Attention-based Binocular Training for Impaired Stereopsis (BRAVE) (BRAVE)

August 31, 2026 updated by: Centre for Eye and Vision Research

Binocular Recovery Through Attention-based Visual Enhancement: A Randomized Controlled Trial (BRAVE Trial)

This study evaluates a novel attention-based binocular visual search training paradigm designed to improve stereopsis (stereo vision) in individuals with impaired binocular vision. Disruptions in balanced binocular input, such as from strabismus or anisometropia, often lead to deficient stereo vision, causing daily visuomotor limitations. While traditional therapies focus on monocular acuity, they frequently fail to restore stereopsis, especially in adults. The investigators propose a unique dichoptic visual search training method that embeds binocular disparity inside an attention-demanding task, encouraging cooperative binocular integration. Participants aged 18-39 with impaired stereopsis will be randomly assigned in a 1:1 ratio to either the active training group (disparity-embeded task) or the active control group (identical task with zero disparity). Both groups complete 5 training sessions over 5-6 weeks. Assessments will occur at baseline, immediately post-training, and at a 12-week follow-up. The primary objective is to determine if the active training group shows significantly greater improvements in local stereoacuity compared to the control group.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
56

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • 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

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

Study Locations

  • Hong Kong
    • Hong Kong SAR
      • Hong Kong, Hong Kong SAR, Hong Kong, HKG
        • Centre for Eye and Vision Research Limited
        • Sub-Investigator:
          • Tingni Li, PhD
        • Sub-Investigator:
          • Yu Yang
        • Principal Investigator:
          • Benjamin Thompson, PhD
        • Contact:
        • Contact:
        • Sub-Investigator:
          • Krista Kelly, PhD
        • Sub-Investigator:
          • Lisa Christian, PhD
        • Sub-Investigator:
          • Xiaofei Hu, PhD
        • Sub-Investigator:
          • Ken WS Tan, PhD
      • Hong Kong, Hong Kong SAR, Hong Kong, HKG
        • The Hong Kong Polytechnic University
        • Sub-Investigator:
          • Allen MY Cheong, PhD
        • Contact:
        • Principal Investigator:
          • Jeffrey TW Leung, PhD

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Aged 18-39 years (inclusive).
  • Deficient or anomalous stereoscopic vision with a stereoacuity >= 70 sec arc or unmeasurable stereoacuity.
  • Best corrected visual acuity (BCVA) of < 0.80 logMAR in both eyes, with at least one eye having a visual acuity of <= 0.1 logMAR (uncorrected or corrected-to-normal with glasses or contact lenses).
  • Normal colour vision.
  • Good general health.

Exclusion Criteria:

  • Previous history of ocular surgery (except for refractive correction surgery, where appropriate).
  • Pre-existing ocular conditions or medications that affect vision or visual function.
  • Pre-existing conditions or medications that affect neuropsychological function.
  • Presence of strabismus over 10 prism diopters at distance in current refractive correction measured by simultaneous prism and cover test, or large eccentric fixation.
  • Previous history of experiencing double vision (diplopia).
  • Identified at risk of developing diplopia due to binocular state and/or poor binocular control.
  • Inability to comprehend psychophysical test instructions given and/or consent for themselves.

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: Parallel Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Active Training Group
Participants complete a dichoptic visual search task where the search target is uniquely paired with crossed binocular disparity under balanced interocular contrast. The training consists of 5 sessions (5 blocks of 192 trials per session) over 5-6 weeks with adaptive disparity adjustment.
Behavioral: Attention-Guided Dichoptic Visual Search Training
A computer-based dichoptic training paradigm in which visual stimuli are presented separately to each eye under balanced interocular contrast . Participants search for conjunction-defined targets across 5 sessions (5 blocks of 192 trials per session). The target stimulus is uniquely paired with crossed binocular disparity to provide depth-based attentional guidance, with target disparity adaptively reduced based on search performance.
Active Comparator: Active Control Group
Participants perform an identical computer-based dichoptic visual search task with the same geometric stimuli, trial structure (5 blocks of 192 trials per session), and interocular contrast balancing, but with zero binocular disparity.
Behavioral: Zero-Disparity Dichoptic Visual Search Task
An active control dichoptic task identical in visual stimuli, trial structure (5 sessions; 5 blocks of 192 trials per session), and interocular contrast balancing to the training arm, but presented with zero binocular disparity (all stimuli appear in the same depth plane without depth cues).

