StemCell Therapy

Human eyesight is a sense which enables animals to perceive the light, different colors, shapes and it serves to the general perception of the environment. It is oriented mainly towards the perception of contrast and thus even contours and it significantly helps with orientation in space. For a human being the eyesight is the most important sense and that is mainly because almost 80% of information from our surroundings is perceived through it.

The human eye (oculus) is the organ of eyesight and is composed of the eye bulb and additional organs. Photosensitive layer is called the retina and contains photoreceptors, highly specialized photosensitive cells, rods and cones thanks to which the image is created. These cells are embedded in the pigmented epithelium which supplies them with nourishment and light isolation.

Vision itself, individual perception of the light, is based on the sensitivity of the eyesight pigments (e.g. rhodopsin) to the light. Under the influence of light the sight pigments decompose and that triggers the cascade chemical reactions which lead to the change of signal into electric potential, impulse, that carries information to the optical centers of the brain.

For the eyesight perception to be perfect we need also parts of the human eye that form its optical system (cornea, vitreous humor, lens, vitreous body) that collects the rays in the way that their focus is on the retina. A defect of optical system causes inability to create a sharp image on the retina and it leads to refractive errors (short-sightedness, long-sightedness, astigmatism).

Human eye equity is the ability to differentiate between two points in space. It depends on the ability of the optical apparatus to concentrate rays on the retina but also depends on the transparency of the human eye, intensity of light and on density and integration of photoreceptors in the given place on the retina.

Ultraviolet rays are the component of sunlight and is divided into UV-A and UV-B and UV-C radiation. UVA rays tan skin and is due to premature skin aging. UV-B rays cause sunburn and are often associated with skin cancer and eye problems such as cataracts. UV-C rays are most dangerous. There are, fortunately, blocked by ozone layer and do not get to the earth's surface.

The color vision is a very complicated psychophysical process during which human eye distinguishes different colors. From the physical point of view the color does not exist and it is only a visual perception which is conditioned by the wavelength of the light. The certain part of the spectrum reflects from different objects, then it falls on the eye where it causes the irritation of the light sensitive elements which react to color the cones. For its realization, it is necessary to have a correct and undisturbed function of the eyesight and the human eye as the receiving organ, the optical path as the transmitting system and the centers of the brain thanks to which we distinguish and thus they are the analyzer of the perception.

When driving a motor vehicle a driver has to continuously monitor not only what is happening on the road but also the data on the panel board. The tilting of his head (in average around 30 degrees) leads to reduction of the sharpness of the image of events happening on the road which is caused by the movement of the eyes. When looking at the speedometer the movement of the eyes exceeds the target by 5 degrees in average and it is immediately balanced with the subsequent movement of the eyes.

If you have uneasiness and it seems to you, that your sight worsen and feeling pain in eyes, you should visit an ophthalmologist. Today, good vision is very important and sight problems should not be ignored, but solved.

Accommodation of the eye is the ability of the human eye to see sharply all objects which are located at various distances in front of the eye depending on the changes of massiveness of the optical system of the eye. The mechanism of eye accommodation is not the same for all animals. For example fish accommodates through the change of position of the lens, some types of birds accommodate through the increase of curvature of the cornea and protraction of the human eye. As far as humans are concerned accommodation is caused by the increased curvature of anterior area of the eye lens while at the same time its thickness also changes. Accommodation is usually the same on both eyes.

More:
Eyesight and vision - About-Vision.com

This entry was posted on August 4, 2016 at 9:41 am and is filed under Eye Sight & Vision. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |