Around one child in fifty has a lazy eye (termed amblyopia) where the eye is structurally normal but the vision fails to develop correctly. Around half of these children also have a squint (strabismus) where each eye has a different direction of gaze. This condition is the commonest cause of visual impairment in one eye in children.

This is a randomised control trial of wearing glasses alone (which will result in some visual improvement, termed refractive adaptation) and wearing glasses combined with using I-BiT Plus.

The hypothesis is that using I-BiT Plus will result in an improved visual outcome.

This study will treat amblyopia (lazy eye) using 3-D computer technology and active shutter glasses. Computer games and DVD's are viewed through the active shutter glasses and are specially prepared to preferentially stimulate the lazy eye; the child can only play the games accurately if they are using their lazy eye. The study is funded by the NIHR and will be undertaken as a randomised control trial to compare this against normal computer games and DVD viewing combined with continuing refractive adaptation (a process that is known to occur for up to 30 weeks). Patients will receive 6 weeks of treatment (recommended 30 mins minimum of play time per day for 6 weeks in the treatment arm) and level of vision will be assessed after 6 weeks and the visual improvement (they will be wearing glasses and also undergoing refractive adaptation) compared with the control. Patients will return to standard care after the trial period which, at 6 weeks, should not affect the final visual outcome in a negative way. The participants will be recruited from patients currently attending one of the 4 trial sites and will have a diagnosis of amblyopia, and be aged between 3 years 6 months and 9 years 11 months. Current treatments for amblyopia include wearing an eye patch over the good eye for up to 6 hours per day, or using eye drops to blur the image in the good eye for periods of 4 weeks at a time. The aim is both to avoid the need for patching or penalisation (which are unpopular treatments) and to get an improved visual outcome.

Assessment study: A study on 62 patients where the investigators will compare the visual acuity, angle of strabismus, stereoacuity and depth of suppression as estimated by I-BiT against measurements made at orthoptic assessment. This data will help interpret the results of the randomised controlled trial and help direct future development.

Inclusion Criteria:

• The child must be aged between 3 years 6 months and 9 years 11 months (upper limit is one day before their 10th birthday on day of consent.)
• Visual acuity difference of at least 0.3 log units, with the amblyopic eye being 0.3 logMAR or worse.
• Must have undergone a minimum of 12 weeks refractive adaptation.
• Those in group one must not have had patching or penalisation at all previously but the other two groups' participants may have had previous occlusion.
• Must not have had previous strabismus surgery (for groups one and two, and for group three, they must start the treatment within 4 weeks of having surgery.
• Must be able to use the I-BiT plus system.

Exclusion Criteria:

• Stimulus deprivation amblyopia.
• Other ocular or neurological disease affecting the visual system (including Down's syndrome, developmental delay,Craniofacial syndrome,Foetal Alcohol Syndrome, and cerebral palsy among other conditions).
• Photosensitive epilepsy.
• Parent, guardian or child not prepared to give consent.