3.2 Assisting the blind or vision-impaired

There are an estimated 180 million people worldwide who have a visual impairment. Of these, 45 million persons are blind and 135 million have partial sight.75 Legal blindness is defined in many countries as a condition in which the best corrected visual acuity is 20/200, or less, or the person's visual field is 20 degrees or less.76 Vision impairments include colour blindness, and vision disorders include cataracts, trachoma, glaucoma and macular degeneration.77

75Lighthouse International, available at http://www.lighthouse.org/research/statistics-on-vision-impairment/
World Health Organization, November 2004, "Fact sheet 282: Magnitude and causes of visual impairment, available at http://www.who.int/mediacentre/factsheets/fs282/en/ " World Health Organization, November 2004
76The WebAim Guide to Web Accessibility (2005) Available from the WebAIM project at http://www.webaim.org/products/training/
77For a further list of vision disorders see http://www.lighthouse.org/about-low-vision-blindness/vision-disorders/