Impact of amblyopia on vision at age 12 years: findings from a population-based study.

Objective: To report prevalence of amblyopia and long-term impact of its treatment on vision in a population-based sample of 12-year-old Australian children.

Methods: Logarithm of minimum angle of resolution (logMAR) visual acuity (VA) was measured in 2353 children (response rate 75.3%); visual impairment was defined as VA<6/12. Amblyopia was defined using various criteria of best-corrected VA, together with an amblyogenic factor and absence of significant organic pathology. Corroborative historical data on previous diagnosis and treatment were obtained from parental questionnaires.

Results: Forty-four children (1.9%) were diagnosed with amblyopia, unilateral in 40 and bilateral in four. Isolated anisometropia was the most frequent cause (41%), followed by strabismus (25%), combined anisometropia and strabismus (23%), and high ametropia (9%). Myopia, hyperopia, and astigmatism were present in 28, 51, and 44% of amblyopic children, respectively, compared to 12, 4, and 9% of non-amblyopic children. Mean best-corrected VA in amblyopic eyes was 44.5 logMAR letters (Snellen equivalent 6/9), range: 11-60 letters. Most children with amblyopia (84%) had been treated. Only 27% were visually impaired in their amblyopic eye.

Conclusions: This report documents a low amblyopia prevalence in a population of 12-year-old Australian children. Amblyopic visual impairment was infrequent in this sample despite absence of mandatory vision screening.