Vergence Disorders, Binocular Vision Dysfunction, Convergence Insufficiency
Conditions
Keywords
Optometric Vision Therapy, Osteopathy, Sham Intervention, Video-oculography, Ocular Motility, Visual Symptoms, Randomized Controlled Trial
Brief summary
Vergence disorders are common binocular vision conditions that can cause symptoms such as eyestrain, blurred vision, headaches, and difficulty maintaining clear vision during near tasks. These symptoms are particularly frequent in situations involving sustained near visual demand, such as prolonged use of digital devices, which is increasingly common in daily life. Optometric vision therapy is considered the reference treatment for vergence disorders. However, not all individuals respond in the same way, and some continue to experience symptoms despite appropriate treatment. For this reason, adjunct therapeutic approaches are being explored to improve clinical outcomes. The purpose of this study is to evaluate whether osteopathic manual therapy, when used as an adjunct to optometric vision therapy, provides additional benefits compared with vision therapy alone or vision therapy combined with a sham osteopathic intervention. This randomized, controlled, double-blind clinical trial will compare three parallel groups and will assess changes in vergence function, oculomotor performance measured by video-oculography, and symptom improvement related to vergence disorders.
Detailed description
Vergence disorders are binocular vision dysfunctions characterized by an impaired ability to coordinate eye movements during visual tasks, particularly at near distances. These disorders are associated with a range of symptoms, including visual discomfort, reduced visual efficiency, and decreased functional performance during sustained near-vision activities. Optometric vision therapy is an evidence-based intervention aimed at improving vergence function and visual efficiency. Despite its effectiveness, clinical response varies among individuals, and a subset of participants may continue to experience persistent symptoms. This variability has prompted interest in adjunctive interventions that may influence neuromuscular, musculoskeletal, or functional components related to oculomotor control. This study is designed as a randomized, controlled, double-blind clinical trial with three parallel arms. Participants diagnosed with vergence disorders will be randomly assigned to one of the following groups: (1) optometric vision therapy combined with osteopathic treatment, (2) optometric vision therapy combined with a sham osteopathic intervention, or (3) optometric vision therapy alone. The primary objective of the study is to evaluate whether the addition of osteopathy to optometric vision therapy results in greater improvements in ocular mobility and efficiency, assessed using video-oculography systems (REMOBI and EyeSeeCam). Secondary objectives include the evaluation of symptom changes associated with vergence disorders using a validated questionnaire (CISS-V15), as well as the exploration of potential relationships between functional ocular impairment, identified somatic dysfunctions, and the anatomical distribution of reported symptoms. Ocular motor performance will be objectively quantified through standardized vergence tasks recorded by video-oculography, including measures of reaction latency, amplitude variability, amplitude error, and neglect rate. Assessments will be conducted at baseline (pre-intervention), post-intervention (within two weeks after completion of the visual therapy program), and at follow-up time points of three and six months after the intervention. The osteopathic intervention consists of a standardized manual treatment protocol targeting somatic dysfunctions potentially related to binocular vision and vergence function. The sham osteopathic intervention is designed to mimic the context, duration, and therapist-participant interaction of the active manual treatment without applying therapeutic osteopathic techniques, in order to preserve participant blinding. The results of this study are expected to contribute to a better understanding of the potential role of osteopathy as an adjunctive intervention in the management of vergence disorders and to provide clinically relevant data on the relationship between somatic dysfunctions and functional visual alterations in individuals with high visual demand.
Interventions
BEHAVIORALOptometric Vision Therapy
Structured optometric vision therapy program consisting of in-office and home-based visual exercises aimed at improving binocular vision and vergence function. The intervention is standardized across participants and delivered by qualified optometrists following a predefined protocol.
BEHAVIORALOsteopathic Manual Therapy
Standardized manual osteopathic intervention delivered as an adjunct to optometric vision therapy. The intervention consists of predefined manual techniques targeting somatic dysfunctions potentially related to binocular vision and vergence, applied according to a fixed protocol and session schedule. The intervention protocol is predefined and documented in detail to ensure consistency across participants.
BEHAVIORALSham Osteopathic Intervention
Sham manual intervention designed to mimic the context, duration, and therapist-participant interaction of the osteopathic intervention without applying therapeutic osteopathic techniques. The procedure is standardized and intended to maintain participant blinding.
