Blindness, Glaucoma, Hemianopia, Hemianopsia, Peripheral Visual Field Defect, Retinitis Pigmentosa
Conditions
Brief summary
This study evaluates a novel collision warning device to help people with severe vision impairment or blindness avoid collisions with obstacles. The main hypothesis to be tested is that the device reduces the number of collisions with obstacles in everyday activities.
Detailed description
Participants with blindness or severe visual field loss (hemianopia or tunnel vision) will be trained to use a collision warning device that alerts them to impending collisions. Participants will use the device at home during everyday mobility for about 1 month. The device is designed to supplement existing mobility devices, such as a long cane or dog guide. The device will provide warnings about potential collisions with mid- or high-level obstacles (which are typically not detected by a long cane).
Interventions
DEVICECollision warning device
The collision warning device is a pocket-sized, electronic system that includes a micro-computer, a clip-on miniature camera, a gyro-sensor, an accelerometer, and a rechargeable battery, all contained within a shoulder bag. It is about the size of a smart phone. When a potential collision is detected by the device it emits a warning to the user, either in the form of an audible beep or a tactile warning through bracelets worn on the wrist. The time to collision will be coded in both the auditory and tactile domains. The device is designed to only give warnings about high risk collisions, so the users will not be continually bombarded by warnings for every potential collision object in the environment.
Sponsors
Massachusetts Eye and Ear Infirmary
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
OTHER
Masking
NONE
Masking description
Although this is a single-arm study, participants will be masked in the sense that they will not know whether the device is operating in the active mode (intervention condition), when it gives warnings, or the silent mode (control condition), when it does not give warnings. The device will be programmed to generate a different randomized active/silent schedule for each subject. The investigator conducting the statistical analyses will also be masked as to whether the device was in the active or silent mode
Intervention model description
The device will operate in two modes: active mode (intervention condition), when it gives warnings and, silent mode (control condition), when it does not give warnings. The device will be programmed to generate a different randomized active/silent schedule for each subject. Participants will not know whether it is in the active or silent mode.
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Blindness (or very limited vision with visual acuity no better than counting fingers), * Or severe peripheral field loss / tunnel vision (≤ 40° remaining visual field) with visual acuity of at least 20/200, * Or homonymous hemianopia with visual acuity of at least 20/200; * Able to walk independently either with or without mobility aids such as a long cane or guide dog (but without the aid of a sighted guide); * Reports at least minor bumps or collisions within the last 3 months;
Exclusion criteria
* Currently participating in a mobility training program * Diagnosed dementia * Significant cognitive decline * Participants with hemianopia will be excluded if they have hemianopia for less than 3 months and/or have spatial neglect
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Number of Collision Incidents (All Contacts) | During the one-month period of device use | Collision incidents recorded by the device in everyday use, including long cane contacts and body contacts with surrounding objects in the environment. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Number of Body Contacts | During the one-month period of device use | Collision incidents with body contacts recorded by the device |
| Device Questionnaire | During the one-month period of device use | 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. |
Countries
United States
Participant flow
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.
Participants by arm
| Arm | Count |
|---|---|
| Silent and Active Mode 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. | 31 |
| Total | 31 |
Withdrawals & dropouts
| Period | Reason | FG000 |
|---|---|---|
| Overall Study | Device failure | 2 |
| Overall Study | Did not use device during home trial | 3 |
| Overall Study | Lost to Follow-up | 5 |
| Overall Study | Withdrawal by Subject | 8 |
Baseline characteristics
| Characteristic | Silent and Active Mode |
|---|---|
| Age, Continuous | 61 Years |
| Amount of vision Better than light perception | 12 Participants |
| Amount of vision Light perception | 8 Participants |
| Amount of vision No light perception | 11 Participants |
| Cause of vision impairment Other | 15 Participants |
| Cause of vision impairment Retinitis Pigmentosa | 8 Participants |
| Cause of vision impairment Retinopathy of prematurity | 5 Participants |
| Cause of vision impairment Unknown | 3 Participants |
| Duration of vision loss | 38 years |
| Ethnicity (NIH/OMB) Hispanic or Latino | 0 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 28 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 3 Participants |
| Habitual mobility aid Guide dog | 3 Participants |
| Habitual mobility aid Long cane | 28 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants |
| Race (NIH/OMB) Asian | 1 Participants |
| Race (NIH/OMB) Black or African American | 8 Participants |
| Race (NIH/OMB) More than one race | 1 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 3 Participants |
| Race (NIH/OMB) White | 18 Participants |
| Region of Enrollment United States | 31 participants |
| Sex: Female, Male Female | 13 Participants |
| Sex: Female, Male Male | 18 Participants |
| Vision impairment onset Adult | 14 Participants |
| Vision impairment onset At birth | 17 Participants |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | 0 / 36 |
| other Total, other adverse events | 6 / 36 |
| serious Total, serious adverse events | 0 / 36 |
Outcome results
Primary
Number of Collision Incidents (All Contacts)
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
Population: 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 | Measure | Value (MEDIAN) |
|---|---|---|
| Silent Mode | Number of Collision Incidents (All Contacts) | 13.79 Rate (contacts per 100 hazards per hour) |
| Active Mode | Number of Collision Incidents (All Contacts) | 9.26 Rate (contacts per 100 hazards per hour) |
Comparison: 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.p-value: <0.00195% CI: [0.536, 0.734]Mixed Models Analysis
Secondary
Device Questionnaire
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
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Silent Mode | Device Questionnaire | Overall satisfaction | 3.68 scores on a scale | Standard Deviation 0.74 |
| Silent Mode | Device Questionnaire | Comfort | 4.08 scores on a scale | Standard Deviation 0.53 |
| Silent Mode | Device Questionnaire | Mobility benefit | 3.05 scores on a scale | Standard Deviation 1.08 |
| Silent Mode | Device Questionnaire | Ease of operation | 3.96 scores on a scale | Standard Deviation 0.49 |
Secondary
Number of Body Contacts
Collision incidents with body contacts recorded by the device
Time frame: During the one-month period of device use
Population: 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 | Measure | Value (MEDIAN) |
|---|---|---|
| Silent Mode | Number of Body Contacts | 1.13 Rate (contacts per 100 hazards per hour) |
| Active Mode | Number of Body Contacts | 1.09 Rate (contacts per 100 hazards per hour) |