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THE BOOMER EFFECT: ACCOMMODATING BOTH AGING-RELATED
DISABILITIES AND COMPUTER-RELATED INJURIES
Jane Berliss-Vincent
Center for Accessible Technology
2547 8th St., Suite 12-A
Berkeley, CA 94710
jbvincent@cforat.org
Introduction
Aging baby boomers will represent a significant spike in national
demographics. Along with this spike in population will almost
inevitably be a spike in the overall number of people with
disabilities attributable to the natural processes of aging. For
example, there are projected to be more than 3.2 million people
with severe visual impairment (functionally defined as the
inability to read a newspaper) in 2000, and almost 6 million by
2030. For individuals with any level of vision impairment, the
estimate is 4.9 million people in 2000 and over 9 million for
2030. (Crews, 1994)
There is also a new cause of disability: prolonged and/or
improper computer use. International studies show the prevalence
of wrist/hand problems among computer users is generally 10-19%,
and may reach 40%. (Bammer, 1990) The
estimated incidence eyestrain or other visual problems
attributable to computer use is between 70 and 88% (Wolff, 1997; Salibello and
Nilsen, 1995). At least one professional reports some level
of physical discomfort among 60% of his patients that use speech
input. (McEvoy, 1999).
The “boomers” will be the first generation to risk
dealing en masse with the effects of computer use before or
simultaneously with dealing with the effects of aging. Therefore,
a need exists to look at both accommodating the inevitable
effects of age and preventing the avoidable effects of extensive
or improper computer use.
The aging-related disabilities discussed in this paper are
natural, predictable consequences of aging that affect vision,
the wrists/hands, and the larynx. This paper does not cover the
full range of normal aging-related disabilities, such as those
related to hearing, nor does it cover common but not inevitable
conditions. It also does not cover disabilities with causes
besides aging or improper computer use. Finally, it does not
cover critical factors such as computing environment (e.g.,
lighting and furniture) or healthy work practices; for details on
these areas, the reader is referred to the author's more
comprehensive work on the topic (Berliss-Vincent, 1999).
Vision
Aging-Related Disabilities
Around age 40, the lens becomes thicker and flatter and the pupil
becomes less able to change diameter, reducing the amount of
light that reaches the retina. The lens hardens, losing some of
its ability to change focus between near and distant objects
(accommodation) and requiring use of corrective lenses for
reading (presbyopia). Sensitivity to glare appears to increase
with age. Individuals may be less able to discriminate between
certain colors, and sensitivity to contrast may be reduced. There
is generally reduction in the size of the visual field. (Morgan, 1986; Werner et al.,
1990) A reduction in eye lubrication is also associated with
age, particularly for menopausal and post-menopausal women. (Roberts, 1991; Group Health
Cooperative, 1996)
Computer Use Injuries
There appears to be a strong correlation between video display
terminal (VDT) use and transient eye problems, such as pain or
discomfort, light sensitivity, insufficient or excessive
production of tears, and redness. (Bergqvist
et al., 1990; Yagimura et al, 1990).
Age also appears to play a role, with reported problems
increasing among older individuals. (Meyer et
al., 1990;Ong and Phoon, 1987)
The American Optometric Association (1997)
identifies three main causes of computer eyestrain: frequent,
long saccadic movements (the “jumps” the eye makes
when reading text), continuous accommodation changes, and
continuous changes in alignment (vergence). These movements
stress the visual system, particularly the musculature.
Computer Design Considerations
- Facilitate adjustability of monitors. An adjustability range
between 5 degrees towards the user and 20 degrees away from the
user may be necessary to avoid glare. (Miller
and Suther, 1983) Monitors that could easily be adjusted
with, for example, the push of a button could accommodate manual
disabilities and increase the likelihood that users would adjust
their monitors properly.
- Maximize the ability to adjust luminance. Akaski et al.
(1990) found that subjects in their early to mid 60s blinked less
frequently with high levels of luminance (screen brightness) than
with low levels. Because improper luminance can be a cause of
eyestrain and dry eye, luminance levels should become easier to
adjust, and there might be some information included about
suggested settings for older users.
