Understanding the visually impaired ...

What do you mean by visual impairment? Whenever I ask a large group of people whether or not they have a visual disability, very few say yes. I ask them if one of them uses assistive technology to overcome his visual disability. Most people are not sure to understand what it is. Invariably, however, when I'm with a group of people, I see many of them, often a majority, who use assistive technology for their vision.

"How many of you have perfect vision? "I ask. At this point, at least some people are beginning to understand the meaning of my questions. A voice in the band launches: "I wear glasses." "Yes," I reply. "You wear glasses and goggles are ...? ". "An assistive technology! "Said someone in the group, and that's exactly what the glasses.

We are all so used to seeing people wear glasses or contact lenses that we do not think that poor vision is a handicap. Scientists and inventors have developed corrective lenses to compensate for the distortions of our eyes, giving us the opportunity to see with perfect vision, although somewhat artificial. Many of us have a natural vision imperfect and we would have a disability without our glasses. Poor vision is so common and it's so easy to correct with glasses that we forget how our lives would be without this incredible device.

Some have a visual impairment that is not so easy to fix, nor easily forgettable. Some of us have no vision at all. The total lack of vision is the extreme level of the state of blindness. In fact, most people who are recognized as blind do have some vision. Blindness is usually defined as a state in which the best corrected visual acuity of 1/10 or less, or a state in which the visual field of the person is 20 degrees or less. Despite the lack of vision, people who are blind are provided with an extraordinary range of assistive technologies that compensate their lack of vision. In this paper we will examine more closely some of these technologies.

Another category of visual impairment, low vision, is a situation common in the elderly, but young people may also have a handicap, or because of a genetic inheritance, traumatic injuries, or diseases.

The last major category of visual impairment is color blindness but it is certainly a misnomer to consider it as a handicap, because the situations in which color-blindness is a handicap are rare. However, it is useful to be aware of the existence of color blindness when designing web content, as we will soon "see".