What Problems Do People with Disabilities Have? and Why?
** Disability has many facets
First, it is important to understand that there are many different
types and severities of impairment which lead to disabilities. Some
types of impairment are:
Within each of these major types, there are many variations and
degrees of impairment. Each of these may present different barriers
and need to be addressed with different strategies.
- Someone with a moderate visual impairment may need some
mechanism to enlarge the image on the screen.
- Someone with a severe visual impairment or who is blind would
find screen enlargement to be of no value and would need
mechanisms to translate the contents of the screen to speech or
- An individual with a mild hearing impairment may just need a
mechanism to increase the volume.
- An individual with a severe hearing impairment or who is deaf
may need to have auditory information presented in some visual
- An individual with a mild physical impairment may just need to
have the behavior of the keyboard and mouse changed slightly in
order for them to be able to effectively use the computer.
- An individual with a more severe physical impairment may need
to have a special keyboard that can be operated by speech,
headpointing or eyegaze.
The following pages provide a brief overview of the major types of
impairments, along with a brief discussion of the implications of
these impairments on computer use.
PLEASE NOTE: It is not up to the application software
developer/ manufacturer to directly meet all of these needs.
Part III will discuss the role of application program
manufacturers versus the role of others in providing
understand the basic problems faced by people with different
types or degrees of impairment and their resulting
Visual impairment represents a continuum, from very poor vision, to people
who can see light but no shapes, to people who have no perception of light at
all. However, for general discussion it is useful to think of this
population as representing two broad groups: those with low vision and those
who are legally blind. The National Society for the Prevention of Blindness
estimates that there are 11 million people in the U.S. who have visual
impairments. This includes both people with low vision and those who are
Low vision is defined as vision that is between 20/40 and 20/200 after
correction. (20/200 means that something at 20 feet would be just as visible
as something at 200 feet would be to someone with normal 20/20 vision) There
are 9-10 million people with low vision. Some of these can read print if it
is large and held close (or viewed through a magnifier). Others can only use
their sight to detect large shapes, colors or contrasts. There are
approximately 1.2 million people with severe visual impairments who are not
A person is termed legally blind when their visual acuity (sharpness of
vision) is 20/200 or worse after correction, or when their field of vision is
less than 20 degrees. There are approximately half a million people in the
U.S. who are legally blind.
Blindness can be present at birth, acquired through illness or accident, or
associated with aging (glaucoma, cataracts, macular degeneration, optic nerve
atrophy, diabetic retinopathy). According to the American Foundation for the
Blind, almost 1 person in every 1,000 under age 45 has a visual impairment of
some type, while 1 in every 13 individuals older than 65 has a visual
impairment which cannot be corrected with glasses. With current demographic
trends toward a larger proportion of elderly, the prevalence of visual
impairments will certainly increase.
** Functional Limitations Caused by Visual Impairments
Functional limitations of people with visual impairments include increased
sensitivity to glare, viewing the world as through a yellowed lens, no
central vision, no peripheral vision, loss of visual acuity or focus, poor
night vision, reduced color distinction ability or a general hazing of all
vision. Those who are legally blind may still retain some perception of
shape and contrast or of light vs. dark (the ability to locate a light
source), or they may be totally blind (having no awareness of environmental
** Difficulties Using Computers and Software
As would be expected, people with visual impairments have the greatest
problem with information displayed on the screen. However, mandatory use of
a mouse or other pointing device requiring eye-hand coordination is also a
problem. Special programs exist to provide individuals with the ability to
magnify the screen image. There are also programs which allow the individual
to have the content of the screen read aloud. However, application programs
sometimes do things in ways that make it difficult or impossible for these
special programs to work well or at all. Individuals with low vision may
also miss messages which pop up at different points on the screen, since
their attention is usually focused on only a small area of the screen at any
** Access to Documentation
Written operating instructions and other documentation may also be
inaccessible if they are not provided in electronic or alternate form (e.g.,
audio tape or braille) and even then people may have difficulty accessing
graphic or pictorial information included in documentation. Because many
people with visual impairments still have some visual capability, many of
them can read with the assistance of magnifiers, bright lighting (for printed
text), and glare reducers. Many are helped immensely by use of larger
lettering, sans-serif typefaces, and high contrast coloring.