- Balance refresh rate and resolution. A refresh rate (how
often the image on the screen is redrawn) under 60 hertz causes a
“flicker” effect which can cause moderate eye
discomforts, and may increase strain associated with large
saccadic eye movements. (Bergqvist et al.,
1995, Wilkins, 1986) A refresh rate of
85 to 90 hertz is optimal, although the refresh rate may be lower
if the luminance is adjustable. (Meyer et al.,
1987)
- Ziefle (1998) found that higher screen
resolution (number of pixels per inch on the screen) settings
optimize user performance and reduce visual fatigue. However, as
screen resolution is increased, the refresh rate will decrease.
Research may need to be done to find the best balance between
these two factors.
- Maximize number of options for adjustment of color and
contrast. Use of color may be significant, particularly when used
to assist individuals in locating information. (Grandjean, 1988) Colors that are not
affected by age-related vision changes (e.g., light oranges)
could be used for locating purposes. Contrast preferences may
also be affected by the presence of screen flicker, for which
light letters on a dark background are preferable, or glare,
where dark letters on a light background are preferable. (Spenhelink and Besnijen, 1995)
- Explore the paper metaphor. Ziefle
(1998) cites several studies to show that individuals can
read materials on paper with less visual fatigue than on a
computer screen. Paper can be used as a metaphor for screen
design by using similar fonts, high resolution, dark letters on a
light background, and anti-aliased letters (letters that include
some gray pixels). (Gould et al., 1987)
Wrists/Hands
Aging-Related Disabilities
With age, muscle strength decreases; by the time an individual
reaches 60, their strength has generally decreased 15-25% from
peak strength at age 35. The muscles in the hand may be
particularly affected. (Abrams et al.,
1995; Grandjean, 1988) Nerve
conduction velocity also tends to become slower with age. (Albert, date?)
Computer Use Injuries
Typing speed appears to play a role in occurrence of repetitive
strain injuries (RSI). Guggenbuhl and Krueger (1990)found that
more than 4 key presses per second put an extensive load on the
fingers’ flexor muscles and increased the load on forearm
muscles. Key activation pressure may also cause injury; Rempel et al. (1991) found that the force
used to activate keys was often 300% greater than necessary. In
addition,Ong and Phoon (1987) found that keystrokes per hour
decreased with age, from 14K at age 25 to 10K at age 45.
Cursor control devices (mice, trackballs, etc.) may also be a
cause of RSI. Injuries to the wrist are likely due to unnatural
positioning; injuries to the fingers are likely due to stress on
the tendons from clicking and/or dragging. (Hagberg, 1995)
Computer Design Considerations
- Design keyboards that accommodate both limited range of
motion and ergonomic hand positioning. Possible innovations could
include re-positioning keys (e.g., placing more keys within reach
of the thumb) and creating adjustable small-footprint
keyboards.
- Explore benefits of various types of keys. Rempel et al. (1999) suggest that keys that
require longer application of pressure with gradually increased
resistance are more comfortable to use than keys requiring
shorter application of pressure with a sharper increase in
resistance upon activation. This may be due to the reduction of
fingertip impact force on activation. Use of other types of keys,
such as membrane keys that activate on light contact, are also
worth exploring.
- Explore mouse design. Computer users over the age of 40 tend
to take more time moving the cursor to the target and spend
proportionately more time making fine adjustments to reach the
target than younger users. (Hsu et al., 1997;
Rivera and Thakor, 1996) This implies that
older computer users may be using the mouse for longer periods
and may run greater risks of injury or discomfort than younger
users. Design strategies to accommodate older users may involve
reducing mouse weight, reducing required amount of force,
improving mouse-finger friction, and maintaining proper mouse
tracking. (Armstrong et al., 1995) Using
keyboard commands as an alternative to the mouse may also be
useful.
Larynx
Aging-Related Disabilities
In the aging individual, the larynx tends to become less moist
and the laryngeal cartilage becomes more rigid. The vocal cords
themselves may “bow” due to atrophy of the inner
muscles and loss of the exterior pad of fat, causing the vocal
cords to close incompletely and resulting in a breathy vocal
quality. There are also significant changes related to gender:
older men’s vocal cords become thinner, resulting in
higher-pitched voices, while women’s cords become thicker
after menopause, resulting in lower pitches. The production of
speech may also be affected by other losses in functional
capability; for example, older individuals may strain their vocal
cords in an effort to compensate for reductions in lung capacity.
