Recruiting

hf-tRNS

Sponsor:

University of Waterloo

Code:

NCT07341763

Conditions

Retinitis Pigmentosa (RP)

Rod Cone Dystrophy

Visually Impaired Persons

Peripheral Visual Field Defect of Both Eyes

Low Vision, Both Eyes

Eligibility Criteria

Sex: All

Age: 18+

Healthy Volunteers: Not accepted

Interventions

Active hf-tRNS.

Placebo/sham hf-tRNS

Study Details

Brief 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. 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.

Conditions

Retinitis Pigmentosa (RP)

Rod Cone Dystrophy

Visually Impaired Persons

Peripheral Visual Field Defect of Both Eyes

Low Vision, Both Eyes

Study ID

NCT07341763

Start date

Jul 1, 2026

Status verified date

Apr, 2026

Completion date

Aug 31, 2027

Anticipated

Primary completion date

Aug 31, 2027

Anticipated

Eligibility Criteria

Eligibility Criteria

Sex: All

Age: 18+

Healthy Volunteers: Not accepted

Inclusion Criteria:

  • 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 binocular visual fields no better than 50 degrees in total in each eye as given by the Humphrey Field analyzer and no better than 50 degrees binocularly as given by 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.

Exclusion Criteria:

  • 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.
  • 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.

Study Design

Enrollment

20 participants

Anticipated

Allocation

Randomized

Intervention Model

Crossover

Primary purpose

Treatment

Interventions and Outcome Measures

Arms

other: Active brain stimulation (study visit 2) and Placebo/Sham (study visit 3)

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).

other: Placebo/sham (study visit 2) and Active brain stimulation (study visit 3)

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).

Interventions

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).

Placebo/sham hf-tRNS

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).

Primary outcome measure

  • Percentage preferred walking speed (PPWS) [ Time Frame: The pre-test and post-tests will take roughly 2 hours to complete. ]

Central Contacts and Locations

Central contacts

Benjamin Thompson, PhD

1+5198884567ben.thompson@uwaterloo.ca

Melanie A Mungalsingh, PhD

melanie.mungalsingh@uwaterloo.ca

Locations

University of Waterloo, School of Optometry and Vision Science

Recruiting

Waterloo, Ontario, Canada, N2L 3G1

Contacts

Benjamin Thompson, PhD

1+15198884567ben.thompson@uwaterloo.ca

Melanie A Mungalsingh, PhD

melanie.mungalsingh@uwaterloo.ca

Principal Investigator:

Benjamin Thompson, PhD

More Information

Sponsor

University of Waterloo

Last update posted

Jul 7, 2026

Last verified

Apr, 2026

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
  • low vision
  • vision loss partial
  • occipital pole
  • primary visual cortex
  • V1
  • neuroplasticity
  • mobility difficulty
  • mobility limitation
  • mobility and independence

Trial information was received from ClinicalTrials.gov and was last updated on 2026-10-07. This information was provided to ClinicalTrials.gov by University of Waterloo on 2026-07-07. Recruitment status is synced daily from ClinicalTrials.gov and may not reflect the sponsor's current status. Confirm during your call.