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The impact of electronic mobility devices for persons who are visually impaired: a systematic review of effects and effectiveness.

Abstract: A systematic review of the international literature was conducted to investigate the effects and effectiveness of electronic mobility devices. Of the 13 studies that were reviewed, all but one demonstrated effects of the use of these devices, and generally, users evaluated the devices' functionality as beneficial.

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With the aim of investigating the circumstances, experiences, and opinions of persons who are visually impaired (that is, those who are blind or have low vision), a sample of approximately 1,000 people in the United Kingdom were surveyed within the Network 1,000 project. When asked what they perceived as a theme of personal importance, they most often mentioned travel, transportation, and (outdoor) mobility (Douglas, Corcoran, & Pavey, 2006). A reason for this response can be seen in the vital role that travel plays in participating in numerous activities of daily living in the areas of leisure, productivity, and self-maintenance; therefore, travel may be regarded as a mediating factor for social inclusion (Jones & Jain, 2006; Primeau, 1996).

There are four common ways that persons who are visually impaired enhance their independent mobility: with human guides, dog guides, long canes, or electronic travel devices (Farmer & Smith, 1997). The engineering of electronic travel devices started in the 1940s, and the first devices became available after some 20 years. Following a period of intensive development, attention shifted toward training and use of such devices in the 1970s and 1980s (Simon, 1984). Recent reliable data on the use of these devices does not exist. Although, in general, the importance of assistive technology for persons who are visually impaired in enabling a variety of activities and improving access to societal or community life is widely agreed upon (Abner & Lahm, 2002; Kapperman, Sticken, & Heinze, 2002; Strobel, Fossa, Panchura, Beaver, & Westbrook, 2003), Simon (1984) noted a "controversy about the usefulness" of electronic travel devices, as illustrated by the following statement by Joffee (1987, p. 389): "The informal consensus of my O&M [orientation and mobility] colleagues more than 15 years after our initial introduction to ETAs [electronic travel aids] is that electronically assisted travel has been a disappointment to both the consumer and the professional. We ... should not allow this disappointment to lead us to overlook the potential that ETAs offer in the rehabilitation process."

Over the past decade, emerging technologies, such as Global Positioning Systems; developments in the field of mobile phones and the Internet; and technological improvements that have made devices for mainstream consumers small, lightweight, portable, and affordable, have been reported to have promising potential for persons who are visually impaired (Baldwin, 2003; Fruchterman, 2003; Gill, 2005). These developments led us to take a closer look at the electronic mobility devices that are available on the market and to determine what is known about their possible impact on the everyday lives of people who use these devices. This review reports what we found about the effects and effectiveness of electronic mobility devices that individuals can use without environmental adaptations. An overview of the devices that fall into this operational definition is provided elsewhere (Roentgen, Gelderblom, Soede, & de Witte, 2008). Note that we use electronic mobility devices as an umbrella term for devices that are used during travel for detecting obstacles, orientation, wayfinding, and navigation systems.

Method

In April 2008, we consulted the following databases--PubMed (1963-2008), MEDLINE (1966-March 2008), CINAHL (1982-February 2008), CRD databases (DARE, HTA, NHS EED) (1995-2006), Cochrane (1967-2008), EMBASE (1989-March 2008), and PsycINFO (1806-April 2008)--and performed searches using several combinations of free-text words and Medical Subject Headings (MESH words), their equivalents found by means of the Thesaurus function of the particular database used. The terms we used were: "visually impaired persons"; "visual* impair"; "vision disorders"; "visual disorder"; "vision-subnormal"; "vision, low"; "blind"; "blindness"; "self-help (devices)"; "assistive technology [device(s)]"; "assistive technologies"; "electronic mobility/travel/orientation/ navigation aid(s)"; "mobility/navigation/wayfinding aid(s)"; "orientation"; "mobility"; "travel"; "navigation"; "wayfinding"; "treatment outcome"; "outcome assessment"; "rehabilitation of vision impaired"; "therapy"; "clinical trials"; "controlled/randomized clinical trials as topic/publication type"; "controlled study"; "follow-up studies"; "effect(s)"; "efficacy"; "effectiveness"; and "mobility performance." In addition, we searched by hand the references of relevant articles, conference proceedings, and three journals that were not indexed in the databases we searched: Closing the Gap, AccessWorld, and Braille Monitor. The search process was completed by asking manufacturers and distributors of existing devices whether they knew of any published or unpublished reports or evaluations of their products.