(Sinard and Hall, 1998; Abrams et al., 1995; Tanner,
1997)
Computer Use Injuries
There is significant anecdotal information suggesting that there
may be deleterious effects on the voice caused by improper use of
either type of speech input. (e.g., Fox, 1998)
To date, however, there appear to be only one published study
specifically on the effects of speech input on the vocal
mechanism. (Singer, 1999; Postma, 1999)
This study (Kambeyanda et al., 1996;
Kambeyanda et al., 1997) indicated
diagnoses of bowed vocal chords, vocal fatigue, chronic
hoarseness, and vocal abuse among a small sample of speech input
users, as well as anecdotal reports of problems from speech input
users.
Computer Design Considerations
- Conduct and disseminate further research on the effects of
speech input on the voice. We have learned too much from the
effects of improper VDT and keyboard/mouse use to assume that
speech input can be used blithely without uncomfortable and
potentially deleterious effects.
Conclusion
Like most computer modifications, modifications designed to meet
the needs of older computer users will likely be greeted with
acceptance and even enthusiasm by all users for the increased
level of comfort they can provide. Flexibility and ease of
modification are key to ongoing comfortable and safe computer
use.
Bibliography
Abrams, W.B., et al., eds. The Merck
Manual of Geriatrics. 2nd edition. Whitehouse Station, NJ: Merck
Research Laboratories, 1995.
Akaski et al., “Physiological
responses of elderly VDT workers.” In Berlinguet, L., &
Berthelette, D., eds., Work with Display Units 89. New York:
Elsevier Science Publishers, 1990, pp. 301-308.
Albert, B. "Carpal tunnel
syndrome." http://www.opendoor.com/albert/one/cts.html,
date?
American Optometric Association.
“The Relationship of Computer Vision Syndrome to
Musculoskeletal Disorders.”, 1997.
Armstrong, T.J., et al.
“Mouse input devices and work-related upper limb
disorders.” In Grieco, A., et al., eds. Work with Display
Units 94. New York: Elsevier Science Publishers, 1995, pp.
375-380.
Bammer, G. “Musculoskeletal
problems.” In Berlinguet, L., and Berthelette, D., eds.,
Work with Display Units 89. New York: Elsevier Science
Publishers, 1990, pp. 113-120.
Bergqvist, U., et al.
“Discomforts and disorders among office workers.” In
Berlinguet, L., and Berthelette, D., eds., Work with Display
Units 89. New York: Elsevier Science Publishers, 1990, pp.
1-11.
Bergqvist, U., et al. “Eye
discomforts during work with visual display units.” In
Grieco, A., et al., eds. Work with Display Units 94. New York:
Elsevier Science Publishers, 1995, pp. 83-88.
Berliss-Vincent,
J. “Generation I: Implications of Aging-Related and
Computer-Related Causes of Disability for Computer Interface
Design.”
Crews, J.E. “The demographic,
social and conceptual contexts of aging and vision loss.”
J. of the American Optometric Association 1994; 65:63-68.
Fox, D. “Avoiding Voice
Strain.” http://cfa-www.harvard.edu/~dcfox/dragon/voice.html;
1998.
Gould, J.D., et al. “Reading
from CRT displays can be as fast as reading from paper.”
Human Factors, 29 (5), 1987, pp. 497-517.
Grandjean, E. Fitting the
task to the man. 4th edition. Philadelphia: Taylor and Francis,
Inc., 1988.
Group Health Coop., Puget Sound.
“Dry eye.” , 1996.
Guggenbuhl, U., and Krueger, H. “Muskuloskeletal
strain.” In Berlinguet, L., and Berthelette, D., eds., Work
with Display Units 89. New York: Elsevier Science Publishers,
1990, pp. 121-128.
