Visual Influences on Vestibular Adaptation

Purpose

The goal of this study is to learn whether a balance-training exercise called incremental vestibulo-ocular reflex adaptation (IVA) is safe and effective for adults with vision impairments, with or without additional vestibular (inner-ear balance) problems. The main questions it aims to answer are: - Does IVA cause only mild, temporary symptoms and no serious adverse events? - Does IVA improve eye-movement reflexes, balance, and walking, and do these improvements differ between people with vision problems alone and those with both vision and vestibular impairments? Researchers will compare adults with vision impairment only to adults who have both vision and vestibular impairments to see whether the groups respond differently to IVA. Participants will: - Complete symptom ratings before and after IVA - Undergo tests of vestibular reflexes (e.g., VOR gain) - Complete balance and walking assessments

Conditions

  • Vestibular Hypofunction
  • Binocular Vision Abnormalities
  • Reduced Vision

Eligibility

Eligible Ages
Between 18 Years and 60 Years
Eligible Sex
All
Accepts Healthy Volunteers
No

Inclusion Criteria

For All Participants (All Groups) - Age 18 to 60 years - Able to provide informed consent Group-Specific Inclusion Criteria: - Group 1: Abnormal Uncorrected Static Visual Acuity (No Vestibular Hypofunction) Normal peripheral vestibular function - Group 2: Abnormal Uncorrected Static Visual Acuity + peripheral Vestibular Hypofunction - Group 3: Binocular Vision Abnormalities (No Vestibular Hypofunction) Normal peripheral vestibular function - Group 4: Binocular Vision Abnormalities + peripheral Vestibular Hypofunction Individuals who have abnormal static visual acuity, a binocular vision abnormality (ocular misalignment, convergence insufficiency), and vestibular loss will be assigned to Group 4. The following definitions will be used when determining group placement: - Abnormal Static Visual Acuity: Uncorrected visual acuity (head is still) ≥0.30 logMAR in both eyes. - Unilateral Vestibular Hypofunction: 60 ms VOR gain <0.80 unilaterally for the lateral semicircular canal. - Bilateral Vestibular Hypofunction: 60 ms VOR gain <0.80 bilaterally for the lateral semicircular canals. - Normal Vestibular Function: 60 ms VOR gain of 0.80 to 1.20 bilaterally for the lateral semicircular canals. - Convergence Insufficiency: ≥6 cm near point of convergence. - Ocular Misalignment: ≥4 prism diopters of manifest deviation of the eyes (tropia) on cover/uncover testing.

Exclusion Criteria

  • Diagnosis of fluctuating vestibular disorders (e.g., benign paroxysmal positional vertigo) - Neurologic conditions (e.g., multiple sclerosis), dementia, - Alcohol or drug abuse, - A major psychiatric disorder (e.g., schizophrenia), - Pain that limits cervical spine range of motion by >50% or that results in an -altered gait pattern.

Study Design

Phase
N/A
Study Type
Interventional
Allocation
Randomized
Intervention Model
Crossover Assignment
Intervention Model Description
Participants will be randomized for the vision condition (with or without correction) in which they will perform IVA during the first study visit. At the second study visit, all participants will cross over to perform IVA in the opposite vision condition
Primary Purpose
Basic Science
Masking
Double (Participant, Investigator)

