Children who are short-sighted spend an average of 3.7 fewer hours a week outside compared with those who have normal vision or are long sighted, a review of previous research has found.
Nearsightedness, or myopia, runs in families and has also been linked to a host of factors including the amount of time spent focusing on near objects, for example when reading, and levels of physical activity.
But simply spending time out of the house may also be enough to protect the eyesight.
The positive effect from being outdoors appeared to be independent from the amount of time children spent reading or playing computer games, or to an increased amount of exercise, researchers said.
Between 15 and 20 per cent of British people are short-sighted but the problem is much more serious in parts of East Asia where as many as 80 per cent of the population is myopic.
One study comparing Chinese children living in different countries found that those in Australia had better vision on average than their peers in China and Singapore.
The Australian group read as much and achieved the same results academically as those in other countries, but tended to spend more time outdoors.
Myopia is caused by having longer eyes and some laboratory-based studies have indicated that chemicals affected by UV rays may control the length of the eye, meaning that a lack of sunlight could make them grow too much, he explained.
He said: “It could be caused by not enough UV radiation, but it could also be spending less time looking into the distance or not enough physical activity.”