Page 467 - Biomedical Engineering and Design Handbook Volume 2, Applications

TECHNOLOGY AND DISABILITIES 445

15.3 COMPUTER ACCESS BY PERSONS WITH DISABILITIES

Computer use by persons who have disabilities has opened up new opportunities for education,
employment, and recreation. The computer offers (1) flexibility (multiple options with the same
hardware), (2) adaptability (e.g., as user’s skills change over time), (3) customization to a spe-
cific user and need (e.g., settings of scanning rate for indirect selection), and (4) specific appli-
cations and/or upgrades that can be based on software rather than hardware (e.g., specific user
profile for Internet browsing in Braille) (Cook and Polgar, 2008). Computer use is often difficult
for individuals who have motor and/or sensory impairments. Successful computer use requires
sensory and perceptual abilities for processing computer outputs, motor control for generating
input to the computer, and cognitive skills (e.g., problem solving, decision making, memory,
language) for understanding the computer functions. When a person with one or more disabili-
ties has difficulty carrying out these functions, engineers are called upon to adapt the computer
to make it accessible.

15.3.1 Adapted Computer Inputs

The most common user computer input is provided via either the keyboard or mouse. We can pro-
vide adapted computer input in many ways, depending on the needs of the consumer. Keyboard alter-
natives have been discussed earlier in this chapter. There are also software adaptations for the most
common problems experienced by people with disabilities when using a standard keyboard. These
are shown in Table 15.2. These software adaptations are included in Accessibility Options in

TABLE 15.2 Minimal Adaptations to the Standard Keyboard and Mouse *
Need addressed Software approach
Modifier key cannot be used at same StickyKeys †
time as another key
User cannot release key before it starts FilterKeys †
to repeat
†
†
User accidentally hits wrong keys SlowKeys , BounceKeys , FilterKeys †
User cannot manipulate mouse MouseKeys †
†
User wants to use augmentative SerialKeys in Windows XP or an
communication device as input alternative (like AAC Keys)
User cannot access keyboard On-screen keyboard (Windows XP and Vista), built-in ASR
(Window Vista)
* Easy Access (part of Universal Access) in Macintosh operating system, Apple Computer, Cupertino, Calif.; Accessibility
Options in Windows XP, Ease of Access in Windows Vista, Microsoft Corp., Seattle, Wash.
† Software modifications developed at the Trace Center, University of Wisconsin, Madison, Wis. These are included as before-
market modifications to the Macintosh operating system or Windows in some personal computers and are available as after-
market versions in others. The function of each program is as follows:
StickyKeys: User can press modifier key, then press second key without holding both down simultaneously.
SlowKeys: A delay can be added before the character selected by hitting a key that is entered into the computer; this means
that the user can release an incorrect key before it is entered.
BounceKeys: Prevents double characters from being entered if the user bounces on the key when pressing and releasing.
FilterKeys: The combination of SlowKeys, BounceKeys, and RepeatKeys in Microsoft Windows.
MouseKeys: Substitutes arrow keys for mouse movements.
SerialKeys: Allows any serial input to replace mouse and keyboard, this function has largely been replaced by USB standard
devices.
Source: From Cook AM and Polgar JM: Cook and Hussey’s Assistive Technologies: Principles and Practice, (3d ed.),
St. Louis, 2007, Mosby Yearbook Publishers, with permission.