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OCR for page 10
Chapter 2
THE DEMOGRAPHY OF BLIND AND VISUALLY IMPAIRED PEDESTRIANS
To meet the needs of visually impaired and blind people by building
more effective mobility aids, it is important to get a better sense of
the size and characteristics of the population to be served. Such
information would be helpful not only for service delivery but also for
the design and development of travel aids that more closely match the
population needs and the patterns of use and nonuse among these indi-
viduals. This chapter reviews the definitions of visual impairment
that are used for purposes of demographic analysis, reports findings
from available statistics about the number and characteristics of the
visually impaired population, and describes what is known about the
patterns of use of travel aids today. The chapter concludes with
recommendations for further work to improve our understanding of
demographic characteristics relevant to the mobility needs of visually
impaired and blind people.
SOME DEFINITIONS
In disability-related research and policy generally, some common
definitions have been developed to describe all types of impairment.
Athough terminology may vary, agreement has emerged around a set of
four concepts: pathology, impairment, disability, and handicap.
Briefly defined, pathology refers to a medically determined disease
or disorder (including trauma, structural abnormality, etch. Impair-
ment refers to lasting consequences of pathology, affecting parts of
the organism. Disability refers to limitations in carrying out tasks.
At this level of analysis, the individual and inevitably such factors
as motivation, training, and the resources {aids) available to help
accomplish tasks are involved.
Handicap refers to limitations in performing social roles (socially
structured sets of tasks). At this level, the characteristics of the
The studies that are the basis for this consensus include reports by
the Social Security Administration, the World Health Organization, and
the Office of Technology Assessment.
10
OCR for page 11
11
social environment, including socioeconomic resources, discrimination,
and characteristics of the individual, are involved.
Whatever criteria are used to identify the population of visually
impaired people in the United States, there are several ways to classify
subgroups of that population in relation to their probable use or nonuse
of mobility aids. The size and demographic characteristics of that
population will presumably be different depending on which of the con-
cepts is under study. There are also likely to be varying degrees of
overlap among the groups defined in this way. Our focus in this report
is on disability--i.e., the limitations of visually impaired people in
carrying out the tasks of mobility. Demographic information about the
visually impaired population in terms of pathology, impairment, and
handicap is important mainly in terms of its relevance to mobility
tasks.
Unfortunately, available statistics on the blind population are
grossly inadequate. We are forced to make estimates that may be out of
date or unrepresentative as well as not focused on the most pertinent
determinants of disability. Psychosocial factors, such as access to
support groups and rehabilitation services and income level, are
important predictors of disability for which there are few available
data.
The measure that is most readily available to draw a demographic
profile, legal blindness, suffers in that it does not address many
relevant factors that contribute to disability. Legal blindness is
defined in terms of two aspects of visual impairment, acuity and field
size (i.e., acuity of 20/200 or worse in the better eye with correction
or a visual field of 20 degrees diameter or less). It does not take
into account other visual factors, such as sensitivity to glare or light
and dark adaptation, that also affect mobility and other visual tasks.
Specific types or degrees of impairment reveal very little about
disability for any individual person. Very often two people with
identical impairments have markedly different disabilities. The field
of nonmedical rehabilitation, in fact, aims to reduce the disabilities
associated with given impairment and justify the need for individual
rehabilitation plans. Although the estimates have many limitations, we
use statistics on the prevalence, incidence, and demographic charac-
teristics of legal blindness in the United States in the next section
to describe the legally blind population.
DEMOGRAPH I C CHARACTER I S T I C S
It is possible to estimate the number of legally blind people--the
prevalence of blindness--in the United States today using the Bureau of
the Census projections of the population and the estimated prevalence
rates. The prevalence rates published in Vision Problems in the United
States (National Society to Prevent Blindness, 1980) and the projected
population for the years 1985 and 2000 are presented in Table 1. These
prevalence rates are generally believed to be underestimates of the true
rates and unrepresentative, since they are based on limited sampling
plans or registries that are out of date. In addition, survey defini-
OCR for page 12
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tions may exclude some people with low vision (i.e., having a visual
impairment that affects mobility but who are not legally blind), thus
contributing to an underestimation of the population of interest.
