Convergence of the eyes: definition. How do we see? Eye Functions

The convergence of the eyes is the reduction of visualaxes while fixing on a closely located object. During this, the pupil narrows. Convergence of the eyes occurs reflexively with binocular vision. Its insufficiency provokes the development of divergent strabismus.

The role of eye convergence

Convergence of the eyes plays an important role in binocular vision during the combination of monocular visual images, creating the necessary conditions for their fusion. In children, it is often disrupted.

Violations of convergence often lead tothe appearance and strengthening of myopia, the development of axial myopia. The phenomenon is serious and undesirable, especially for children and their parents. To do this, the convergence of the eyes must be diagnosed. How to check?

The adult needs to put the child face to himself, close one eye to himself.
Approximately in the middle of the distance putvertically pencil in such a way that an adult with an open eye saw him superimposed on the child's half face, and the upper end was located at the level of his eyes.
Invite the child to look into the adult's open eye and find out how many pencils he sees while doing this.
If the child sees a "one" pencil, then the process ends. His binocular vision is broken.
If "two" pencils, it is necessary that he only looked at the top of the object, which should be slowly brought closer to the child's face.
If there is no convergence, as the pencil approaches the face of the child, one eye tends towards the nose, the second - towards the temple.
In the presence of convergence, the child's eyes symmetrically rotate to the nose, until the distance decreases to 5 cm.
Then the child is invited to look at the pencil 1-1,5 minutes. If the convergence of the eyes is stable, they should be turned equally to the nose.
Offer the kid without a pencil to focus both eyes to the nose. If it turns out, then he has "volitional convergence."

Treatment of violations of convergence

If the convergence of the eyes is absent, a therapeutic exercise should be performed daily:

Set a pencil 30 cm apart and look past it. In this case, two images of the object should be seen.
First you need to look at the image of the "right" pencil, so that the "left" pencil can also be seen, then look at the "left" pencil without losing sight of the other.
Such a fixation to continue to do further, first in a slow, then at an accelerating pace.

To strengthen the convergence apply exercises that are done daily. During the day they can alternate.

Exercise 1. Set vertically the pencil 20 cm from the eyes, 20 seconds to look away, fixing attention on the double images of the object, then look at the pencil and look at it for 5 seconds, then again look out and repeat the actions.

Exercise 2. Place the pencil vertically at arm's length, slowly approach the eyes before double vision occurs, then slowly push it away from yourself.

Exercise 3 is used for volitional convergence. Stand facing the window to see the horizon. With the will of the will to reduce the eyes to the bridge of the nose, hold in this position for 7 seconds, then look into the distance and again reduce the eyes.

Structure of human eyes

More than 80% of information people get thanks to what and how we see. The structure of the visual organ is very complicated. It depends on the function of the eyes.

The human eyeball is a sphere of irregular shape. It is located inside the skull orbits. From birth to death, the eye cavities increase twofold.

An important place is occupied by the optic nerve. It transfers information to the occipital cortex, then it is analyzed.

Thanks to the lacrimal gland, the surface of the eye remains moist. Tears well lubricate the conjunctiva.

In the structure of the human eye, the muscles of the eyeball act in concert with each other. Eyelids cover the eye, protecting against negative factors. The eyelashes perform the same function.

Interrelation of the structure and function of the eyes

To understand the structure of the visual organ, you should compare it with the camera. It creates an image by focusing on the subject and allowing a certain amount of light to pass through the diaphragm.

When the beam hits the eye, it passes through the cornea, where 75% of the light is focused. Then it hits the pupil, where its amount is regulated.

The lens is the second lens of the eye. Its shape is altered by the tension or relaxation of the muscles. Focused light reaches the retina, in which it transforms into a nerve impulse. When the image reaches the brain centers, it becomes possible to enjoy the world, to see colors and objects. In other words, everything as we see in real life.

The structure proves how complex the eyes are. Experts still can not find a way how to transplant the muscles of the eyeball, since the optic nerve is very sensitive.

Central vision

It received its name because it is provided by the central part of the retina and the central fovea. Such sight allows a person to distinguish between forms and small parts of objects.

If it even slightly decreases, a person immediately becomes noticeable.

The main characteristic of central vision is acuity. Her research is important in assessing the human visual apparatus as a whole, to track various pathological processes.

Visual acuity is the ability of the eye to see two points that are close to each other, at a certain distance.

Also there is the concept of the angle of view, which is the angle that is formed between the extreme points of the object being surveyed and the nodal point of the visual organ.

Peripheral vision

Thanks to him, a person can navigate in space and see in the semi-darkness.

Turn your head to the right and look with your eyes.some object, let it be a picture on the wall, and fix a look on its separate element. If it is seen well, it speaks of central vision. However, in addition to this object, other great things fall into the field of vision. For example, the door to the room, the closet, the dog sitting next to the floor. These objects are visible indistinctly, but are in the field of view, and there is an opportunity to catch movement. This peripheral vision.

The eyes of people, not moving, can cover 180 degrees of the horizon and a little less (about 130^about) along the vertical meridian.

The visual acuity is greater in comparison with the peripheral one. This is due to the fact that the number of cones from the center to the peripheral part of the retina is much reduced.

What vision is normal

Normal vision in humans is associated with the refraction of the light beam in the eye, not deviated from the norm. So, the lens, the cornea, the lens transmit the image image to the retina of the eye, to the yellow spot.

Everyone has his own standard of vision. It is determined by the type of line the patient sees on the Golovin-Sivtsev table. A known unit means that it reads 10 lines. This is normal vision.

Violation of refraction

Refraction is the refraction of light in the eye.

If the beam is refracted correctly, the imagefocused exactly on the retina. The opposite situation (violation of refraction) provokes the development and appearance of hyperopia and myopia. In their presence, the image is blurred, double. For correction, medical glasses and lenses are used, causing the light beam to focus on the retina.