The results of the searches of the seven aforementioned databases resulted in 1,855 titles, varying between 49 and 545 per database. Screening these titles on the basis of the search question that was formulated in advance led to 142 potentially relevant abstracts. Since the abstracts stemmed from different databases, some appeared more than once, and these redundant abstracts were excluded. Of the 107 abstracts that we read, 93 did not meet the criteria for inclusion because the electronic mobility devices that were discussed relied on environmental adaptations, were no longer available, or were prototypes that were still being developed. Full-text copies of the remaining 14 possibly relevant articles were obtained. Of these articles, 8 were excluded because they provided merely technical or functional descriptions of the devices. An additional 7 relevant articles were identified through a hand search, so that a total of 13 articles (6 from the database search and 7 from the hand search) were included. Given the small number of studies on the impact of existing electronic mobility devices, no studies were excluded because of qualitative criteria. Furthermore, the period of years searched was not restricted, since the cut-off point was determined by the availability of the devices.

Results

Only 2 of the 13 studies concerned electronic mobility devices that are designed to be used for navigation. Both dealt with just 1 of 10 available devices that an individual who is visually impaired can actually use: the BrailleNote GPS (Ponchilla, MacKenzie et al., 2007; Ponchilla, Rak, Freeland, & LaGrow, 2007). The remaining 11 studies evaluated 5 of the 13 available obstacle-detection and orientation devices: the UltraCane (n = 1) (Penrod, Bauder, Simmons, Belcher, & Corley, 2007), Teletact and Tom Pouce (n = 1) (Farcy et al., 2006), the Laser Cane (n = 4) (Blasch, Long, & Griffin-Shirley, 1989; Darling, Goodrich, & Wiley, 1977; Jacobson & Smith, 1983; Simon, 1984), and the Sonic Pathfinder (n = 5) (Clark-Carter, Heyes, & Howarth, 1986; Dodds, Clark-Carter, & Howarth, 1984; Heyes, Durinck, & Beaton, 1988; LaGrow, 1999; McKinley, Goldfarb, & Goodrich, 1994). At this point, it should be noted that previous studies evaluated earlier versions of the devices and that the Laser Cane was always assessed together with other devices that are no longer available, such as the Mowat Sensor, the Sonicguide, and the Pathsounder.

STUDY DESIGN

All 8 of the studies in which an experimental design was chosen made use of a within-subjects group design, also known as a repeated-measures design or a single-subject alternating treatment design. In 3 of those studies, two experiments were conducted: the first in a within-group design and the second in a single-subject design. As LaGrow (1999) reported, in this experimental design, after the baseline is established by measuring performance without using the electronic mobility device, but only the usual skills of the participants using their regular mobility device, one or more measurements of the experimental conditions are taken to determine whether there is control of the independent variable over the dependent variable. The independent variable is defined as the use of the electronic mobility device. In one of the experiments the device was used with different settings of the ultrasonic range to create different amounts of preview (Clark-Carter et al., 1986). The dependent variables are described as elapsed time, or the time taken or spent to perform a certain task or to complete a route, on the one hand, and unintentional contacts, also referred to as the number and type of errors made in using the devices, or the ability to detect landmarks or shorelining, on the other hand. In several studies, following the experiment, the participants were asked to provide a subjective evaluation of the use of the device as a qualitative supplement. The other studies were designed in the form of a field trial (Heyes et al., 1988), survey (Blasch et al., 1989; Simon, 1984; Jacobson & Smith, 1983), or follow-up (Darling et al., 1977).

DATA COLLECTION

Data collection in the studies with an experimental design was accomplished through observation of the participants' performance. In two studies, the attendance of a second observer was mentioned as a method to enhance reliability through interobserver agreement (Ponchilla, Rak et al., 2007; Penrod et al., 2007). The field trial that took place in the United Kingdom monitored the resulting changes in everyday life during half a year; for the Australian trial, the kind of data collection was not described (Heyes et al., 1988). Most of the surveys made use of in-depth telephone interviews, and one used a mailed questionnaire. In addition to a telephone interview in the follow-up study, the participants were directly observed in the natural environment to gain objective and comparable information on their mobility skills (Darling et al., 1977).