These sources remain, however, the best estimates available today.
For large groups of people who share the same category of impair-
ment, it is possible to draw some inferences about disability and the
presence of mobility problems in a probabilistic sense, even though the
prediction will not be valid for all individuals in the group. There-
fore it is important to examine the characteristics of the legally
blind population that might be useful in making inferences about
disability: age, age at onset, degree of impairment, other impairments,
and social factors.
Age
The number of cases of blindness for different age categories can
be calculated by multiplying the prevalence rate times the population
count for each age category. That calculation or estimate is shown for
the years 1985 and 2000 in Table 1.
The prevalence of blindness in the population is greatest in the
older age categories. This is in part due to the simple accumulation
of incidence with age, but this alone cannot explain the large increase
in prevalence in the oldest age categories. Figure 1 shows the 1985
estimates plotted as percentages by age groups. For example, the age
group 20-44 is almost 40 percent of the population, yet it constitutes
only 17.5 percent of the blind population. The age group 75-84 con-
stitutes approximately 4 percent of the population in the United States
and 24 percent of the blind population.
More than half the blind people in the United States today are over
the age of 64. This can be seen graphically by plotting the ratio of
the percentage of blind people in each age group to the percentage of
people in the U.S. population in the same age group (Figure 2~. People
under the age of 45 are underrepresented in the blind population,
whereas people in the 85 and older group are overrepresented in the
blind population by better than a factor of 12.
The U.S. population is aging. The median age increases each year--
or, put differently, the relative proportion of people in the older age
groups is on the rise. By the year 2000, it is predicted that the U.S.
population will increase by 12 percent, yet the blind population will
increase by 29 percent. This prediction assumes constant rates of
prevalence; thus, all the disproportionate increase is due to the aging
phenomenon in the U.S. population. The assumption of constant rates
could lead to inaccurate estimates if, for example, there occur
improvements in eye care and the prevention and treatment of eye
problems or, conversely, greater incidence of impairment.
Although over half of all blind people are over the age of 64,
there remains a large and significant group of people who are blind
before the age of 20, approximately 7 percent, and an even larger group
who are blind before the age of 45, approximately 24 percent. For
OCR for page 14
14
50
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APopulabon (19~)
-
.,
1 r' , , , ,
egal Blindness (1985)
_ ~
0~4 5-19 20~44 45~64 65-74 75-84 85+
AGE CATEGORIES
FIGURE 1 Distribution of legal blindness in the general population by
age group, 1985e
12
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AGE CATEGORIES
FIGURE 2 Ratio of percentage of blind people to the percentage of
people in U.S. population by age group, 1985.
OCR for page 15
15
these individuals, blindness is a condition of life during the period
in which they are likely to be most economically productive.
Onset of Visual Problems
The age at which impairment occurs is an important factor. The
usual classifications distinguish between those who are blind from
birth or at less than five years of age--congenital blindness--and
those who have lost sight at older ages--adventitious blindness. The
key to this distinction is the role that early visual experience plays
in establishing spatial concepts and visual memories, which later aid
functioning when visual impairments reduce or eliminate the ability to
see.
Table 2 presents the incidence of legal blindness--i.e., new cases
of legal blindness by age and etiology published in Vision Problems in
the United States as estimated for the year 1978. The rate of incidence
in the population is roughly stable at O.01 percent until the age of
45; it then increases for each age group, achieving its highest rate,
0.27 percent, for the 85 and older age group. The distribution of
etiologies within age groups changes with age. For example, the most
frequent causes of blindness under the age of 20 are infectious
diseases, injuries, and prenatal influences. After the age of 44 the
major causes are chronic diseases such as diabetes and macular
degeneration.
Visual loss has several dimensions: the age at onset, the end
point or eventual level of loss, and the rate of progress to reach the
end point. Each of these dimensions may affect a person's mobility
rehabilitation program.
