For the purposes of this chapter, the term “blind person” means, and the term “blind” refers to, a person who is totally blind, has impaired vision of not more than 20/200 visual acuity in the better eye and for whom vision cannot be improved to better than 20/200, or whose better eye has a limitation in the field of vision so that the widest diameter of the visual field subtends an angle no greater than twenty degrees.