It provides visual perception of world around.
This system consists of a number of the structural elements which are carrying out the functions.
And all these functions are connected among themselves. They that also define properties of optical system of eyes.
Optical system of an eye: structure, features and properties
Between a sklery and vascular cover there is a cornea. Between a vascular cover and a retina there is a raduzhka and a crystalline lens round which, the vascular cover forms a ciliary body.
What represents the sclero?
The sclero – the external cover of an eyeball having milky-white color (whites of the eye which we see) and rather dense structure. Atop skler, the eyeball is covered by a cornea – a transparent film which protects an eye from drying, dust and hit of small microorganisms. Besides, through a cornea light to "information centers" of an eyeball arrives.
What does the vascular cover represent?
The vascular (average) cover of an eye provides food of visual body. It consists of a set of vessels and capillaries.
Being under a cornea, the vascular cover smoothly passes into a raduzhka. Raduzhka – the peculiar cover defining color of eyes. And in the center of a raduzhka there is a pupil.
The pupil is, some kind of "batcher" of light arriving to an eye. If lighting very bright, both natural, and artificial, - a pupil is narrowed. This process is called – mioz. If the lighting muffled or in general is absent, the pupil extends. This process is called – midriaz.
All streams of light directed to an eye are caught by a crystalline lens. The crystalline lens is not a cover, but the "lens" extrapolating the caught light to an eye retina. This "lens" has a biconvex form and flexible structure.
Thanks to flexibility of structure, the crystalline lens is capable to change the curvature that determines the clearness and clarity of sight. Curvature of a crystalline lens changes thus: the ciliary body formed by a flow a vascular cover of a crystalline lens presses or relaxes in relation to a crystalline lens. Thus, there is an accurate vision of the different subjects which are at one distance.
The optical system of an eye – isn't imaginable without akkomadition – ability of an eye clearly to see the subjects which are on different removal. It is reached by light refraction change by a crystalline lens.
What does the eye retina represent?
The eye retina – an internal photosensitive cover which accepts light information and transfers her to a brain by means of nervous fibers.
Here to contain photoreceptors which happen two types – sticks and flasks. Flasks are responsible for color sight of days in the afternoon, and also in the conditions of artificial lighting. Sticks, more sensitive to light, are responsible for sight in a night-time and at weak lighting.