Many authors have proposed phases through which an individual
progresses from the onset of a disability. There is general agreement
that some internal or psychological adjustments should occur prior to
entering a mobility program for the-disabled person to obtain maximum
benefits.
Rehabilitation professionals have observed that individuals with
slowly progressing loss of vision, such as retinitis pigmentosa (RP),
tend to have a difficult time accepting mobility aids because of the
stigma imposed by the aid and the lack of a specific timetable for when
their vision will decrease. There often seems to be a hope that either
the condition will not progress or that a cure will be found. Entering
into a rehabilitation program and using a mobility aid seem to conflict
with this hope and often severely affect the person's acceptance of
mobility instruction. This type of individual can be contrasted to
those who have a fixed loss with remaining vision (macular degenera-
tion), who can be told that the condition will not progress to total
blindness. Once the condition has stabilized r mobility instruction and
the use of mobility aids are generally quite successful.
A characteristic of some RP patients is a slow adaptation to
changes in light level. A transient problem of this sort may call for
special devices to aid mobility during this transitory state.
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16
TABLE 2 New Cases of Legal Blindness (Incidence) According to Etiology in the
United States, 1978 (numbers in thousands)
0-5 5-19 20-44 45-64 65-74 75-84 85+ Total
I nf ectious
diseases
200 100 200 250 50 50
Injuries/
poisonings 200 350
Neoplasms 100 150
General
diseases
50 100 1,050
Prenatal
influence 800 2, 250
Unknown or 150 650
unspecif fed
Multiple
etiologies
Total
As Percentage
of Population:
-- 850
500 400
100 50 50 1, 650
100 100 -a - 450
4,700 4,300 6,700 3,900 20,800
1,500 1,150 300
1,750 3,600 2,550
-- 50 100
1,500 3,650 5,200
200 -- 6,200
3,000 1,150 15,850
650 850 1,350
800 3,800
10,850 8,150 11,350 5,900 46,600
.01 .01 .01 .02 .05 .16 .27 .02
SOURCE: National Society to Prevent Blindness { 1980)
.
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Degree of Visual Impairment
The legally blind population can be partitioned into those people
who are "totally blind," in the sense that they have no sensitivity to
light, and those with some sensitivity to light. It is obvious that
the lower boundary of useful vision may be defined variously for various
tasks and for different situations such as twilight or darkness. It is
less obvious, but also true, that there is room for debate about the
upper boundary of total blindness as well. For example, the category
of "total blindness" is sometimes grouped with vision measured as
n light perception only" to form the category oF nno useful vision," but
it is disputable whether light perception does provide useful informa-
tion. Although there have been some efforts to partition this category
further (Colenbrander and Spivey, 1976), there is a need to determine
whether the proposed categories are functionally related to differences
in accomplishing mobility tasks. 2 It is highly probable that
different levels of disability affect the choice of mobility aids or
the way in which they are used. For example, two broad categories of
visual loss, reduced acuity and reduced visual field, present very
different functional difficulties. Therefore, it is reasonable to
expect that the possible use of mobility aids will vary depending on
the type and severity of visual disability.
Table 3 shows the prevalence (total number of cases in the
population) and incidence (number of new cases added each year) of
legal blindness by degree of impairment in terms of number of cases and
percentages estimated for the year 1978 based on the data reported in
Vision Problems in the United States. The rate of both prevalence and
incidence increase for all impairment categories with age. Roughly 20
percent of the legally blind could be categorized as having "no useful
vision" (by adding together the categories of "total blindness" and
2Levels of blindness and visual impairment have been proposed for
planning individual rehabilitation programs, travel capability, legal
status, tax exemption, supplemental social security awards, and the
like:
I. Blindness:
1. No light perception (total blindness)
2. Light perception and crude form recognition
3. Gross pattern recognition (light-assisted orientation)
II. Low Vision:
Best vision in better eye with conventional glasses or
contact lenses to approximately 20/200 or 20/200 with
gross field defects.
Approximately 20/100 - 20/70 with or without field
defects.
