Correctable and non-correctable visual impairment in a population-based sample of 12-year-old Australian children

PURPOSE: To document the prevalence of correctable and non,correctable visual impairment in a representative sample of Australian children, predominantly age 12 years. DESIGN: Population based cross-sectional study. METHODS: Logarithm of the minimum angle of resolution (logMAR) visual acuity was measured in both eyes unaided, with spectacles if worn, and after subjective refraction if required, in 2353 children, examined during 2004 to 2005. Cycloplegic autorefraction (using cyclopentolate) and dilated fundus examination were perk formed. Using a cut-off of 0.3 logMAR units (< 20/40) presenting visual impairment was defined using unaided visual acuity if spectacles were not worn or with usual correction if spectacles were worn. Impairment not eliminated by refraction was considered non-correctable; any difference between this and presenting impairment was defined as correctable impairment. Myopia was defined as spherical equivalent refraction (SER) <=-0.50 diopters (D), hyperopia as SER >=+2.0 diopters, anisometropia as SER difference >= 1.00 diopters, and astigmatism as cylinder >= 1.0 diopters. Amblyopia was defined as corrected visual acuity < 0.3 logMAR not attributable to an under, lying structural eye or visual pathway abnormality. RESULTS: Visual impairment was found in the worse eye of 117 children (5.0%) and comprised correctable (82%) and non-correctable impairment (18%). Correct, able impairment was due to myopia in 67 (69.8%), hyperopia in 11 (11.5%) and astigmatism in 32 subjects (33.3%). Causes of non-correctable impairment were: amblyopia 66.7%, congenital glaucoma 9.5%, optic nerve hypoplasia 9.5%, congenital nystagmus 4.8%, and cortical blindness 4.8%. CONCLUSIONS: Visual impairment had a relatively low prevalence in this older childhood population, a large proportion of which was correctable by refraction alone.