Does amblyopia have a functional impact?

Amblyopia is a common childhood developmental disorder in which there is dysfunction of the processing of visual information. There is a wide range of functional deficits and adaptations that occur in amblyopic vision but amblyopia is usually clinically manifested as a monocular visual impairment. Stereoacuity may or may not be affected and the better eye may have sub-clinical deficits. Preschool vision screening programmes were established in many industrialised countries in the 1970’s after animal studies established a “critical period” during which amblyopia should be treated. Presently there is much scientific debate about the effectiveness of these screening programmes. Central to this debate is that it is not known if amblyopia has a long-term impact on everyday life or what its utility is. While preschool vision screening programmes are thought to reduce the prevalence and severity of amblyopia for those who participate, it is not known if they reduce the functional consequences of amblyopia for the individual or its impact at a population level. In the last decade, the evidence-based knowledge on many aspects of amblyopia has grown significantly, but experts continue to call for more research on whether amblyopia has a long-term impact on everyday life. The aim of this thesis is to assess the functional impact associated with amblyopia using data from The Dunedin Multidisciplinary Health and Development Study, a longitudinal population birth cohort (born 1972-3, n=1037, retention rate age 32 years 96%). Visual examinations were conducted when the study participants were 7, 9, 11 and 15 years of age. Study members with amblyopia or recovered amblyopia were compared with those without amblyopia in the outcome domains of childhood motor development, teenage self-esteem and adult socio-economic status (occupation, highest educational qualification, reading ability and income). There was no significant association between amblyopia or having recovered from amblyopia and impaired fine or gross motor ability from age 3 to age 11 years. Amblyopia or having recovered from amblyopia was not associated with reduced self-esteem at ages 11 and 13 years. Amblyopia or having recovered from amblyopia was associated with a higher status occupation in adult females. Amblyopia or having recovered from amblyopia was not associated with the highest educational qualification achieved by age 32 years, reading ability up to age 18 years or income at age 32 years. Within this cohort, amblyopia or having recovered from amblyopia was not associated with a significant adverse functional impact on childhood motor development, teenage self-esteem and adult socio-economic outcomes. The wide range of functional deficits and adaptations that occur in amblyopic vision do not seem to translate into functionally significant differences within this cohort. The implications for the New Zealand preschool vision screening programme are discussed with a recommendation to optimise the programme to match the current evidence-base. The important issue of the risk of bilateral visual impairment arising through loss of vision in the better eye of individuals with amblyopia will be examined in a future Dunedin Multidisciplinary Health and Development Study