III. Partial Vision:
1. Approximately 20/60 or better: uses approach
magnification and simple magnifier.
OCR for page 18
18
TABLE 3 Prevalence and Incidence of Legal Blindness by Level of
Impairment in the United States, 1978
Prevalence Incidence
-
Number Percent Number Percent
Totally blind 52,300 11 3,100 7
Light perception 57,200 11 4,200 9
Light projection 5,600 1 450 1
Less than 5/200 81,450 16 7,200 15
5/200 to 10/200 49,200 10 5,800 12
10/200 to 20/200 78,950 16 7,200 15
20/200 111,200 23 1,250 27
Restricted field 35,450 8 4,050 9
Unknown 26,650 6 2,100 5
SOURCE: National Society to Prevent Blindness (1980~.
"light perceptions), and 15 percent of new cases fall into this group
Most experts believe that the 20/200 category is overstated because
many physicians do not attempt to determine the full extent of visual
impairment once they have determined that an individual is legally
blind (e.g., 20/200~. Thus many cases in this category may actually
more or less severely impaired (American Medical Association, 19841.
Additional Impairments
A key factor in mobility problems is the presence or absence of
other impairments. More than 50 percent of individuals with visual
impairments also have one or more other impairments (Kirchner, 1985),
either due to the same pathology (as in diabetes or in Usher's syndrome,
in which deafness occurs) or with an independent etiology. The types
and significance of such impairments range widely: mental retardation,
affecting the ability to learn how to use an aid; emotional illness,
which may affect the motivation to use an aid; orthopedic impairments,
which limit ambulation directly; hearing impairments, which limit the
use of some types of aids; and other health conditions, such as heart
disease, which can result in weakness or pain. All these conditions
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19
affect the type of information that the aid must provide and the type
of service it might provide--for example, assistance for a visually
impaired individual who uses a wheelchair.
The psychosocial characteristics of the individual that we have
been discussing (e.g., income, access to services, impact of type of
onset, etc.) provide relevant information for dealing with the disabling
effects of vision loss on mobility that cannot be obtained from
knowledge of the medical diagnosis alone. In fact, information on
diagnosis is often used as an indirect (and weak) indicator of one or
more of the above variables. Obviously, for purposes of the medical
treatment of the pathology or for programs directed at prevention, the
information on causes is more directly relevant. Knowledge of diagnosis
might also be sought as an indicator of mortality rates. This informa-
tion may raise difficult ethical issues with regard to public policy
requiring the allocation of resources (e.g., for expensive mobility
aids). In general, with the exception of diabetes, we do not have
reason to expect high age-specific mortality rates due to the major
causes of blindness in the United States.
Social Factors
Social factors affecting the need for, access to, and acceptability
of mobility aids must also be considered. These factors are shared
with the nonimpaired population. Some of them are relevant epidemio-
logically, i.e., related to the rates of underlying impairment. Some
have independent effects on the rates of disability--that is, two
people with the same impairment may have different degrees of disability
depending on their social status. The latter effects occur because
social groups have differential access to resources, and/or social
norms make certain tasks more important; cultural influences may also
make certain types of mobility aids unacceptable.
Several national studies, which differ in the ways they identify
the population with visual loss (and therefore use different estimated
prevalence rates) nevertheless lead to fairly consistent generalizations
about which social factors are important and in what connections.
Specifically, age has been consistently found to be the strongest
correlate of rates of visual impairment--prevalence rates increasing
with age. Age is also one of the main bases for defining social roles
and therefore the scope and nature of mobility tasks. Age may also
operate through social psychological means to indicate sources of
resistance to the use of certain aids.
A second major social factor is income. Income has been found to
be inversely related to prevalence of severe visual impairment, either
because vision loss has led to loss of employment or because poverty
has led to poor health conditions or poor access to health care. Among
persons with severe visual impairment, those with low income are more
likely to incur greater disabilities and greater handicap. This
correlation may result from having fewer of the resources needed to
accomplish tasks and receiving generally less social approval to
maintain their roles as fully functioning employees or citizens.