Key coping strategies for those who are blind or have severe visual
impairments include the use of braille, large raised lettering or raised line
drawings, braille and audio tape. Note, however, that braille is preferred
by only about 10% of people who are blind (normally those blind from early in
life). Those who use braille, however, usually have strong preferences for
it, especially for shorter documents. Raised lettering must be large and is
therefore better for providing simple labels on raised line drawings than for
Hearing impairments are among the most prevalent chronic disabilities in the
U.S. More than 15 million people have some form of hearing impairment.
Almost two million are deaf.
Hearing impairments are classified into degrees based on the average hearing
level for various frequencies (pitches) by decibels (volume) required to
hear, and also by the ability to understand speech. Loudness of normal
conversation is usually 40-60 decibels. A person is considered deaf when
sound must reach at least 90 decibels (5-10 times louder than normal speech)
to be heard, and even amplified speech cannot be understood, even with a
Hearing impairments can be found in all age groups, but loss of hearing
acuity is part of the natural aging process. Of those aged 65 to 74, 23%
have hearing impairments, while almost 40% over age 75 have hearing
impairments. The number of individuals with hearing impairments will increase
with the increasing age of the population and the increase in the severity of
Hearing impairment may be sensorineural or conductive. Sensorineural
involves damage to the nerves used in hearing (i.e., the problem is in
transfer from ear to brain). Causes include aging, exposure to noise,
trauma, infection, tumors and other disease. Conductive hearing loss is
caused by damage to the ear canal and mechanical parts of the inner ear.
Causes include birth defects, trauma, foreign bodies or tumors.
** Functional Limitations Caused by Hearing Impairments
The functional limitations faced by people with hearing impairment fall into
First, individuals may not be able to hear auditory information if it is not
presented loudly enough as compared to the background noise. The ability to
control volume or to plug headphones or other devices into a headphone jack
are the primary strategies for dealing with this problem.
Second, individuals who are deaf or who have more severe hearing impairments
will not receive any information which is presented only in auditory form.
Beeps which are accompanied by an on-screen visual indication prevent this
problem. They also avoid the problem of the sound output being too quiet,
since the auditory information is also provided visually. With newer systems
which include voice output, presentation of the text on-screen or the ability
to turn on captions may be necessary.
Third, as voice input becomes more prevalent, it too will present a problem
for many deaf individuals. While many have some residual speech, which they
work to maintain, those who are deaf from birth or a very early age often are
unable to learn to speak or have very poor speech. Thus, alternatives to
voice input will be necessary for these individuals to access products which
require voice input.
Fourth, many individuals who are deaf communicate primarily through ASL
(American Sign Language). It should be noted, however, that this is a
completely different language from English. Thus, deaf people who primarily
use ASL may understand English only as a second language (and may therefore
not be as proficient with English as native speakers).
** Access to Support Services
Because individuals who are deaf cannot hear and sometimes cannot speak, they
have difficulty using telephone support services. Special telecommunication
devices for the deaf (TDDs) have been developed, however, which allow
individuals to communicate over the phone using text and a modem. In order
for these users to access phone-in support services, software companies would
need to have TDD-equipped support personnel. Individuals who are deaf are
also be unable to take advantage of support systems that use touch-tone input
and recorded voice output.
