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Collision Warning Device for Blind and Visually Impaired

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ClinicalTrials.gov Identifier: NCT03057496
Recruitment Status : Completed
First Posted : February 20, 2017
Results First Posted : December 21, 2020
Last Update Posted : February 10, 2021
Sponsor:
Information provided by (Responsible Party):
Alexandra Bowers, Massachusetts Eye and Ear Infirmary

Study Type Interventional
Study Design Allocation: N/A;   Intervention Model: Single Group Assignment;   Masking: None (Open Label);   Primary Purpose: Other
Conditions Hemianopia
Hemianopsia
Peripheral Visual Field Defect
Blindness
Retinitis Pigmentosa
Glaucoma
Intervention Device: Collision warning device
Enrollment 49
Recruitment Details Subjects were recruited between January 2018 and May 2019 via referrals from the Carroll Center for the Blind, the Massachusetts Commission for the Blind and practitioners at vision rehabilitation clinics in the Greater Boston area, and via a pool of volunteers who had previously participated in studies in our lab.
Pre-assignment Details  
Arm/Group Title Silent and Active Mode
Hide Arm/Group Description During the period of home-use of the device, all participants experienced both the silent and active modes on a random schedule. Thus participant flow was the same for silent and active modes and is described for all participants together.
Period Title: Overall Study
Started 49
Started Home-use Trial 36
Completed 31
Not Completed 18
Reason Not Completed
Withdrawal by Subject             8
Lost to Follow-up             5
Did not use device during home trial             3
Device failure             2
Arm/Group Title Silent and Active Mode
Hide Arm/Group Description During the period of home-use of the device, all participants experienced both the silent and active modes on a random schedule. Thus the baseline measures are the same for active and silent modes (as it was the same participants for both modes) and are reported together.
Overall Number of Baseline Participants 31
Hide Baseline Analysis Population Description
The baseline analysis population includes only those subjects who completed the one-month period of device use and had data successfully recorded by the device.
Age, Continuous  
Median (Full Range)
Unit of measure:  Years
Number Analyzed 31 participants
61
(25 to 73)
Sex: Female, Male  
Measure Type: Count of Participants
Unit of measure:  Participants
Number Analyzed 31 participants
Female
13
  41.9%
Male
18
  58.1%
Ethnicity (NIH/OMB)  
Measure Type: Count of Participants
Unit of measure:  Participants
Number Analyzed 31 participants
Hispanic or Latino
0
   0.0%
Not Hispanic or Latino
28
  90.3%
Unknown or Not Reported
3
   9.7%
Race (NIH/OMB)  
Measure Type: Count of Participants
Unit of measure:  Participants
Number Analyzed 31 participants
American Indian or Alaska Native
0
   0.0%
Asian
1
   3.2%
Native Hawaiian or Other Pacific Islander
0
   0.0%
Black or African American
8
  25.8%
White
18
  58.1%
More than one race
1
   3.2%
Unknown or Not Reported
3
   9.7%
Region of Enrollment  
Measure Type: Number
Unit of measure:  Participants
United States Number Analyzed 31 participants
31
Habitual mobility aid  
Measure Type: Count of Participants
Unit of measure:  Participants
Number Analyzed 31 participants
Long cane
28
  90.3%
Guide dog
3
   9.7%
Cause of vision impairment  
Measure Type: Count of Participants
Unit of measure:  Participants
Number Analyzed 31 participants
Retinitis Pigmentosa
8
  25.8%
Retinopathy of prematurity
5
  16.1%
Other
15
  48.4%
Unknown
3
   9.7%
Vision impairment onset  
Measure Type: Count of Participants
Unit of measure:  Participants
Number Analyzed 31 participants
At birth
17
  54.8%
Adult
14
  45.2%
Duration of vision loss  
Median (Full Range)
Unit of measure:  Years
Number Analyzed 31 participants
38
(5 to 73)
Amount of vision  
Measure Type: Count of Participants
Unit of measure:  Participants
Number Analyzed 31 participants
No light perception
11
  35.5%
Light perception
8
  25.8%
Better than light perception
12
  38.7%
1.Primary Outcome
Title Number of Collision Incidents (All Contacts)
Hide Description Collision incidents recorded by the device in everyday use, including long cane contacts and body contacts with surrounding objects in the environment.
Time Frame During the one-month period of device use
Hide Outcome Measure Data
Hide Analysis Population Description
The device switched between active and silent modes on a random schedule so data about collision incidents were available for each subject for both conditions
Arm/Group Title Silent Mode Active Mode
Hide Arm/Group Description:
Participants used the collision warning device as much as possible for about one month during everyday activities, when walking indoors and outdoors. The device switched between silent and active mode on a random schedule. In the silent mode the device detected potential collisions but did not provide any active warnings to the users.
Participants used the collision warning device as much as possible for about one month during everyday activities, when walking indoors and outdoors. The device switched between silent and active mode on a random schedule. In the active mode the device detected potential collisions and gave active warnings to the users via vibro-tactile wristbands.
Overall Number of Participants Analyzed 31 31
Median (Inter-Quartile Range)
Unit of Measure: Rate (contacts per 100 hazards per hour)
13.79
(7.28 to 24.29)
9.26
(6.56 to 14.96)
Hide Statistical Analysis 1
Statistical Analysis Overview Comparison Group Selection Silent Mode, Active Mode
Comments A within-subject comparison was performed. Each subject included in the analysis used the device in both the active and the silent mode. Comparison was between the two device operating modes. The null hypothesis was that there was no difference in the rate of contacts between active and silent modes.
Type of Statistical Test Superiority
Comments [Not Specified]
Statistical Test of Hypothesis P-Value < 0.001
Comments Since the outcome (contacts) represented over-dispersed count data and there were repeated measurements per subject, a generalized mixed effects model with a negative binomial family was used with each subject treated as a random intercept.
Method Mixed Models Analysis
Comments Fixed factors were included in the model to account for factors other than device operating mode that might affect collision rates.
Method of Estimation Estimation Parameter Rate ratio
Estimated Value 0.627
Confidence Interval (2-Sided) 95%
0.536 to 0.734
Parameter Dispersion
Type: Standard Error of the Mean
Value: 0.08
Estimation Comments Silent mode is the denominator for the rate ratio.
2.Secondary Outcome
Title Number of Body Contacts
Hide Description Collision incidents with body contacts recorded by the device
Time Frame During the one-month period of device use
Hide Outcome Measure Data
Hide Analysis Population Description
The device switched between active and silent modes on a random schedule so data about collision incidents were available for each subject for both conditions
Arm/Group Title Silent Mode Active Mode
Hide Arm/Group Description:
Participants used the collision warning device as much as possible for about one month during everyday activities, when walking indoors and outdoors. The device switched between silent and active mode on a random schedule. In the silent mode the device detected potential collisions but did not provide any active warnings to the users.
Participants used the collision warning device as much as possible for about one month during everyday activities, when walking indoors and outdoors. The device switched between silent and active mode on a random schedule. In the active mode the device detected potential collisions and gave active warnings to the users via vibro-tactile wristbands.
Overall Number of Participants Analyzed 31 31
Median (Inter-Quartile Range)
Unit of Measure: Rate (contacts per 100 hazards per hour)
1.13
(0.45 to 3.08)
1.09
(0.3 to 1.97)
3.Secondary Outcome
Title Device Questionnaire
Hide Description Questionnaire addressing participants' experiences of using the device. Scores were on a 5-point rating scale (1 to 5) with higher scores representing a better score. Questions were grouped into four main categories: i) overall satisfaction, ii) comfort, iii) mobility benefit, and iv) ease of operation. An average score was computed for questions within each category.
Time Frame During the one-month period of device use
Hide Outcome Measure Data
Hide Analysis Population Description
[Not Specified]
Arm/Group Title Silent and Active Mode
Hide Arm/Group Description:
Since participants did not know when the device was in either the silent or the active mode, it was not possible for them to answer questions specific to each mode. The questionnaire was completed after using the device for one month and therefore represents ratings of the device for the whole duration of the trial including both active and silent operating modes.
Overall Number of Participants Analyzed 30
Mean (Standard Deviation)
Unit of Measure: scores on a scale
Overall satisfaction 3.68  (0.74)
Comfort 4.08  (0.53)
Mobility benefit 3.05  (1.08)
Ease of operation 3.96  (0.49)
Time Frame Adverse event data were collected during the one-month period when subjects were using the device.
Adverse Event Reporting Description A brief questionnaire was administered to each subject by telephone each week during the one-month period of device use to check on how much they were using the device and whether they had encountered any difficulties. One question specifically asked whether the subject had experienced any adverse events.
 
