Retinitis Pigmentosa (RP)NCT07341763
Brain Stimulation Effects on Orientation and Mobility Skills in Adults With Vision Impairment
A study testing Active hf-tRNS. in people with Retinitis Pigmentosa (RP) and Rod Cone Dystrophy, run by University of Waterloo at 1 site in Canada.
Trial summary
This pilot clinical trial evaluates whether non-invasive brain stimulation improves the orientation and mobility (O\&M) skills of individuals with constricted visual fields in both eyes. The study is composed of three visits. The first visit is meant to confirm eligibility by performing a few clinical tests. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Retinitis Pigmentosa (RP), Rod Cone Dystrophy, Visually Impaired Persons
- What is being tested?
- Active hf-tRNS.
- Type of treatment
- Medical device
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 20 participants
- Where
- 1 siteCanada
- Study dates
- 1 Nov 2026to 31 Aug 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Are healthy, capacitated adults with binocular constricted visual field loss (due to either retinitis pigmentosa (RP), rod-cone dystrophy, or advanced glaucoma) resulting in functional vision losses. These individuals with visual impairments can be those who have been previously trained by an Orientation and Mobility (O\&M) specialist to independently travel with the long white cane daily (since the length of the white cane and tip at the base are based on personal preference, they should be willing to use their own white cane for the study), and those who do not necessarily use a cane for travelling.
- Have binocular visual acuity or best corrected binocular visual acuity no worse than 6/12 or 20/40 or +0.30 logMAR (inclusive) with no eccentric viewing and visual fields no better than 50 degrees in total in each eye as given by the Humphrey Field analyzer and arc perimeter test. The Humphrey Field Analyzer measures static visual field test, whereas the Arc perimeter test measures kinetic visual field test. Measuring kinetic and static visual field would promote a greater understanding of the individual's daily performance.
- Are over the age of 18 (inclusive) and has full legal capacity to provide informed consent.
- Have read and fully comprehends the information in the consent letter.
- Are willing and capable of adhering to instructions and maintaining the outlined appointment schedule.
Who cannot join
- Are involved in other recent eye-related studies, either clinical or research-related. To be eligible they would have to wait at least one week for studies not involving brain stimulation, and four weeks for studies in which they receive brain stimulation before they could participate in this study.
- Have been diagnosed with dementia or self-reported dementia with no formal diagnosis.
- Have been diagnosed with a cognitive impairment or self-reported cognitive impairment with no formal diagnosis.
- Have been diagnosed with physical or motor impairments resulting in walking and/or balancing issues or self-reported physical or motor impairments resulting in walking and/or balancing issues with no formal diagnosis.
- Have been diagnosed with vestibular disorders or dysfunctions which affects one's balance and/or mobility or self-reported vestibular disorders or dysfunctions which affects one's balance and/or mobility with no formal diagnosis.
- Are unable to follow the researcher's instructions.
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- Are anticipating treatment (including ocular surgery) for any eye disease within the duration of the study.
- Have any ocular pathology in addition to retinitis pigmentosa (RP), rod-cone dystrophy, or advanced glaucoma, which can diminish their visual acuity and/or their visual field, however wearing glasses or contact lenses, as well as mild cataract of grade 2 or below is acceptable.
- Have severe hearing impairment.
- Are pregnant or trying to get pregnant.
- Fit any of the typical contraindicators for brain stimulation. See contraindicator section below.
- For all participants the contraindications for brain stimulation are:
- Diagnosed with epilepsy or have previously experienced an epileptic seizure.
- Implanted medication pump or implanted electronic device, including defibrillator or pacemaker.
- Any metal implants in the head (excluding tooth fillings).
- Active electric implants anywhere in the body (especially the head region).
- On psychoactive medication for any psychiatric or neurological conditions including but not limited to depression and schizophrenia.
- Areas of sensitive skin located on the face or head, or a skin condition on the face, or regularly use medication to alleviate skin irritation on the face.
- Recurring headaches.
- Previous head injury or skull fracture or head/brain surgery.
- Heart disease, neurological condition, or a history of cardiac or neurological surgery.
