People with visual impairment represent about 1,5% of the whole population. They can be devided into the four groups, within which there is a wide individual variety.
We deal with:
a) blind people – people with the complete loss of vision perception and also people who are able to perceive only light, but they not able to locate its source.
b) people with residual sight – individuals who have preserved remnants of vision so that they can recognize the light, contours and shapes of objects, but are not able to use their best corrected sight as the dominant and the only sensor for work, stereopsis and retrieval of information.
c) people with low vision – people who in spite of the best possible correction have problems to perform any work for that sight is essential. These people have seriously damaged sight, but have its considerable residual vision that can be effectively used.
d) people with binocular vision disorders – individuals with disorders of functional balance and physiological eyes alignment cooperation. It is a disorder of binocular visual skills and causes problems in stereopsis.