Inclusion criteria and rationale for patient selection
| Criteria | Comment |
|---|---|
| Children aged 3–7 years | Accurate measurements of letter based visual acuity are unattainable in 50% of children under the age of 3 years but attainable in 75% of children 3.25 years of age.28 It is important that measurements are consistent and accurate, thus children under the age of 3 years are excluded from the study. Children over 7 years of age are not included as they fall outside the accepted sensitive period for visual development |
| Visual acuity of 0.1 log units or lower in worst eye and/or interocular difference of at least 0.1 log units | Visual acuity of 0.1 log units or worse is considered to be abnormal in this age group |
| Presence of anisometropia and/or strabismus | This group forms the majority of the population of children with amblyopia29 |
| No other ocular pathology | Form deprivation amblyopia is excluded because this forms a clinical entity distinct from the general population with amblyopia |
| No previous occlusion treatment | Dose-response functions in previously treated children may differ from those in whom treatment has already been undertaken |
| Knowledge of previous spectacle history | All subjects undergo full adaptation to their spectacles before entering the occlusion phase of the study. If children enter the study having already been prescribed spectacles it is important to establish that full spectacle adaptation has occurred |
| No learning difficulties | To obtain accurate and consistent measurements of visual function from every subject it is necessary to exclude patients with learning difficulties |
| Parental/guardian consent | In accordance with local ethics committee requirements |