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20
Economic factors not only affect the individual, but also involve
aggregate costs to society as a whole. A 1976 report on the social and
economic costs of visual disability (Cahill and Woolsey, 1976) estimates
that the loss in tax revenue and the costs of rehabilitation services,
supplemental security income, eye care, etc., Is over 9350 million (in
1976 dollars) per year. In addition, there is an estimated loss of
income of over $1.4 billion and direct medical costs, which probably
cannot be reduced, of approximately $3.6 billion per year (in 1976
dollars). In 1984 there were over 250,000 tax exemptions on federal
income tax returns claimed for blindness.
APPROACHES TO AIDING MOBILITY
There are two major elements of the mobility problem that result
from blindness. First, the blind traveler with no pattern vision must
avoid obstacles and detect drop-offs. The second problem, which is
less obvious and equally serious, is navigation. Sighted travelers
have many landmarks, most of which are known through vision, to guide
their way. These landmarks not only identify the location but are used
in the memorial representation or cognitive map of the area. Deprived
of vision, the blind person must use other types of landmarks and
information to orient and navigate.
A variety of aids have been developed to help the blind traveler.
These include long canes, dog guides, and electronic travel aids. A
variety of ETA s has been developed, including sound echo ranging
devices, reflected light ranging devices, a computer vision system that
speaks messages to the blind traveler, and a dog guide robot.
ETAs can be roughly classified using a two-way classification
scheme, illustrated in Figure 3. One dimension of the classification
scheme derives from two philosophical approaches to the problem:
sensory substitution and sensory supplementation. Sensory substitution
attempts to use one of the blind person's remaining sensory systems as
a substitute for vision. In this approach, the function of an ETA is
to transduce and transform visual information into information that can
be perceived by another sense. Both the factual and auditory sensory
modalities have been used as substitutes for vision. Critics of this
approach point out that converting visual information to auditory
information could overload the capacity of the auditory system and that
the ETA's auditory signal often competes with naturally occurring and
useful auditory information.
Sensory supplementation starts with the observation that many blind
people achieve a high degree of mobility without electronic aids. The
function of an ETA therefore is to provide additional information that
is critical and not available otherwise. A device that could detect an
object blocking a path and signal its presence supplements the informa-
tion already available to the blind traveler. The problem dealt with
by this approach is to discover what information about the environment
is necessary for mobility and, of equal importance, when it is needed.
Critics of this approach point out that the critical information is
often embedded in a complex array of sensory information. Moreover,
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21
Transduce and
Translate
Transduce,
Process, and Translate
Sensory Substitution
Supplementation
Sonicguide
Seeing with skin
Mowat Sensor Guide Dog Robot
Laser Cane Computer Vision
Pathsounder
Nottingham
Obstacle
Detector
FIGURE 3 Two-way classification scheme of electronic travel aids.
the critical information may be relational and dynamic in its nature.
Human sensory systems have the ability to analyze and interpret complex
information flows, and this ability is lost with substitution systems.
The second dimension of the classification scheme divides ETAs into
two categories: those that transduce and transform environmental
information and those that transduce, process, and then transform
environmental information (see Figure 3~.
The boundaries of the classification scheme are not sharp; some of
the devices categorized actually straddle the boundaries or have aspects
that fit into more than one category. This is especially true of the
signal processing that goes on in the device, since few if any devices
simply transduce environmental information.
Of all the devices listed, only the Guide Dog Robot attempts to
comoletelv solve the navioati on Oral "m
_~ ¢~ ... it contains a complete
internal navigation system. All the other devices assume that the
cognitive capabilities of the blind person will suffice if the
appropriate information is provided through sensory substitution or by
information supplementation.
PATTERNS OF USE AND NONUSE
It is significant that none of these devices seems to be widely
used or very popular. The initial impetus of ETAs came from engineers
and researchers. The primary evaluation and testing concentrated on
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22
the mechanics of the device and the testing of the unique application
of some instrumentation (e.g., lasers). These devices and the promise
of new technologies were initially viewed as viable alternatives to the
long cane or dog guide. After greater interaction with mobility
specialists and other professionals working in the area of blindness,
ETAs were suggested as a supplement to the primary mobility aid (i.e.,
the long cane or dog guide).
