An interventional study of Active hf-tRNS. and Placebo/sham hf-tRNS in Retinitis Pigmentosa (RP), Rod Cone Dystrophy and Visually Impaired Persons, sponsored by University of Waterloo. Recruiting at 1 site in Canada. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-03.
Sponsored by University of Waterloo · Not applicable, Interventional, and Treatment
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.
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.
278 studies on the registry are indexed under Retinitis Pigmentosa; 72 are open to participants now.
This study's planned enrollment of 20 is below the median of 27 across 179 interventional studies indexed under Retinitis Pigmentosa.
Browse Retinitis Pigmentosa studies →University of Waterloo is the lead sponsor of 90 studies on the registry; 7 are open to participants now.
Of its 12 completed or terminated interventional studies of FDA-regulated products, 9 (75%) have results posted.
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The criteria were revised on the registry on Nov 3, 2026. See what changed
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
For all participants the for brain stimulation are:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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).
Device: Active hf-tRNS. · Device: Placebo/sham hf-tRNS
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).
Device: Active hf-tRNS. · Device: Placebo/sham 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).
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).
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.
Time frame: The pre-test and post-tests will take roughly 2 hours to complete.
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.
Time frame: 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).
Time frame: The pre-test and post-tests will take roughly 2 hours to complete.
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: Yes — The IPD which underlie results in a publication will be made available after deidentification upon reasonable requests to the research team.
Supporting information: Study protocol, Statistical analysis plan
Time frame: The IPD will be available upon publication, and no more than 9 months after the publication.
Access criteria: The IPD will be shared to researchers who provide a methodologically sound proposal.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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