Arm/Group Title Silent and Active Mode
Hide Arm/Group Description During the period of home-use of the device, all participants experienced both the silent and active modes on a random schedule. Neither the subject nor the researcher recording adverse events knew whether the device was in silent or active mode at the time when an event occurred, thus the adverse events are reported for all participants and both modes together.
All-Cause Mortality
Silent and Active Mode
Affected / at Risk (%)
Total   0/36 (0.00%)    
Hide Serious Adverse Events
Silent and Active Mode
Affected / at Risk (%) # Events
Total   0/36 (0.00%)    
Hide Other (Not Including Serious) Adverse Events
Frequency Threshold for Reporting Other Adverse Events 0%
Silent and Active Mode
Affected / at Risk (%) # Events
Total   6/36 (16.67%)    
General disorders   
Minor contact with object in the environment  [1]  6/36 (16.67%)  8
Indicates events were collected by systematic assessment
[1]
A minor contact, brushing against or bumping into an object (e.g., bushes, overhanging branches) in the environment when walking
Certain Agreements
Principal Investigators are NOT employed by the organization sponsoring the study.
There is NOT an agreement between Principal Investigators and the Sponsor (or its agents) that restricts the PI's rights to discuss or publish trial results after the trial is completed.
Results Point of Contact
Layout table for Results Point of Contact information
Name/Title: Alex Bowers
Organization: Schepens Eye Research Institute of Massachusetts Eye and Ear
Phone: 617 912 2512
EMail: alex_bowers@meei.harvard.edu
Layout table for additonal information
Responsible Party: Alexandra Bowers, Massachusetts Eye and Ear Infirmary
ClinicalTrials.gov Identifier: NCT03057496    
Other Study ID Numbers: 1007377
First Submitted: February 14, 2017
First Posted: February 20, 2017
Results First Submitted: October 30, 2020
Results First Posted: December 21, 2020
Last Update Posted: February 10, 2021