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.

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