Australian researchers have found that children who spend the most time outdoors are least likely to suffer from myopia.
Myopia (nearsightedness or shortsightedness) has become far more common in recent years and experts suggest as many as 80 percent of people in highly-educated groups are sufferers.
Dr. Kathryn A. Rose from the University of Sydney says it has been suggested that a possible cause is that work that requires a person to focus on something close up such as reading for long periods, could contribute to myopia.
Dr. Rose and her colleagues looked at 1,765 six-year-olds and 2,367 twelve-year-olds, from 51 Sydney schools, who participated in the Sydney Myopia Study from 2003 to 2005 in order to investigate how viewing activities at various distances might influence their risk of myopia.
The children were all given a comprehensive eye examination and both parents and children completed detailed questionnaires on their activity and it was found that while just 1.5 percent of the six-year-olds were myopic, 12.8 percent of the older children were affected.
Both age groups spent on average about 2.3 hours outside each day and while time spent outside had no significant relationship to myopia prevalence among the younger children, nor did the amount of close work they did, among the 12-year-olds, those who spent more than 2.8 hours outside every day were less likely to be myopic than their peers who spent more of their time indoors.
It was found that children who spent less than 1.6 hours outdoors every day and more than 3.1 hours in near-work activity had double to triple the likelihood of being nearsighted, compared to children who spent the most time outside and the least time in close-up work.
Dr. Rose says while it remains unclear why being outside is protective, it is likely that the high levels of light experienced outside compared to inside, allows retinal dopamine to be released in response to the light, and dopamine is known to be able to block eye growth.
Dr. Rose says myopia is caused when the eyeball grows too long and the key factor appears to be being outdoors whether having a picnic or playing sport, as both will protect a child's eyes from growing excessively, which is the major cause of myopia.
The researchers advise parents to ensure that their children spend time outside because the more time they spend outdoors, the less likely they are to develop myopia and this is the case regardless of whether they are doing close work such as reading and studying.