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
Trial Snapshot
- Phase
- Not Applicable
- Status
- Recruiting
- Sponsor
- University of Waterloo
- Enrollment
- 20
- Locations
- 1
- Primary Endpoint
- Percentage preferred walking speed (PPWS)
Study Overview
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.
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 encountered. 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 are made of light materials such as polystyrene, rubber foam, soft cardboard, 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.
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Crossover
- Primary Purpose
- Treatment
- Masking
- Double (Participant, Investigator)
Masking Description
Each participant will experience active brain stimulation and placebo (sham)stimulation. The participant and the researcher will be blind to which session the participant receives active brain stimulation and placebo.
Eligibility Criteria
- Ages
- 18 Years to — (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- No
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.
Arms & Interventions
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).
Intervention: Active hf-tRNS. (Device)
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).
Intervention: Placebo/sham hf-tRNS (Device)
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).
Intervention: Active hf-tRNS. (Device)
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).
Intervention: Placebo/sham hf-tRNS (Device)
Outcomes
Primary Outcomes
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.
Secondary Outcomes
- Visual detection distance (VDD)(The pre-test and post-tests will take roughly 2 hours to complete.)
- Visual identification distance (VID)(The pre-test and post-tests will take roughly 2 hours to complete.)
- Number of orientation and mobility errors.(The pre-test and post-tests will take roughly 2 hours to complete.)
Investigators
Ben Thompson
Director and Professor, School of Optometry and Vision Science.
University of Waterloo