| ObjectiveTo describe and analysis the circumstance of refraction,eye using, parents'education and living condition in Liangying town of Shantou city, so as to investigate the related factors of adolescence myopia, especially the relationship between population density and myopia , intended to better understand the reasons for observed differences in urban versus rural myopia prevalence among Chinese adolescence.MethodsSubjects from all Year 1 and 2 of 6 middle schools were selected with method of cluster random sampling, who took visual acuity examinations and questionnaires.Visual acuity examination included uncorrected distance visual acuity and cycloplegic auto-refraction in both eyes. All subjects with vision of≤6/12 in either eye, and a random 50% sample with vision>6/12 in both eyes underwent cycloplegic auto-refraction.Questionnaires were used to ascertain age, gender, address, near work (time and working distance), time spent outdoors, parental education, and living conditions like family conditions, housing type and so on.Data on population and total area for each of 30 villages/urban areas in Lingying were obtained from the county-level Ministry of Education. All statistical analyses were performed using the Statistical Software SPSS.Results1. Among 5844 participants of consenting parents, 4612 (78.9%) completed examinations, 2957 were refracted per protocol and 2480 (83.9%) of these had questionnaire data.2. Participants with refractive and questionnaire data had a mean age of 13.7±1.1 years. 44% (n=092) were boys with mean age of 13.8±1.1 years, while 56% (n=1388) were girls with mean age of 13.6±1.0 years. Statistical differences between boys and girls in age(P<0.001).3. The mean total weekly hours spent in all near work activities for all participants was 38.3 hours(11.9 hours in homework, 6.7 hours in other reading, 14.1 hours in watching TV and 5.6 hours in playing video games or computer use), while corresponding preferring working distances were 0.29m, 0.29m, 2.61m and 0.36m, diopter-hours per week were 46.7, 25.5, 6.9 and 17.1 respectively. The mean total weekly hours spent in outdoor activity was 5.6 hours.4. Students with spherical equivalent refractive error≤-2D in both eyes reported significantly more time (P=0.02 and P=0.004 for homework and other reading respectively), less distance(P=0.02 for both) and more diopter-hours(P=0.005 and P<0.001 respectively) of near work in homework and other reading than did students without such myopia, but self-reported outdoor activity, watching TV and playing video games or computer use did not differ between these two groups.5. The mean population density of villages/urban areas in which students with spherical equivalent refractive error≤-2D in both eyes reported living was significantly higher than that for students with>-2D in either eye (P>0.001), although parental education and development score did not differ between the two groups (P=0.75 and P= 0.13 respectively).6. In multivariate models, age (P<0.001), diopter-hours of near work (P=0.02) and population density (P=0.003), but not gender, time spent outdoors, parental education or development index, were significantly associated with spherical equivalent refractive error.ConclusionAge, near work and population density appears to be associated with myopia risk independent of gender, parental educational level, time spent outdoors and economic development.
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