Physical impairments vary greatly. They include paralysis (complete or
partial), severe weakness, interference with control, missing limbs, and
speech impairment. Causes include cerebral palsy, spinal cord injury,
traumatic head injury (includes stroke), injuries or diseases resulting in
amputation, or various diseases such as arthritis, ALS (Lou Gehrig's
Disease), multiple sclerosis or muscular dystrophy. Cerebral Palsy (CP). CP
is defined as damage to the motor areas of the brain prior to brain maturity
(in most cases, this occurs before, during or shortly after birth). There
are 400,000-700,000 individuals in the U.S. with CP. The most common types
are spastic, where the muscles are tense and contracted and voluntary
movement is very difficult, and athetoid, where there is constant,
uncontrolled motion. Most cases are combinations of the two types.
Spinal Cord Injury. Spinal cord injury can result in paralysis or paresis
(weakening). The extent of paralysis/paresis and the parts of the body
effected are determined by how high or low on the spine the damage occurs and
the type of damage to the cord. Quadriplegia involves all four limbs and is
caused by injury to the cervical (upper) region of the spine; paraplegia
involves only the lower extremities. There are 150,000 to 175,000 people
with spinal cord injuries in the U.S.
Head Injury and Stroke. The term "head injury" is used to describe a huge
array of injuries, including concussion, brain stem injury, closed head
injury, cerebral hemorrhage, depressed skull fracture, foreign object (e.g.,
bullet), anoxia, and post-operative infections. Like spinal cord injuries,
head injury and also stroke often results in paralysis and paresis, but there
can be a variety of other effects as well. Currently about 1,000,000
Americans (1 in 250) suffer from effects of head injuries, and over 2,000,000
people in the U.S. have suffered strokes. However, many of these do not have
permanent or severe disabilities.
Arthritis. Arthritis is defined as pain in joints, usually reducing range of
motion and causing weakness. Rheumatoid arthritis is a chronic syndrome.
Osteoarthritis is a degenerative joint disease. About 1% of the U.S.
population (or 2.4 million people) are affected by arthritis.
ALS (Lou Gehrig's Disease). ALS is a fatal degenerative disease of the
central nervous system characterized by slowly progressive paralysis of the
voluntary muscles. The major symptom is progressive muscle weakness
involving the limbs, trunk, breathing muscles, throat and tongue, leading to
partial paralysis and severe speech diffi- culties. This is not a rare
disease. About 2 out of 125,000 people will develop ALS each year. It
strikes mostly those between age 40 and 70, and men twice as often as women.
Multiple Sclerosis (MS). MS is defined as a progressive disease of the
central nervous system characterized by the destruction of the insulating
material covering nerve fibers. The problems these individuals experience
include poor muscle control, weakness and fatigue, difficulty walking,
talking, seeing, sensing or grasping objects. It is estimated that about
300,000 in the U.S. suffer from this disease.
Muscular Dystrophy (MD). MD is a hereditary, progressive condition resulting
in muscular weakness and loss of control, contractions and difficulty in
walking and breathing. About 10,000 new cases are reported per year.
** Functional Limitations Caused by Physical Impairments
Problems faced by individuals with physical impairments include poor muscle
control, weakness and fatigue, difficulty talking, seeing, sensing or
grasping (due to pain or weakness), difficulty reaching things, and
difficulty doing complex or compound manipulations (push and turn).
Individuals with spinal cord injuries may be unable to use their limbs and
may use "mouthsticks" for most manipulations.
Individuals with movement impairments may have difficulty with programs which
require a response in a specified period of time, especially if it is short.
Individuals with impaired movement or who must use a mouthstick or headstick
have difficulty in using pointing devices. Programs which require the use of
a mouse or pointing devices and have no option for keyboard control of the
program present problems. Individuals who can use only one hand or who use a
headstick or mouthstick to operate the keyboard have difficulty pressing two
keys at the same time.
