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Understanding
the Population
q People
who could benefit from more universal designs include many both with and without
disabilities.
q In
some cases, people may experience difficulty in using products as a result of the
environment or an unusual circumstance.
Beneficiaries
of universal design include:
q People
in a noisy shopping mall who cannot hear a kiosk
q People
who are driving their car who must operate their radio or phone without looking at it
q People
who left their glasses in their room
q People
who are getting older
q People
with disabilities
q Almost
anyone
To
design for the general population
q It
is important to understand the diversity, problems, tools, and abilities of its members.
Categories
of Disabilities
q Visual
Impairments
q Hearing
Impairments
q Physical
Impairments
q Cognitive/Language
Impairments
Visual
Impairments
q There
are an estimated 8.6 million people with visual impairments (3.4% of the U.S. population).
In the elderly population the percentage of persons with visual impairments is very high.
q legally
blind
q Low
vision
Legally
Blind
q Visual
acuity (sharpness of vision) is 20/200 or worse after correction
q Field
of vision is less than 20 degrees
q There
are approximately 580,000 people in the U.S. who are legally blind.
Low
vision
q includes
(after correction) problems such as
o dimness of vision
o haziness
o film over the eye
o foggy vision
o extreme near- or farsightedness
o distortion of vision
o spots before the eyes
Hearing
Impairments
q One
of the most prevalent chronic disabilities in the U.S.
q Approximately
22 million people in the U.S. (8.2%) have hearing impairments.
q Of
those, 2.4 million have severe to profound impairments.
Deafness
q An
extreme inability to discriminate conversational speech through the ear.
q Deaf
people are those who cannot use their hearing for communication.
q Usually,
a person is considered deaf when sound must reach at least 90 decibels (5 to 10 times
louder than normal speech) to be heard, and even amplified speech cannot be understood.
Hard
of Hearing
q People with a lesser degree of
hearing impairment
q Loss of hearing acuity is part of
the natural aging process.
q 23% of those aged 65 to 74 have
hearing impairments and almost 40% over age 75 have hearing impairments.
q The number of individuals with
hearing impairments will increase with the increasing age of the population and the
increase in the severity of noise exposure.
Two
Types of Hearing Impairment
q Sensorineural hearing
loss
o involves damage to the auditory
pathways within the central nervous system, beginning with the cochlea and auditory nerve,
and including the brain stem and cerebral cortex.
q Conductive hearing loss
o Damage to the outer or middle
ear which interferes with sound waves reaching the cochlea. Causes include heredity,
infections, tumors, accidents and aging (presbycusis, or “old hearing”).
Physical
Impairments
Problems
faced by individuals with physical impairments include:
q poor
muscle control
q weakness
and fatigue
q difficulty
walking, talking, seeing, speaking, sensing or grasping (due to pain or weakness)
q difficulty
reaching things
q difficulty
doing complex or compound manipulations (push and turn).
q inablity
to use limbs
q Twisting
motions may be difficult or impossible for people with many types of physical disabilities
(including cerebral palsy, spinal cord injury, arthritis, multiple sclerosis, muscular
dystrophy, etc.).
Assistive
Devices
q Some
people must rely on assistive devices which take advantage of their specific abilities
q Commonly
used assistive devices include:
o mobility
aids (e.g., crutches, wheelchairs)
o manipulation
aids (e.g., prosthetics, orthotics, reachers)
o communication
aids (e.g., single switch-based artificial voice)
o Computer/device
interface aids (e.g., eyegaze-operated keyboard) .
Types
of Physical Impairments
q Neuromuscular
impairments
q paralysis
q weakness
q interference
with control, via spasticity
q Skeletal
impairments
q joint movement limitations
(either mechanical or due to pain)
q small limbs
q missing limbs
q abnormal trunk size
Causes
of Physical Impairments
q Arthritis
q Cerebral
Palsy (CP)
q Spinal
Cord Injury
q Head
Injury (cerebral trauma).
q Stroke
(cerebral vascular accident; CVA).
q Loss
of Limbs or Digits (Amputation or Congenital)
q Parkinson’s
Disease
q Multiple
Sclerosis (MS)
q ALS
(Lou Gehrig’s Disease)
q Muscular
Dystrophy (MD)
Cognitive/Language
Impairments
q There
are very few assistive devices for people with cognitive impairments.
q Simple
cueing aids or memory aids are sometimes used.
q As a
rule, these individuals benefit from use of simple displays, low language loading, use of
patterns, simple, obvious sequences and cued sequences.
Types
of Cognitive/Language Impairments
q Mental
Retardation.
o A
person is considered mentally retarded if they have an IQ below 70 and if they have
difficulty functioning independently.
o About
3% of Americans are mentally retarded.
o Causes
include: infections, Down Syndrome, premature birth, birth trauma, or lack of oxygen may
all cause retardation.
q Language
and Learning Disabilities
o Aphasia,
an impairment in the ability to interpret or formulate language symbols as a result of
brain damage.
o Specific
learning disabilities are chronic conditions of presumed neurological origin which
selectively interfere with the development, integration, and/or demonstration of verbal
and/or non-verbal abilities.
o Many
people with learning disabilities are highly intelligent aside from their specific
learning disability. 1-8% of school-aged children and youth have specific learning
disabilities.
q Age-Related
Disease
o Alzheimer’s
disease is a degenerative disease that leads to progressive intellectual decline,
confusion and disorientation.
o Dementia
is a brain disease that results in the progressive loss of mental functions, often
beginning with memory, learning, attention and judgment deficits.
o The
underlying cause is obstruction of blood flow to the brain. Some kinds of dementia are
curable, while others are not.
Seizure
Disorders
q Epilepsy
is a chronic neurological disorder.
o It is reported that approximately 1 person in 15
has a seizure of some sort during his life, and between .5% and 1.5% of the general
population have chronic, recurring seizures.
o Seizures
can vary from momentary loss of attention to grand mal seizures which result in the severe
loss of motor control and awareness.
Multiple
Impairments
q It
is common to find that whatever caused a single type of impairment also caused others.
q Deaf-blindness
is one commonly identified combination.
q People with developmental disabilities may have a
combination of mental and physical impairments that result in substantial functional
limitations in three or more areas of major life activity.
q Diabetes,
which can cause blindness, also often causes loss of sensation in the fingers. (Impossible
to read Braille)
q Cerebral
palsy is often accompanied by visual impairments, by hearing and language disorders, or by
cognitive impairments.
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If you have questions or comments about any of the material contained in this web, please e-mail Janet Schrock at janets@sfsu.edu. This page was last updated Thursday, January 24, 2002. |