- Current or historical cancerous or noncancerous brain tumor, or other abnormalities in brain structure.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Melanie A Mungalsingh, PhD contact
Canada1 site, 1 recruiting
- Recruiting
University of Waterloo, School of Optometry and Vision Science
Waterloo, Ontario, N2L 3G1
Benjamin Thompson, PhD, 1+15198884567 ext. 39398, ben.thompson@uwaterloo.ca
Melanie A Mungalsingh, PhD, melanie.mungalsingh@uwaterloo.ca
About this study
Official title: A Randomized, Double-Blind, Placebo-Controlled Pilot Study to Evaluate Non-invasive Brain Stimulation Effects on Orientation and Mobility Performance in Adults With Visual Impairments
This pilot clinical trial evaluates whether non-invasive brain stimulation improves the orientation and mobility (O\&M) skills of individuals with constricted visual fields in both eyes. The study is composed of three visits. The first visit is meant to confirm eligibility by performing a few clinical tests. Eligible participants will then complete two additional visits, one in which the participants receive active stimulation, and one in which the participants receive placebo (sham) stimulation. Stimulation will be administered in a randomized, double-blind order. To evaluate improvement, various measures of O\&M performance will be assessed on a standardized obstacle course featuring static natural and artificial obstacles at defined intervals after the intervention. We hypothesize that the application of hf-tRNS to V1 will improve the orientation and mobility skills of individuals with constricted visual fields immediately following stimulation as a results of enhanced periphery through modulation of the mechanisms responsible for crowding, thereby reducing crowding effects and improving contrast for individuals with rod-cone dystrophy and RP (genetic conditions), whereas for individuals with glaucoma (a neurogenerative condition), any improvement noted would be attributed to be enhanced processing of visual signal in the affected periphery. The results will inform the design of a future, larger-scale study.
Read the detailed description
This within-subject crossover pilot study involves applying a weak focused electrical current to the head, to target areas of visual processing, more specifically the primary visual cortex (V1) within the occipital pole. The purpose of this study is to investigate the efficacy of high-frequency transcranial random noise stimulation (hf-tRNS), a safe and well-established form of brain stimulation on O\&M performance of individuals with constricted visual fields in both eyes due to either retinitis pigmentosa (RP), rod-cone dystrophy, or advanced glaucoma.
Participants will be recruited from university-affiliated clinics as well as local clinical practices. After obtaining full informed consent at the first visit, participants will complete clinical tests to confirm that the eligibility criteria of the study are met. These tests include measuring the participant's corrected binocular distance and near visual acuities, binocular contrast sensitivity, binocularity, as well as peripheral visual fields. Researchers will also ensure that it safe for the participant to undergo brain stimulation using a list of contraindicators for brain stimulation interventions and verify that participants are free from physical or motor impairments as well as vestibular disorders or dysfunctions that can impact the participant's walking and balancing abilities.
During the two subsequent visits, the effects of stimulation (which lasts 20 minutes) will be studied 2 and 30 minutes after stimulation. To evaluate improvement, various measures of O\&M performance will be targeted as participants complete an O\&M course divided into 4 sections and composed of an array of static natural and artificial (man-made) obstacles. Participants will be instructed to walk along the various sections at a comfortable pace, safely negotiating the obstacles without touching any of the obstacles. Participants will also be told in which sections obstacles will be encounter. Static natural obstacles refer to fixed/steady/stable obstacles that are either readily found in the environment (e.g., potted plants) or form part of the architecture of the building (e.g., a pole or a sealed doorway). Artificial obstacles will be made of light material such as polystyrene, rubber foam, soft cardboard, burlap, light plastic, or paper. Static natural/real obstacles will be at foot level, foot to knee height, as well as shoulder and head heights, whereas artificial obstacles will be placed either above the knee, waist, at the shoulder or head height. Individuals with constricted field loss in both eyes who use a long white cane for travelling and have received O\&M training (including caning skills) from an orientation and mobility professional will be asked to complete the course with their cane. However, individuals with constricted visual field in both eyes who do not use a cane can also complete the same course.
Measures of performance include the primary outcome measure percentage preferred walking speed (PPWS), that is the walking speed of the individual who is visually impaired in an environment with obstacles expressed as a percentage of their preferred walking speed in an unobstructed path. Secondary outcome measures include: the time taken to complete each of the 4 sections of the course, visual detection distance (VDD) (the distance at which an individual detects an obstacle in the travel path, even if it cannot be identified), and visual identification distance (VID) (the distance at which an individual can correctly identify an obstacle in the travel path).
Course section #1 will not consist of obstacles. The time taken to complete the course section, and preferred walking speed in an unobstructed path (obtained from the completion time and length of the straight, flat path) will be measured.
