Page 468 - Biomedical Engineering and Design Handbook Volume 2, Applications

446 REHABILITATION ENGINEERING AND PROSTHETICS DESIGN

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Windows XP , Easy Access in Windows Vista , and Universal Access in Macintosh operating sys-
TM
tems. They are accessed and adjusted for an individual user through the control panel. Universal
Access for the Macintosh includes Easy Access and Zoom. Easy access features are shown in
Table 15.2. Zoom is described later in this chapter.
For persons who have cognitive difficulties we can increase access by using concept keyboards.
These keyboards replace the letters and numbers of the keyboard with pictures, symbols, or words
that represent the concepts required by the software. For example, a program designed to teach mon-
etary concepts might use a concept keyboard in which each key is a coin, rather than a number or
letter. The user can push on the coin and have that amount entered into the program. Such keyboards
have been used in point-of-sale applications to allow individuals who have intellectual disabilities to
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work as cashiers. The Intellikeys keyboard is often used as a concept keyboard.
Alternatives to the use of a mouse for computer input that are often used by persons with
disabilities include trackballs, a head-controlled mouse, a continuous joystick, eye pointing, and the
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use of the arrow keys on the numeric keypad (called MouseKeys; see Table 15.2). Head control for
mouse emulation employs an infrared system, which detects a reflected beam to measure head posi-
tion relative to a fixed reference point for the cursor (the center of the screen). As the user moves her
head away from this point in any direction, the cursor is moved on the screen. Commercial systems ¶
use a wireless approach in which a reflective dot is placed on the user’s forehead and serves as the
reflective target. This allows the user to move around more freely. These head-controlled systems are
intended for individuals who have limited arm and hand control and who can accurately control head
movement. For example, persons with high-level spinal cord injuries who cannot use any limb move-
ment often find these head pointers to be rapid and easy to use. On the other hand, individuals who
have random head movement (e.g., due to cerebral palsy) or who do not have trunk alignment with
the vertical axis of the video screen because of poor sitting posture often have significantly more
trouble using this type of input device.
In some severe physical disabilities, the user may only be able to move his eyes. In this case, we
can use a system that detects the user’s eye movements to control mouse pointing. Two basic
approaches are used in the design of eye-controlled systems. One of these uses an infrared video
camera mounted below the computer monitor. An infrared beam is aimed at the eye and reflected
back into the camera. As the user directs his eye gaze at different points of the computer monitor
screen, signal-processing software is used to analyze the camera images and determine where and
for how long the person is looking on the screen. The user makes a selection by looking at it for a
specified period of time, which can be adjusted according to the user’s needs. The EyeGaze System,
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Quick Glance, ERICA , and Tobii are examples of this type. The design principles and approach
to the ERICA system are described by Lankford (2000). The second approach uses a head-mounted
viewer attached to one side of the frame of a standard pair of glasses in front of the eye. Eye move-
ments are tracked and converted into keyboard input by a separate control unit. One example of this
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type of system is VisionKey. An eye-controlled system is beneficial for individuals who have little
or no movement in their limbs and may also have limited speech; for example, someone who has had
a brain stem stroke, has amyotrophic lateral sclerosis (ALS), or high-level quadriplegia.
In each of these alternative pointing devices, input to the pointing device moves a pointer on the
screen. One approach uses an onscreen keyboard that displays all of the keys on a standard keyboard.
Once the pointer is moved to the desired item, the user can make a selection by either pausing for a
preset time (called acceptance time selection) or pressing a switch (called manual selection). There
is an on-screen keyboard utility in Windows TM with basic functionality. Two modes of entry are

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Microsoft, Seattle, Wash.
†
Apple Computers, Cupertino, Calif.
‡
Intellitools, Richmond, Calif., www.intellitools.com.
§
Included with Windows and Macintosh operating systems.
¶
HeadMouse, Origin Instruments, http://www.orin.com/; Tracker, Madentec Limited, http://www.madentec.com.
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Eye Response Technologies, Charlottesville, Va. www.eyeresponse.com.
‡‡
TobiiTechnology, San Francisco, Calif., www.tobii.com.
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H.K. EyeCan Ltd., Ottawa, Canada, www.eyecan.ca.