A Randomized Trial of Base-in Prism Reading Glasses Convergence Insufficiency in Children

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.