Prevalence And Ethnic Variations In Strabismus And Amblyopia Among Elementary School Children In Yunnan Province

ObjectivesThe survey was conducted in Yunnan to compare the prevalence of strabismus and amblyopia among multi-ethnic elementary school children in southwestern China.MethodsThis was a cross-sectional and school-based study conducted from December 2014 to January 2015.Randomized cluster sampling was used in selecting school students in two targeted areas of Yunnan Province-Mangshi County and Youngbi County.The study investigated the prevalence and ethnic variations of strabismus,amblyopia and related risk factors.Questionnaires were distributed to all enrolled children who were required to fill out the questionnaire under their parents'supervision,and each child received a comprehensive ophthalmologic examination including visual acuity,eye alignment,ocular motility,stereopsis,refraction,anterior and posterior segment eye examination.Data of the questionnaires and clinical examination was collected and computerized for statistical analysis.ResultsA total of 9,263 children consisting of 4,347 Han,3,352 Yi,799 Dai,as well as 765 Bai children were analyzed in the study.Manifested strabismus was detected in 3.53%of the overall population.The prevalence of strabismus was 3.29%in Han,4.12%in Yi,2.25%in Dai,and 3.66%in Bai ethnic groups.Significant difference in prevalence was indicated among the four ethnic groups(P = 0.046).The overall sample was divided into three groups by age(6 to 8 years,9 to 11 years,and 12 to 14 years),exhibiting a pattern of increasing prevalence in older age groups,ranging from 2.31%to 4.96%.Significant statistical difference was indicated among three age groups,with P<0.001.Amblyopia occurred in 132 children(1.43%)overall,with no statistical differences in gender and age.The prevalence of amblyopia was 1.66%in Han,1.04%in Yi,2.00%in Dai,and 1.18%in Bai ethnic groups,however,no statistical difference was detected(P = 0.062).Refractive error and strabismus were the two major factors associated with amblyopia.ConclusionsThis study is the first rigorous investigation of the prevalence of strabismus and amblyopia in multi-ethnic elementary school children in China.The prevalence of strabismus and amblyopia were 3.53%and 1.43%,respectively.The prevalence of strabismus was lowest in ethnic Dai and highest in ethnic Yi and similar in ethnic Han and Bai,exhibiting a trend of increased prevalence of strabismus in the older age group.The prevalence of amblyopia varied among the ethnicities,with the lower prevalence found in Yi children and the higher in Dai children.