Course section #2 will consist of obstacles and will be an indoor space leading to a more opened space within the building. The time taken to complete the course section, and preferred walking speed in an obstructed path (obtained from the completion time and length of the path) will be measured. The percentage preferred walking speed (PPWS) will be calculated. PPWS is the preferred walking speed of the individual in course section #2 expressed as a percentage of the participant's preferred walking speed in course section #1.
Course sections #3 and #4 will be used for measuring VDD and VID. Each course will be a straight indoor corridor consisting of only one obstacle, and the obstacle will be different for each of the two sections. Moreover, course section #3 will be used as a training course for measuring VDD and VID. The time taken to complete the course section, visual detection distance (VDD), and visual identification distance (VID) will be measured in course sections #3 and #4.
It is important to note that for course section # 2, the location of the obstacles in each trial (pre, post 1, and post 2) will not be varied, but rather the location of the obstacles on each treatment day will be randomized. Moreover, given that courses 3 and 4 only have one obstacle each, it would also help to change what the actual object is for both courses for each trial on both treatment days, as well as the distance they are positioned. Therefore, with respect to courses 3 and 4, each participant will have to detect and hence identify a total of 12 single obstacles. In addition, two researchers will always be with the participant at all times. One will be with the participant to provide instructions and record data; whilst the other will be ahead of the participant to make sure the path is clear, record the times, and confirm that the obstacles are still in place (when applicable).
There will be two stimulation sessions (one with active stimulation and one with placebo (the order will be randomized so that neither the participant nor the researcher will know what the subject will receive)). At the two stimulation sessions the primary and secondary outcome measures will be evaluated as the participant completes the O\&M course before stimulation (O\&M pretest), as well as 2 mins after stimulation (O\&M post-test 1/immediately after stimulation), and 30 mins after stimulation (O\&M post-test 2/30 minutes after stimulation).
We hypothesize that the application of hf-tRNS to V1 will improve the orientation and mobility skills of individuals with constricted visual fields immediately following stimulation as a results of enhanced periphery through modulation of the mechanisms responsible for crowding, thereby reducing crowding effects and improving contrast for individuals with rod-cone dystrophy and RP (genetic conditions),whereas for individuals with glaucoma (a neurogenerative condition) who have little to no functional peripheral vision, any improvement noted would be attributed to be enhanced processing of visual signal in the affected periphery. The objective of this study is to improve the fundamental visual processes of individuals with constricted visual fields using hf-tRNS. From a scientific perspective, the investigators hope to discover whether brain stimulation can serve as an additional rehabilitation tool for improving the O\&M skills of individuals with constricted visual fields. Investigators expect that participants will experience temporary O\&M improvements, however, there will not be any lasting improvements in O\&M skills from such a single session within subject study design. If the results of this study show a positive effect, the data will be used to power a larger study. All procedures will occur at the Human Visual Neuroscience Laboratory, University of Waterloo, Ontario, Canada.
- Conditions
- Retinitis Pigmentosa (RP), Rod Cone Dystrophy, Visually Impaired Persons, Peripheral Visual Field Defect of Both Eyes, Low Vision, Both Eyes, Vision Loss Partial
- Being tested
- Active hf-tRNS., Placebo/sham hf-tRNS
- Keywords
- Retinitis Pigmentosa (RP), Rod Cone dystrophy, Advanced Glaucoma, Visually Impaired Persons, Peripheral Visual Field Defect of Both Eyes, Low Vision, Both eyes, Brain stimulation, tES, tRNS, hf-tRNS, transcranial electrical stimulation, transcranial random noise stimulation, high-frequency transcranial random noise stimulation, Long white cane, white cane, mobility cane, walking, orientation and mobility, orientation, mobility
- Medical subject headings
- Retinitis Pigmentosa, Cone-Rod Dystrophies, Vision, Low, Orientation, Spatial, Mobility Limitation, Glaucoma
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Active hf-tRNS.Device
Active hf-tRNS: A weak alternating electric current is applied to the head through two electrodes to affect the cortical excitability of the targeted cells in the brain.
Stimulation instrument: neuroConn DC Stimulator Plus 2019 (Direct current stimulator Model number 0021, power: 1.2 W, charger: 2.9 V (maximum 160 mA)) (neurocaregroup.com), or neuroConn DC Stimulator MC 2016 (Multi-channel stimulator Model number 0028, power: 24 W, rating: 12 V (maximum 2 A)) (neurocaregroup.com).
Placebo/sham hf-tRNSDevice
Placebo/sham hf-tRNS: The tRNS machine will be used as in active stimulation, except the electrical current will not be applied.