MEASUREMENT INSTRUMENTS

The participants' mobility performance was measured on indoor and outdoor routes, using existing or natural as created or artificial routes and obstacles. It was common for the route or task to be timed while (unintentional) contacts with obstacles at different heights or with the inner or outer shoreline were counted and specified, in some cases referred to as "safety" errors. Furthermore, the detection and identification of objects and landmarks and the participants' positions on the pavement were registered. The proportion between the actual distance traveled and the number of seconds taken to travel the distance was expressed as an efficiency rate (Ponchilla, Rak et al., 2007). Farcy et al. (2006) compared the performance of persons who were visually impaired to that of sighted pedestrians, presented as an efficiency percentage, in an attempt to develop an objective measurement instrument. One study measured the percentage preferred walking speed (PPWS), which relates to the time taken to travel a route when using the device at a person's most comfortable pace (McKinley et al., 1994). In one study, filming was used for objective documentation (Dodds et al., 1984), and in another study, special equipment (the "wheel" and foot switches) was used to measure walking speed (Clark-Carter et al., 1986). In the surveys, in-depth telephone interviews and one mailed questionnaire were developed to investigate the participants' frequency of and attitudes toward the use of electronic mobility devices, training, perceived mobility performance, perceived safety and efficiency in travel, travel patterns and habits, and satisfaction. One study focused on the role that electronic mobility devices could play in participation in the community, especially employment (Jacobson & Smith, 1983). The measurement instruments used in the field trials were not specified (Heyes et al., 1988).

SAMPLE

In the experimental studies, the sample size varied from 1 to 19, and for the other studies, it varied from 5 to 298. The field trial in the United Kingdom had 30 participants, but for the Australian trial, the number of participants was not given. Three studies included not only persons who were visually impaired, but blindfolded sighted participants, most of whom were O&M students. For one experimental study, only the latter were included (Penrod et al., 2007). Of the participants with visual impairments, considerably more were functionally blind than had low vision, and more were male than female. The ages of the participants varied between 18 and 86 years. For the studies that used an experimental design, no drop-out was reported. The response rates of the surveys and the follow-up study, all of which were intended to survey a definite, whole population of users of electronic mobility devices, varied between 46% and 100%.

STUDY RESULTS

In an experimental setting, the only navigation system that was evaluated, BrailleNote GPS, combined with a special technique the authors defined as geotracking, was found to have a significant effect on locating targets, even relatively small objects. This effect was considered to compensate for one of the shortcomings of commercial GPS devices: their lack of accuracy (Ponchilla, MacKenzie et al., 2007). In a real-life situation, described as travel in a familiar neighborhood, the use of the BrailleNote GPS in creased the ability of participants to reorient themselves and to do so within a shorter period of time. Furthermore, an obviously greater efficiency in locating a target address, less the distance traveled to reach it and a higher efficiency rate (feet per second), could be assessed. On the basis of these findings, the authors reported a "marked improvement in wayfinding performance, even in extremely familiar areas" (Ponchilla, Rak et al., 2007, p. 398).

In general, the studies with an experimental design that evaluated electronic mobility devices that were aimed at detecting obstacles and at orientation found that these devices increased the participants' ability to detect landmarks and obstacles, resulting in a lower degree of unintentional contacts and errors, and decreased the participants' walking speed.

There were three exceptions to this general finding. First, LaGrow (1999) observed no marked effects. Second, ClarkCarter et al.'s (1986) study used an experimental condition with just one obstacle and reported a significant effect on walking speed: The participants walked noticeably faster through an increased amount of preview. Third, Farcy et al.'s (2006) study did not take measurement of speed into consideration.

When the participants were asked to express their attitudes toward the use of the devices, the majority perceived their travel to be safer, more comfortable, and less stressful when using the devices and stated that the devices functioned in the intended way. Traveling at a slower pace, if recognized by the users, was not considered to be a problem. The main findings of the Australian field trial were the ease of use and of acquiring skills and the users' positive responses (Heyes et al., 1988). The field trial held in the United Kingdom did not mention the main findings.

The surveys and the follow-up study revealed that the number of persons who continued to use their electronic mobility devices varied from 44% (n = 8), 47% (n = 140), and 79% (n = 74) to 100% (n = 5). One reason for the nonuse of the devices was that they were viewed as helpful in the initial stage, but were no longer needed after participants familiarized themselves with their surroundings (Darling et al., 1977; Jacobson & Smith, 1983). Other reasons were associated with personal, health, or design problems, but not with the functionality of the devices. Even though there were some technical malfunctions and situations in which the devices were reportedly used inappropriately, the positive experiences of the users generally outweighed the negative ones. Aside from reliability and the view that the devices functioned in the way they were supposed to, most of the users valued the additional information provided by the devices, resulting in safer and more comfortable travel. For the majority, both the quality and amount of travel increased, while for the remainder, they were unchanged. Table 1 presents the most important facts concerning the 13 studies.

