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Taiwan is one of the countries with high prevalence of myopia.1 The purpose of this study is to compare the change of ocular refraction among freshmen between 1988 and 2005 in National Taiwan University.2

The mean refractive status of total 4686 freshmen was −4.25±2.74 D in 1988 (−4.12±2.72 D for male and −4.41±2.75 D for female). In 2005, it was −4.93±2.82 D (−4.93±2.83 D for male and −4.93±2.80 D for female) of total 3709 freshmen. The result was shown in the Table 1. The prevalence of myopia was 95.9% in 2005, while it was 91.3% in 1988. The prevalence of high myopia (over −6.0 D) increased to 38.4% (38.1% for male and 38.8% for female) in 2005, while it was 23.5% (22.2% for male and 25.1% for female) in 1988. The distribution curve in 2005 compared to 1988 was obviously more myopic-shifted. Detail analysis of refractive status among male and female freshmen in 1988 and 2005 was showed in Table 2. There was a significant difference between 1988 and 2005 (χ2 test, P<0.0001). The incidence of both low myopia (−0.25 to −3.0 D) and moderate myopia (−3.0 D to −6.0 D) decreased around 5%. However, the high myopic rate (<−6.0 D) was increased more than 10%. There was a significant increase in high myopia. (Fisher's exact test, P<0.05). Besides, if we defined pathological myopia according to Tokoro's classification,3 the rate of pathological myopia (<−8.0 D) in female and male in 2005 was 15.0 and 10.6%, respectively.

Table 1 The prevalence of myopia and high myopia
Table 2 The distribution of refractive status in 1988 and 2005

The results of our studies demonstrated that the prevalence of myopia, especially high myopia increased among the freshmen in National Taiwan University. These findings may be explained by two possible reasons. First, we found the age of onset of myopia decreased from 12 years in 1983 to 8 years in 2000 in our previous nationwide survey.1 Second, myopia is influenced not only by genetic factors but also environmental factors. Environmental factors may play important role in the development or progression of myopia.4, 5 This high-prevalence rate of high myopia and its complications strike us to make more close observation in this high educational group.