Genetic and environmental-genetic interaction rules for the myopia based on a family exposed to risk from a myopic environment.

OBJECTIVE To quantitatively assess the role of heredity and environmental factors in myopia based on the family with enough exposed to risk from myopic environment for establishment of environmental and genetic index (EGI). METHODS A pedigree analysis unit was defined as one child (university student), father, and mother. Information pertaining to visual acuity, experience in participating in the college entrance examination in mainland of China (regarded as a strong environmental risk for myopia), and occupation for pedigree analysis units were obtained. The difference between effect of both genetic and environmental factors (myopia prevalence in children with two myopic parents) and environmental factors (myopia prevalence in children of whom neither parent was myopic) was defined as the EGI. Multiple regression analysis was performed for 114 pedigree using diopters of father, mother, average diopters in parents, maximum and minimum diopters in father and mother as variables. A total of 353 farmers and 162 farmer families were used as a control group. RESULTS A distinct difference in myopia rate (96.2% versus 57.7%) was observed for children from parents with myopia and parents without myopia (EGI=0.385). The maximum diopter was included to regression equation which was statistically significant. The prevalence of myopia was 9.9% in the farmer. The prevalence in children is similar between the farmer and other families. CONCLUSION A new genetic rule that myopia in children was directly related with maximum diopters in father and mother may be suggested. Environmental factors may play a leading role in the formation of myopia.