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Change in Local Stereoacuity
Time Frame: Baseline (T0) and Immediately Post-Training (T1, within 7 days after Session 5, approximately 5-6 weeks from baseline).
Measured using the Randot Stereotest - Circles test (graded disparities from 400 to 20 arcsec, 10 levels) under standardized lighting at 40 cm. The score is recorded as the finest disparity correctly identified (in log arcseconds). Nil stereopsis is assigned 3000 arcsec (3.477 log arcsec). The primary metric is the between-group difference in the change score.
Baseline (T0) and Immediately Post-Training (T1, within 7 days after Session 5, approximately 5-6 weeks from baseline).

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Retention of Local Stereoacuity Gains
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Measured using the Randot Stereotest - Circles test under crossed disparity (log10 arcsec; nil stereopsis assigned 3000 arcsec) to evaluate long-term maintenance of training effects
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Uncrossed Local Stereoacuity
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Measured using the Randot Stereotest - Circles test with the test booklet rotated 180 degrees (log10 arcsec; nil stereopsis assigned 3000 arcsec).
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Global Stereoacuity
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Measured with the Randot Preschool Stereotest (random-dot stereograms, 800 to 40 arcsec, 6 levels) under both crossed and uncrossed disparity conditions (log10 arcsec; nil stereopsis assigned 3000 arcsec).
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Laboratory-Based Stereoacuity Threshold
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Psychophysical stereoacuity threshold (75% threshold in log10 arcsec) measured using a 4-alternative forced-choice staircase ring test administered dichoptically.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Best-Corrected Visual Acuity (BCVA)
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Monocular (affected/dominant eyes) and binocular distance visual acuity measured using an electronic ETDRS logMAR chart at 4 meters (recorded in logMAR units).
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Interocular Suppression Status
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Binocular status classified into categorical states (fusion, suppression, or diplopia) using the Worth 4-dot test at near (40 cm) and distance (3 m).
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Interocular Suppression Strength (Contrast Balance Ratio)
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Effective suppression depth quantified by the interocular contrast ratio at the perceptual balance point measured via a dichoptic letter-polarity task.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Visual Evoked Potentials (VEPs)
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Peak latencies (ms) and amplitudes (μV) of the transient pattern-reversal VEP N75-P100-N135 complex across high-contrast and isoluminant red-green conditions, alongside harmonic amplitudes/phases (2F, 4F) from steady-state VEPs, recorded via a 64-channel EEG system.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Electrophysiological Marker of Attentional Selection (N2pc Component)
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Mean amplitude (μV) of the posterior contralateral-minus-ipsilateral difference wave (N2pc) extracted across predefined parieto-occipital electrodes (P7, PO7, P8, PO8) during a modified spatial cueing task.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Behavioral Selective Attention
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Spatial cueing effects on mean reaction time (ms) and response accuracy (%) derived from the modified spatial cueing task.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Visual Search Efficiency
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Visual search slope (reaction time as a function of set size, in ms/item) measured from a 192-trial zero-disparity dichoptic visual search task.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Visuomotor Coordination Completion Time and Kinematic Parameters
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Visuomotor dexterity and kinematic performance are assessed using the Grooved Pegboard Test separately for dominant and non-dominant hands. Hand movements during the task are video recorded for detailed kinematic tracking. The primary quantitative metric for this outcome is the total completion time (in seconds) required to successfully place all 25 grooved pegs (shorter duration indicates better motor speed and coordination). Secondary kinematic metrics extracted from video analyses include mean peg-insertion duration (seconds), inter-peg temporal variability across the 25 trials (coefficient of variation, CV), and total drop/error counts.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Change in Quality of Life Scores
Time Frame: Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).
Domain scores assessed via the World Health Organization Quality of Life Instrument-Short Form (WHO QoL-BREF) and the Amblyopia and Strabismus Questionnaire (A&SQ). Higher scores indicate superior functional visual ability and quality of life. For both questionnaires, domain and composite scores are linearly transformed to a standardized 0 to 100 scale, where higher scores represent superior functional visual ability, fewer daily limitations, and better overall quality of life.
Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).

Collaborators and Investigators

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

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Centre for Eye and Vision Research

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
The Hong Kong Polytechnic University
University of Waterloo

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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
November 1, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 31, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
March 30, 2029

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
August 31, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 31, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
September 3, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 3, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 31, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • RP1.4_BRAVE

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Anonymized data will be shared on request.

IPD Sharing Time Frame

After publication of study results for an indefinite period.

IPD Sharing Access Criteria

Upon reasonable request and approved by the study principal investigator.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP

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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