By Mike Paciello
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Print-impaired persons include the blind and low vision users. However, the term is not limited to individuals who experience sensory loss in their eyes. Print-impaired people also include those who have limited or no use of their hands or fingers in order to turn pages of a book or to access a keyboard or mouse interface for electronic documents. People with cognitive disabilities (for example, dyslexia) are sometimes included within the print-impaired category.
It’s important for the sake of information and client design that you keep in mind the broader category of the print-impaired. By doing so, you’re sure to design user interfaces and information that is accessible to the blind and visually impaired.
Blind users generally will have either a synthetic speech synthesizer or refreshable Braille display attached to their PC. The speech synthesizer vocalizes the onscreen data. Refreshable Braille displays convert ASCII character streams to Braille and then output that data to a Braille display. (If you’ve never seen a refreshable Braille display, rent the movie “Sneakers”. The movie character “Whistler” is blind. He uses an ALVA refreshable Braille display to read the imbedded code on a computer microchip.)
The key to reading a web document or displayed server messages is that the output stream is ASCII text. Since many blind users rely on character-cell browsers (LYNX, W3, CERN Line Mode Browser) that read the ASCII in conjunction with their synthesizers and Braille displays, it is critical that imbedded images also contain meaningful text descriptions. This is accomplished by using the ALT attribute to the <IMG> in HTML.
If you cannot use the ALT attribute (probably for aesthetic reasons), try to include a description of the image, picture or graphical element somewhere physically close to the image as possible. This is even more important when the image intent is to convey a concept. Be sure to use text to convey conceptual images.
Never use bitmap images of text. They are impossible for the blind to read. Low vision users can enlarge them, but persons who are legally or totally without any sight, can never read text images.
Navigation is a challenge for blind and visually impaired users. Wherever possible, try to minimize the number of multiple hypertext links that appear in a single line of text.
Navigation is also difficult in web pages that feature multi-column displays. These are a nightmare for the blind. In addition to speech synthesizers, blind users require application software called “screen access” or “screen reader” software. Most of these applications (including those for GUI interfaces) are only capable of reading one line of text at a time. Thus, when the browser displays a multi-column document, the screen reader reads each line, jumping from column to column until it reaches the end of the line. This makes it very difficult for the user to follow, since there is no logical construct for the screen reader to follow. If you are a publisher of on-line journals, newspapers, or magazines, consider providing an alternative view of your text that is not multi-column in format and that can be downloaded.
Client (particularly browser) developers should look at opportunities to include hooks for screen readers and screen magnifiers. Additionally, in every case, include keyboard equivalents for mouse commands.
Lastly, the richness of the description of the document structure is the greatest friend of the blind user, particularly those who use Braille displays or print documents that must be translated to Braille. As a result, HTML is ideal because it provides knowledge about a document’s construct that is important to the Braille translation software. Titles, paragraphs, lists, tables, etc..etc.. all contain their own formatting constructs. Braille translation software identifies the entity, associates that with a format, and then does the proper translation for the blind user.
Documents that contain no tangible entity or formatting information are useless to blind users. Recently, this issue was raised to Adobe concerning their Portable Document Format (PDF), which is becoming increasingly popular on the Web because of it’s appealing visual appearance through a browser. This is ideal for a sighted user, but the source document provides no internal element descriptors that can be easily accessed and subsequently translated for the blind user. The good news is that Adobe is aware of the problem and has recently responded with an accessibility plan to deal with the inaccessibility of PDF.
