(to 80%) information on world around we receive the Most part through eyes.
Our eyes are specially intended to supply us with the information on depth, distance, size, movement and colour. Besides they are capable to move upwards, downwards and in both parties, giving us as much as possible wide review. The human eye can be compared to the camera. The forward wall of an eye operates as an objective lens. The lens is the bent fragment of a transparent material which refracts rays of light passing through it.
The Pupil is similar to the diaphragm located behind an objective. Extending or being narrowed, it regulates quantity of light getting into an eye. The internal cover of an eye, or a retina is "¶ю=юяыхэър" and "ІъЁрэ" on which it is focused "¶ю=юёэшьюъ".
As eyes operate
Actually the eye is arranged much more difficult. If cameras simply embody the image on a film people and animals are capable to distinguish the information which has got on a retina and to operate on the basis of the seen.
The matter is that the eye is connected to a brain by means of an optic nerve. This nerve is in the special shoot attached to a back wall of an eye. It also transmits signals arriving on a retina in the form of impulses which are deciphered in a brain.
Each eye sees subjects under a bit different corner, directing in mozgsvoj a signal. Our brain in the earliest childhood "ѕёш=ё " to reduce together both images so that we did not see double contours. The images imposed against each other allow to see volume of subjects, and that one subject is ahead or behind another. This phenomenon is known as tridimentionality of the image, or "3-D".
Besides, the brain allows us to distinguish top and a bottom correctly. Refracting at passage through a crystalline lens, light leaves the turned image on a retina. Our brain "ёёш=№трх=" it and immediately overturns "ё heads on эюуш". However the newborn first sees all subjects turned.
Why the pupil size changes?
The Pupil is an aperture in the center pigmentirovannoj an iris of the eye. Raduzhka supervises quantity of light getting to an eye through a pupil. At very bright light it is narrowed, and the pupil decreases till the sizes of a tiny point, passing in an eye only a little bit of light. At dim illumination it relaxes, and the pupil extends, opening access to light. Pupils can extend and when you are captured by any strong feeling, for example, love or fear.
As the eye is arranged?
The Human eye has the sphere form. In the center of its forward department there is hardly a convex transparent layer, or a cornea. It is connected to fiber, or skleroj, covering almost all external surface of an eye. Sklera it is covered by the thin covers penetrated by the smallest blood vessels.
The Cornea - the first lens through which takes place a light beam. At it motionless focus, and it never changes neither positions, nor forms. Under a cornea there is an iris of the eye, or "шЁшё". In the Greek language this word means "Ёрфѕур". More often raduzhki happen blue, green or brown. As a matter of fact, the iris of the eye represents a muscular disk with an aperture in the center. This aperture also is a pupil, through which light gets in an eye.
The Space between a cornea and raduzhkoj is filled by transparent substance which is called as an intraocular liquid. It protects a cornea from pathogenic microbes.
Behind an iris of the eye there is a second objective, or a crystalline lens. It is much more mobile and is flexible, rather than a cornea. On a place it is kept by the whole network of fibres which are called as suspending sheaves. From different directions the crystalline lens is surrounded tsiliarnymi by muscles which give it various forms. We will tell, when you look at any remote subject, these muscles relax, the crystalline lens increases in diameter and becomes more flat. At a sight at closer subject curvature of a crystalline lens increases. Behind a crystalline lens there is the internal chamber of an eye filled with jellylike substance which name steklovidnym a body. Light should pass at first through this substance and only after that gets on a retina - a layer covering back and lateral walls of the internal chamber of an eye.
the Internal structure of an eye
The Spherical form, hardness and elasticity to an eyeball is given by the jellylike liquid filling it named steklovidnym a body. On the place in an eye-socket of eyes it is kept by a special shoot. In it there is an optic nerve transmitting in a brain visual signals.
Sticks and kolbochki
The Retina consists of 130 million photosensitive cages which name sticks and kolbochkami. Sticks are sensitive to light, but do not distinguish colours, except for dark blue and green. Kolbochki catch all colours and help us to see more accurately, but cease to work at an illumination lack. That is why with approach of twilight our sight weakens, we distinguish colours is worse and all we see in dark blue or serozelenyh tones. Frenchmen name this time of days "ёрёюь ёшэхт№".
At very bright light of a stick are closed, conceding all work kolbochkam. In process of easing of light of a stick revive, but it occurs not at once: when you come into a dark room from the street filled in with the sun, eyes only gradually get used to darkness, and at an exit on a sunlight you for an instant as though grow blind.
