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Disabilities & Medical Conditions That Can Affect Web Accessibility

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How do different disabilities and medical conditions affect access to the Web?

The range of disabilities which can be impacted by Website design is tremendous. While the most common category is blindness or low-vision, there are a wide range of potential issues for persons with sensory, physical or cognitive disabilities. Medical conditions that may not constitute a disability may also affect web accessibility, including injury-related and aging-related conditions, which may be temporary or chronic.

Blindness

To access the Web, many individuals who are blind rely on screen readers -- software that reads text on the screen and outputs this information to a speech synthesizer or refreshable Braille display. They may use rapid navigation strategies such as tabbing through the headings or links on Web pages rather than reading every word on the page in sequence.

Examples of barriers that people with blindness may encounter on the Web include:

  • images that do not have alternative text
  • complex images (e.g., graphs or charts) that are not adequately described
  • video that is not described in text or audio
  • tables that do not make sense when read serially (in a cell-by-cell or "linearized" mode)
  • forms that cannot be tabbed through in a logical sequence or that are poorly labeled
  • browsers and authoring tools that lack keyboard support for all commands
  • color that is used as a unique marker to emphasize text on a Web site (should be offset with other or additional demarcation like symbols (e.g., “items in green below and also denoted with asterisks (*) are required).
  • non-standard document formats that may be difficult for their screen reader to interpret

Partial or Low Vision

Particularly with the growing population of individuals over 50, issues with fading eyesight are becoming more and more important. To use the Web, some people with low vision use extra-large monitors, and increase the size of system fonts and images. Others use screen magnifiers or screen enhancement software.

Barriers that people with low vision may encounter on the Web include:

  • Web pages with absolute font sizes that do not change (enlarge or reduce) easily
  • Web pages that, because of inconsistent layout, are difficult to navigate when enlarged, due to loss of surrounding context
  • Web pages, or images on Web pages, that have poor contrast, and whose contrast cannot be easily changed through user override of author style sheets
  • text presented as images, which prevents wrapping to the next line when enlarged

Color Blindness

Color blindness is a lack of sensitivity to certain colors. Common forms of color blindness include difficulty distinguishing between red and green, or between yellow and blue. To use the Web, some people with color blindness use their own style sheets to override the font and background color choices of the author.

Barriers that people with color blindness may encounter on the Web include:

  • color that is used as a unique marker to emphasize text on a Web site (should be offset with other or additional demarcation like symbols (e.g., “items in green below and also denoted with asterisks (*) are required”).
  • text that inadequately contrasts with background color or patterns
  • browsers that do not support user override of authors' style sheets

Deaf/Hard of Hearing

To use the Web, many people who are deaf rely on captions for audio content. They may need to turn on the captions on an audio file as they browse a page; concentrate harder to read what is on a page; or rely on supplemental images to highlight context.

Barriers that people who are deaf may encounter on the Web include:

  • lack of captions or transcripts of audio on the Web, including webcasts

Mobility Disabilities

To use the Web, people with mobility disabilities affecting the hands or arms may use a specialized mouse; a keyboard with a layout of keys that matches their range of hand motion; a pointing device such as a head-mouse, head-pointer or mouth-stick; voice-recognition software; or other assistive technologies to access and interact with the information on Websites.

Barriers that people with motor disabilities affecting the hands or arms may encounter include:

  • time-limited response options on Web pages
  • browsers and authoring tools that do not support keyboard alternatives for mouse commands
  • forms that cannot be tabbed through in a logical order

Learning and Cognitive Disabilities

Individuals with learning and cognitive disabilities may have difficulty processing language or numbers, may be easily distracted, or may be unable to remember or focus on large amounts of information. They may need to turn off animations on a site in order to be able to focus on the site's content.

Barriers that people with learning disabilities may encounter on the Web can include:

  • distracting visual or audio elements that cannot easily be turned off
  • lack of clear and consistent organization of Websites
  • time-limited response options on Web pages

Seizure Disorders

Some individuals with seizure disorders may need to turn off animations, blinking text, or certain frequencies of audio. Avoidance of these visual or audio frequencies in Web sites helps prevent triggering of seizures.

Barriers can include:

  • use of visual or audio frequencies that can trigger seizures (e.g., rapidly blinking text)