Stimulation instrument: neuroConn DC Stimulator Plus 2019 (Direct current stimulator Model number 0021, power: 1.2 W, charger: 2.9 V (maximum 160 mA)) (neurocaregroup.com), or neuroConn DC Stimulator MC 2016 (Multi-channel stimulator Model number 0028, power: 24 W, rating: 12 V (maximum 2 A)) (neurocaregroup.com).
| Study group | Role | What they receive |
|---|---|---|
| Active brain stimulation (study visit 2) and Placebo/Sham (study visit 3) | Other | Participants in this arm will be exposed to active stimulation for 20 minutes whilst seated quietly at treatment session 1 (study visit 2). They will then complete the orientation and mobility (O\&M) course 2-minutes and 30-minutes after stimulation. It is important to note that they will also complete the course before undergoing stimulation. In addition, individuals with constricted visual fields in both eyes who use a white cane for travelling will be encouraged to use their personal cane for the course, whereas those who do not use a cane will complete the course as they naturally would for any travel paths. Forty-eight hours later the same participants in this arm will be exposed to placebo/sham stimulation (study visit 3) and except for the treatment they receive that day, the same protocol from the previous visit will be executed, and the same outcome measures evaluated. Interventions: Active hf-tRNS at treatment (study visit 2); Placebo/sham hf-tRNS (study visit 3). Receives: Device: Active hf-tRNS.; Device: Placebo/sham hf-tRNS |
| Placebo/sham (study visit 2) and Active brain stimulation (study visit 3) | Other | Participants in this arm will be exposed to placebo/sham stimulation for 20 minutes whilst seated quietly at treatment session 1 (study visit 2). They will then proceed to complete the orientation and mobility (O\&M) course 2-minutes and 30-minutes after stimulation. It is important to note that they will also complete the course before undergoing stimulation. In addition, individuals with constricted visual fields in both eyes who use a white cane for travelling will be encouraged to use their personal cane for the course, whereas those who do not use a cane will complete the course as they naturally would for any travel paths. Forty-eight hours later the same participants in this arm will be exposed to active stimulation (study visit 3) and except for the treatment they receive that day, the same protocol from the previous visit will be executed, and the same outcome measures evaluated. Interventions: Placebo/sham hf-tRNS at treatment (study visit 2); Active hf-tRNS (study visit 3). Receives: Device: Active hf-tRNS.; Device: Placebo/sham hf-tRNS |
What is being measured
The primary outcome is the main question the study is designed to answer.
Percentage preferred walking speed (PPWS)
- Change in Percentage preferred walking speed (PPWS (%)) before and right after (2 mins) active stimulation.
- Change in Percentage preferred walking speed (PPWS (%)) before and 30-minutes after active stimulation.
- Change in Percentage preferred walking speed (PPWS (%)) before and right after (2 mins) placebo/sham stimulation.
- Change in Percentage preferred walking speed (PPWS (%)) before and 30-minutes after placebo/sham stimulation.
- Behavioural Measure: The participant will first complete section #1, which is obstacle free. The time taken to complete the section and preferred walking speed in an unobstructed path (obtained from the completion time and length of the straight, flat path) will be measured. They will then proceed to complete section #2, which has obstacles. The time taken to complete the section, and preferred walking speed in an obstructed path will be measured. PPWS= (preferred walking speed course 1/ preferred walking speed course 2)*100.
Measured: The pre-test and post-tests will take roughly 2 hours to complete.
Secondary outcomes (2)
Visual detection distance (VDD)
- Change in Visual detection distance (VDD (m)) before and right after (2 mins) active stimulation.
- Change in Visual detection distance (VDD (m)) before and 30-minutes after active stimulation.
- Change in Visual detection distance (VDD (m)) before and right after (2 mins) placebo/sham stimulation.
- Change in Visual detection distance (VDD (m)) before and 30-minutes after placebo/sham stimulation.
- Behavioural Measure: Participants will be instructed to walk along the various sections at a comfortable pace, safely negotiating the obstacle without touching any of them. The participant will complete sections #3 and #4. Each section will be a straight indoor corridor consisting of only one obstacle. Moreover, section #3 will be used as a training course, whereas section #4 is meant to collect data. The time it takes to first detect the obstacle and the distance from the participant to the obstacle, the moment it is first detected will be measured. This distance is VDD.
Measured: The pre-test and post-tests will take roughly 2 hours to complete.
