A Longitudinal Study of the Development of Myopia in Chinese Children: A Life Table Treatment

Summary

Studies of the incidence and prevalence of myopia must demonstrate that the sample is representative of the population being studied and must justify the statistical treatment of cases that are lost to observation. A life table treatment is appropriate and is used to present the results of a prospective study of the development of myopia in Chinese children. Hong Kong children taking part in a study of growth and nutrition were recruited into the myopia study. All but one child joined (n = 123), so that there was no bias from self-selection. Refractions have been carried out annually since the children were 7 years of age. The incidence and prevalence of myopia were calculated on the basis of two different assumptions: (1) that none of the subjects lost to observation had become myopic during the previous year, and (2) that subjects lost to observation were as likely to have become myopic as the subjects retained. The real situation is probably somewhere between these two. At the age of 7 years, the prevalence of myopia was 11%. By the age of 12 years, it was 55% to 58%, depending on which of the above assumptions was applied.