It has only been during the last 15 years that follow-up evaluations
have been done to determine the usefulness and success of ETAS. There
have been very few studies of this nature published, and they represent
a great deal of variation in methodology, sample size, and number of
data gathered. Sample sizes range from 5 to 74 individuals. The
methods used for gathering data include mail questionnaires, phone
questionnaires, direct observation, and personal interview. The length
of time the visually impaired person had the device ranged from a few
months to about 11 years. The ETAs used by the subjects included the
Soniaguide, the Mowat Sensor, the Laser Cane, and the Russell Path-
sounder. (See Chapter 6 for a description of these aids.)
Airasian (1973) mailed questionnaires to 94 individuals trained to
use the Sonicguide (74 were returned). Many dimensions of attitudes
about training f design difficulties and inconveniences, and adequacy of
the device, range, and signals were gathered from the questionnaire.
One basic question on the questionnarie was whether the person still
had the Sonicguide. More than 10 percent no longer had the device, 11
percent still had it but had not decided about returning it, and 79
percent planned to keep the device.
Darling et ale (1977) evaluated the 26 blind veterans receiving ETA
training at the Western Blind Rehabilitation Center in Palo Alto, Calif.
The procedure involved a phone survey and direct observation in the
veterans' home area. Of the 26 veterans who had been trained, 3 had
moved and 5 did not use the device. Of the remaining 18 subjects, 12
had the Sonicguide and 6 had the Laser Cane. The time since training
ranged from 1 to 5 years.
Of the 12 veterans having the Sonicquide, 5 were using it and 7 did
not use it. Of the 6 people who had taken the laser cane training, only
3 were using the aid. Therefore, of the original 26 veterans, only 8
were known to be using an ETA.
Farmer (1978) reported on 18 veterans who completed training in the
use of the laser cane. Of these individuals, 11 people were using the
laser cane for a period of 2 to 8 years.
A telephone interview was conducted by Morrissette et al. (19811.
This study involved 15 veterans who had been trained to use the Mowat
Sensor. The length of use varied from 3 to 24 months. All subjects
reported the aid to be helpful and continued to use it, although the
amount of use varied as well as the particular uses.
Finally, Simon {1984) studied five individuals who received their
training at the New York Association for the Blind. Four received
training with the Laser Cane and one was trained to use the Sonicguide.
The training took place 3.5 to 5.5 years previous to the telephone
interview. All five individuals reported that they still used the
devices.
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23
These studies represent four separate and independent efforts to
determine the success and utility of ETAs. On the basis of personal
communication with ETA distributors, it was determined that approxi-
mately 3,000-3,500 devices had been sold by 1985. These data, which
are anecdotal and crude at best, are not a true representation of the
number of devices owned by visually impaired individuals: many of the
devices were sold to agencies for training, research, and/or
demonstrations, and not to individual users.
RECOMMENDATIONS
On the basis of these findings, the working group makes the
following recommendations in the area of information regarding the
demography of blind and visually impaired pedestrians.
Surveys of ETA Users and Technology Diffusion
Approximately 3,000-3,500 electronic travel aids have been sold;
this represents a small fraction of potential users. Very little is
known about who purchased these ETAs, whether they remain in service,
and whether training was adequate. Studies designed to evaluate ETA
performance have sampled fewer than 5 percent of the 3,500 purchasers
of these devices.
It would be helpful for researchers to work toward developing a
model of the diffusion of mobility-related technologies, drawing on the
general literature on the diffusion of innovations. Current experience
suggests that key groups in such a model would include, in addition to
the population of potential users of mobility technologies: (1)
rehabilitation personnel and mobility specialists, (2) administrators
of agencies that provide mobility training, and (3) opinion leaders
among blind and low-vision consumers.