Discussion

The literature search resulted in a small number of scientific publications that reported on studies with lower methodological quality. These findings are in line with those of Virgili and Rubin (2006), who conducted a systematic review of the effects of O&M training. On the other hand, the literature search process also revealed that there is far more work on the subject than is represented by articles that are accessible through a database search, particularly with respect to the rich knowledge and experiences of the O&M profession. It is noteworthy that more of the included studies described in this article were identified through a hand search than through an electronic search of databases.

Measured by the parameters that underlie the assessment of the methodological quality of Cochrane systematic reviews, the designs of the studies described in this article could be judged as being of a lower quality. Apart from the PPWS, no standardized methods or existing measurement instruments were used. Furthermore, questionnaires and mobility courses were mostly self-created and not validated, and little is known about their reliability. Some samples included sighted blindfolded students instead of persons who were visually impaired, and the generally small number of participants in the experimental studies and most of the surveys led to the conclusion that the results could not be generalized to the population of people with visual impairments. More than once, participants who were described as having excellent O&M skills were included in the experiments and hence were not representative of the heterogeneous group of persons who are visually impaired. Furthermore, the demographic factors represented in the studies' samples did not correspond with the characteristics of this population. The studies that attempted to investigate the entire population of owners of electronic mobility devices or persons with visual impairments who were trained on a certain device were self-evidently more representative of the population being discussed.

What is striking is the generally high level of user satisfaction, even in studies that displayed no or negative effects. This discrepancy between the objective measurement of mobility performance and the participants' subjective experiences and attitudes toward the use of electronic mobility devices prompted LaGrow (1999) to reconsider whether measures other than efficiency of travel would be more appropriate for evaluating the efficacy of electronic mobility devices. It should also be noted that studies with an experimental design mainly included novice users and therefore assessed an initial stage in the use of electronic mobility devices in which more information about the environment could be gained at the expense of travel speed, whereas experienced users, surveyed on the long-term consequences of the use of these devices, stated that they traveled faster when using the devices (Blasch et al., 1989; Simon, 1984). One possible explanation could be familiarization; another could be that mobility performance was self-reported instead of objectively measured.

With regard to the chronology of the studies described in this article, in the late 1970s and 1980s much attention was paid to the frequency of use and users' personal attitudes, surveyed by means of in-depth interviews that provided more qualitative and subjective findings. Subsequently, the effects and efficiency of electronic mobility devices were investigated in studies with an experimental single-subject or within-subject design. With the exception of the UltraCane as an obstacle-detection and orientation device and the BrailleNote GPS as a navigation system, no studies of the effects of more recent devices could be found. Moreover, there appears to be a gap between 1999 and 2006--a period in which, after the emergence of commercial GPS, the first navigation systems and devices for persons who are visually impaired became available.

Conclusion

The included studies are so diverse that it would not be possible to pool the results from them. However, in the majority of studies, positive effects of the use of electronic mobility devices were found. These effects included improved wayfinding performance; the detection of obstacles, objects, landmarks, and travel path alignment; and feelings of safer, more comfortable, and less stressful travel accompanied by a higher quality and increased frequency of travel. The negative effects that were found in some of the studies with an experimental design were restricted to decreased travel speed and, in some of the surveys and the follow-up study, to high rates of participants who discontinued the use of electronic mobility devices (as opposed to those participants who were described as enthusiastic users). It is of note that the reasons for nonuse appeared not to be associated with the devices' functionality, but, as we mentioned earlier, were associated with the participants' health conditions or personal situations, because of their design or in consequence of familiarization with the environment that was traveled.

The results of this systematic review stress that electronic mobility devices could have promising potential for persons who are visually impaired. They also indicate that more insight is needed into the measurement of the mobility of the target group, but there is also a need to evaluate other aspects of travel than mobility performance alone, especially with regard to the evaluation of navigation systems that are intended to render new behavior possible, such as wayfinding and independent travel in unknown environments. Mobility should be assessed in its broader context, including the intention of travel, since travel should be regarded as a prerequisite for participation in activities. Therefore, future research needs to investigate the long-term consequences of the use of electronic mobility devices, such as changes in travel patterns or habits and resulting changes in a person's occupation. But more attention should also be paid to other aspects that are generally important for the provision of assistive technology, such as the match between the individual user and the most suitable device; the importance of training and motivation for using or continuing to use the devices; and the costs, prescription, and service delivery of electronic mobility devices.

