The therapy of amblyopia: an analysis comparing the results of amblyopia therapy utilizing two pooled data sets.

CONTEXT: We previously presented the results of an original pooled data set of 961 amblyopic patients who underwent patching therapy for amblyopia from 1965 to 1994 (study group 1). Three types of amblyopia were considered: anisometropic, anisometropic-strabismic, and strabismic. Analysis of this group's success was related to the age at which therapy was initiated, the type of amblyopia, and the depth of visual loss before treatment was begun. The purpose of the current study is to test the validity of these findings on a second group of 961 amblyopes employing the data set used by Woodruff and associates in their publications (study group 2). These 2 data sets, after adjustment to conform to the definitions of age, amblyopia, anisometropia, and similar items utilized in common between the 2 study groups, will be compared for the risk factors predictive of successful occlusion therapy. OUTCOME: As in the previous study, the success of occlusion therapy is defined as a visual acuity of 20/40 or better at the end of treatment. RESULTS: Success by the 20/40 criteria was achieved in 73.7% in study group 1 and in 59.9% in study group 2. By category, the rate of success in study group 1 was 77.2% in strabismic amblyopia, 67.2% in anisometropic-strabismic amblyopia, and 66.0% in anisometropic amblyopia. In study group 2, success was 61.2% in strabismic amblyopia, 51.2% in anisometropic-strabismic amblyopia, and 63.0% in anisometropic amblyopia. Study group 1 univariate analysis related success in each group to the age at which therapy was initiated, the type of amblyopia, and the depth of visual loss before treatment in each group. In study group 2, univariate analysis related success of occlusion therapy to age and the depth of visual loss before treatment. Type of amblyopia was not related to outcome success in this group. When the 2 data sets were pooled, the risk factors for success were age and depth of visual loss at onset of treatment. CONCLUSIONS: Factors that appeared closely related to a successful outcome of patching therapy were patient age and depth of visual loss before treatment. These conclusions further support the value of early detection and screening for amblyopia, its prevention, where possible, and its adequate and vigorous treatment when it is detected and diagnosed.

Factors affecting treatment compliance in amblyopia.

Amblyopia is the most common form of visual disability in children. Successful treatment by patching depends on compliance, but evidence of factors affecting compliance is limited and contradictory. Because there is a well established relationship between social deprivation and access to health care, we hypothesized that social deprivation might be associated with noncompliance. Data from a historical cohort of 961 children from seven English orthoptic clinics starting treatment for amblyopia in 1983 were used to study factors affecting compliance with amblyopia treatment. Children were classified as noncompliant if they failed to attend all appointments prescribed during the first year of treatment. There was a significant difference in compliance between centers (P = .0001). Overall, children with anisometropic amblyopia were more compliant than those with strabismus but this varied significantly between centers. A relationship between social deprivation and compliance was also found (P = .00001). Only 41% of children from the most deprived wards were compliant compared with 61% in the least deprived wards. Compliance was not found to be related to age at starting treatment.

Social deprivation and age at presentation in amblyopia.

BACKGROUND: Amblyopia is the most common visual disability in children. Early treatment is thought to be more effective, and therefore factors affecting the age at presentation are important. A relationship between social deprivation and access to health care and screening services is well known. We hypothesized that social deprivation might be associated with later presentation of amblyopia, particularly of anisometropic amblyopia which depends on vision screening for referral. METHODS: Data from a historical cohort of 897 children with amblyopia, from seven UK orthoptic clinics, were used to test this hypothesis. Social deprivation was measured by the Townsend score of the ward in which the child lived. RESULTS: A relationship between social deprivation and age at presentation was found in children with anisometropic amblyopia even after adjusting for differences between clinics (p = 0.01) but no similar association was evident in children with amblyopia associated with strabismus. There was a difference of 22 months in the average age at presentation between children with anisometropic amblyopia in the most deprived and least deprived areas of the study. CONCLUSIONS: If screening for anisometropic amblyopia is to be undertaken, priority should be given to screening children from areas of social deprivation.

The presentation of children with amblyopia.

This study reports the presentation of 961 children who underwent amblyopia treatment at seven orthoptic centres in the United Kingdom. We confirmed previous authors' findings of a small but significant increased incidence of left-sided compared with right-sided amblyopia overall. For pure anisometropic amblyopia this difference was very marked and a possible pathophysiological mechanism is proposed. The mean age of presentation for anismetropic, strabismic and mixed amblyopia was 5.6, 3.3 and 4.4 years, respectively. Neither sex nor race affected the age of presentation. Despite their older age, children with pure anisometropic amblyopia had the best initial visual acuity, with 25% of anisometropes having an initial visual acuity of less than 6/18 compared with 39% of strabismics and 50% of mixed amblyopes. The ages and initial acuities of the strabismic patients in this series are at least as favourable as those of patients reported from outside the UK. There were variations in the age and proportion of patients presenting with anisometropic amblyopia at the different centres, suggesting a failure in the referral of anisometropic amblyopia of importance in interpreting epidemiological studies.

Factors affecting the outcome of children treated for amblyopia.

The outcome of treatment for amblyopia and the factors that affect this are not well understood. A major reason for this has been the exclusion from previous large studies of a sometimes unknown number of patients because of failure to comply with treatment. This paper analyses the outcome of amblyopia treatment in a retrospective review of the orthoptic records of a cohort of 961 children treated for amblyopia at seven centres who first attended in 1983. The final visual acuity was recorded by Snellen or matching methods in 894 children (93%). Of these, 48% achieved 6/9 or better, 35% less than 6/9 but better than or equal to 6/18, and 17% achieved less than 6/18. The outcome was best for pure anisometropic amblyopia, intermediate for pure strabismic amblyopia and least good for mixed strabismic and anisometropic amblyopia with a final visual acuity of 6/10.2, 6/12.8 and 6/14.8 respectively. While the age at start of treatment did not correlate with final visual acuity both poor initial visual acuity and poor compliance were associated with poor outcome. The main factor affecting the outcome of amblyopia treatment is the initial visual acuity. Comparison with the literature suggests that the results of treatment in this country may be falling far short of what would be possible in ideal circumstances with unlimited resources.

Occlusion for amblyopia: a comprehensive survey of outcome.

The results of a long term follow up of all patients from a single health district started on occlusion for amblyopia in 1983 are reported. Three hundred and sixty-eight patients started treatment, their average age was four years seven months, the average amount of daily occlusion was 1.5 hours and the average length of follow up was 31 months. 37% of cases achieved a final visual acuity of 6/9 or better and another 33% a visual acuity of 6/12 or 6/18.23% did not achieve 6/18 and treatment of these patients was regarded as failure. Data for the remainder (7%) were incomplete. The success rate of occlusion treatment varied little with the age of starting treatment. The group with combined strabismus and anisometropia responded least well to treatment.

The incidence and prevalence of amblyopia detected in childhood.

We present incidence estimates for amblyopia using data from a study of a cohort of 364 children from a single English county who were referred during 1983 for occlusion therapy. Using a criterion of a visual acuity of 6/12 or worse to define amblyopia, we estimate that 3.0% of the county's children develop the condition. Successful treatment of some of these children means that 1.9% will remain amblyopic as adults.