Non-invasive Brain Stimulation for Treating Symptomatic Convergence Insufficiency

Study Overview
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Brief Summary
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The goal of this randomized controlled trial is to test the effectiveness of non-invasive brain stimulation in treating adults with symptomatic convergence insufficiency compared to vergence/accommodative therapy. The main questions it aims to answer are: Can non-invasive brain stimulation shorten the treatment time of office-based vergence/accommodative therapy for convergence insufficiency? Is non-invasive brain stimulation alone just as effective as office-based vergence/accommodative therapy in treating convergence insufficiency? The investigators hypothesize that non-invasive brain stimulation will shorten the treatment time from 12 weeks to 8 weeks of office-based vergence/accommodative therapy and that non-invasive brain stimulation alone would be equally effective as office-based vergence/accommodative therapy in improving symptomatic convergence insufficiency. Participants will be randomized into one of three treatment groups: Non-invasive brain stimulation with office-based vergence/accommodative therapy. Sham stimulation with office-based vergence/accommodative therapy. Non-invasive brain stimulation only. Researchers will compare baseline measurements of near point of convergence (NPC) and positive fusional vergence (PFV) to post-treatment measurements for each group.

Official Title
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A Randomized Controlled Study Using Non-invasive Brain Stimulation to Facilitate the Effectiveness of Vergence/Accommodative Therapy in Symptomatic Convergence Insufficiency

Conditions
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Convergence Insufficiency

Intervention / Treatment
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* Device: Anodal-Transcranial Direct Current Stimulation
* Behavioral: Office-Based Vergence/Accommodative Therapy
* Device: Sham Transcranial Direct Current Stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Best-corrected visual acuity of > 20/25 in each eye at distance and near Exophoria at near at least 4∆ greater than at far Receded near point of convergence of > 6 cm break Insufficient positive fusional vergence at near (< 15∆ base-out blur or break) CISS score of 16 and greater for children or 21 and greater for adults Have had a dilated fundus examination within the last 12 months Informed consent and willingness to participate in the study and be randomized Exclusion Criteria: Previously treated for convergence insufficiency with home- or office-based vergence/accommodative therapy Amblyopia (> 2-line difference in best-corrected visual acuity between the two eyes) Constant strabismus History of strabismus surgery Convergence insufficiency secondary to acquired brain injury or neurological disorder Manifest or latent nystagmus Systemic disease known to affect accommodation, vergence, and ocular motility including multiple sclerosis, Graves disease, myasthenia gravis, Parkinson's disease, cerebral palsy, and diabetes Developmental disability, attention deficit hyperactivity disorder (ADHD), learning disability or cognitive dysfunction that would interfere with treatment Taking medications that can affect normal neurological function including antipsychotics, antiepileptics, and opioids Presence of metal or electronic implants in or on the body, including pacemakers

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: NIBS-OBVAT<br>8 sessions of non-invasive brain stimulation with 8 weeks of office-based vergence/accommodative therapy. | Device: Anodal-Transcranial Direct Current Stimulation<br>* Non-invasive brain stimulation will involve the use of anodal transcranial direct current stimulation to apply a 2 milliamp current over the left frontal eye field for approximately 30 minutes with a ramp up to the maximum programmed current and ramp down of 10 seconds.<br>* Other names: a-tDCS;Behavioral: Office-Based Vergence/Accommodative Therapy<br>* Office-based vergence accommodative therapy involves weekly in-office appointments with the therapist lasting approximately 60 minutes per visit during which time in-office procedures will be performed, and home therapy procedures will be demonstrated. Participants will be prescribed 15 minutes of home reinforcement therapy procedures to be completed 5 days per week. Therapy will consist of two phases adapted from the Convergence Insufficiency Treatment Trial (CITT). Therapy procedures will include gross convergence, accommodation. non-computer based vergence, and computer-based vergence.<br>* Other names: Orthoptic training;|
| Active Comparator: NIBS<br>8 sessions of non-invasive brain stimulation only. | Device: Anodal-Transcranial Direct Current Stimulation<br>* Non-invasive brain stimulation will involve the use of anodal transcranial direct current stimulation to apply a 2 milliamp current over the left frontal eye field for approximately 30 minutes with a ramp up to the maximum programmed current and ramp down of 10 seconds.<br>* Other names: a-tDCS;|
| Sham Comparator: OBVAT<br>8 sessions of sham stimulation with 8 weeks of office-based vergence/accommodative therapy. | Behavioral: Office-Based Vergence/Accommodative Therapy<br>* Office-based vergence accommodative therapy involves weekly in-office appointments with the therapist lasting approximately 60 minutes per visit during which time in-office procedures will be performed, and home therapy procedures will be demonstrated. Participants will be prescribed 15 minutes of home reinforcement therapy procedures to be completed 5 days per week. Therapy will consist of two phases adapted from the Convergence Insufficiency Treatment Trial (CITT). Therapy procedures will include gross convergence, accommodation. non-computer based vergence, and computer-based vergence.<br>* Other names: Orthoptic training;Device: Sham Transcranial Direct Current Stimulation<br>* Sham transcranial direct current stimulation will be applied over the left frontal eye field with the current ramping up for 20 seconds before ramping down for 20 seconds. The 2 milliamp current stimulation will occur for only a few seconds at the start and at the end of the 30 minutes.<br>* Other names: Sham tDCS;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Near Point of Convergence (NPC) | A change in the NPC break and recovery values measured in centimeters (cm) from baseline after treatment. | 4 weeks, 6 weeks, and 8 weeks during treatment; 6 months and 12 months post-treatment | 
| Positive Fusional Vergence (PFV) | A change in the near PFV blur, break, and recovery values measured in prism diopters (∆) from baseline after treatment. | 4 weeks, 6 weeks, and 8 weeks during treatment; 6 months and 12 months post-treatment | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Convergence Insufficiency Symptoms Survey (CISS) | A change in the CISS score from baseline after treatment. The minimum score is 0 and the maximum score is 60. Lower scores indicate a better outcome. | 8 weeks during treatment; 6 months and 12 months post-treatment | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Convergence Insufficiency, Non-invasive Brain Stimulation, Office-Based Vergence/Accommodative Therapy, Frontal Eye Fields, Transcranial Direct Current Stimulation