well, there is a big difference between blindness and legal blindness. as we know that the blindness can be the loss of vision, and when you suffer blindness, you will not see things. on the other hand, legal blindness is a measurement of best corrected vision. generally speaking, legal blindness means a person has a vision that is 20/200 in a person's best eye with correction. and people who are legally blindness, will have some vision, but their field of vision may be very narrow or blurry. Or they may have blind spots that glasses cannot correct.
When you talk about the legally blindness, many people may confuse about its definition. Actually the real definition of "legal blindness" is that your vision field may be as most as 20 degrees. That is to say, your best level of vision that you can achieve or the best vision you can be corrected to is limited to 20 degrees even when you wear the glasses. Many people feel that they are legally blind. The reason why they feel this can't leave with the fact that they cannot see a foot in front of their face after they remove their glasses or contact lenses which are the vision help for them. However, when they put on their vision correction like eyeglasses or contact lenses, they can only see 20/20. However, the blindness means that you could see anything even if you wear the eyeglasses or contact lenses. There exists the big difference between the blindness and legally blindness.