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DP Fan, DS C Lam, S-J Chew, JT F Lau; Epidemiology of Myopia in Hong Kong: Prevalence, Incidence and Risk Factor Analysis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1511.
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Purpose: The aims of the study are to find out the prevalence and incidence of myopia in Hong Kong school children, and to correlate the above data with possible risk factors - including parental history of myopia and the amount of visual tasks in the study subjects. Methods:I t is a cohort study with 19 schools randomly selected in Hong Kong. All the randomly selected children with receive an ophthalmic examination including visual acuity testing, cycloplegic refraction and measurement of ocular dimensions. The visual tasks of children are assessed by completing a 1-week diary to record the time spent and the distance of each visual activity. The questionnaires on the family history of myopia are also recorded by the parents. A 1-year longitudinal follow-up study is performed. Results: Complete examinations were performed on 7,560 primary school children aged 5 to 16 years (mean = 9.33). Hong Kong has one of the highest prevalence (36.1%) of school myopia in the world. The mean refractive error was -0.33D (standard error = 0.022D) (Range, -13.125 to +14.250D). Among the myopic children, 3.24% of them have high myopia of -6.00D or more. It is found that children with one or two myopic parent have 1.82 to 3.23 times higher risk of having myopia compared to children without myopic parent indicating a genetic predisposition. Moreover, environmental predisposition is also confirmed. It is found that increase in near work is associated with increase risk of myopia in children. The incidence of myopia is 144.1 per 1000 primary school children annually. The average annual progression is -0.40D per year. The incidence of myopia among children decreases with increasing age when the amount of visual task is controlled. The spherical equivalent (SE) of the astigmatic group is -1.143D. This is significantly more myopia than the group without astigmatism (SE = -0.154D, p<0.0001). The rate of myopic progression is also higher for the astigmatic group. (-0.464D/year) compared to the non-astigmatic group (-0.375D/year) (p = 0.0408). Conclusion: Hong Kong has a high prevalence and incidence of myopia in primary school children. Both genetic and environmental factors are important predisposing factors in the development of myopia. Visual deprivation from astigmatism can be a risk factor of myopia development and myopia progression.
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