RECOMMENDATION: We recommend that a systematic survey of the total
or a large sample of ETA purchasers be carried out. This survey should
obtain demographic data on purchasers, training history, data on when,
how, and how often the devices are used, individual differences in ETA
use, and some measure of users' satisfaction with the devices. For a
survey of this type to yield broadly useful data, comparison groups
should be sampled from among the users of dog guides and long canes; it
is very likely that these groups overlap. The study should be designed
to estimate the probabilities of multiple device use (e.g., Sonicguide
and dog guide) and to reveal the device selection factors that are
currently operating in the marketplace.
RECOMMENDATION: We recommend that a study be designed on the dif-
fusion of mobility-related technologies. It could be done through a
survey of rehabilitation personnel, mobility specialists, administra-
tors, and opinion leaders among blind and visually impaired consumers.
The study should gather data on geographic distribution of potential
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users, relevant training and experience, attitudes toward alternative
technologies, and interrelations with the other groups. Consideration
should be given to the cost-effectiveness of ETAs.
A Normative Data Base
RECOMMENDATION- There is an urgent need for a normative data base
that contains information about the entire population of visually
impaired and blind people. It should be possible, among other things,
to interrogate this data base for information about personal data that
indicate readiness for various sensory aids and how sensory readiness
changes as a function of maturation and development, from infancy to
old age.
A Survey of the Needs of Older Blind People
The prevalence of blindness in the population is greatest among
older people. More than half the blind people in the United States
today are over the age of 64. Given the growing proportion of people
in the older age groups and the particular mobility needs of the
elderly, we need to known more about the mobility requirements and
preferences of elderly blind and visually impaired people.
RECOMMENDATION: We recommend that a survey be conducted of the
mobility requirements and preferences of elderly blind and visually
impaired people. The survey should be designed to yield information
about the variety, severity, and distribution of their visual impair-
ments and of other sensory, motor, and cognitive impairments that may
affect their need for and ability to use mobility aids. The survey
should also provide a description of their travel requirements and an
indication of the travel techniques and aids that would be most helpful
in meeting those requirements.
Review and Analysis of Existing Data Bases
There are no nationally representative data bases designed to
provide measures describing the number or characteristics of visually
impaired people who have specific mobility needs and problems. The
opportunity does exist to obtain information from existing data bases
that in the short run and at little expense could provide generally
useful information.
RECOMMENDATION: We recommend that existing national (or more
local) representative data bases be reviewed and analyzed to extract
information on the specific mobility needs and problems of visually
impaired people. Likely sources include the ongoing Health Interview
Surveys of the National Center for Health Statistics as well as the
Work and Disability Study of the Social Security Administration
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conducted in 1978. Studies conducted for purposes of public
transportation planning might also be likely candidates for the
extraction of such information.
Study of Multiple Impairments
On the basis of national studies, we found that more than 50
percent of the severely visually impaired population has at least one
additional impairment.
RECOMMENDATION: We recommend that an intensive study be conducted
on the interaction of visual impairments with other cognitive, sensory,
and physical impairments and their effect on mobility problems.
Development of a Research Agenda
Efforts by engineers and inventors to develop electronic aids for
the blind have been sporadic and piecemeal. All too often, when a new
aid is developed, it has all the inherent difficulties of previous
attempts. The development of specific guidelines and research
protocols, which can systematically evaluate aids and make
recommendations for future scientists, is needed since funding is so
limited. Progress can be made more efficiently and quickly through the
accumulation of research findings rather than by individual trial and
error.
RECOMMENDATION: We recommend that either a federal agency or
professional association concerned with these Problems convene an
: ~ ~ · _ _ . ~ . . _ .
~~cera~sc~p.~nary pane' to define a basic research agenda (or minimum
data set) that would be widely disseminated to enable researchers
working with small samples to produce reports that could permit
cumulation of findings across studies. Models for this activity may be
sought in the area of research on long-term care and possibly in
clinical research areas identified by the National Institutes of Health.
Representative terms from entire chapter:
mobility aids
