Table 1

 Eligibility and exclusion criteria

Eligibility criteria:
• Age 9 to <18 years.
• Best corrected visual acuity of 20/25 or better in both eyes at distance and near.
• Willingness to wear eyeglasses to correct refractive error, if necessary.
• Exophoria at near at least 4 Δ greater than at far.
• Insufficient positive fusional convergence at near (fails Sheard’s criterion).
• Receded near point of convergence of ⩾6 cm break.
• Appreciation of at least 500 seconds of arc on the forms part of the Randot Stereotest.
• CI Symptom Survey-V15 score ⩾16.
• Informed consent and willingness to participate in the study and be randomised.
Exclusion criteria
• CI previously treated with prism, pencil push ups, or office based vision therapy/orthoptics (no more than 2 months of treatment within the past year).
• Amblyopia.
• Constant strabismus.
• History of strabismus surgery.
• Anisometropia >1.50 D (spherical equivalent) difference between eyes.
• Previous refractive surgery.
• Vertical heterophoria greater than 1 Δ.
• Systemic diseases known to affect accommodation, vergence, and ocular motility such as multiple sclerosis, Grave’s thyroid disease, myasthenia gravis, diabetes, and Parkinson’s disease.
• Any ocular or systemic medication known to affect accommodation or vergence.
• Monocular accommodative amplitude less than 4 D in either eye as measured by the push up method.
• Manifest or latent nystagmus.
• Attention deficit hyperactivity disorder or learning disability diagnosis by parental report that, in the investigator’s opinion, would interfere with treatment.