This category contains a wide range of impairments including impairments of
thinking, memory, language, learning and perception. Causes include birth
defects, head injuries, stroke, diseases and aging-related conditions. Some
commonly known types and causes of cognitive/language impairment are:
Mental Retardation. A person is considered mentally retarded if they have an
IQ below 70 (average IQ is 100) and if they have difficulty functioning
independently. An estimated 1% of Americans (2.4 million) are mentally
retarded. For most, the cause is unknown, although infections, Down's
Syndrome, premature birth, birth trauma, or lack of oxygen may all cause
retardation. Those considered mildly retarded (80-85%) have an IQ between 55
and 69 and achieve 4th to 7th grade levels. They usually function well in
the community and can hold down semi-skilled and unskilled jobs.
Language and Learning Disabilities. This is a general term referring to a
wide range of disorders manifested by significant difficulties in listening,
speaking, reading, writing, reasoning, and calculating/integrating
perceptual/cognitive information. These disorders are presumed to be due to
central nervous system dysfunction. It is estimated that over 43% of
children in special education programs in the U.S. (1.9 million) have some
type of language and learning disability.
Head Injury and Stroke. This group includes individuals with closed and open
head injuries as well as those suffering strokes. These injuries usually
result in physical impairments, cognitive impairments or both. There are
approximately 400,000 to 600,000 people with head injuries and approximately
2 million people who have suffered a stroke.
Alzheimer's Disease. This is a degenerative disease that leads to
progressive intellectual decline, confusion and disorientation. 5% of
Americans over 65 have Alzheimer's; 20% of those above 80 have it.
Dementia. This is a brain disease that results in the progressive loss of
mental functions, often beginning with memory, learning, attention and
judgment deficits. The underlying cause is obstruction of blood flow to the
brain. Some kinds of dementia are curable, while others are not. 5% of the
population over 65 has severe dementia, with 10% having mild or moderate
impairment. 30% of those over 85 are affected.
** Functional Limitations Caused by Cognitive Impairments
Cognitive impairments are varied, but may be categorized as memory,
perception, problem-solving, and conceptualizing disabilities. Memory
problems include difficulty getting information from short-term storage
(20-40 seconds, 5-10 items), long term and remote memory. This includes
difficulty recognizing and retrieving information. Perception problems
include difficulty taking in, attending to, and discriminating sensory
information. Difficulties in problem solving include recognizing the
problem, identifying, choosing and implementing solutions, and evaluation of
outcome. Conceptual difficulties can include problems in sequencing,
generalizing previously learned information, categorizing, cause and effect,
abstract concepts, comprehension and skill development. Language im-
pairments can cause difficulty in comprehension and/or expression of written
and/or spoken language. Problems can occur both in the use of software and
in understanding manuals written at too high a technical/comprehension level.
Approximately 1 million U.S. workers (age 18-69) report impaired abilities to
read, reason and/or understand spoken or written information as a result of a
chronic disabling condition.
There are few assistive devices for people with cognitive impairments.
Simple cuing aids or memory aids are sometimes used. As a rule, these
individuals benefit from use of simple displays, low language loading, use of
patterns, simple, obvious sequences and cued sequences.
A number of injuries or conditions can result in seizure disorders. Seizures
can vary from momentary loss of attention to grand mal seizures which result
in the severe loss of motor control and awareness.
Seizures can be triggered in people with photosensitive epilepsy by rapidly
flashing light, particularly in the 10-25 hz range. This can be caused by
screen refresh or by rapidly flashing different images on the screen. The
brighter the flash, and the larger the portion of the screen involved, the
more significant the visual stimulation. Somewhere between 1 in 25,000 and 1
in 10,000 people in the US have seizure disorders.
It is all too common to find that whatever caused a single type of impairment
also caused others. This is particularly true where disease or trauma is
severe, or in the case of impairments caused by aging.
Diabetes, which can cause blindness, also often causes loss of sensation in
the fingers. Unfortunately, this makes braille or raised lettering
impossible to read. Cerebral palsy is accompanied by visual impairments in
40% of cases, by hearing and language disorders in 20% of cases, and by
cognitive impairments in 60% of cases. Individuals who have hearing
impairments caused by aging also often have visual impairments.