Arm Groups

ArmDescriptionAssigned Intervention
Experimental
Group 1: Abnormal Uncorrected Static Visual Acuity (No Vestibular Hypofunction) 		Adults with abnormal uncorrected distance visual acuity and normal vestibular function. This group will be part of Experiment 1. This experiment studies people whose main visual problem is reduced uncorrected distance visual acuity (i.e., blurry vision without glasses/contacts). Experiment 1 tests the effect of blurry vision on VOR adaptation
  • Device: StableEyes: Incremental Vestibulo-Ocular Reflex Adaptation (IVA)
    IVA is delivered using the StableEyes device, which includes a lightweight head-mounted unit with inertial sensors and a micromirror that controls the position of a low-power laser target projected onto a wall. The device adjusts the target's movement based on the participant's head velocity to create a controlled visual error signal that induces vestibulo-ocular reflex (VOR) adaptation. During each session, participants sit about one meter from a blank wall and perform rapid, self-generated head impulses while visually tracking the moving laser target. The target appears at neutral, moves at a fraction of head velocity during each impulse, and briefly disappears before reappearing at center. Each session lasts 15 minutes and includes roughly 150 head impulses in the horizontal or vertical plane. The procedure has been well-tolerated in prior studies with no reported adverse events.
Experimental
Group 2: Abnormal Uncorrected Static Visual Acuity + Vestibular Hypofunction 		Adults with abnormal uncorrected distance visual acuity and unilateral vestibular hypofunction. This group will be part of Experiment 1. This experiment studies people whose main visual problem is reduced uncorrected distance visual acuity (i.e., blurry vision without glasses/contacts). Experiment 1 tests the effect of blurry vision on VOR adaptation
  • Device: StableEyes: Incremental Vestibulo-Ocular Reflex Adaptation (IVA)
    IVA is delivered using the StableEyes device, which includes a lightweight head-mounted unit with inertial sensors and a micromirror that controls the position of a low-power laser target projected onto a wall. The device adjusts the target's movement based on the participant's head velocity to create a controlled visual error signal that induces vestibulo-ocular reflex (VOR) adaptation. During each session, participants sit about one meter from a blank wall and perform rapid, self-generated head impulses while visually tracking the moving laser target. The target appears at neutral, moves at a fraction of head velocity during each impulse, and briefly disappears before reappearing at center. Each session lasts 15 minutes and includes roughly 150 head impulses in the horizontal or vertical plane. The procedure has been well-tolerated in prior studies with no reported adverse events.
Experimental
Group 3: Binocular Vision Abnormalities (No Vestibular Hypofunction) 		Adults with binocular vision abnormalities (e.g., convergence insufficiency, ocular misalignment) and normal vestibular function. This group will be part of Experiment 2. This experiment studies people whose main visual problem is how the two eyes work together (e.g., convergence insufficiency, ocular misalignment). Experiment 2 tests the effect of binocular vision dysfunction on VOR adaptation
  • Device: StableEyes: Incremental Vestibulo-Ocular Reflex Adaptation (IVA)
    IVA is delivered using the StableEyes device, which includes a lightweight head-mounted unit with inertial sensors and a micromirror that controls the position of a low-power laser target projected onto a wall. The device adjusts the target's movement based on the participant's head velocity to create a controlled visual error signal that induces vestibulo-ocular reflex (VOR) adaptation. During each session, participants sit about one meter from a blank wall and perform rapid, self-generated head impulses while visually tracking the moving laser target. The target appears at neutral, moves at a fraction of head velocity during each impulse, and briefly disappears before reappearing at center. Each session lasts 15 minutes and includes roughly 150 head impulses in the horizontal or vertical plane. The procedure has been well-tolerated in prior studies with no reported adverse events.
Experimental
Group 4: Binocular Vision Abnormalities + Vestibular Hypofunction 		Adults with binocular vision abnormalities and unilateral vestibular hypofunction. This group will be part of Experiment 2. This experiment studies people whose main visual problem is how the two eyes work together (e.g., convergence insufficiency, ocular misalignment). Experiment 2 tests the effect of binocular vision dysfunction on VOR adaptation
  • Device: StableEyes: Incremental Vestibulo-Ocular Reflex Adaptation (IVA)
    IVA is delivered using the StableEyes device, which includes a lightweight head-mounted unit with inertial sensors and a micromirror that controls the position of a low-power laser target projected onto a wall. The device adjusts the target's movement based on the participant's head velocity to create a controlled visual error signal that induces vestibulo-ocular reflex (VOR) adaptation. During each session, participants sit about one meter from a blank wall and perform rapid, self-generated head impulses while visually tracking the moving laser target. The target appears at neutral, moves at a fraction of head velocity during each impulse, and briefly disappears before reappearing at center. Each session lasts 15 minutes and includes roughly 150 head impulses in the horizontal or vertical plane. The procedure has been well-tolerated in prior studies with no reported adverse events.

Recruiting Locations

Dizziness and Balance Center
Atlanta, Georgia 30329
Contact:
Colin Grove, PT, DPT, PhD
404-712-8685
colin.r.grove@emory.edu

More Details

Status
Recruiting
Sponsor
Emory University

Study Contact

Colin R Grove, PT,DPT,PhD
(404) 712-8685
colin.riess.grove@emory.edu

Detailed Description

Impairment of vestibular pathways can lead to deficits in balance, gait, and gaze stability. Gaze-stability exercises are a central component of vestibular rehabilitation and have been shown to improve vision during head movement as well as functional mobility in individuals with peripheral or central vestibular dysfunction. Improvements in gaze stability may occur through vestibulo-ocular reflex (VOR) adaptation or through compensatory saccadic eye movements. However, many adults with vestibular hypofunction also present with uncorrected visual acuity deficits or binocular vision abnormalities, such as low vision, convergence insufficiency, or ocular misalignment. These visual conditions are common but understudied in the context of vestibular rehabilitation, and it is not known whether they limit the capacity for VOR adaptation. Incremental vestibulo-ocular reflex adaptation (IVA) is a non-invasive, 15-minute training method that strengthens the VOR by exposing users to a controlled visual error signal. IVA uses a moving laser target whose velocity is programmed as a function of the participant's head movement, producing immediate increases in VOR gain. The method can be customized to provide unilateral, bilateral, or asymmetric adaptation, allowing targeted training for individuals with unilateral or bilateral vestibular deficits. IVA has been studied extensively in adults with vestibular hypofunction, but its effectiveness in individuals with impaired visual acuity or binocular vision abnormalities has not been evaluated. This study will examine whether reduced static visual acuity or binocular vision abnormalities affect the magnitude of VOR adaptation in adults with and without vestibular hypofunction. Two experiments will be conducted using a cross-over design. Experiment 1 will enroll adults with abnormal uncorrected static visual acuity, with and withoutvestibular hypofunction, to compare VOR adaptation with and without vision correction. Experiment 2 will enroll adults with binocular vision abnormalities, with and without vestibular hypofunction, to evaluate VOR adaptation in their best corrected visual state. All participants will complete IVA training during two study visits separated by a washout period.