Visual identification distance (VID)
- Change in Visual identification distance (VID (m)) before and right after (2 mins) active stimulation.
- Change in Visual identification distance (VID (m)) before and 30-minutes after active stimulation.
- Change in Visual identification distance (VID (m)) before and right after (2 mins) placebo/sham stimulation.
- Change in Visual identification distance (VID (m)) before and 30-minutes after placebo/sham stimulation.
- Behavioural Measure: Participants will be instructed to walk along the various sections at a comfortable pace, safely negotiating the obstacle without touching any of them. The participant will complete sections #3 and #4. Each section will be a straight indoor corridor consisting of one obstacle. Section #3 will be used for training, whereas section #4 is meant to collect data. The time it takes to correctly identify the obstacle just detected, and the distance from the participant to the obstacle, the moment they first identify it will be measured (VID).
Measured: The pre-test and post-tests will take roughly 2 hours to complete.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted14 Jan 2026
- Study start1 Nov 2026 (estimated)
- Primary completion31 Aug 2027 (estimated)
- Study completion31 Aug 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Retinitis Pigmentosa (RP)Studies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- The study is a randomized, double-blind, placebo-controlled pilot study. There will be two brain stimulation/intervention sessions. The participant will receive active stimulation at one session and placebo at another sessions. Intervention sessions will be separated by 48 hours. The order will be randomized so that neither the participant nor the researcher will know what the participant will receive at each session.
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 20 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Waterloo
- Sponsor type
- University, hospital or other
- Collaborators
- The Hong Kong Polytechnic University
- Responsible party
- Principal investigator, Ben Thompson, University of Waterloo
- Investigators
- Benjamin Thompson, PhD, Principal investigator, University of Waterloo
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07341763
- Sponsor's protocol ID
- REB #47153
- Status last verified
- Apr 2026
- First submitted
- 5 Jan 2026
- Last updated
- 3 Nov 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: The IPD which underlie results in a publication will be made available after deidentification upon reasonable requests to the research team.
Study at a glance
From the registry record, last updated by the sponsor on 3 Nov 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Randomized, Double-Blind, Placebo-Controlled Pilot Study to Evaluate Non-invasive Brain Stimulation Effects on Orientation and Mobility Performance in Adults With Visual Impairments
- ClinicalTrials.gov ID
- NCT07341763
- Acronym / sponsor ID
- REB #47153
- Conditions
- Retinitis Pigmentosa (RP), Rod Cone Dystrophy, Visually Impaired Persons, Peripheral Visual Field Defect of Both Eyes, Low Vision, Both Eyes, Vision Loss Partial
- Keywords
- Retinitis Pigmentosa (RP), Rod Cone dystrophy, Advanced Glaucoma, Visually Impaired Persons, Peripheral Visual Field Defect of Both Eyes, Low Vision, Both eyes, Brain stimulation, tES
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 20 participants (estimated)
- Lead sponsor
- University of WaterlooUniversity, hospital or other
- Collaborators
- The Hong Kong Polytechnic University
- Study start
- 1 Nov 2026 (estimated)
- Primary completion
- 31 Aug 2027 (estimated)
- Study completion
- 31 Aug 2027 (estimated)
- First posted
- 14 Jan 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This pilot clinical trial evaluates whether non-invasive brain stimulation improves the orientation and mobility (O\&M) skills of individuals with constricted visual fields in both eyes. The study is composed of three visits. The first visit is meant to confirm eligibility by performing a few clinical tests. Eligible participants will then complete two additional visits, one in which the participants receive active stimulation, and one in which the participants receive placebo (sham) stimulation. Stimulation will be administered in a randomized, double-blind order. To evaluate improvement, various measures of O\&M performance will be assessed on a standardized obstacle course featuring static natural and artificial obstacles at defined intervals after the intervention. We hypothesize that the application of hf-tRNS to V1 will improve the orientation and mobility skills of individuals with constricted visual fields immediately following stimulation as a results of enhanced periphery through modulation of the mechanisms responsible for crowding, thereby reducing crowding effects and improving contrast for individuals with rod-cone dystrophy and RP (genetic conditions), whereas for individuals with glaucoma (a neurogenerative condition), any improvement noted would be attributed to be enhanced processing of visual signal in the affected periphery. The results will inform the design of a future, larger-scale study.
