| | Refractive Errors | The cornea is a part of the eye that helps to focus light for creation an image on the retina. The way of its work can be compared with the lens of a camera that focuses light for creating an image on film. This curving and focusing of light is also wide-known as refraction. As a rule the shape of the cornea and the eye are not perfect and the reflection on the retina is sometimes blurred or wried. Such imperfections in the focusing power of the eye are called refractive errors.
Refractive errors have 3 main types:
1. Myopia (or nearsightedness) – people with such disease have more difficulties in seeing distant objects than near objects.
2. Hyperopia (or farsightedness) – people with this disease vice versa have more difficulties in seeing near objects than distant objects.
3. Astigmatism – is a distortion of the image on the retina caused by the abnormalities in the cornea or lens of the eye.
Mixture of myopia and astigmatism or hyperopia and astigmatism are possible. Contact lenses and glasses are considered to compensate for the imperfections of eyes. Refractive surgery contains surgical procedures designed at improving the focusing power of the eye. In LASIK surgery, in its turn, accurate and controlled removal of corneal tissue with a help of special laser reshapes the cornea and in such way alter its focusing power.
LASIK is considered as more complicated procedure unlike PRK. It is used for all degrees of nearsightedness. The surgeon works with a knife called a microkeratome and cut a flap of corneal tissue, thus removes necessary tissue beneath it with the laser and after that replaces the flap. While working with LASIK, the skill of the surgeon to make an incisionis more important, then in the PRK method, as here the machine does most of the work.
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