Amblyopia ('lazy eye') is the commonest visual disorder of childhood and is caused by an interruption to visual development. Occlusion of the better eye by patching is the mainstay of treatment, so forcing use, of the affected eye. We have little understanding of how much treatment is required for improvement, so occlusion may continue for many months. This is both demanding for the child and family as a whole. Treatment outcome is frequently unsatisfactory. Compliance is often poor, thus we do not know precisely how much treatment the child actually receives or how much is required.

To overcome this, we have designed an instrument that permits us to measure occlusion: an occlusion dose monitor (ODM) which provides an objective record of how much occlusion a child actually receives. Recently we have observed that 75% of improvement induced by occlusion occurs in the first four weeks of treatment. In this study we explore the possibility that by intensive treatment the period of amblyopia therapy can be shortened - i.e. treatment will be more efficient, more effective, and more 'family-friendly'. The study hypothesis is that 12 hours/day of patching is more effective than 6 hours/day.

The identification and subsequent management of amblyopia are major consumers of health service resource, and within the hospital sector account for around 80-90% of visits to the children's eye service. Occlusion of the better eye is the mainstay of treatment and because we have little understanding of the dose-response relationship this may continue for many months and sometimes for many hundreds of hours. This is demanding for the child and family as a whole and yet the outcome is frequently unsatisfactory. Currently, there is no reliable data on the kinetics of visual improvement, so occlusion tends to be prescribed on an ad hoc basis. Recent pilot research has shown that 75% of the treatment-generated improvement occurs within the first 4 weeks when 6 hours/day occlusion is prescribed.

In this study we explore the possibility that by intensive treatment the period of amblyopia therapy can be shortened - i.e. made both more efficient and hopefully more effective. The purpose of the present study, the Randomized Occlusion Treatment of Amblyopia Study (ROTAS), is to compare two frequently employed patching regimens: 'substantial' (6 hrs/day) against 'maximal' (12 hrs/day) patching. Our experimental design incorporates objective occlusion monitoring and is able to discriminate the beneficial effect of refractive correction from that of occlusion. The study comprises three phases: 'baseline', 'refractive adaptation' and 'occlusion.' Our aim is to provide guidelines for patient management based, for the first time, on experimentally determined and statistically verifiable relationships between treatment and outcome.

Inclusion Criteria:

• 3 to 8 years of age;
• Presence of anisometropia and/or strabismus;
• inter-ocular acuity difference of at least 0.1 logMAR
• parental consent

Exclusion Criteria:

• history of previous occlusion therapy
• ocular pathology
• learning difficulties