| Background: Myopia is an important cause of correctable visual impairment and preventable blindness all over the world. Both genetic and environmental factors contribute to the development of myopia. It is reported that the prevalence of myopia in East Asia were higher than in western countries. Therefore, little is known about ethnic differences in refractive status in Chinese populations.
Methods: This is a cross-sectional cohort study of myopia among college students in Shanghai, China. 5083 college students from Donghua universities were enrolled in this study. All participants first responded to a detailed questionnaire, and then undertook a standardized ophthalmologic examination, including visual acuity, a slit-lamp examination, and non-cycloplegic autorefraction. Statistical analysis was carried out using the SPSS software.
Results: The mean spherical equivalent refraction(SER) of the college students was – 4.08 ± 2.42D, and the normal range of the refraction was – 4.14 to – 4.01D . 95.47% of the subjects were myopic (SER < – 0.50D), 19.51% were highly myopic (SER < – 6.0D), only 3.28% were refractive normal (– 0.50D ≦ SER ≦0.5D). It was presumably that being post-graduate, Han ethnic group, having myopic mother and father was associated with greater risk.
Conclusions: The prevalence of myopia and high myopia in this multi-ethnic college students population was extremely high, which indicated that population of higher education might be more liable to myopia. Subjects from different ethnic groups in specific areas of China may had different probability of suffering myopia, some minority ethnic groups in Northwest and Central China were less myopic. | 