Some forms of blindness are caused by illnesses of a retina which damage sticks and kolbochki. Scientists develop methods of their stimulation by implantation of electrodes. One more way of restoration of a retina is a change of the present sticks and kolbochek, received of fabrics of a human fruit.
Kolbochki are concentrated in a pole to a back wall of a retina, and the majority of sticks is located round it.
The Pole is near to a place of an exit of an optic nerve where in a retina there is a small rupture. Light beams do not influence this site, and it means that in a back wall of each eye is tiny "ёыхяюх я =эю".
Movement of eyeballs
Usually is better we see the central site of a retina, therefore, properly to make out a subject, we turn eyeballs, and even all head. The eyeball is kept in an eye-socket by six muscles, providing to it considerable freedom of movement.
From damages our eyes are protected by the whole set of protective means. They are reliably hidden in the bone eye-sockets which have been laid out by a soft fatty fabric. At falling or blow the eye-socket, rather than a eye will be more likely damaged.
In front, including under centuries, the eye is covered by a continuous transparent cover, or konjunktivoj which protects and washes a plaintive liquid its surface. Tears are developed by the special glands located in external corners of an eye, and their surplus is taken away through internal corners.
The Internal cover of eyelids helps to clear an eye at blinking. We close eyelids when we wish to protect eyes from bright light or the motes scratching a cornea. Eyelashes too in some measure help to protect eyes from a dust soaring in air. Even eyebrows have a appointment. They take away drops of sweat flowing down from a forehead from eyes.
Short-sightedness and a far-sightedness
Short-sightedness and a far-sightedness concern the most frequent infringements of sight. Short-sighted people badly see the remote subjects, and far-sighted that is nearby. These lacks of sight are almost always caused by the eyeball form. That sight was faultless, the eyeball too should have the ideal form of a sphere. However at short-sighted people perednezadny diameter of eyeballs is extended, and at far-sighted - is truncated. Short-sightedness and a far-sightedness is easy for correcting, having put on points or contact lenses. Recently scientific have opened a new way of correction of short-sightedness by surgical uploshchenija corneas.
At radical keratotomii on a cornea cuts become, and after their healing the cornea becomes more flat. If operation is carried out by means of the laser, the short-sightedness indicator is entered into the computer, and that calculates that it is necessary to make with a cornea to return normal sight.
The eyeball Form can and affect in another way sight, causing astigmatizm. Usually it meets together with short-sightedness or a far-sightedness. Curvature of walls of a cornea should be everywhere identical, as at a football. But at some people the cornea is more similar to an oval ball for Rugby football, and their eyes cannot correctly focus light beams.
We say that the eye mows, when it is directed aside from other eye - often to a nose or a temple, and sometimes upwards or downwards. The reason of it often happens "ыхэі" one of the muscles operating movement of an eyeball. That "яюфё=хуэѕ=і" mowing eye to the normal work, a healthy eye close a bandage. If it does not help, it is necessary to wear glasses or to do operation.
the Glaucoma and a cataract
The Glaucoma is an illness of eyes at which the volume of a watery liquid in the chamber between an iris of the eye and a cornea increases, causing a pain and increase of intraocular pressure. Sight worsens, and if glaucoma not to treat, there can come a total blindness. Sometimes by means of the laser in an iris of the eye the tiny drainage aperture for outflow of a liquid which allows to lower pressure inside is cut.
The Cataract is a cataract at which the patient looks at the world as though through a freezing window. The cataract develops slowly and does not cause a pain. It delete, destroying a crystalline lens a special ultrasonic probe. A remote crystalline lens replace with a tiny plastic lens.
- the Person blinks one - two times each 10 seconds. Each blinking lasts third of second. It means that for the 12-sentry day you spend for blinking of 25 minutes. Newborn babies at all do not blink and start it to do approximately from 6 months.
- We cry from affliction, but anybody plainly does not know why. During crying it is necessary often smorkatsja because surplus of tears flows down in a nose cavity through tiny apertures in a century.
- Carrots in a diet really help to see better in the dark. The matter is that vitamin A with which carrots are rich, helps to work more effectively to retina sticks. At eye illnesses it is useful to eat also cabbage and other green sheet vegetables.
- the Human eye distinguishes to 10 million colour shades. However people, unlike insects, do not see ultra-violet radiation.