7 it is approximately 80% of the size of the adult visual field. In the development of the visual field, sexual characteristics are observed. At the age of 6, the field of view in boys is larger than in girls; at 7-8 years, the reverse ratio is observed. In subsequent years, the dimensions of the visual field are the same, and from the age of 13-14, its dimensions are larger in girls. The specified age and gender features of the development of the field of vision should be taken into account when organizing individual education for children, since the field of view (the bandwidth of the visual analyzer and, consequently, learning opportunities) determines the amount of information perceived by the child.

In the process of ontogenesis, the capacity of the visual sensory system also changes. Until the age of 12-13, there are no significant differences between boys and girls, and from the age of 12-13 in girls, the throughput of the visual analyzer becomes higher, and this difference persists in subsequent years. It is interesting that by the age of 10-11 this figure is approaching the level of an adult, which is normally 2-4 bps.

Age features of vision in children.

Vision hygiene

Prepared by:

Lebedeva Svetlana Anatolievna

MBDOU kindergarten

compensating type No. 93

Moscow region

Nizhny Novgorod

Introduction
The device and work of the eye

How the eye works




Vision hygiene
3.1. eyes and reading
3.2. Eyes and computer
3.3. Vision and TV
3.4. Lighting Requirements
Conclusion
Bibliography

Introduction

See everything, understand everything, know everything, experience everything,
All forms, all colors to absorb with your eyes,
To walk all over the earth with burning feet,
Take it all in and make it happen again.

Maximilian Voloshin

Eyes are given to man to see the world, they are a way of understanding three-dimensional, color and stereoscopic images.

Preservation of vision is one of the most important conditions for active human activity at any age.

The role of vision in human life cannot be overestimated. Vision provides the possibility of labor and creative activity. Through the eyes, we receive most of the information about the world around us compared to other senses.

The source of information about the external environment around us is complex nervous devices - the sense organs. The German naturalist and physicist G. Helmholtz wrote: “Of all the human senses, the eye has always been recognized as the best gift and wonderful product of the creative power of nature. Poets have sung about it, orators have praised it, philosophers have glorified it as a measure of what organic forces are capable of, and physicists have tried to imitate it as an unattainable model of optical instruments.

The organ of vision serves as the most important tool for understanding the external world. The main information about the world around us enters the brain through the eyes. Centuries passed until the fundamental question was solved, how the image of the outside world is formed on the retina. The eye sends information to the brain, which is transformed through the retina and optic nerve into a visual image in the brain. The visual act has always been mysterious and mysterious for a person.

I will talk about all this in more detail in this control work.

For me, working on the material on this topic was useful and informative: I figured out the structure of the eye, the age-related features of vision in children, and the prevention of visual disorders. At the end of the work in the application, she presented a set of exercises to relieve eye fatigue, multifunctional exercises for the eyes and visual gymnastics for children.

The device and work of the eye

The visual analyzer enables a person to navigate in the environment, comparing and analyzing its various situations.

The human eye has the shape of an almost regular ball (about 25 mm in diameter). The outer (protein) shell of the eye is called the sclera, has a thickness of about 1 mm and consists of an elastic cartilage-like opaque white tissue. At the same time, the anterior (slightly convex) part of the sclera (cornea) is transparent to light rays (it looks like a round "window"). The sclera as a whole is a kind of superficial skeleton of the eye, maintaining its spherical shape and at the same time providing light transmission into the eye through the cornea.

The inner surface of the opaque part of the sclera is covered with a choroid, consisting of a network of small blood vessels. In turn, the choroid of the eye is, as it were, lined with a light-sensitive retina, consisting of light-sensitive nerve endings.

Thus, the sclera, choroid and retina form a kind of three-layer outer shell, which contains all the optical elements of the eye: the lens, the vitreous body, the eye fluid that fills the anterior and posterior chambers, and the iris. Outside, to the right and left of the eye, there are rectus muscles that rotate the eye in a vertical plane. Acting simultaneously with both pairs of rectus muscles, you can turn the eye in any plane. All nerve fibers, leaving the retina, are combined into one optic nerve, going to the corresponding visual zone of the cerebral cortex. In the center of the exit of the optic nerve there is a blind spot that is not sensitive to light.

