This study is designed to compare the use of special prism glasses to placebo treatment for children with symptomatic convergence insufficiency.

The Base-in for Convergence Insufficiency Treatment Trial (BI-CITT) is a multi-center, placebo-controlled, masked, clinical trial designed to compare the benefits of base-in prism for patients with convergence insufficiency (CI).

The goals of this clinical trial are:

• To compare the effectiveness of Base-in prism and Placebo eyeglasses for the treatment of CI in children
• To study the long-term effect of these treatments for CI
• To identify factors that may be associated with successful treatment of CI with base-in prism

Inclusion Criteria:

• Age: 9 to <19 years.
• Best corrected visual acuity of ≥20/25 in each eye at distance and near
• Willingness to wear eyeglasses or contact lenses to correct refractive error, if necessary
• Willingness to wear glasses for reading and other near work
• Exophoria at near at least 4 greater than at far
• Insufficient positive fusional convergence (fails Sheard's criterion)
• Receded near point of convergence of  6 cm break
• Random dot stereopsis appreciation using a 500 seconds of arc target.
• CI Symptom Survey score  16

Exclusion Criteria:

• Amblyopia (> 2 line difference in best corrected visual acuity between the two eyes).
• Constant strabismus
• History of strabismus surgery.
• Anisometropia  2D in any meridian between the eyes.
• Prior refractive surgery.
• Vertical heterophoria greater than 1 .
• Systemic diseases known to affect accommodation, vergence and ocular motility such as: multiple sclerosis, Graves thyroid disease, myasthenia gravis, diabetes, Parkinson disease.
• Any ocular or systemic medication known to affect accommodation or vergence (Anti-anxiety agents (Librium or Valium), Anti-arrhythmic agents (Cifenline or Cibenzoline), Anticholinergics (Motion sickness patch (scopolamine), Bladder spasmolytic drugs (Propiverine), Chloroquine, Phenothiazines (Compazine, Mellaril, or Thorazine), Tricyclic antidepressants (Elavil, Nortriptyline, or Tofranil)
• Accommodative amplitude <5 D in either eye as measured by the Donder's push-up method.
• Manifest or latent nystagmus.
• Developmental disability, mental retardation, attention deficit hyperactivity disorder (ADHD), or learning disability diagnosis in children that in the investigator's discretion would interfere with treatment.
• Household member or sibling already enrolled in the BI-CITT.
• Any eye care professional, ophthalmic technician, ophthalmology or optometry resident or optometry student.