Refractive and corneal astigmatism in white school children in northern ireland.

PURPOSE To study the prevalence of and relation between refractive and corneal astigmatism in white school children in Northern Ireland and to describe the association between refractive astigmatism and refractive error. METHODS Stratified random clustering was used to recruit 1053 white children, 392 aged 6-7 years and 661 aged 12-13 years. Eye examinations included cycloplegic autorefraction and ocular biometric measures of axial length and corneal curvature. RESULTS The prevalence of refractive astigmatism (≥ 1 DC) did not differ significantly between 6- to 7-year-old children (24%; 95% confidence interval [CI], 19-30) and 12- to 13-year-old children (20%; 95% CI, 14-25). The prevalence of corneal astigmatism (≥ 1 DC) also did not differ significantly between 6- to 7-year-old children (29%; 95% CI, 24-34) and 12- to 13-year-old children (25%; 95% CI, 21-28). While levels of refractive astigmatism and corneal astigmatism were similar, refractive astigmatism was predominantly oblique (76%; 95% CI, 67-85, of 6- to 7-year-olds; 59%; 95% CI, 48-70, of 12- to 13-year-olds), but corneal astigmatism was predominantly with-the-rule (80%; 95% CI, 72-87, of 6- to 7-year-olds; 82%; 95% CI, 74-90, of 12- to 13-year-olds). The prevalence of refractive astigmatism was associated with increasing myopia and hyperopia. CONCLUSIONS This study is the first to provide robust population-based data on the prevalence of astigmatism in white school children in the United Kingdom. The prevalence of refractive astigmatism and corneal astigmatism is stable between 6 and 7 years and 12 and 13 years, although this finding would need to be confirmed by prospective studies. There is a high prevalence of refractive and corneal astigmatism which is associated with ametropia.