Particular attention should be paid to such an important element of the eye as the lens, the change in the shape of which largely determines the work of the eye. If the lens could not change its shape during the operation of the eye, then the image of the object under consideration would sometimes be built in front of the retina, and sometimes behind it. Only in some cases would it fall on the retina. In reality, however, the image of the object under consideration always (in the normal eye) falls precisely on the retina. This is achieved due to the fact that the lens has the ability to take a shape corresponding to the distance at which the object in question is located. So, for example, when the object in question is close to the eye, the muscle compresses the lens so much that its shape becomes more convex. Due to this, the image of the object under consideration falls precisely on the retina and becomes as clear as possible.

When viewing a distant object, the muscle, on the contrary, stretches the lens, which leads to the creation of a clear image of the distant object and its placement on the retina. The property of the lens to create on the retina a clear image of the object in question, located at different distances from the eye, is called accommodation.

How the eye works

When viewing an object, the iris of the eye (pupil) opens so wide that the light stream passing through it is sufficient to create the illumination on the retina necessary for the confident operation of the eye. If this did not work out right away, then the aiming of the eye at the object by turning with the help of the rectus muscles will be refined, and at the same time the lens will be focused with the help of the ciliary muscle.

In everyday life, this process of “tuning” the eye when moving from viewing one object to another occurs continuously throughout the day, and automatically, and it occurs after we transfer our gaze from object to object.

Our visual analyzer is capable of distinguishing objects up to tenths of a mm in size, distinguishing colors in the range from 411 to 650 ml with great accuracy, and also distinguishing an infinite number of images.

About 90% of all the information we receive comes through the visual analyzer. What conditions are necessary for a person to see without difficulty?

A person sees well only if the rays from the object intersect at the main focus located on the retina. Such an eye, as a rule, has normal vision and is called emmetropic. If the rays cross behind the retina, then this is a far-sighted (hyperopic) eye, and if the rays cross closer than the retina, the eye is myopic (myopic).

Age features of the organ of vision

The vision of a child, unlike the vision of an adult, is in the process of becoming and improving.

From the first days of life, the child sees the world around him, but only gradually begins to understand what he sees. In parallel with the growth and development of the whole organism, there is also a great variability of all elements of the eye, the formation of its optical system. This is a long process, especially intense between the year and five years of a child's life. At this age, the size of the eye, the weight of the eyeball, and the refractive power of the eye increase significantly.

In newborns, the size of the eyeball is smaller than in adults (the diameter of the eyeball is 17.3 mm, and in an adult it is 24.3 mm). In this regard, the rays of light coming from distant objects converge behind the retina, that is, the newborn is characterized by natural farsightedness. An early visual reaction of a child can be attributed to an orienting reflex to light irritation, or to a flashing object. The child reacts to light irritation or an approaching object by turning the head and torso. At 3-6 weeks, the baby is able to fix the gaze. Up to 2 years, the eyeball increases by 40%, by 5 years - by 70% of its original volume, and by the age of 12-14 it reaches the size of an adult's eyeball.

The visual analyzer is immature at the time of the birth of the child. The development of the retina ends by 12 months of age. Myelination of the optic nerves and optic nerve pathways begins at the end of the intrauterine period of development and ends at 3–4 months of a child's life. The maturation of the cortical part of the analyzer ends only by the age of 7 years.

Lacrimal fluid has an important protective value, as it moisturizes the anterior surface of the cornea and conjunctiva. At birth, it is secreted in a small amount, and by 1.5–2 months, during crying, there is an increase in the formation of lacrimal fluid. In a newborn, the pupils are narrow due to the underdevelopment of the iris muscle.

In the first days of a child's life, there is no coordination of eye movements (the eyes move independently of each other). It appears in 2-3 weeks. Visual concentration - fixation of the gaze on the object appears 3-4 weeks after birth. The duration of this eye reaction is only 1–2 minutes. As the child grows and develops, the coordination of eye movements improves, fixing the gaze becomes longer.