The authors thank the InSight Society for funding this study within the InSight program of ZonMw, an organization for health, research, and development in the Netherlands.

References

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Uta R. Roentgen, M.Se., Ph.D. Candidate, Zuyd University, Postbus 550, 6400 AN Heerlen, the Netherlands: e-mail: <u.r.roentgen@hszuyd.nl>. Gert Jan Gelderblom, Ph.D., senior researcher, Zuyd University, the Netherlands; e-mail: <g.j.gelderblom@hszuyd.nl>. Mathijs Soede, Ph.D., associate professor. Zuyd University, the Netherlands; e-mail: <m.soede@hszuyd.nl>. Luc P. de Witte, M.D., Ph.D., professor, Zuyd University, the Netherlands, and professor for technology in care, Faculty of Health, Medicine and Life Science, Maastricht University, Postbus 616, 6200 MD Maastricht, the Netherlands; e-mail: <l.de.witte@hszuyd.nl>.
Table 1
Included studies on electronic mobility devices, ordered
chronologically.

Study and device       Design, sample

Ponchilla, MacKenzie   Experiment (Exp) 1:
et al. (2007)          within-subjects group
United States          design; n = 10 sighted-
BGPS                   blindfolded, 3 low
                       vision, and 6 blind. Exp
                       2: single-subject A-B-A-
                       B design; n = 1 blind.

Ponchilla, Rak et      Exp 1: single-subject
al. (2007)             alternating treatment
United States          design; n = 2 blind, 1
BGPS                   low vision. Exp 2:
                       single-subject A-B-BC-B-
                       BC design; n blind.

Penrod et al. (2007)   Single-subject design, A-
United States          B-A-B reversal design; n
UC                     5 sighted blindfolded,

Farcy et al. (2006)    Repeated measures,
France                 within-subjects design; n
TT, TP                 = 4 sighted, 14 blind,

LaGrow (1999)          Single-subject design.
New Zealand;           Exp 1 : simple reversal
SP                     A-B-A-B design; n = 1
                       blind. Exp 2: A-B-A; n =
                       1 blind; B-A-B-A design;
                       n = 1 blind,

McKinley et al.        Repeated measures,
(1994) United          within-subjects A-B-A-B-
States SP              A-B design; n = 8
                       visually impaired,

Blasch et al. (1989)   National survey of all
United States and      individuals trained to
Canada MS, SG, LC, PS  use electronic mobility
                       devices, aged 18 or older
                       (n = 641); 46% were
                       interviewed: n = 298.

Heyes et al. (1988)    Field trials. Australia:
Australia and          visually impaired RGDAA
United Kingdom SP      clients. United Kingdom
                       (UK): n = 30 visually
                       impaired.

Clark-Carter et        Repeated measures,
al. (1986) United      within-subject A-B-C-D-E
Kingdom SP             design; n 2 sighted
                       blindfolded, 4 blind,

Dodds et al. (1984)    Repeated measures,
United Kingdom         within-subject A-B-B
SP                     design; n = 6 blind.

Simon (1984)           Survey of all individuals
United States          who had received training
SG, LC                 in electronic travel
                       devices at The
                       Lighthouse, 1976-78;
                       n = 5.

Jacobson & Smith       Survey of all SG owners
(1983) United States   (n = 106) and 28 LC owners;
SG, LC                 70% response rate:
                       n = 94.

Darling et al. (1977)  Follow-up study of all
United States          veterans trained with
SG, LC                 electronic travel devices
                       (n = 26); 69% were
                       included: n = 18.

                       Data collection,
Study and device       measurement

Ponchilla, MacKenzie   Observation of locating
et al. (2007)          a target.
United States
BGPS

Ponchilla, Rak et      Observation of time to
al. (2007)             reorient and efficiency
United States          rate in reaching a target
BGPS                   location.

Penrod et al. (2007)   Observation of mobility
United States          performance on an outdoor
UC                     route,

Farcy et al. (2006)    Observation of mobility
France                 performance on 16 indoor
TT, TP                 and outdoor routes.

LaGrow (1999)          Observation of travel on
New Zealand;           3 outdoor routes and 1
SP                     indoor route in
                       challenging environments,

McKinley et al.        Observation of travel on
(1994) United          3 different routes.
States SP

Blasch et al. (1989)   45-to 60-minute telephone
United States and      interviews; 308 questions
Canada MS, SG, LC, PS  on training, travel
                       habits, safety and
                       efficiency in travel, and
                       attitudes toward the use
                       of electronic mobility
                       devices.