Sponsors
Jordi Zaragoza
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
DOUBLE (Subject, Outcomes Assessor)
Masking description
Double-blind (Participants and Outcomes Assessors). The osteopathic treatment provider is not blinded due to the nature of the manual intervention. Participants are unaware of group allocation, and the sham intervention is designed to mimic the context, duration, and therapist-participant interaction of the active osteopathic treatment to maintain blinding.
Intervention model description
Randomized, controlled, double-blind clinical trial with three parallel arms comparing: (1) optometric vision therapy combined with osteopathic treatment; (2) optometric vision therapy combined with sham osteopathic intervention; and (3) optometric vision therapy alone. Participants and outcome assessors will be blinded to group allocation.
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* Adult workers (≥18 years) whose regular occupational duties involve screen-based work. * Presence of symptoms consistent with binocular vision dysfunction, defined as a Convergence Insufficiency Symptom Survey (CISS-V15) score ≥21 at baseline screening.
Exclusion criteria
* Severe ocular disease or systemic conditions affecting vision (e.g., age-related macular degeneration, retinopathies, glaucoma, keratoconus). * Neurological disorders affecting ocular motility or visual function (e.g., multiple sclerosis; cranial nerve III, IV, V, or VI palsy). * Manifest ocular deviation not suitable for management with visual therapy. * Inadequate refractive correction or prism requirement \>10 prism diopters (\>10Δ). * Refractive surgery (LASIK/PRK), cataract surgery, or any ocular surgery likely to influence binocular vision within the past 6 months. * Use of medications known to affect ocular motility or accommodative function. * Cognitive impairment or neurological conditions interfering with adherence to therapy instructions. * Suppression or severe amblyopia limiting response to visual therapy. * Best-corrected visual acuity \<0.5 decimal (equivalent to worse than 20/40) at distance or near.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in vergence reaction latency measured by video-oculography (REMOBI and EyeSeeCam) | Baseline (pre-intervention); post-intervention (within 2 weeks after the last visual therapy session); 3 months after post-intervention assessment; 6 months after post-intervention assessment. | Reaction latency (milliseconds) during standardized binocular convergence and divergence tasks recorded using video-oculography systems (REMOBI and EyeSeeCam). Lower latency values indicate better vergence motor performance. |
| Change in vergence amplitude variability measured by video-oculography (REMOBI and EyeSeeCam) | Baseline (pre-intervention); post-intervention (within 2 weeks after the last visual therapy session); 3 months after post-intervention assessment; 6 months after post-intervention assessment. | Variability of vergence response amplitude (%) during standardized binocular convergence and divergence tasks recorded using video-oculography systems (REMOBI and EyeSeeCam). Higher variability indicates lower stability of vergence motor control. |
| Change in vergence amplitude error measured by video-oculography (REMOBI and EyeSeeCam) | Baseline (pre-intervention); post-intervention (within 2 weeks after the last visual therapy session); 3 months after post-intervention assessment; 6 months after post-intervention assessment. | Amplitude error (%) of vergence responses relative to the target stimulus during standardized convergence and divergence tasks, automatically quantified by video-oculography systems (REMOBI and EyeSeeCam). Lower error values indicate more accurate vergence performance. |
| Change in vergence neglect rate measured by video-oculography (REMOBI and EyeSeeCam) | Baseline (pre-intervention); post-intervention (within 2 weeks after the last visual therapy session); 3 months after post-intervention assessment; 6 months after post-intervention assessment. | Neglect rate (%) defined as the proportion of trials with absent or undetected vergence response during standardized convergence and divergence tasks, recorded automatically by video-oculography systems (REMOBI and EyeSeeCam). Lower neglect rates indicate improved vergence function. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in Convergence Insufficiency Symptom Survey score (CISS-V15) | Baseline (pre-intervention); immediately after the post-intervention assessment (within 2 weeks after the last visual therapy session); 3 months after post-intervention assessment; 6 months after post-intervention assessment. | Total score of the Convergence Insufficiency Symptom Survey (CISS-V15; range 0-60). Higher scores indicate greater symptom burden related to binocular vision dysfunction. |
Countries
Andorra
Contacts
CONTACTJORDI Z ZARAGOZA BORT, MSc
CONTACTJORDI Z ZARAGOZA BORT, DO
PRINCIPAL_INVESTIGATORJORDI Z ZARAGOZA BORT, DO
Private Practice, Andorra
Outcome results
None listed