Detailed description
This within-subject crossover pilot study involves applying a weak focused electrical current to the head, to target areas of visual processing, more specifically the primary visual cortex (V1) within the occipital pole. The purpose of this study is to investigate the efficacy of high-frequency transcranial random noise stimulation (hf-tRNS), a safe and well-established form of brain stimulation on O\&M performance of individuals with constricted visual fields in both eyes due to either retinitis pigmentosa (RP), rod-cone dystrophy, or advanced glaucoma.
Participants will be recruited from university-affiliated clinics as well as local clinical practices. After obtaining full informed consent at the first visit, participants will complete clinical tests to confirm that the eligibility criteria of the study are met. These tests include measuring the participant's corrected binocular distance and near visual acuities, binocular contrast sensitivity, binocularity, as well as peripheral visual fields. Researchers will also ensure that it safe for the participant to undergo brain stimulation using a list of contraindicators for brain stimulation interventions and verify that participants are free from physical or motor impairments as well as vestibular disorders or dysfunctions that can impact the participant's walking and balancing abilities.
During the two subsequent visits, the effects of stimulation (which lasts 20 minutes) will be studied 2 and 30 minutes after stimulation. To evaluate improvement, various measures of O\&M performance will be targeted as participants complete an O\&M course divided into 4 sections and composed of an array of static natural and artificial (man-made) obstacles. Participants will be instructed to walk along the various sections at a comfortable pace, safely negotiating the obstacles without touching any of the obstacles. Participants will also be told in which sections obstacles will be encounter. Static natural obstacles refer to fixed/steady/stable obstacles that are either readily found in the environment (e.g., potted plants) or form part of the architecture of the building (e.g., a pole or a sealed doorway). Artificial obstacles will be made of light material such as polystyrene, rubber foam, soft cardboard, burlap, light plastic, or paper. Static natural/real obstacles will be at foot level, foot to knee height, as well as shoulder and head heights, whereas artificial obstacles will be placed either above the knee, waist, at the shoulder or head height. Individuals with constricted field loss in both eyes who use a long white cane for travelling and have received O\&M training (including caning skills) from an orientation and mobility professional will be asked to complete the course with their cane. However, individuals with constricted visual field in both eyes who do not use a cane can also complete the same course.
Measures of performance include the primary outcome measure percentage preferred walking speed (PPWS), that is the walking speed of the individual who is visually impaired in an environment with obstacles expressed as a percentage of their preferred walking speed in an unobstructed path. Secondary outcome measures include: the time taken to complete each of the 4 sections of the course, visual detection distance (VDD) (the distance at which an individual detects an obstacle in the travel path, even if it cannot be identified), and visual identification distance (VID) (the distance at which an individual can correctly identify an obstacle in the travel path).
Course section #1 will not consist of obstacles. The time taken to complete the course section, and preferred walking speed in an unobstructed path (obtained from the completion time and length of the straight, flat path) will be measured.
Course section #2 will consist of obstacles and will be an indoor space leading to a more opened space within the building. The time taken to complete the course section, and preferred walking speed in an obstructed path (obtained from the completion time and length of the path) will be measured. The percentage preferred walking speed (PPWS) will be calculated. PPWS is the preferred walking speed of the individual in course section #2 expressed as a percentage of the participant's preferred walking speed in course section #1.
Course sections #3 and #4 will be used for measuring VDD and VID. Each course will be a straight indoor corridor consisting of only one obstacle, and the obstacle will be different for each of the two sections. Moreover, course section #3 will be used as a training course for measuring VDD and VID. The time taken to complete the course section, visual detection distance (VDD), and visual identification distance (VID) will be measured in course sections #3 and #4.
It is important to note that for course section # 2, the location of the obstacles in each trial (pre, post 1, and post 2) will not be varied, but rather the location of the obstacles on each treatment day will be randomized. Moreover, given that courses 3 and 4 only have one obstacle each, it would also help to change what the actual object is for both courses for each trial on both treatment days, as well as the distance they are positioned. Therefore, with respect to courses 3 and 4, each participant will have to detect and hence identify a total of 12 single obstacles. In addition, two researchers will always be with the participant at all times. One will be with the participant to provide instructions and record data; whilst the other will be ahead of the participant to make sure the path is clear, record the times, and confirm that the obstacles are still in place (when applicable).
There will be two stimulation sessions (one with active stimulation and one with placebo (the order will be randomized so that neither the participant nor the researcher will know what the subject will receive)). At the two stimulation sessions the primary and secondary outcome measures will be evaluated as the participant completes the O\&M course before stimulation (O\&M pretest), as well as 2 mins after stimulation (O\&M post-test 1/immediately after stimulation), and 30 mins after stimulation (O\&M post-test 2/30 minutes after stimulation).
