Attention-based Binocular Training for Impaired Stereopsis (BRAVE)

NCT07803458 | Not Yet Recruiting

• 1 other identifier: RP1.4_BRAVE
• Study Type: interventional
• Target: 56
• Locations: 1 country
• Sites: 2

Brief Summary

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.

Conditions

Amblyopia; Strabismus; Anisometropia; Binocular Vision Abnormalities; Binocular Vision Disorder

Keywords

Stereopsis; Depth Perception; Visual Search; Visual Attention; Dichoptic Training

Outcome Measures

Primary Outcomes (1)

• Change in Local Stereoacuity

  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 Outcomes (13)

• Retention of Local Stereoacuity Gains

  Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).

• Change in Uncrossed Local Stereoacuity

  Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).

• Change in Global Stereoacuity

  Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).

• Change in Laboratory-Based Stereoacuity Threshold

  Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).

• Change in Best-Corrected Visual Acuity (BCVA)

  Baseline (T0), Immediately Post-Training (T1), and 12-Week Follow-Up (T2).

Study Arms (2)

Active Training Group

EXPERIMENTAL

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

Active Control Group

ACTIVE COMPARATOR

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

Interventions

Attention-Guided Dichoptic Visual Search Training BEHAVIORAL

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 Training Group

Zero-Disparity Dichoptic Visual Search Task BEHAVIORAL

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).

Active Control Group

Eligibility Criteria

• Age: 18 Years - 39 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Centre for Eye and Vision Research: lead
• The Hong Kong Polytechnic University: collaborator
• University of Waterloo: collaborator

Study Sites (2)

Centre for Eye and Vision Research Limited

Hong Kong, Hong Kong SAR, HKG, Hong Kong

Location

The Hong Kong Polytechnic University

Hong Kong, Hong Kong SAR, HKG, Hong Kong

Location

MeSH Terms

Conditions

Amblyopia; Strabismus; Anisometropia

Condition Hierarchy (Ancestors)

Brain Diseases; Central Nervous System Diseases; Nervous System Diseases; Vision Disorders; Sensation Disorders; Neurologic Manifestations; Eye Diseases; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Ocular Motility Disorders; Cranial Nerve Diseases; Refractive Errors

Central Study Contacts

Jeffrey TW Leung, PhD

CONTACT

+852-64080394; jeffrey.tw.leung@polyu.edu.hk

Benjamin Thompson, PhD

CONTACT

+852-31699631; ben.thompson@cevr.hk

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: August 31, 2026
• First Posted: September 3, 2026
• Study Start (Estimated): November 1, 2026
• Primary Completion (Estimated): December 31, 2028
• Study Completion (Estimated): March 30, 2029
• Last Updated: September 3, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP
• Time Frame: After publication of study results for an indefinite period.
• Access Criteria: Upon reasonable request and approved by the study principal investigator.

Locations

HK (2)