Age features of color perception

A newborn child does not differentiate colors due to the immaturity of the cones in the retina. In addition, there are fewer of them than sticks. Judging by the development of conditioned reflexes in a child, color differentiation begins at 5–6 months. It is by 6 months of a child's life that the central part of the retina develops, where the cones are concentrated. However, the conscious perception of colors is formed later. Children can correctly name colors at the age of 2.5-3 years. At 3 years old, the child distinguishes the ratio of the brightness of colors (darker, paler colored object). For the development of color differentiation, it is advisable for parents to demonstrate colored toys. By the age of 4, the child perceives all colors. The ability to distinguish colors increases significantly by the age of 10–12 years.

Age features of the optical system of the eye

The lens in children is very elastic, so it has a greater ability to change its curvature than in adults. However, starting from the age of 10, the elasticity of the lens decreases and decreases.accommodation volume- the adoption by the lens of the most convex shape after the maximum flattening, or vice versa, the adoption of the lens of the maximum flattening after the most convex shape. In this regard, the position of the nearest point of clear vision changes.Closest point of clear vision(the smallest distance from the eye at which the object is clearly visible) moves away with age: at 10 years old it is at a distance of 7 cm, at 15 years old - 8 cm, 20 - 9 cm, at 22 years old -10 cm, at 25 years old - 12 cm, at 30 years old - 14 cm, etc. Thus, with age, in order to see better, the object must be removed from the eyes.

At the age of 6-7 years, binocular vision is formed. During this period, the boundaries of the field of view expand significantly.

Visual acuity in children of different ages

In newborns, visual acuity is very low. By 6 months it increases and is 0.1, at 12 months - 0.2, and at the age of 5-6 years it is 0.8-1.0. In adolescents, visual acuity increases to 0.9–1.0. In the first months of a child's life, visual acuity is very low, at the age of three, only 5% of children have it normal, in seven-year-olds - in 55%, in nine-year-olds - in 66%, in 12-13-year-olds - 90%, in adolescents 14 - 16 years old - visual acuity, like an adult.

The field of vision in children is narrower than in adults, but by the age of 6–8 it expands rapidly and this process continues up to 20 years. The perception of space (spatial vision) in a child is formed from the age of 3 months due to the maturation of the retina and the cortical part of the visual analyzer. The perception of the shape of an object (volumetric vision) begins to form from the age of 5 months. The child determines the shape of the object by eye at the age of 5–6 years.

At an early age, between 6–9 months, the child begins to develop a stereoscopic perception of space (he perceives the depth, remoteness of the location of objects).

Most six-year-old children have developed visual acuity and all parts of the visual analyzer are completely differentiated. By the age of 6, visual acuity approaches normal.

In blind children, the peripheral, conductive, or central structures of the visual system are morphologically and functionally not differentiated.

The eyes of young children are characterized by slight farsightedness (1–3 diopters), due to the spherical shape of the eyeball and the shortened anterior-posterior axis of the eye. By the age of 7-12, farsightedness (hypermetropia) disappears and the eyes become emmetropic, as a result of an increase in the anterior-posterior axis of the eye. However, in 30-40% of children, due to a significant increase in the anterior-posterior size of the eyeballs and, accordingly, the removal of the retina from the refractive media of the eye (lens), myopia develops.

It should be noted that among students entering the first grade, from 15 to 20%children have visual acuity below one, however, much more often due to farsightedness. It is quite obvious that the refractive error in these children was not acquired at school, but appeared already at preschool age. These data indicate the need for the closest attention to the vision of children and the maximum expansion of preventive measures. They should start from preschool age, when it is still possible to promote the correct age-related development of vision.

Vision hygiene

One of the reasons leading to the deterioration of human health, including his vision, has become scientific and technological progress. Books, newspapers and magazines, and now also a computer, without which life is already impossible to imagine, have caused a decrease in motor activity and led to excessive stress on the central nervous system, as well as on vision. Both the habitat and food have changed, and both are not for the better. It is not surprising that the number of people suffering from visual pathology is steadily increasing, and many ophthalmic diseases have become much younger.

The prevention of visual disorders should be based on modern theoretical views on the cause of visual impairment in preschool age. The study of the etiology of visual disorders and especially the formation of myopia in children has been and is being given great attention for many years. It is known that visual defects are formed under the influence of a complex complex of numerous factors, in which external (exogenous) and internal (endogenous) influences intertwine. In all cases, the conditions of the external environment are decisive. There are a lot of them, but the nature, duration and conditions of visual load are of particular importance in childhood.

