Adaptive technologies for people with a vision impairment
Text/graphics enlargement software
Screen readers
Speech synthesisers
Electronic Braille displays
Microsoft active accessibility (MSAA)
Text/graphics enlargement software
People who have some useful vision may use this software. While some limited facilities to enlarge onscreen display are available within Windows and Macintosh systems, more powerful, purpose-built software is available. It is used in conjunction with the operating system and regular applications such as word processing, spreadsheets, e-mail and web browsers.
FEATURES
- Magnification of up to 36 times can be achieved.
- Magnification can apply to all or selected portions of the screen.
- Colours may be selected independently of the host application.
- Some screen magnifiers also include synthetic speech output.
LIMITATIONS
- The increased magnification results in a slower reading speed.
- The original layout of material is distorted, making it easy to lose one’s place.
- Software cost can be high.
EXAMPLES
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Screen readers
People with little or no useful vision can use a screen reader to access computers.
Screen readers are available for Microsoft Windows, Linux and Apple Macintosh OS X Tiger.
The screen reader is used in conjunction with the operating system and regular applications such as word processing, spreadsheets, email and web browsers. Note that for good web access, either Internet Explorer V.5 (or higher, preferably the latest-V6 at time of writing) or Mozilla Firefox V1.5 is necessary.
FEATURES
- Screen readers monitor text on the screen and send material to a speech synthesiser or electronic Braille display.
- In some cases, the screen reader 'decides' what is sent-menu items, dialog boxes, highlighted text, etc.
- The user can choose what is sent-current line, sentence, whole document, etc.
- Text attributes and other formatting characteristics can be identified by the screen reader.
- Information on web pages can be presented selectively. For example, the user may choose to be given simply a list of the links or frames contained on the page.
- Some screen readers allow the user to navigate by such web page elements as links, frames, tables, headings and paragraphs.
- Screen readers make most web pages at least reasonably accessible, and provide excellent access where designers are incorporating accessibility.
LIMITATIONS
- Generally, graphics (especially items such as drawings, photographs and maps) cannot be accessed.
- Material such as flow charts and animations cannot be accessed.
- Inappropriate use of multi-column and tabular layout can be troublesome.
EXAMPLES
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Speech synthesisers
People with little or no useful vision can use a speech synthesiser in conjunction with software such as a screen reader. People with literacy problems can also use it. Text stored on the computer is converted into synthesised (or artificial) speech. The synthesiser can be an external box, which connects to a computer port, or a dedicated card inside the computer. More recently, software synthesisers have become available which make use of sound cards incorporated into current computers to produce high quality speech.
FEATURES
- Good examples pronounce a wide range of words well.
- Speed and pitch can be selected and changed by users.
- In some examples, one of a number of voices can be chosen.
- Speech can be heard through a speaker or earphones, depending on personal preference and situation.
LIMITATIONS
- The document layout is not immediately apparent.
- Compromise, between presentation of too much information (level of punctuation, etc) and not enough, is necessary (controlled through screen reader or other driver software).
- Some familiarisation is necessary to become comfortable with synthetic speech.
EXAMPLES
- Dectalk Access 32 utilises the computer's sound card. Nine voices are available, including adult male and female and children. For details, see http://www.gwmicro.com.
- ETI-Eloquence utilises the computer's sound card. It is supplied with both JAWS and Window-Eyes screen readers. See http://www.nuance.com/realspeak/assistive/#eti for details.
- Keynote external synthesisers are incorporated into specialised personal data assistants from Pulse Data International-see http://www.pulsedata.com for manufacturer and local supplier details.
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Electronic Braille displays
People with little or no useful vision can use an electronic Braille display. One Braille cell can have up to eight dots in a 2 x 4 matrix. In an electronic display, the dots are formed by plastic pins which are raised and lowered electronically. The display connects to the computer via one of its ports. Information is sent to it by a screen reader.
FEATURES
- Due to high cost and bulk, the number of cells is limited. Examples range from 18 to 80 cells.
- A Braille display can provide more immediate information about screen layout than a speech synthesiser.
- The user is able to select which part of the screen to display at any time.
LIMITATIONS
- Cost is high.
- Many moving parts can result in relatively frequent maintenance.
EXAMPLES
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Microsoft active accessibility (MSAA)
This is coding developed by Microsoft and built into some of its own products as well as some from other software producers. It is very effective, for example, in Internet Explorer V.5 and above. It allows developers of adaptive technology, such as screen readers, to access underlying information and present it to the user in more meaningful ways. For example, MSAA makes it possible for a screen reader to present information effectively from a web page that would otherwise, at best, be very confusing to people with vision loss. Note that although MSAA can interpret poorly-designed pages with reasonable clarity via a screen reader, web developers should not use this as a substitute for good design. For more information, see http://www.msdn.microsoft.com/library/default.asp?
url=/library/en-us/dnanchor/html/accessibility.asp or go to the Microsoft website and search.
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