Danish Rural Eye Study: the association of preschool vision screening with the prevalence of amblyopia

Purpose To determine the prevalence of amblyopia in Denmark before and after the initiation of the Danish national preschool vision screening programme. Methods In a population-based cross-sectional study, 3826 participants of the Danish General Suburban Population Study (GESUS) aged 20 years and older from a Danish rural municipality received a complete general health examination and an ophthalmological interview and examination. This study included a comprehensive ophthalmologic interview, measurement of best corrected visual acuity (BCVA) in each eye, Hirschberg's test for strabismus and two 45-degree retinal fundus photographs of each eye. A complete ophthalmologic examination was performed when indicated. Results The prevalence of monocular visual impairment (MVI) was 4.26% (95% CI, 3.66–4.95, n = 163). Amblyopia was the most common cause, accounting for 33%. The prevalence of amblyopia was 1.44% (95% CI, 1.01–1.81, n = 55), being higher among non-preschool vision screened persons compared to those who were offered (estimated 95% attendance) preschool vision screening (1.78%, n = 41, 95% CI 1.24–2.33 versus 0.44%, n = 2, 95% CI, 0.12–1.60, p = 0.024). The leading cause of amblyopia was anisometropia (45.5%, 25/55). Conclusions Amblyopia was the most common cause of MVI. Following the initiation of the Danish national preschool vision screening programme, which has an approximate attendance rate of 95%, the prevalence of amblyopia decreased by fourfold.