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Handbook of the patient
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Anatomy of an eye
The person sees by eyes, but by means of eyes, whence the information is transferred through an optic nerve, chiasmus, visual pathes in the certain areas of occipital shares of a brain cortex where is formed that picture of an external world which we see. All these bodies also make our visual analyzer or visual system.Presence of two eyes allows to make our sight stereoscopic (that is to form the three-dimensional image). The right retinal side of each eye transfers through an optic nerve "the right part" of image in the right part of a brain, the left retinal side similarly operates. Then two parts of the image right and left - connects together by the brain. As each eye perceives the "own" picture, the infringement of joint movement of the right and left eyes can break binocular sight. Simply speaking, you will see simultaneously two absolutely different pictures.  Structure of an eye The eye can be named the difficult optical device. Its primary aim is "to transfer" the right image to an optic nerve. The basic functions of an eye:
The forward chamber of eye is a space between a cornea and iris. It is filled with an intraocular liquid. Iris likes a circle in form with an aperture inside (pupil). Iris consist of muscles, by which reduction and relaxation varies the sizes of a pupil. It enters into a choroid. Iris is responsible for color of eyes (if it’s blue then, in it has a few of pigmentary cells, if it’s brown - then a lot). It carries out the same function, that the diaphragm in the camera, adjusting light stream. Pupil is an aperture in iris. Its size usually depend on a level of light exposure. The more light, the pupil is less. Crystalline lens is a "natural lens" of eye. It is transparent, elastic - can change the form, almost instantly "directing focus" this ensured that the person sees well and close, and in the distance. It settles down in a capsule, it is kept by ciliary zonule. The crystalline lens, as well as a cornea, is a part of optical system of an eye. Vitreous body is a gellike transparent substance located in a back part of an eye. Vitreous body supports the form of an eyeball, takes part in an intraocular metabolism. Enters into optical system of an eye. The retina consist of photoreceptors (they are sensitive to light) and nervous cells. The cells-receptors located in a retina, share on two types: conuses and sticks. In these cells, developing enzyme rhodopsin, occurs transformation of energy of light (photons) to electric energy of a nervous tissue, i.e. photochemical reaction. Sticks have a high photosensitivity and allow to see at bad illumination, also they are responsible for peripheral sight. Conuses, on the contrary, demand for its work a lot of light, but they allow to make out fine details (they are responsible for the central sight), enable to distinguish colors. The greatest congestion of conuses is in central fossa (macula), responsible for the highest visual acuity. The retina adjoins to choroid, but on many sites loosely. Here it also tend to detach at various diseases of retina. Sclera is the opaque eyeball shell, passing in forward part of an eyeball in a transparent cornea. There are 6 oculomotorius muscles at the sclera. In has a small amount of the nervous endings and vessels. The choroid covers a back part of sclera, the retina to which it is closely connected. The choroid is responsible for blood supply of intraocular structures. At diseases of a retina it is very often involved in pathological process. There are no nervous endings in choroid, so there is no pains during its illness, usually signalling on any malfunctions. Optic nerve. By means of an optic nerve signals from the nervous endings are transferred in a brain. Structure of cornea The knowledge of a structure of a cornea especially is useful to those who wants to understand how there passes eximer-laser correction and why it passes so, and to persons who will have an operation on a cornea.  Bowman’s membrane is located direct under epithelium. It is responsible for protection and participates in a feed of a cornea. It is not restored at damage. Strom is the most volumetric part of a cornea. Its basic part – are the collagenic fibres located by horizontal layers. It also contains the cells responsible for restoration. Descemet's membrane separates strom from endothely. Has high elasticity, it is steady against damages. Endothely - is responsible for a transparency of a cornea and participates in its feed. It restores very badly. It carries out very important function of "the active pump", responsible for the superfluous liquid not to accumulate in a cornea (otherwise will take place its edema). Thus endothely supports transparency of a cornea. The amount endothelial cells during a life is gradually reduced from 3500 on mm2 at a birth up to 1500 - 2000 cells on mm2 in advanced age. Reduction in density of these cells can occur because of various diseases, traumas, operations, etc. At density 800 cells on mm2 cornea becomes edematic, lowers and loses the transparency. The lacrimal film on a surface epithelium, which also plays a significant role in optical properties of an eye, frequently name the sixth layer of a cornea.  top
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