The Influence of Parental Myopia on Children's Myopia in Different Generations of Parent-Offspring Pairs in South Korea.

PURPOSE: To compare the heritabilities of myopia and high myopia across three different generations in Korea.

METHODS: Parent-offspring pairs of different age groups were included: two parents and their offspring aged 10-19 ("young families"), two parents and their offspring aged 20-29 ("middle-aged families"), and two parents and their offspring aged 30-45 ("older families") were selected from the 2008-2012 Korea National Health and Nutrition Examination Survey. Variance component methods were used to obtain the heritability estimates for myopia and high myopia using parent-offspring pairs from three generations. Spherical equivalents measured in the right eyes were used.

RESULTS: From the 2008-2012 data, 2,716, 1,211, and 477 offspring from 1,807 young, 956 middle-aged, and 434 older families were eligible for the study, respectively. For myopia, the additive genetic portion of phenotypic variance was smaller in the younger families (74.7% in the older families, 48.1% in the middle-aged families, and 40.1% in the young families), and the non-shared environmental portion was greater in the younger families (12.4% in older families, 24.9% in middle-aged families, and 46.5% in young families). In contrast, for high myopia, the additive genetic portion remained roughly constant at approximately 60% in all three generations.

CONCLUSIONS: With myopia, the environmental portion of the phenotypic variance increased and the additive genetic portion decreased as South Korea became more urbanized. With high myopia, the additive genetic portion remained roughly constant at approximately 60%, despite the urbanization.