AIM: To explore the characteristics of astigmatism distribution among preschool children from Tongzhou District, Beijing, discuss its categorizations, severity, and the effect on preschoolers' vision, and clarify the influence of cycloplegic refraction on the detection of astigmatism.METHODS:In this cross-sectional study conducted from December 2021 to January 2022, a cluster random sampling method was utilized to assess 1 498 preschool children(2 996 eyes)from Tongzhou District, Beijing. The sample comprised 791 males and 707 females, with 222 children aged 3 to <4 years, 521 children aged 4 to <5 years, 647 children aged 5 to <6 years, and 108 children aged 6 to <7 years. Evaluations included visual acuity, anterior segment, computerized optometry, and cycloplegic refraction.RESULTS:Prior to cycloplegic refraction, the prevalence of astigmatism was found to be 61.88%(927/1498). For post-cycloplegic refraction, this percentage slightly increased to 64.02%(959/1498, P=0.095). Following cycloplegic refraction, the distribution of astigmatism severity was as follows: 51.87%(777/1498)had mild astigmatism, 9.41%(141/1498)had moderate astigmatism, and 2.74%(41/1498)had severe astigmatism. Astigmatism was predominantly with-the-rule across all age groups, with compound hyperopic astigmatism being the most frequent type. In cases of subnormal vision caused by astigmatism: low degree accounted for 9.38%, moderate degree accounted for 25.4%,and high degree accounted for 52.6%.CONCLUSION:The findings reveal a high incidence of astigmatism in preschool children, predominantly in a mild nature. Cycloplegic refraction was observed to have a negligible effect on the rate of astigmatism detection. Moreover, its impact on vision becomes more significant as the degree of astigmatism increases.