The long-established practices of early childhood screening for amblyopia and patching of the dominant eye are not supported by evidence of good clinical outcome. Williams and colleagues used a large longitudinal study of child development in southwest England to analyze the outcomes of screening and early intervention in children with amblyopia.
All children who were born in the region during a six-month period were eligible for the study. The 3,490 participating children received the usual early screening administered by family physicians and nurse practitioners and, later, screening for visual acuity by school nurses. Participants in the study were randomly allocated to normal amblyopia surveillance or intensive screening and intervention. Children in the intensive-screening group received age-appropriate visual testing and assessment by an orthoptist at eight, 12, 18, 25, 31, and 37 months of age. Children in the control group were assessed by an orthoptist at 37 months of age. All children who failed acuity or cover testing were referred to a hospital-based eye service.
At 7.5 years, data were available for 1,088 (54 percent) of the intensive-screening group and 826 (55 percent) of the control group. The prevalence of amblyopia in the intensive-screening group was 0.6 percent, significantly less than the 1.8 percent prevalence in the control group. Mean visual acuity in the amblyopic eye was significantly better in children treated in the intensive-screening group than in children in the control group who also had been treated for amblyopia. The proportion of children appropriately referred for hospital treatment before three years of age was significantly higher (48 percent) in the intensive-screening group than in the control group (13 percent). In multivariate analysis, maternal education was the only variable that was significantly associated with outcome.
The authors conclude that children who required treatment for amblyopia were four times more likely to remain amblyopic if they were screened only at 37 months of age. In addition, early treatment for amblyopia was more effective than later interventions.
editor's note: The “inverse care law” strikes again! Families with more resources and comfort with the health care system benefited most from the services, even when treatment was free. Despite problems with follow-up, this study provides evidence that early detection and intervention for amblyopia improves vision in young children. The implications for their academic and social development are obvious. Our challenge is to find ways to ensure that all children are screened and treated, especially those from the most vulnerable families.—a.d.w.