Description of The Unseen Minority: A Social History of Blindness in the United States: 5. The Facts Of Blindness
There is no single definition of blindness. Total blindness, legal blindness (determining entitlement to benefits and protections), and functional blindness (involving vision loss that leaves one "partially sighted" or visually impaired) are the three terms most widely used, but definitions vary according to state laws. An early AFB focus was standardizing vision testing. Although medical advances have eliminated many causes of vision loss, increasing longevity has increased the numbers of older Americans who are blind or visually impaired.