Two-Year Longitudinal Changes in Refractive Errors and Optical Components Among a Group of Chinese Factory Workers
A total of 118 factory workers in southern China were followed for 2 years by evaluating their subjective refraction, corneal curvatures, and ocular biometric results. Initial cross-sectional data showed that the mean spherical equivalent refraction was about -0.50 D, and more than 70% of the group were emmetropic. They were divided into four categories according to the nature of their work: laborers, who do little close work; supervisors, who do some desk work; electronic goods or toy packers, who do 8 hr of close work (at about 30–40 cm distance); quality control workers, who do close work (at less than 18 cm). All four groups had an increase in myopia. The highest increase (-0.40D) was in the group required to work with eyes less than 18 cm from the work for 8 hr. This increase was significantly greater than in the other three groups (one-way ANOVA, P < 0.05). Axial length elongation is responsible for the increase in myopia. The results from these young adults suggest that myopia can develop even after the normal growth period. Only those who were engaged in intensive close work developed significant late-onset myopia. Environmental factors have a strong influence on the development of myopia among the Chinese population.