vision correctable to 20/20

Vi nekdo, co znamena, kdyz jako jedna podminka na prijeti do zamestnani je, “must have vision correctable to 20/20”. Intuitivne si myslim ze jsou to dioptrie do max 2, ale nevim…diky

Without wanting to be an important person, Help forum is much better place for this kind of questions.

Přesouvám do Helpfora.

Jde o to, že se zrak musí být korigovatelný do normálních mezí. To je zejména parametr pro piloty.Nejsou to dioptrie, ale vzdálenost od tabule s písmeny ve stopách. Více zde:

http://en.wikipedia.org/…isual_acuity

Konkrétní citát zde:

In the expression, 20/40 vision, the 20 is the distance in feet between the subject and the chart. The 40 means that the subject can read the chart (from 20 feet away) as well as a normal person could read the same chart from 40 feet away. This is calculated by finding the smallest optotype they can identify and calculating the distance at which it has a visual angle of 5 arcminutes.

The metric equivalent of 20/20 vision is 6/6 vision. At 20 feet or 6 metres, a human eye with nominal performance is able to separate lines that are one arc minute apart (equivalent to lines that are spaced 1.75 mm apart). A vision of 20/20 is considered nominal performance for human distance vision. A vision of 20/40 is considered half as good as nominal performance. A vision of 20/10 is considered twice as good as nominal performance.[2]

The 20/x number does not directly relate to the eyeglass prescription required to correct vision, because it does not specify the nature of the problem corrected by the lens, only the resulting performance. Instead an eye exam seeks to find the prescription that will provide the best corrected visual performance achievable. This may be greater or lesser than 6/6 for many reasons. In other words, 20/20 vision or 6/6 vision does not necessarily correspond to the best possible visual acuity a subject may achieve, but once this standard is attained the subject is considered to have achieved “normal” visual acuity.