Oculomotor Rehabilitation After Concussion in Adults: A Feasibility Study

Background Concussion is a common form of mild traumatic brain injury (mTBI) that produces a broad and heterogeneous range of symptoms and functional deficits affecting daily activities including work, school, sport, and social participation. Recovery is highly individualized and influenced by injury characteristics, personal medical history (e.g., anxiety, migraine history), and biological sex and sociocultural gender. Over 50% of individuals from the general population experience symptoms beyond four weeks. In mixed-mechanism populations, mean time to recovery is approximately 6.5 weeks for females and 5.5 weeks for males, suggesting that females may experience a longer symptom course following concussion.

Among the most prevalent clinical profiles of concussion are symptoms attributable to oculomotor dysfunction. Functional deficits in saccades, smooth pursuits, vergence, and pupillary light reflex occur far more frequently than structural injuries, making them a feasible and clinically important rehabilitation target. These deficits can manifest as blurred vision, dizziness, light sensitivity, eye strain, and difficulty tolerating visually busy environments, with downstream impacts on return to work, school, and sport. Without directed rehabilitation, these symptoms often persist.

Oculomotor rehabilitation (OMR) aims to retrain impaired eye movement functions through targeted, restitutive exercise protocols. A systematic review conducted by the study team demonstrated improvements in near point of convergence, reading rate, and visual search and attention following OMR; however, certainty of evidence was rated as low due to methodological limitations, small sample sizes, and variability in protocols. Since that review, additional studies have been published strengthening the evidence base, though existing randomized controlled trials have focused predominantly on adolescents and young adults, limiting generalizability to older adult populations.

Interest in virtual reality (VR)-based OMR delivery has grown substantially. A recent scoping review identified 10 studies using VR for post-concussion vestibular rehabilitation, reporting good tolerability and greater participant enjoyment relative to traditional approaches. To the investigators' knowledge, no published study has systematically examined the feasibility, acceptability, or perceived benefit of delivering OMR via head-mounted VR goggles combined with mobile application-based home exercise programming in adults with persisting oculomotor deficits post-concussion.

Biological sex and sociocultural gender differences in concussion reporting, symptom experience, and recovery have been documented, yet sex and gender have not been adequately explored in the context of OMR. This trial is designed to collect sex-disaggregated data to inform future research in this area.

Objectives The primary objective is to assess the feasibility of a future fully powered RCT, operationalized across four a priori criteria: recruitment, retention, adherence, and technology reliability.

The secondary objective is proof-of-concept, operationalized a priori as participant-rated perceived benefit (0-4 scale) at study completion.

Study Design This is a feasibility RCT with two parallel intervention groups, a 1:1 allocation ratio, conducted at Toronto Rehabilitation Institute (TRI)-University Health Network (UHN), Ontario, Canada.

Recruitment Participants are recruited through hospital- and community-based concussion clinics, community-based brain injury organizations, and social media platforms. Individuals who participated in prior research at the Hull-Ellis Concussion and Research Clinic, had not recovered, and had indicated willingness to be contacted for future eligible studies are also approached. Interested individuals undergo telephone-based screening followed by in-person confirmation of visually based eligibility criteria. Written informed consent is obtained prior to enrolment.

Eligibility

• Adults (18 to 42 years of age) with a diagnosis of a concussion by a medical doctor between 30 days and 12 months prior
• Endorsed oculomotor related symptoms indicated by rating "moderate" or "severe" blurred-vision, double vision and/or light sensitivity.
• Normal stereopsis (depth perception) as measured with the Stereo Fly Test
• Equal (within one line difference) visual acuity between eyes as measured with the Snellen Eye Chart (Snellen, 1892) (corrected, as applicable)
• Intact extraocular movements and visual fields
• Pupils equal, round, and reactive to light and accommodation
• Healthy fundoscopic findings
• Ability to read and communicate in English

Exclusion Criteria:

• Diagnosed eye disease (i.e. gloucoma)
• Visual acuity less than 20/80
• Severe neurocognitive deficits expected to interfere with participation
• Residence more than 100 km from the study site.

Baseline Measures Baseline data include demographics, medical history, injury characteristics, and the following validated questionnaires: Brain Injury Visual Symptom Survey (BIVSS), Convergence Insufficiency Symptoms Survey (CISS), RPQ, Patient Health Questionnaire-9 (PHQ-9), Fatigue Severity Scale (FSS), Insomnia Severity Index (ISI), Sheehan Disability Scale (SDS), Traditional Masculinity and Femininity Scales (TMS/TFS), and the Visually Induced Motion Sickness Susceptibility Questionnaire (VIMSSQ). Clinical assessments include near point of convergence break (NPC, in centimeters) and critical flicker fusion (CFF, in hertz).

Interventions Oculomotor Rehabilitation (OMR) Group: Participants receive six weekly in-person sessions of progressive, personalized OMR delivered via head-mounted VR goggles (FOVE) using NeuroFlex software, targeting saccades, smooth pursuits, vergence, gaze stability, optokinetic reflex, and anti-saccades. Sessions increase progressively in difficulty and duration based on individual tolerance. Between sessions, participants complete daily home-based eye movement exercises via a study-specific mobile application, targeting at least 10 minutes per day, five days per week.

Usual Care (UC) Group: Participants receive education on visual symptom-limiting strategies (e.g., pacing, screen modification). No active or sham intervention is provided.

Randomization and Allocation Participants are randomized 1:1 to OMR or UC following consent, using a blinded, sex-stratified randomization schema with variable block sizes generated a priori. Blinding of participants and study personnel after allocation is not possible given the nature of the intervention.

Outcome Measures Primary Feasibility Outcomes are assessed against a priori traffic light criteria (Green/Amber/Red) and include: recruitment rate, randomization rate, compliance to allocated arm, and retention rate.

Additional Feasibility Outcomes include: magnitude of co-intervention, VR tolerability, homework participation, study experience rating (0-4), technology reliability, and the ability of the technology to capture change in oculomotor metrics between baseline and final assessment.

Secondary Outcome: Participant-rated perceived benefit (0-4) at study completion.

Data Analysis Descriptive statistics are used to summarize feasibility outcomes and participant characteristics. The study is not powered for efficacy testing and between-group comparisons are not emphasized. Variability estimates will inform power calculations for a future full-scale RCT. Data are captured in REDCap and analyzed in SPSS (Version 25). A missing data threshold of 5% is set a priori, with complete case analysis below this threshold and multiple imputation applied above it.

Findings from this feasibility trial will be used to inform the design of a future fully powered pragmatic RCT. Feasibility metrics including recruitment and retention rates, compliance to allocated arm, and technology reliability, will be evaluated against a priori traffic light criteria to determine whether, and under what conditions, progression to a full trial is warranted. Variability estimates across candidate clinical outcomes and review of recent published literature will additionally inform outcome selection and power analysis planning for the future trial.