Table 1 Inclusion criteria, exclusion criteria, and diagnostic criteria

Inclusion criteria

 Age 18–35 years

 Best correct visual acuity of 20/25 or better in each eye at distance (5 m) and near (40 cm)

 Random-dot stereopsis better than or equal to 480 s of arc (40 cm)

 No previous prism or near add before study enrollment

 Willing to wear appropriate refractive correction for at least 2 weeks before vision therapy (spectacles are required for diopters that meet the following criteria)

 Myopia ≤ -0.75 D spherical equivalent in either eye

 Hyperopia ≥  + 2.00 D spherical equivalent in either eye

 Anisometropia ≥ 0.75 D spherical equivalent

 Astigmatism ≥ 1.00 D in either eye

Exclusion criteria

  ≥ 2^△ esophoria at distance

 History of strabismus, amblyopia, manifest or latent nystagmus

 History of vision therapy

 Organic lesions of the eye

 History of any ocular surgery

 History of head trauma or known disease of the brain

 Systemic or mental diseases, such as diabetes or anxiety, affecting accommodation, vergence, and ocular motility

 Use of ocular or systemic medications containing atropine, pirenzepine, or antiepileptic in the past 3 months

Diagnostic criteria

 Convergence Insufficiency

  We enrolled participants with convergence insufficiency who had a near exophoria at least 4△ greater than distance exophoria and met at least two of the following three criteria:

   1) Near point of convergence break point ≥ 6 cm

   2) Reduced near positive fusional vergence(break point ≤ 15△ or failed Sheard’s criterion)

   3) Convergence Insufficiency Survey Score ≥ 21 points

 Accommodative Dysfunctions

  We enrolled participants with accommodative dysfunction who met at least one of the following two criteria:

   1) The monocular amplitude of accommodation ≥ 2 diopters below the minimum prediction(15-age/4)

   2) Monocular accommodative infacility ≤ 6 cycles per minute with ± 2.00 D lenses