We hypothesize that the application of hf-tRNS to V1 will improve the orientation and mobility skills of individuals with constricted visual fields immediately following stimulation as a results of enhanced periphery through modulation of the mechanisms responsible for crowding, thereby reducing crowding effects and improving contrast for individuals with rod-cone dystrophy and RP (genetic conditions),whereas for individuals with glaucoma (a neurogenerative condition) who have little to no functional peripheral vision, any improvement noted would be attributed to be enhanced processing of visual signal in the affected periphery. The objective of this study is to improve the fundamental visual processes of individuals with constricted visual fields using hf-tRNS. From a scientific perspective, the investigators hope to discover whether brain stimulation can serve as an additional rehabilitation tool for improving the O\&M skills of individuals with constricted visual fields. Investigators expect that participants will experience temporary O\&M improvements, however, there will not be any lasting improvements in O\&M skills from such a single session within subject study design. If the results of this study show a positive effect, the data will be used to power a larger study. All procedures will occur at the Human Visual Neuroscience Laboratory, University of Waterloo, Ontario, Canada.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, investigator)
- Number of arms
- 2
- Model description
- The study is a randomized, double-blind, placebo-controlled pilot study. There will be two brain stimulation/intervention sessions. The participant will receive active stimulation at one session and placebo at another sessions. Intervention sessions will be separated by 48 hours. The order will be randomized so that neither the participant nor the researcher will know what the participant will receive at each session.
| Arm | Type | Receives |
|---|---|---|
| Active brain stimulation (study visit 2) and Placebo/Sham (study visit 3) | Other | Device: Active hf-tRNS., Device: Placebo/sham hf-tRNSParticipants in this arm will be exposed to active stimulation for 20 minutes whilst seated quietly at treatment session 1 (study visit 2). They will then complete the orientation and mobility (O\&M) course 2-minutes and 30-minutes after stimulation. It is important to note that they will also complete the course before undergoing stimulation. In addition, individuals with constricted visual fields in both eyes who use a white cane for travelling will be encouraged to use their personal cane for the course, whereas those who do not use a cane will complete the course as they naturally would for any travel paths. Forty-eight hours later the same participants in this arm will be exposed to placebo/sham stimulation (study visit 3) and except for the treatment they receive that day, the same protocol from the previous visit will be executed, and the same outcome measures evaluated. Interventions: Active hf-tRNS at treatment (study visit 2); Placebo/sham hf-tRNS (study visit 3). |
| Placebo/sham (study visit 2) and Active brain stimulation (study visit 3) | Other | Device: Active hf-tRNS., Device: Placebo/sham hf-tRNSParticipants in this arm will be exposed to placebo/sham stimulation for 20 minutes whilst seated quietly at treatment session 1 (study visit 2). They will then proceed to complete the orientation and mobility (O\&M) course 2-minutes and 30-minutes after stimulation. It is important to note that they will also complete the course before undergoing stimulation. In addition, individuals with constricted visual fields in both eyes who use a white cane for travelling will be encouraged to use their personal cane for the course, whereas those who do not use a cane will complete the course as they naturally would for any travel paths. Forty-eight hours later the same participants in this arm will be exposed to active stimulation (study visit 3) and except for the treatment they receive that day, the same protocol from the previous visit will be executed, and the same outcome measures evaluated. Interventions: Placebo/sham hf-tRNS at treatment (study visit 2); Active hf-tRNS (study visit 3). |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (5 listed)
- Are healthy, capacitated adults with binocular constricted visual field loss (due to either retinitis pigmentosa (RP), rod-cone dystrophy, or advanced glaucoma) resulting in functional vision losses. These individuals with visual impairments can be those who have been previously trained by an Orientation and Mobility (O\&M) specialist to independently travel with the long white cane daily (since the length of the white cane and tip at the base are based on personal preference, they should be willing to use their own white cane for the study), and those who do not necessarily use a cane for travelling.
- Have binocular visual acuity or best corrected binocular visual acuity no worse than 6/12 or 20/40 or +0.30 logMAR (inclusive) with no eccentric viewing and visual fields no better than 50 degrees in total in each eye as given by the Humphrey Field analyzer and arc perimeter test. The Humphrey Field Analyzer measures static visual field test, whereas the Arc perimeter test measures kinetic visual field test. Measuring kinetic and static visual field would promote a greater understanding of the individual's daily performance.
