Non-invasive Induction of Metaplasticity for Amblyopia

The goal of this clinical trial is to determine the efficacy of flicker therapy as an adjunct therapy to treat amblyopia beyond the critical period in adolescents and adults aged 14-40 years who have amblyopia of ≥3 lines of interocular best-corrected (with glasses) visual acuity difference. The main questions it aims to answer are: * Does flicker therapy enable clinically meaningful and durable visual recovery from amblyopia? * Do flicker therapy-treated patients show a change in amblyopic eye visual acuity (lines)? Participants will undergo daily flicker therapy for 1 hour per day.

Inclusion Criteria: * Age ≥14 and ≤40 years * Amblyopia associated with strabismus and/or anisometropia * Criteria for strabismus: must meet at least one of the following: heterotropia at distance and/or near with or without spectacle correction, history of strabismus surgery, documented history of strabismus that is no longer present and felt by the investigator could have caused the amblyopia * Criteria for anisometropia: must meet at least one of the following: * ≥ 0.50 D difference in spherical equivalent between eyes * ≥ 1.50 D difference in astigmatism in any meridian between the eyes * Visual acuity measured in each eye within 7 days prior to enrollment using ETDRS protocol on a study certified visual acuity tester as follows: * Amblyopic eye visual acuity of 20/40 - 20/400 * Fellow eye visual acuity of ≥ 20/25. * Spectacle correction for measurement of enrollment visual acuity must meet the following criteria and be based on a cycloplegic refraction \< 6 months old: * Requirement for spectacle correction: * Spherical equivalent must be within 0.50 D of fully correcting anisometropia * Hyperopia ≥ 3.00 D must be corrected * Hyperopia may not be under-corrected by \>1.50 D spherical equivalent and must be symmetrically reduced in each eye * Cylinder power must be within 0.50 D of fully correcting the astigmatism * Cylinder axis must be within 6 degrees of the axis when the cylinder power is ≥ 1.00 D * Myopia of the amblyopic eye \>0.50 D spherical equivalent must be corrected * Myopia may not be under-corrected by \>0.25 D or overcorrected by \> 0.50D * Spectacles meeting the above criteria must be worn until visual acuity in amblyopic eye has not improved ≥ 1 line (5 letters) by the same testing method during 2 consecutive visual acuity measurements at least 4 weeks apart (i.e. minimum of 12 weeks spectacle correction) * Dilated eye examination within 6 months prior to enrollment * Subject must be available for at least 4 months of follow-up, have access to a phone, and be willing to be contacted * By investigator judgment, the subject is likely to comply with prescribed treatment (i.e. no prior history of poor compliance) and complete all follow up visits Exclusion Criteria: * Myopia \> -6.00 D spherical equivalent * Presence of associated findings that could cause reduced visual acuity * Nystagmus does not exclude the subject if the above visual acuity criteria are met * Treatment with topical atropine within the past 12 weeks * Previous intraocular or refractive surgery * Strabismus surgery planned within 16 weeks * Current vision therapy or orthoptics * History of seizures * Known past or present susceptibility to seizures at the discretion of the investigator * Known past or present psychological problems * Known contraindications or inability to use of a head-mounted device (over one's glasses) and/or exposure to flickering light * Current use of medication for the treatment of seizures, bipolar disorder, or migraine * Use of any medication with neuromodulatory effects, including * Medications that reduce seizure thresholds