Visual Disabilities
http://www.webaim.org/articles/visual/

WebAIM
2004

Abstract:

Whenever I ask a large group of people whether or not they have a visual disability, very few of them answer that they do. Then I ask whether or not anyone uses any assistive technology to overcome their visual disability. Most people are unsure what I mean. Invariably, though, as I look out across the group, I see many of them--often a majority--using an assistive technology for their vision at that very moment.