legal blindness

In North America, the definition of legal blindness is vision that is 20/200 or less in the best seeing eye, despite using the best correction possible (i.e., up-to-date glasses). A 20/200 vision measurement on the Snellen chart means that if a “legally blind person” stood 20 feet away from a vision chart, they could read only as good as a “normal person” standing 200 feet away.  Another definition of legal blindness is used for people with severely constricted peripheral vision (typically 20 degrees or less).  These people may have good central vision on an eye chart, but their peripheral vision is so constricted that its like they are looking through a “soda straw.”  This amount of vision is unsafe for driving (or duck hunting) so it is also called “legal blindness.”