Non-invasive Brain Stimulation for Treating Symptomatic Convergence Insufficiency

Midwestern University150 enrolled

Overview

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: 1. Can non-invasive brain stimulation shorten the treatment time of office-based vergence/accommodative therapy for convergence insufficiency? 2. 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: 1. Non-invasive brain stimulation with office-based vergence/accommodative therapy. 2. Sham stimulation with office-based vergence/accommodative therapy. 3. 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.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Enrollment

150

Conditions

Convergence Insufficiency

Interventions

Anodal-Transcranial Direct Current StimulationDEVICE

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 20 minutes with a ramp up to the maximum programmed current and ramp down of 20 seconds.

Office-Based Vergence/Accommodative TherapyBEHAVIORAL

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.

Sham Transcranial Direct Current StimulationDEVICE

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 20 minutes.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 40 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

Near Point of Convergence (NPC)

A change in the NPC break and recovery values measured in centimeters (cm) from baseline after treatment.

Time frame: 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.

Time frame: 4 weeks, 6 weeks, and 8 weeks during treatment; 6 months and 12 months post-treatment

Secondary Outcomes

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.

Time frame: 8 weeks during treatment; 6 months and 12 months post-treatment