The greatest load on vision occurs during compulsory classes in kindergarten, and therefore control over their duration and rational construction is very important. Moreover, the established duration of classes - 25 minutes for the senior group and 30 minutes for the preparatory group for school - does not correspond to the functional state of the children's body. With such a load in children, along with the deterioration of certain indicators of the body (pulse, respiration, muscle strength), a drop in visual functions is also observed. The deterioration of these indicators continues even after a 10-minute break. Daily repetitive decline in visual function under the influence of activities can contribute to the development of visual disorders. And, above all, this applies to writing, counting, reading, which require a lot of eye strain. In this regard, it is advisable to follow a number of recommendations.

First of all, you should limit the duration of activities associated with the stress of accommodation of the eye. This can be achieved with a timely change during the classes of different activities. Purely visual work should not exceed 5-10 minutes in the younger group of the kindergarten and 15-20 minutes in the older and preparatory groups for school. After such a duration of classes, it is important to switch the attention of children to activities that are not related to visual strain (retelling what has been read, reading poetry, didactic games, etc.). If for some reason it is impossible to change the nature of the lesson itself, then it is necessary to provide for a 2-3-minute physical culture pause.

Such an alternation of activities is also unfavorable for vision, when the first and the next after it are of the same type in nature and require staticand eye strain. It is desirable that the second lesson was associated with physical activity. It could be gymnastics ormusic .

It is important for the protection of the eyesight of children that the organization of classes at home is hygienically correct. At home, children especially like to draw, sculpt, and at an older preschool age - to read, write, and perform various work with a children's designer. These activities against the background of high static stress require constant active participation of vision. Therefore, parents should monitor the nature of the child's activities at home.

First of all, the total duration of homework during the day should not exceed 40 minutes at the age of 3 to 5 years and 1 hour at 6-7 years. It is desirable that children study both in the first and in the second half of the day, and that there is enough time between morning and evening classes for active games, being outdoors, and work.

Once again, it should be emphasized that at home, the same type of activities associated with eye strain should not be long.

Therefore, it is important to timely switch children to a more active and less visually stressful type of activity. In the case of continuing monotonous activities, parents should interrupt them every 10-15 minutes to rest. Children should be given the opportunity to walk or run around the room, do some physical exercises, and to relax accommodation, go to the window and look into the distance.

eyes and reading

Reading puts a serious strain on the organs of vision, especially in children. The process consists in moving the eye along the line, during which stops are made for the perception and comprehension of the text. Most often, such stops, not having sufficient reading skills, are made by preschoolers - they even have to return to the already read text. At such moments, the load on vision reaches its maximum.

According to the results of the research, it turned out that mental fatigue slows down the speed of reading and perception of the text, which increases the frequency of recurrent eye movements. Even more visual hygiene in children is violated by incorrect "visual stereotypes" - stooping while reading, insufficient or too bright lighting, the habit of reading lying down, on the move or while driving (in a car or subway).

With a strong tilt of the head forward, the bend of the cervical vertebrae compresses the carotid artery, narrowing its lumen. This leads to a deterioration in the blood supply to the brain and organs of vision, and together with insufficient blood flow, oxygen starvation of the tissues occurs.

The optimal conditions for the eyes when reading are zonal lighting in the form of a lamp installed to the left of the child and directed at the book. Reading in diffused and reflected light causes eye strain and, consequently, eye fatigue.

The quality of the font is also important: it is preferable to choose prints with a clear font on white paper.

Reading should be avoided during vibration and movement, when the distance between the eyes and the book is constantly decreasing and increasing.

Even if all the conditions of visual hygiene are observed, you need to take a break every 45-50 minutes and change the type of activity for 10-15 minutes - while walking, do gymnastics for the eyes. Children should adhere to the same scheme during their studies - this will ensure rest for their eyes and compliance with the correct hygiene of the student's eyesight.

Eyes and computer

When working at a computer, the general lighting and tone of the room play an important role for the vision of adults and children.