- Are over the age of 18 (inclusive) and has full legal capacity to provide informed consent.
- Have read and fully comprehends the information in the consent letter.
- Are willing and capable of adhering to instructions and maintaining the outlined appointment schedule.
Key exclusion criteria (22 listed)
- Are involved in other recent eye-related studies, either clinical or research-related. To be eligible they would have to wait at least one week for studies not involving brain stimulation, and four weeks for studies in which they receive brain stimulation before they could participate in this study.
- Have been diagnosed with dementia or self-reported dementia with no formal diagnosis.
- Have been diagnosed with a cognitive impairment or self-reported cognitive impairment with no formal diagnosis.
- Have been diagnosed with physical or motor impairments resulting in walking and/or balancing issues or self-reported physical or motor impairments resulting in walking and/or balancing issues with no formal diagnosis.
- Have been diagnosed with vestibular disorders or dysfunctions which affects one's balance and/or mobility or self-reported vestibular disorders or dysfunctions which affects one's balance and/or mobility with no formal diagnosis.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Active hf-tRNS.Active hf-tRNS: A weak alternating electric current is applied to the head through two electrodes to affect the cortical excitability of the targeted cells in the brain. Stimulation instrument: neuroConn DC Stimulator Plus 2019 (Direct current stimulator Model number 0021, power: 1.2 W, charger: 2.9 V (maximum 160 mA)) (neurocaregroup.com), or neuroConn DC Stimulator MC 2016 (Multi-channel stimulator Model number 0028, power: 24 W, rating: 12 V (maximum 2 A)) (neurocaregroup.com). | Device | Active brain stimulation (study visit 2) and Placebo/Sham (study visit 3), Placebo/sham (study visit 2) and Active brain stimulation (study visit 3) |
| Placebo/sham hf-tRNSPlacebo/sham hf-tRNS: The tRNS machine will be used as in active stimulation, except the electrical current will not be applied. Stimulation instrument: neuroConn DC Stimulator Plus 2019 (Direct current stimulator Model number 0021, power: 1.2 W, charger: 2.9 V (maximum 160 mA)) (neurocaregroup.com), or neuroConn DC Stimulator MC 2016 (Multi-channel stimulator Model number 0028, power: 24 W, rating: 12 V (maximum 2 A)) (neurocaregroup.com). | Device | Active brain stimulation (study visit 2) and Placebo/Sham (study visit 3), Placebo/sham (study visit 2) and Active brain stimulation (study visit 3) |
Primary outcome
Percentage preferred walking speed (PPWS)
Time frame: The pre-test and post-tests will take roughly 2 hours to complete.
* Change in Percentage preferred walking speed (PPWS (%)) before and right after (2 mins) active stimulation. * Change in Percentage preferred walking speed (PPWS (%)) before and 30-minutes after active stimulation. * Change in Percentage preferred walking speed (PPWS (%)) before and right after (2 mins) placebo/sham stimulation. * Change in Percentage preferred walking speed (PPWS (%)) before and 30-minutes after placebo/sham stimulation. * Behavioural Measure: The participant will first complete section #1, which is obstacle free. The time taken to complete the section and preferred walking speed in an unobstructed path (obtained from the completion time and length of the straight, flat path) will be measured. They will then proceed to complete section #2, which has obstacles. The time taken to complete the section, and preferred walking speed in an obstructed path will be measured. PPWS= (preferred walking speed course 1/ preferred walking speed course 2)*100.
2 secondary outcomes
Visual detection distance (VDD)
Time frame: The pre-test and post-tests will take roughly 2 hours to complete.
Visual identification distance (VID)
Time frame: The pre-test and post-tests will take roughly 2 hours to complete.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 3 Nov 2026.
- Individual participant dataSharing planned: Yes. The IPD which underlie results in a publication will be made available after deidentification upon reasonable requests to the research team.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Melanie A Mungalsingh, PhD contact
Benjamin Thompson, PhD principal investigator
University of Waterloo
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Active hf-tRNS. in people with Retinitis Pigmentosa (RP) and Rod Cone Dystrophy, run by University of Waterloo at 1 site in Canada.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 22 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 3 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Benjamin Thompson, PhD (1+5198884567 ext. 39398, ben.thompson@uwaterloo.ca), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Percentage preferred walking speed (PPWS) (time frame: The pre-test and post-tests will take roughly 2 hours to complete.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 3 Nov 2026; AzTrials last refreshed its copy on 6 Nov 2026.