Visual Influences on Vestibular Adaptation

Effects of Impaired Visual Acuity and Binocular Control Abnormalities (VABC) on Vestibulo-ocular Reflex (VOR) Adaptation in Adults With and Without Vestibular Hypofunction

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

Study Overview

• Status: Recruiting
• Conditions: Vestibular Hypofunction; Binocular Vision Abnormalities; Reduced Vision
• Intervention / Treatment: Device: StableEyes: Incremental Vestibulo-Ocular Reflex Adaptation (IVA)

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.

• Study Type: Interventional
• Enrollment (Estimated): 100
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Colin R Grove, PT,DPT,PhD; Phone Number: (404) 712-8685; Email: colin.riess.grove@emory.edu
• Study Contact Backup: Name: Hannah M Morris; Email: hannah.m.morris@emory.edu

Study Locations

• United States
  • Georgia
    • Atlanta, Georgia, United States, 30329
      • Recruiting
      • Dizziness and Balance Center
      • Principal Investigator: David Sandlin, MD
      • Contact: Colin Grove, PT, DPT, PhD; Phone Number: 404-712-8685; Email: colin.r.grove@emory.edu
      • Principal Investigator: Colin Grove, PT, DPT, PhD
    • Atlanta, Georgia, United States, 30322
      • Not yet recruiting
      • Emory Ophthalmology Clinics
      • Contact: Jason Peragallo, MD
      • Contact: Hannah Morris; Email: hannah.m.morris@emory.edu
      • Principal Investigator: David Sandlin, MD

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

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 Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Vestibulo-Ocular Reflex (VOR) Gain	VOR gain will be measured using the video head impulse test (vHIT). Gain is calculated as eye velocity divided by head velocity during high-acceleration, moderate velocity, small amplitude head rotations in the plane of the semicircular canals. This outcome quantifies the strength of the vestibulo-ocular reflex, with higher gain values indicating stronger VOR responses, with normal gain = 0.8 to 1.2. The change in VOR gain from before to after training will be used to assess VOR adaptation. IVA: Incremental Vestibulo-Ocular Reflex Adaptation	Baseline (visit 1) (before and after after IVA intervention), Visit 2 (2-10 days from baseline) (before and after IVA intervention)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Modified Clinical Test of Sensory Interaction in Balance (mCTSIB)	Participants stand under four sensory conditions (eyes open/closed on firm/foam surfaces). Outcomes include time maintained (0-120 seconds) and postural sway metrics from inertial measurement units. Higher times indicate better balance.	Baseline (visit 1) (before and after after IVA intervention), Visit 2 (2-10 days from baseline) (before and after IVA intervention)
Change in Gait Disorientation Test (GDT)	Participants walk 20 feet with eyes open and eyes closed. The GDT score is the difference in time between the two conditions. Larger differences indicate greater gait disorientation.	Baseline (visit 1) (before and after after IVA intervention), Visit 2 (2-10 days from baseline) (before and after IVA intervention)
Symptom Severity During IVA (Verbal Analog Scales)	Symptom tolerance during incremental VOR adaptation (IVA) will be assessed using verbal analog scales. Participants will rate the severity of blurry vision, eye strain, dizziness, and headache on 0-10 scales, where 0 indicates no symptoms and 10 indicates the worst imaginable symptoms. Ratings will be collected immediately before and after each IVA session to quantify changes in self-reported symptom severity.	Baseline (visit 1) (before and after after IVA intervention), Visit 2 (2-10 days from baseline) (before and after IVA intervention)

Collaborators and Investigators

• Sponsor: Emory University
• Investigators: Principal Investigator: Colin Grove, PT, DPT, PhD, Emory University

Study record dates

Study Major Dates

• Study Start (Actual): February 4, 2026
• Primary Completion (Estimated): December 1, 2029
• Study Completion (Estimated): December 1, 2029

Study Registration Dates

• First Submitted: January 20, 2026
• First Submitted That Met QC Criteria: January 27, 2026
• First Posted (Actual): February 2, 2026

Study Record Updates

• Last Update Posted (Actual): April 17, 2026
• Last Update Submitted That Met QC Criteria: April 14, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: video head impulse test; vestibulo-ocular reflex; incremental vestibulo-ocular reflex adaptation; abnormal uncorrected static visual acuity; Gait Disorientation Test; vertical and torsional alignment nulling; dynamic visual acuity test; modified Clinical Test of Sensory Interaction in Balance
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Eye Diseases; Vision Disorders; Sensation Disorders; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Vision, Low
• Other Study ID Numbers: 2025P012555

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: A complete de-identified dataset will be shared.
• IPD Sharing Time Frame: 12 months after the primary outcome is published; indefinitely
• IPD Sharing Access Criteria: Mechanism: Through the Open Science Framework or Emroy Dataverse
• 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: Yes
• product manufactured in and exported from the U.S.: Yes