Attention-based Binocular Training for Impaired Stereopsis (BRAVE)

N/ANot Yet RecruitingNCT07803458

Centre for Eye and Vision Research56 enrolled

Overview

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 Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

SINGLE

Enrollment

Conditions

Amblyopia Strabismus

Interventions

Attention-Guided Dichoptic Visual Search TrainingBEHAVIORAL

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.

Zero-Disparity Dichoptic Visual Search TaskBEHAVIORAL

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).

Eligibility

Sex: ALLMin age: 18 YearsMax age: 39 YearsHealthy volunteers:

Medical Language ↔ Plain English

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.

Outcomes

Primary Outcomes

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.

Time frame: Baseline (T0) and Immediately Post-Training (T1, within 7 days after Session 5, approximately 5-6 weeks from baseline).

Secondary Outcomes

Retention of Local Stereoacuity Gains

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