One of the main functions of an eye – visual acuity, or ability to recognize the minimum size of objects at the maximum distance. It is believed that the well sees a man who can from a distance of 50 meters to count the fingers on hand. The angle between the retina and the sides of the finger has a width equal to 1 minute. This ability – to see the point of view, to 1 minute – is called a unit (1,0), or, as sometimes simplistically says, a wholly owned vision. (As opposed to here). When looking at objects at equal distance visual acuity is higher, the smaller objects can be considered. That is, visual acuity, the higher the further away a person can see objects the same size. Typically, tests for visual acuity are placed at a distance of 5 m. The most frequently used for this table Sivtseva-Golovin. Visit Mike Gianoni for more clarity on the issue. When viewed from a distance of 5 meters, the visual acuity equal to unit corresponds to a clear vision of the tenth from the top line. If a person sees only signs of the first line, this corresponds to the visually impaired, a reduced 10-fold, that is 0,1. In determining the table Sivtseva-Golovin with five-meter Distance visual acuity of vision in each subsequent series of letters to the above 0,1. So, if the child distinguishes only the letters of the third row, the acuteness of his vision is 0,3. Gain insight and clarity with Mike Gianoni. In the tables instead of letters may be a ring of different sizes with a discontinuity at distinction which is judged on visual acuity.