Identify Optimal Non-invasive Brain Stimulation Paradigm for Improving Peripheral Vision
Trial Snapshot
- Phase
- Not Applicable
- Status
- Recruiting
- Enrollment
- 40
- Locations
- 1
- Primary Endpoint
- High-resolution perimetry (HRP)
Study Overview
Brief Summary
Glaucoma is a complex disease that can result in progressive vision loss. There are no treatments that restore vision lost to glaucoma. However, recent studies have shown that vision can be improved by non-invasive brain (NIBS) stimulation and visual training. In this study, we aim to compare and find out the optimal non-invasive brain stimulation model (transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS)) for improving peripheral vision in glaucoma patients. The proposed treatment is the application of transcranial electrical stimulation (tES) onto the participant's head, with brain stimulation aimed at the Primary Visual Cortex toward the occipital pole. The investigators hypothesize that the tES will enable higher performance in the reading task and secondary measures due to an increase in the cortical excitability of the stimulated brain cells, and tRNS will generate the greatest acute improvement in peripheral vision than either a-tDCS, tACS, or sham stimulation.
Detailed Description
This study uses a within-subjects, double-blind, placebo-controlled design and will be carried out in Hong Kong (The Hong Kong Polytechnic University).
Participants who will be recruited are 40 glaucoma patients aged 18 to 80, diagnosed with primary open-angle or normal-tension glaucoma with relative scotoma in both eyes. All participants will take part in 4 stimulation sessions (completion of active a-tDCS, tACS, tRNS, and sham stimulation in random order) with at least 48-hour separation between visits to wash out active stimulation effects.
The primary outcome is high-resolution perimetry that will be used to measure the visual field of participants. The secondary outcome is multifocal visual evoked potential (mfVEP) that will be used to measure the electrophysiological changes in the visual cortex.
The study consists of 5 visits:
Visit 1: Eligibility assessment (refer to the inclusion and exclusion criteria).
Study Design
- Study Type
- Interventional
- Allocation
- Randomized
- Intervention Model
- Crossover
- Primary Purpose
- Treatment
- Masking
- Double (Participant, Investigator)
Eligibility Criteria
- Ages
- 18 Years to 80 Years (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- No
Inclusion Criteria
- •Age range from 18 to 80 years;
- •Diagnosis of primary open angle or normal tension glaucoma with relative scotoma in both eyes;
- •A relative scotoma defined as a Humphrey Field Analyser (HFA) threshold perimetry loss (mean deviation of ≤-6dB) within the central 30° of the visual field for at least one eye;
- •Best-corrected distance visual acuity of 6/12 or better (equivalent to 0.3 logMAR acuity or better to confirm that participant's central vision is preserved);
- •Stable vision and visual field loss for at least 3 months;
- •With a cognitive functional score of 22 or above in the Montreal Cognitive Assessment - Hong Kong version (HK-MoCA) (to confirm participant's intact cognitive function).
Exclusion Criteria
- •Ocular diseases other than glaucoma (e.g. age-related macular degeneration, diabetic retinopathy, moderate to severe cataract) or severe hearing impairment (to ensure that participant can hear the instructions clearly during assessments and training);
- •Severe medical problems (e.g. stroke, Parkinson's disease) or self-reported neurological (e.g. brain surgery, brain tumor, peripheral neuropathy), or cognitive disorders (e.g. diagnosed dementia or cognitive impairment);
- •Self-reported vestibular or cerebellar dysfunction, history of vertigo;
- •Using any medications for any neurological conditions or psychiatric drugs (e.g. sedative, hypnotic) that might interfere with motor control;
- •Contraindications for non-invasive brain stimulation.
Arms & Interventions
sham group
This group is defined as the participants who will receive sham stimulation at the first session. Participants in this group will receive 4 stimulation types (active a-tDCS, tACS, tRNS, and sham) in random order with at least a 48-hour separation between visits.
Intervention: transcranial electrical stimulation (tES) (Device)
tDCS group
This group is defined as the participants who will receive tDCS at the first session. Participants in this group will receive 4 stimulation types (active a-tDCS, tACS, tRNS, and sham) in random order with at least a 48-hour separation between visits.
Intervention: transcranial electrical stimulation (tES) (Device)
tACS group
This group is defined as the participants who will receive tACS at the first session. Participants in this group will receive 4 stimulation types (active a-tDCS, tACS, tRNS, and sham) in random order with at least a 48-hour separation between visits.
Intervention: transcranial electrical stimulation (tES) (Device)
tRNS group
This group is defined as the participants who will receive tRNS at the first session. Participants in this group will receive 4 stimulation types (active a-tDCS, tACS, tRNS, and sham) in random order with at least a 48-hour separation between visits.
Intervention: transcranial electrical stimulation (tES) (Device)
Outcomes
Primary Outcomes
High-resolution perimetry (HRP)
Time Frame: 0.5-1 hour
Visual field will be measured using high-resolution perimetry (HRP, HighTechVision, Sweden), which is a valid and reliable computer-based campimetric visual field assessment. Suprathreshold stimuli will be presented in random order at 474 different positions to one eye (i.e. the eye with larger field loss) while fixation is monitored. Detection accuracy and response times will be recorded to map the patient's area of residual vision (i.e. relative scotoma). Testing will occur pre- and immediately post- stimulation.
Secondary Outcomes
- Multifocal visual evoked potential (mfVEP)(0.5-1 hour)
Investigators
Allen MY Cheong
Associate professor
The Hong Kong Polytechnic University