Hagberg, M. “The
‘mouse-arm syndrome’ – concurrence of
musculoskeletal symptoms and possible pathegenesis among VDU
operators.” In Grieco, A., et al., eds. Work with Display
Units 94. New York: Elsevier Science Publishers, 1995, pp.
381-385.
Hsu, S.H., et al. “Age-related
differences in remote pointing performance.” Proceedings of
the Human Factors and Ergonomics Society 41st annual meeting.
Santa Monica: Human Factors and Ergonomics Society, 1997, pp.
148-151.
Kambeyanda, D., et al.
“Potential problems associated with use of speech
recognition products.” Proceedings of the 1996 RESNA
Conference. Washington, DC: RESNA?, 1996, pp. 119-?
Kambeyanda, D., et al.
“Potential problems associated with use of speech
recognition products.” Assistive Technology 1997;9, pp.
95-101.
McEvoy, A. “Protect your
vocal cords.” PC World, January 1999, p. 136.
Meyer, J.-J., et al.
“Discomfort and disability glare in VDT operators.”
In Berlinguet, L., and Berthelette, D., eds., Work with Display
Units 89. New York: Elsevier Science Publishers, 1990, pp.
29-37.
Meyer, J.-J., et al. “Sensitivity to light and visual
strain in VDT operators.” In Knave, B., and Wideback, P.G.,
eds., Work with Display Units 86. New York: Elsevier Sci.
Publishers, 1987, pp. 485-489.
Miller, W., and Suther, T.W.
“Display station anthropometrics.” Hum. Factors 1983,
25 (4), pp. 401-408.
Morgan, M.W. “Changes in
visual function in the aging eye.” In Rosenbloom, A.A., and
Morgan, M.W., eds. Vision and aging: general and clinical
perspectives. New York: Prof. Press Books, 1986.
Ong, C.-N. and Phoon, W.-O.
“Influence of age on performance and health.” In
Knave, B., and Wideback, P.G., eds., Work with Display Units 86.
New York: Elsevier Sci. Publishers, 1987, pp. 211-215.
Postma, G. Personal correspondence. September 22, 1999.
Rempel, D., et al.
“Fingertip forces while using three different
keyboards.” Proceedings of the Human Factors and Ergo.
Society. Santa Monica: Human Factors and Ergo. Society, 1991, pp.
253-255.
Rempel, D., et al. “Effect
of keyboard keyswitch design on hand pain.” J. of
Occupational and Environmental Medicine, 41 (2), February 1999,
pp. 111-119.
Rivera, C.N., and Thakor, N.V.
“Effects of age and disability on tracking tasks with a
computer mouse: accuracy and linearity.” J. of
Rehabilitation Research and Development, 33 (1), 1996, pp.
6-15.
Roberts, D.K.
“Keratoconjunctivitis sicca.” J. of the American
Optometric Assn., 1991, 62, pp. 187-199.
Salibello, C. and Nilsen, E.
“Is there a typical VDT patient? A demographic
analysis.” J. of the American Optometric Association, 66
(8), August 1995, pp. 479-483.
Sinard, R.J., and Hall, D.
“The aging voice.” Geriatrics, 53 (7), July 1998, pp.
76-79.
Singer, Lois. Personal
correspondence, October 28, 1999.
Spenhelink, G.P.J., and Besnijen,
J. “Brightness: highest luminance or background
luminance?” In Grieco, A., et al., eds. Work with Display
Units 94. New York: Elsevier Sci. Pubs., 1995, pp. 311-316.
Tanner, D.C. “Voice
Disorders--An Overview.”; 1997
Werner, J.S., et al. “Light,
vision, and aging.” Optometry and Vision Science, 67 (2),
1990, pp. 214-222.
Wilkins, A. “Intermittent
illumination from visual display units and fluorescent lighting
affects movement of the eyes across text.” Human Factors,
28 (1), 1986, pp. 75-81.
Wolff, D. “Ergonomics.” ,
1997
Yagimurra, Y., et al.
“Study of the relationship between lacrimation and blink in
VDT work.” Ergonomics, 33 (6), 1990, pp. 799-809.
Ziefle, M. “Effects of
display resolution on visual performance.” Human Factors,
40 (4), December 1998.
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