Myopia and high myopia - genetics and environmental factors

Prevention of myopia is now urgent, since there is an epidemic of high myopia, as well as ordinary myopia, in East Asia. The prevalence of high myopia is now around 20%, compared to about 1% in older generations. This new, acquired, high myopia has an unusual developmental pattern, sitting at around 1% up to the age of 11-13, and then increasing over the next 10 years, presumably as a result of early onset environmental myopia progressing to high myopia. A critical unanswered question is whether this acquired high myopia carries the same pathological burden as the older genetic form. This question is generally important, because the prevalence of myopia appears to be rising in Europe and North America, and the prevalence of high myopia is probably increasing as well. Fortunately, it is now generally accepted that environmental change in educational pressures and the time that children spend outdoors must be responsible for the 3-4-fold increase in the prevalence of myopia in East Asia. In contrast, identified SNPs currently account for less than 5% of phenotypic variation. Recent trials based on increasing the amount of time that children spend outdoors suggest that incident myopia, and hence high myopia, can be prevented.