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The human eye consists of a simple object-lens with two elements - cornea and lens. The amount of light entering the eye is controlled by the iris, which is located between cornea and lens. In the middle of the iris is a pupil, which astringes or expands depending on the intensity of the light and thus regulates the input of beams into the eye. The light spreads through a transparent vitreous body and a reversed image is created on the sensitized retina. The retina is a sensitized part of the eye and responds to a sensor or film in the camera. If the retina equalized to the surface, it would create a circle with a diameter of about 42 mm corresponding with a diagonal of a film. The retina consists of sensitized cells - about 130 millions of rods and 7 millions of cones. In this case the eye can works as a 137 megapixel camera. Cones are less sensitive, but are able to distinguish colors. Rods are much more sensitive, but their role is providing of only black and white vision. In order, the eye works properly we can’t forget to mention some additional organs, which also have a major impact on a perfect vision. These include extraocular muscles that provide eye movements so we can change a direction of the eyeview. Furthermore, we can include a socket eye, which is like a bony box with the eye inside. Its main function is to protect the eyeball. It is also necessary to mention eyelids and lacrimal apparatus. |
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The eye cornea is the transparent front elastic and the mostly curved part of the exterior ligamentous layer of the human eye. It has the shape of horizontally placed convex and comprises 20% of the surface of the eyeball. It is colorless, completely transparent and avascular. Together with the conjunctiva, sclera and tear film it represents a mechanical and chemically impermeable barrier between interior and exterior environment. On the outside it borders with the air and on the inside it is in contact with the aqueous humour. Due to its refractive power the eye cornea is the most important part of the visual system and it is a critical factor as far as the quality of the vision is concerned.
The human eye consists of a simple objective which has two parts. These are the cornea and the lens. The amount of light which enters the eye is controlled by the iris which is located between the cornea and the lens. The pupil is located in the middle of the iris and it dilates and contracts depending on the intensity of illumination and thereby regulates the amount of light which enters the human eye.
The retina is the individual organ of sight and forms the internal layer of the human eye. It covers whole ventricular side of the eyeball right to the pupillary edge of the iris. It attaches to the middle layer of the eye wall through its external surface and the vitreous body attaches to its internal surface. The retina functions as the film in a camera. It catches the image and sends it to the visual centers of the brain through the optic nerve. We divide the retina into two structurally and functionally different sections. Posterior section, which is situated in the posterior part of the eyeball behind the level of the equator, is formed by the optic part of the retina, its part in front of the equator.Human eye and vision
Refractive errors
Eye diseases and disorders
Eye surgery
Eyeglasses and contacts
