Although 161 genetic factors play a part in causing myopia—now the most common eye problem—the lack of sunlight, especially when we are young, is a significant factor, say researchers at the Johannes Gutenberg University in Mainz. "Send your kids to play outside for two hours every day," says lead researcher Norbert Pfeiffer.
Many of the genetic factors identified are involved in the ability to process light, say the researchers who analysed the eye health and genetic make-up of more than 250,000 participants around the world.
Their findings—which quadruples the known number of genetic factors that cause myopia—confirm the current theory that the internal layer of the eye communicates with the outer to increase the length of the eye, a critical factor in the development of myopia.
A lack of sunshine can have two elements: the geographical location of a country and social activity that keeps people, and especially young children, indoors for long periods. The rise of myopia is most marked in South-East Asia, even though it is a region that has far more natural sunlight than countries in the northern hemisphere. But the region has also seen a major cultural shift in the past decade, with more children going to school.
Myopia (also known as near-sightedness) is also caused by doing close-up work, such as working on a PC or smartphone, in poorly-lit rooms. The eye adapts to the poor light, and becomes more elongated, but, over time, it can become too elongated, making the cornea and lens focus on an image in front of the retina instead of directly on it, which makes distant objects appear blurry.