Make sure that there are no significant differences in brightness between light sources: all lamps and fixtures should have approximately the same brightness. At the same time, the power of the lamps should not be too strong - bright light irritates the eyes to the same extent as insufficient lighting.

To maintain the hygiene of the eyes of adults and children, the coating of walls, ceilings and furnishings in the study or the child's room should have a low reflection coefficient so as not to create glare. Shiny surfaces have no place in a room where adults or children spend a significant part of their time.

In bright sunshine, shade windows with curtains or blinds - to prevent visual impairment, it is better to use more stable artificial lighting.

The desktop - your own or the student's table - should be positioned so that the angle between the window and the table is at least 50 degrees. It is unacceptable to place the table directly in front of the window or so that the light is directed at the back of the person sitting at the table. Children's desktop lighting should be about 3-5 times higher than the general illumination of the room.

The table lamp should be placed on the left for right-handers and on the right for left-handers.

These rules apply to both the organization of the office and the room for children.

Vision and TV

The main cause of visual impairment in preschool children is television. How long and how often an adult needs to watch TV is solely his decision. But you need to remember that too long watching TV causes excessive stress of accommodation and can lead to a gradual deterioration of vision. Uncontrolled spending time in front of the TV is especially dangerous for children's eyesight.

Regularly take breaks during which to do gymnastics for the eyes, and also at least 1 time in 2 years to be examined by an ophthalmologist.

Hygiene of vision in children, as well as other family members, includes observing the rules for installing a TV.

The minimum TV screen distance can be calculated using the following formula: for HD (high definition) screens, divide the diagonal in inches by 26.4. The resulting number will indicate the minimum distance in meters. For a conventional TV, the diagonal in inches should be divided by 26.4 and the resulting number multiplied by 1.8.
Sit on the sofa in front of the TV: the screen should be at eye level, no higher or lower, without creating an uncomfortable viewing angle.
Arrange light sources so that they do not cast glare on the screen.
Do not watch TV in complete darkness, keep a dim lamp with diffused light turned on, located out of sight of adults and children watching TV.

3.4. Lighting requirement

With good lighting, all body functions proceed more intensively, mood improves, activity and working capacity of the child increase. Natural daylight is considered the best. For greater illumination, the windows of game and group rooms usually face south, southeast or southwest. Light should not obscure either opposite buildings or tall trees.

Neither flowers, which can absorb up to 30% of the light, nor foreign objects, nor curtains should interfere with the passage of light into the room where the children are. In game and group rooms, only narrow curtains made of light, well-washable fabric are allowed, which are located on the rings along the edges of the windows and are used in cases where it is necessary to limit the passage of direct sunlight into the room. Matted and chalked window panes are not allowed in children's institutions. It is necessary to take care that the glasses are smooth and of high quality.

Our full and interesting life until old age largely depends on vision. Good vision is something that some people can only dream of, while others simply do not attach importance to it, because they have it. However, neglecting certain rules common to all, you can lose your eyesight ...

Conclusion

The initial accumulation of the necessary information and its further replenishment is carried out with the help of the sense organs, among which the role of vision is, of course, the leading one. It is not for nothing that folk wisdom says: “It is better to see once than hear a hundred times”, thus emphasizing the significantly greater information content of vision compared to other senses. Therefore, along with many issues of raising and educating children, the protection of their eyesight plays an important role.

For the protection of vision, not only the correct organization of compulsory classes is important, but also the regime of the day as a whole. Proper alternation during the day of different types of activities - wakefulness and rest, sufficient physical activity, maximum stay in the air, timely and rational nutrition, systematichardening - this is a set of necessary conditions for the proper organization of the daily routine. Their systematic implementation will contribute to the well-being of children, maintaining the functional state of the nervous system at a high level and, therefore, will positively affect the processes of growth and development of both individual body functions, including visual ones, and the whole body.

Bibliography

Hygienic bases of education of children from 3 to 7 years: Book. For doshk workers. institutions / E.M. Belostotskaya, T.F. Vinogradova, L.Ya. Kanevskaya, V.I. Telenchi; Comp. IN AND. Telenchi. - M.: Prisveschenie, 1987. - 143 p.: ill.