The purpose of this study is to test whether a binocular treatment can improve vision and motor function in young children with amblyopia. The proposed treatment is an animation series that has been modified so that different characters in the animation are presented to each eye. The contrast of the images shown to the amblyopic eye is higher than the contrast of the images shown to the fellow eye. The aim of the treatment is to promote co-operation between the two eyes and improve visual and motor outcomes. We will compare the benefits of this binocular treatment to patching, whereby the better eye is occluded with an eye patch for two hours per day to force the usage of the weaker eye. We hypothesize that the binocular treatment will improve vision and motor outcomes in young children with amblyopia, and that these improvements will be superior to any effects of patching.

This is a prospective study with study sites in Ontario, Canada (University of Waterloo); Quebec, Canada (University of McGill); Texas, United States of America (Retina Foundation of the Southwest); and Queensland, Australia (Queensland University of Technology). There are three study conditions. 1) binocular treatment at home, 2) binocular treatment in office and, 3) standard patching therapy.

Participants will be recruited from university-affiliated clinics and local clinical practices. Following full informed consent, participants will complete baseline testing to confirm eligibility and provide pre-treatment measurements of visual acuity, stereopsis, interocular suppression and motor function. Eligible participants will then be randomized to either binocular treatment or patching.

The treatment consists of dichoptically presented children's animations with all characters seen by the amblyopic eye and only a subset of characters seen by the fellow eye. Images shown to the amblyopic eye will be presented at 100% contrast and images presented to the fellow eye will be presented at 20% contrast on session 1 and contrast will increment by 10% of the prior session's contrast level for each subsequent session. Participants will complete 4 x 1-hour sessions per week for two weeks. After 2 weeks of treatment, participants will be offered the opportunity to complete an additional 2 weeks (8 hours) of treatment. Treatment will take place in the home or in-office depending on the study site.

The control group will patch for 2 hours every day, at home, for 2 weeks. A calendar will be provided (to both groups) in order for parents to track compliance. After 2 weeks of patching, participants in the control group have the option to crossover to the treatment group for an additional 2 weeks.

The primary analysis will compare visual acuity improvements from baseline between the binocular treatment and patching groups after 2 weeks of treatment. Secondary analyses will include comparisons of binocular vision and motor function outcomes between the binocular treatment and patching groups, comparisons of at-home vs. in-office binocular treatment outcomes and an evaluation of crossover effects.

Inclusion Criteria:

• Aged 3-5.9 years old (36-83 months at the time of registration)
• Confirmed diagnosis of amblyopia
• Best-corrected visual acuity of 20/32 - 20/100 in the amblyopic eye
• Best-corrected visual acuity of 20/16 - 20/40 in fellow eye for ages 3-4, and 20/16-20/32 for ages 5-5.9
• Interocular difference in visual acuity of 3 lines or greater
• If anisometropic, anisometropia (≥1.00D)
• Wearing glasses for 8+ weeks + no change in VA w/ glasses for 4-6 weeks
• Must be able to experience simultaneous perception when viewing the binocular treatment stimuli with an appropriate interocular contrast offset
• Doctor and parent must be willing to forego patching/drops for 4 week study period

Exclusion Criteria:

• strabismus
• Diagnosed eye disease or visual disorder other than amblyopia or anisometropia
• >8 weeks premature
• Diagnosed or suspected developmental delay (eg. learning disability, autism, Down syndrome)
• Diagnosed systemic disease (eg. diabetes, lupus, albinism)

Study team members measuring outcome variables will be masked to treatment group.