Visual Impairment
Visual impairments include individuals with low or no vision as well as those with color-blindness.
Most people who are "legally blind" have some vision. If a person's vision acuity can only be corrected to 20/200 or less or he the field of vision is 20 degrees or less, the definition of "legally blind" is met.
Statistics
More than nineteen million people over the age of 18 reportedly have vision trouble based on 2004 survey data from the National Center for Health Statistics (Lethbridge-Cejku, Rose & Vickerie, 2006). Slatin and Rush (2003) point out that due to such conditions as macular degeneration, glaucoma, and diabetic retinopathy, the incidence of low vision among those over 50 is substantially higher than in the general population.
Accessibility and Visual Impairments
"People with low or limited vision tend to benefit from larger, simpler, open fonts..." and the use of contrasting colors. Individuals with low vision may use large fonts or use screen magnification software to make Web information easier to see and read. However, not all users know about these options to customize their software (Slatin & Rush, 2003, p. 500).
For people who are blind they basically "do not use their eyes to access the web because whatever vision they have is not useful enough for this kind of task." Navigating with a mouse is difficult because they do not know where it is on the screen. The monitor is obviously not useful because they cannot see the information presented on it. (WebAim Visual Disabilities ). In many cases, users will rely on screen reading software and keyboard navigation.
People with color blindness may experience difficulties on the Web when color alone is used to convey information. For example, if a form asks the user to complete the items in red, a person with some forms of color-blindness may have difficulty identifying them.
Resources
For more information on visual disabilities:
- Lethbridge-Cejku, M., Rose, D. & Vickerie, J. (2006). Summary Health Statistics for U.S. Adults: National Health Interview Survey, 2004. National Center for Health Statistics. Vital and Health Statistics 10 (228). Available at http://www.cdc.gov/nchs/data/series/sr_10/sr10_228.pdf
- Slatin, J. M. & Rush, S. (2003). Maximum Accessibility: Making Your Web Site More Usable for Everyone. Boston, MA: Addison-Wesley.
- WebAim Visual Disabilities. Available at http://www.webaim.org/articles/visual/
