Binocularly Balanced Viewing Study (BALANCE)

Phase 2a Two-site Randomised Controlled Trial to Determine Safety of and Adherence With a New 'Binocularly Balanced Viewing' Treatment for Unilateral Amblyopia Compared With Standard Treatment in Children Age 3-8 Years

Amblyopia is treated by glasses and patches or blurring eyedrops to the good eye. This works in about 70% of children, but parents and children strongly dislike these treatments which may carry on for years and involve frequent clinic visits. In this pilot trial, 66 children will receive, at random, either a Nintendo 3DSXL console with movies, or standard patching/blurring eye-drop treatment. The Investigators will monitor adverse events (double vision), change in the balance between the two eyes and in visual acuity over 16 weeks.

"Lazy eye" (amblyopia) is the commonest sight problem in children, affecting about one in 30 children. It is caused by a difference in spectacle prescription between the eyes and/or a squint (eye misalignment), with the brain ignoring one eye. Amblyopia is treated by glasses and patches or blurring eyedrops to the good eye. This works in about 70% of children, but parents and children strongly dislike these treatments which may carry on for years and involve frequent clinic visits. The Investigators have developed an exciting new treatment: children watch customized movies for an hour a day on a hand-held 3D computer-game console. The Investigators blur the picture that the good eye sees to match it with what the weaker eye sees. They have tested this approach on 22 children, with an average improvement in vision by three lines on the test chart over 8 - 24 weeks, which may be faster than with standard treatment. Parents and children the Investigators have spoken with like both the idea of research in this area and the engaging nature of this device. The Investigators now need to assess how the new treatment compares with standard treatment, but first need to ensure that the new treatment is safe and that families will use it. In this pilot trial, 66 children will receive, at random, either a Nintendo 3DSXL console with movies, or standard patching/blurring eye-drop treatment. The Investigators will monitor adverse events (double vision), change in the balance between the two eyes and in visual acuity over 16 weeks. Parents and children have helped develop this pilot - this involvement will be continued throughout the study. At study completion, children and parents will be involved in deciding how best to communicate the findings on hospital websites, in newsletters, at conferences and in medical journals.

The experimental intervention will be BBV treatment, i.e. viewing movies for one hour or 2x30min/day on a Nintendo 3DSXL console. With this technology, the Investigators will show blurred images to the better-seeing eye and normal images to the amblyopic eye, encouraging the use of the amblyopic eye and improving acuity.

The control intervention will be either atropine eyedrops twice a week or daily occlusion (patching) therapy of the better-seeing eye (which are the current standards). As per clinical standard, parents will be offered the choice of occlusion or eyedrop treatment.

The dose of BBV therapy will be one hour a day or 2x30 min/day (depending on child's attention span and/or need to implement the treatment around the family daily routine).

The prescribed dose of occlusion treatment / patching (parental choice) will depend on the severity of amblyopia, as by current clinical practice based on PEDIG studies

To measure changes in suppression/interocular balance (considered to precede double vision) at 16 weeks from baseline, using a novel test of interocular balance, a contrast-sensitivity test presented on a PC

Inclusion Criteria: Age between 3.0 and less than 8.0 years unilateral anisometropic, strabismic or combined mechanism amblyopia best-corrected crowded logMAR visual acuity (BCVA) in the amblyopic eye worse than 0.2logMar best corrected visual acuity in the better seeing eye 0.2 or better difference in best corrected visual acuity between the two eyes of 0.2 logMAR or more adapted to spectacles with no improvement in acuity in affected eye for two consecutive visits no previous treatment for amblyopia other than glasses Exclusion Criteria: ocular cause for reduced visual acuity inability to co-operate with assessment tests other developmental disorders or learning or neurological disability that would impact on adherence to treatment photopic epilepsy myopia with spherical equivalent of greater than -6.00DS previous intraocular surgery inability to perform a crowded letter logMAR visual acuity test using a clinical trials standard testing method (ATS-HOTV protocol), either by naming or by matching letters

Dahlmann-Noor AH, Greenwood JA, Skilton A, Baker D, Ludden S, Davis A, Dehbi HM, Dakin SC. Phase 2a randomised controlled feasibility trial of a new 'balanced binocular viewing' treatment for unilateral amblyopia in children age 3-8 years: trial protocol. BMJ Open. 2022 May 24;12(5):e051423. doi: 10.1136/bmjopen-2021-051423.