Heyes et al. (1988)    Australia: not reported.
Australia and          UK: monitoring the
United Kingdom SP      resultant changes in
                       lifestyle over a 6-month
                       period.

Clark-Carter et        Measuring walking speed
al. (1986) United      on a route, 5 amounts of
Kingdom SP             preview.

Dodds et al. (1984)    Video recording of the
United Kingdom         participants' behavior
SP                     and their verbal
                       commentaries together
                       with the devices' output.

Simon (1984)           45-to 60-minute in-depth
United States          telephone interviews; 29
SG, LC                 open-ended questions on
                       the frequency of use of
                       and consumer satisfaction
                       with the devices.

Jacobson & Smith       20-item mailed
(1983) United States   questionnaire concerning
SG, LC                 job title, training
                       with devices, current
                       use and attitudes about
                       usefulness.

Darling et al. (1977)  Telephone interviews on
United States          prior mobility training,
SG, LC                 use of devices, travel
                       patterns; observation
                       and assessment of
                       mobility skills,
                       residences, and places
                       of employment.

Study and device       Results

Ponchilla, MacKenzie   Exp 1: significant effect
et al. (2007)          BGPS-geotracking. Exp 2:
United States          mean error distance
BGPS                   decreased, performance
                       improved.

Ponchilla, Rak et      Exp 1 : time decreased,
al. (2007)             ability improved,
United States          efficiency increased. Exp
BGPS                   2: efficiency increased
                       when using BGPS, and
                       increased more when using
                       BGPS plus electronic
                       waypoints.

Penrod et al. (2007)   Efficacy in landmark
United States          determination and
UC                     obstacle identification
                       or avoidance increased;
                       route execution times
                       increased.

Farcy et al. (2006)    Efficiency increased.
France
TT, TP

LaGrow (1999)          Exp 1 : time increased;
New Zealand;           mean number of
SP                     unintentional contacts
                       varied across phases and
                       routes. Exp 2: time did
                       not decrease; mean number
                       of unintentional contacts
                       slightly decreased;
                       positive attitudes.

McKinley et al.        PPWS stayed the same or
(1994) United          decreased, obstacle
States SP              avoidance increased;
                       travel skills, improved;
                       positive attitudes

Blasch et al. (1989)   47% used their devices;
United States and      frequency of travel
Canada MS, SG, LC, PS  increased, more rapid,
                       efficient, confident,
                       safer and less stressful;
                       cane and body contacts
                       decreased, obstacle
                       avoidance improved;
                       reasons discontinued use.

Heyes et al. (1988)    Australia: simple and
Australia and          relevant information,
United Kingdom SP      easy (to learn) to
                       use. UK: not reported.

Clark-Carter et        Walking speed
al. (1986) United      significantly increased
Kingdom SP             with 3.5 m (increased)
                       preview.

Dodds et al. (1984)    No significant changes in
United Kingdom         cane contacts outer
SP                     shoreline, major safety
                       errors and productive
                       walking time; cane and
                       body contacts inner
                       shoreline and cane
                       contacts obstacles
                       decreased; more central
                       sidewalk position.

Simon (1984)           100% still used their
United States          devices; positive
SG, LC                 features: additional
                       information, locating
                       obstacles and downward
                       drops, positive
                       attitudes; negative
                       features (mechanical
                       difficulties, adverse
                       weather conditions).

Jacobson & Smith       79% still used their
(1983) United States   devices; judged to be
SG, LC                 useful, recommended for
                       obtaining and keeping a
                       job; problems: adverse
                       environmental conditions,
                       malfunctioning.

Darling et al. (1977)  44% used devices
United States          effectively in locating
SG, LC                 obstacles and landmarks;
                       amount of travel
                       improved; SG
                       malfunctioned less
                       frequently than LC;
                       reasons for discontinued
                       use.

Note: BGPS = BrailleNote GPS, UC = UltraCane, TT = Teletact,
TP = Tom Pouce, SP Sonic Pathfinder, MS Mowat Sensor, SG =
Sonicguide, LC = Laser Cane, PS = Pathsounder, and RGDAA =
Royal Guide Dog Association of Australia.
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Article Details
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Author:Roentgen, Uta R.; Gelderblom, Gert Jan; Soede, Mathijs; de Witte, Luc P.
Publication:Journal of Visual Impairment & Blindness
Geographic Code:4EUNE
Date:Dec 1, 2009
Words:5380
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