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How does the eye and how it works?
As there nearsightedness and farsightedness?

In everyday life we often use the device, which in its structure is very similar to the eyes and works on the same principle. This camera. As with many other things, the invention of photography, people just simulated what already exists in nature! Now you will see this.

The human eye in the form of wrong ball with a diameter of about 2.5 see This ball is called the eyeball. The eye receives light that is reflected from the surrounding objects. The device which receives the light that is on the back wall of the eyeball (from the inside) and is called the RETINA. It consists of several layers of light-sensitive cells that process available to them the information and send it to the brain through the optic nerve.

Eye structure
The structure of the eye

But in order that the light rays entering the eye on all sides, focused on such a small area occupied by the retina, they have to undergo refraction and focus it on the retina. To do this in an eyeball is a natural biconvex lens - the LENS. It is located in the front part of the eyeball.

The lens is able to change its curvature. Of course, he does this not by myself, but with the help of special ciliary muscle. To tune to a vision of close objects, the lens increases the curvature becomes more prominent and stronger refracts light. For seeing distant objects, the lens becomes flatter.

Property of the lens to change its refractive power, and with it the focal point of all eyes, is called ACCOMMODATION.

The principle of accommodation

In the refraction of light is also involved substance that filled the majority (2/3) of the eyeball - the vitreous body. It consists of transparent gelatinous substance, which not only involved in the refraction of light, but also provides the shape of the eye and its incompressibility.

Light enters the lens, not on the entire front surface of the eye, and through a small hole in the pupil (we see him as a black circle in the center of the eye). The size of the pupil, and thus the amount of light governed by special muscles. These muscles are located in the iris surrounding the pupil (IRIS). Iris, in addition to muscle, contains pigment cells that determine the color of our eyes.


Watch with your own eyes in the mirror and you will see that if the eye be directed bright light, the pupil narrows, and in the darkness he, on the contrary, becomes large - expanding. So-ophthalmic apparatus protects the retina from the destructive action of bright light.

The outside of the eyeball is covered with a durable protein shell thickness of 0.3-1 mm - the SCLERA. It consists of fibers formed by the protein collagen, and performs protective and support function. The sclera is white with milk, low tide, except the front wall, which is transparent. It is called the CORNEA. The cornea is the primary refraction of rays of light

Under the protein shell is the CHOROID, which is rich in blood capillaries and provides the cells of the eyes food. It is the iris from the pupil. On the periphery of the iris enters the CILIARY, or CILIARY BODY. Its thickness is of the ciliary muscle, which, as you remember, changes the curvature of the lens and is used for accommodation.

Between the cornea and the iris, as well as between the iris and lens are space - the camera eye is filled with a transparent, svetoprelomlyayuschaya fluid, which nourishes the cornea and lens.

Eye protection also provide eyelids - upper and lower - and eyelashes. In the thickness of the century are the lacrimal gland. The fluid they produce, constantly moistens the mucous membrane of the eye.

Under the eyelids is 3 pairs of muscles, which provide the mobility of the eyeball. One pair turns his eyes to the left and to the right, the other up and down, and the third rotates it relative to the optical axis.

Muscles provide not only turns the eyeball, but also to change its shape. The fact that the eyes are in General also participated in the focus of the image. If the focus is outside of the retina, the eye is a little drawn out, to see up close. Conversely, rounded, when a person sees distant objects.

If the optical system is changed, in such eyes appear myopia or hyperopia. People suffering from these diseases, the focus falls not on the retina, but in front of it or behind it, and so they see all the objects blurred.

Myopia and hyperopia
Myopia and hyperopia

When myopia in the eye is stretched tight sheath of the eyeball (sclera) in the front-rear direction. Eyes instead acquires a spherical shape of the ellipsoid. Because of this lengthening of the longitudinal axis of the eye image of the subject in focus is not on the retina, but in front of her, and man seeks to bring to the eyes or uses the glasses with the scattering (minus) lenses to reduce the refractive power of the lens.

Hyperopia develops, if the eyeball is shorter in the longitudinal direction. The light rays in this state are going for the retina. In order for such eyes could see well, you need to place the collectors "plus" points.

Myopia and hyperopia
Correction of myopia and hyperopia (B)

Summarize all that was said above. Light enters the eye through the cornea, passes successively through the liquid of the anterior chamber, lens and vitreous body, and eventually falls on the retina, consisting of light-sensitive cells

Now back to the device camera. Role svetoprelomlyayuschaya system (lens) the camera plays the lens system. Aperture regulating the size of the light beam that enters the lens, plays the role of a pupil. And the "retina" of the camera is a film (analogue cameras) or the photosensitive matrix (in digital cameras). However, an important difference of the retina from the photosensitive matrix of the camera is that in its cells is not only perception of light, but the initial analysis of visual information and highlighting the most important elements of visual images, such as the direction and speed of movement of the object, its size.

The eyes

The eyes


The principle of operation of the camera

The principle of operation of the camera

By the way...

On the retina and the photosensitive matrix of the camera is formed a reduced inverted image of the outside world - the laws of optics. But you see the world is not upside down, because in the visual center of the brain is the analysis of the information received with regard to this "amendment".

But newborn babies see the world upside down until about three weeks. For three weeks the brain is trained to overturn what he saw.

There is an interesting experiment, which was written by George M. Stratton of Kalifornische University. If you wear glasses, which turn the visual world upside down, in the early days it is perfect disorientation in space. But after a week, the person gets used to "reverse" the world around him, and even fewer realize that the world is upside-down; he formed a new visual-motor coordination. If you then remove the glasses-turncoats, the person is again violation occurs orientation in space, which soon passes. This experiment demonstrates the flexibility of the visual system and the brain in General.

Training video:
As we can see

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How do you see?


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Total votes: 88

Your comments:

2014-05-25 18:45:56
Because I want to become an ophthalmologist, it is a good article and in General for girls 11 years it's all clear
2014-04-10 20:15:20
Thanks for the article! It is very interesting.
2014-03-04 20:09:28
Too surprising. It is difficult to understand Cho is written here. For a report to Classe unlikely to fit
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