Combined Non-Invasive Brain and Visual Stimulation for Vision Improvement

March 23, 2026 updated by: Allen MY Cheong, The Hong Kong Polytechnic University

Evaluation of Combined Non-invasive Brain Stimulation (NIBS) and Visual Tetanic Stimulation (VTS) for Vision Enhancement: A Randomized, Single-blind, Cross-over Trial

Glaucoma is a complex disease that can result in progressive vision loss. It is the second leading cause of blindness, accounting for 23% of permanent blindness in Hong Kong. There are no treatments that restore vision lost to glaucoma. This study will examine the effect of transcranial direct current stimulation (NIBS) on improving quality of life, visual function and functional performance in patients with peripheral field loss due to glaucoma.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

This study uses a prospective, single-masked, randomized, cross-over, placebo-controlled training RCT design.

The eligible participants will be randomly allocated into 4 groups:

(A) Transcranial direct current stimulation; (B) Visual Tetanic Stimulation; (C) Transcranial direct current stimulation+ Visual Tetanic Stimulation; (D) Sham. All participants will underwent all the 4 types of intervention with a 14 days washing out period between intervention types:

All participants will complete twenty-six study visits:

Visit 1: Eligibility assessment (refer to the recruitment criteria); Visit 2: Outcome measures (Pre-intervention/ baseline); Visit 3-7: 5 sessions intervention (1st intervention block); Visit 8: Post 1 outcome measures; Visit 9-13: 5 sessions intervention (2nd intervention block); Visit 14: Post 2 outcome measures; Visit 15-19: 5 sessions intervention (3rd intervention block); Visit 20: Post 3 outcome measures; Visit 21-25: 5 sessions intervention (4th intervention block); Visit 26: Post 4 outcome measures

Eight sessions of assessment will be conducted: (1) Baseline-1; (2) Post-1 (after 5-sessions training); (3) Baseline-2; (4) Post-2 (after 5-sessions training); (5) Baseline-3; (6) Post-3 (after 5-sessions training); (7) Baseline-4; and (8) Post-4 (after 5-sessions training).

Study Type

Interventional

Enrollment (Estimated)

56

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

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 24 degree 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 motor control;
  • Contraindications for non-invasive brain stimulation.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Triple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Visual Tetanic Stimulation (VTS)
Participant will receive 5 training sessions with VTS: about 1 hour per session
Other: VTS
Around 1 hour
Active Comparator: Transcranial direct current stimulation (NIBS)
Participant will receive 5 training sessions with NIBS: about 1 hour per session
Other: NIBS
Around 1 hour
Experimental: Transcranial direct current stimulation+ Visual Tetanic Stimulation (NIBS+VTS)
Participant will receive 5 training sessions with NIBS+VTS: about 1 hour per session
Other: NIBS+VTS
Around 1 hour
Placebo Comparator: Sham
Participant will receive 5 training sessions with Sham: about 1 hour per session
Other: Sham
Around 1 hour

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Visual field test
Time Frame: Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)
Visual field test is measured monocularly using the 24-2 Swedish interactive threshold algorithm (SITA) standard tests by Humphrey visual field analyzer (HFA, Carl Zeiss Meditec Inc., California). The mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI) are recorded, and the MD of the 24-2 visual field test will be used as the primary outcome of intervention effect.
Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)
Electroencephalography (EEG)
Time Frame: Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)

Electrophysiological function is assessed using a 64-channel high-resolution electroencephalography (EEG) system. EEG outcome measures include spectral power in the delta, theta, alpha, beta, and gamma frequency bands, with particular focus on alpha-band activity, as well as functional connectivity measures derived from scalp EEG recordings, including coherence, phase-based connectivity, and related network indices.

Pattern-reversal visual evoked potentials (PR-VEP) are recorded during presentation of a high-contrast checkerboard stimulus to the central 20-degree visual field under monocular viewing conditions. Stimuli are presented at 0.5 Hz and 1.5 Hz with 40 reversals. PR-VEP outcome measures include N75 latency, P100 latency, N135 latency, and N75-P100 and/or P100-N135 amplitude.
Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)
Optical Coherence Tomography (OCT)
Time Frame: Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)
Retinal nerve fiber layer is measured using spectral-domain Optical Coherence Tomography (OCT). Peripapillary retinal nerve fiber layer thickness is obtained from a circular scan centered on the optic nerve head. Ganglion cell thickness is measure using macular OCT imaging
Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)
Optical Coherence Tomography Angiography (OCT-A)
Time Frame: Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)
Evaluation of retinal vascular function in glaucoma patients is measured. Detailed visualisation of microvasculature structure within the retina and optic nerve head is measured, change of ocular perfusion is shown.
Baseline (before the first intervention session), and immediately before and after each intervention block (5 session of intervention)

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

The Hong Kong Polytechnic University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

April 20, 2026

Primary Completion (Estimated)

June 30, 2027

Study Completion (Estimated)

July 10, 2027

Study Registration Dates

First Submitted

March 10, 2026

First Submitted That Met QC Criteria

March 17, 2026

First Posted (Actual)

March 20, 2026

Study Record Updates

Last Update Posted (Actual)

March 24, 2026

Last Update Submitted That Met QC Criteria

March 23, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • HSEARS20251208001

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

De-identified individual participant data (IPD) underlying the results reported in this study will be shared via the Open Science Framework (OSF). These data will include participant-level demographic and clinical characteristics, baseline assessments, intervention-related variables, and primary and secondary outcome data necessary to reproduce the reported analyses. Supporting documents, including the study protocol, statistical analysis plan, data dictionary, and study materials, will also be made available on OSF.

IPD Sharing Time Frame

De-identified individual participant data and supporting documents will be made available beginning within 6 months after publication of the primary study results and will remain available indefinitely on the Open Science Framework (OSF).

IPD Sharing Access Criteria

will be publicly available

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF
  • ANALYTIC_CODE
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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