How the eyeball is made.

The eyeball, or the organ of vision, in spite ofits miniature size, has a very complex anatomical structure. Macroscopically this organ has the form of a ball, which is not quite perfect, because Its visible front has more curvature than the back surface hidden from the eyes. This fact also causes the disparity in the size of the eye in different directions. Because of the convexity of the cornea, the anterior-posterior size of the organ of vision is greatest. On average, in an adult healthy person, it approaches 24 mm. The transverse and vertical axes are approximately the same: the average size of the transverse axis of the eye is 23.6 mm and 23.3 mm in the vertical axis.

Structure of the eyeball

In the organ of vision, there are three important shells that perform distinct functions.

1. Outer, or fibrous membrane.In it, two parts are distinguished, which are completely different in anatomical terms. The largest part of the fibrous membrane belongs to the sclera, or the belly, the rest to the cornea. Sclera is an absolutely opaque fabric with a whitish shade. It is because of its color that the eyeball, in particular its opaque part, was called the protein. In clinical practice, the condition of sclera can determine the various pathological conditions that occur in the eye and in the body as a whole. Thus, the redness of the eyeball can speak of acute inflammatory phenomena in the organ of vision: conjunctivitis, keratitis, uveitis, etc. A yellowing of the gall bladder indirectly indicates a liver disease - hepatitis. The eyeball, which is also represented in the front with a cornea, appears in this place to be colored brown, green or blue. However, this is not the cornea itself, but the iris radiating through it. The cornea is absolutely colorless and transparent, there are no blood vessels in it, only a clot of nerve endings, which allows it to be the most sensitive element in the body. If the eyeball is represented as a percentage of parts of its fibrous membrane, then the cornea accounts for less than 16%.
2. Middle, or choroid.It is adjacent to the fibrous, but not all its length, but only in its scleral part. Where the sclera passes into the cornea, the vascular tract separates from it and goes some distance from the cornea. In the middle shell, three parts are distinguished: iris, ciliary (ciliary) body and choroid. The iris serves as a kind of diaphragm, which regulates the light stream that goes deep into the eye, to its light-absorbing structures. The function of the regulator on itself is taken by the pupil, which can expand with a deficit of light and narrow down - with its excess. The ciliary body is necessary for the constant development of intraocular fluid, necessary for feeding the eye, maintaining the tone in it. The choroid, or actually the choroid, is represented by a network of blood vessels that supply blood to the internal structures of the eye.
3. Inner or mesh shell.This is the most important part of the organ of vision, which reacts to light and transmits the received visual information further into the brain cortical structures. The retina is a very thin and fragile tissue, in which, as a rule, two main areas are distinguished: ciliary, which does not have highly differentiated cells, and optically active, in which these cells exist. Their separation (dentate line) can be seen in the course of such a study as cycloscopy, when the eye fundus is being examined.

The eyeball, in addition to the shells inside it, hasvitreous body, which gives it a characteristic rounded shape and participates in the light refraction, as well as the lens, which participates in accommodative processes and the refraction of light beams.