New York, March 29 (IANS): A century-old belief that high daylight levels in schools could prevent short sight or myopia may be true even today, suggests a study.

The results, published in the journal Perspectives in Public Health, compared the history of school myopia with the bone disease rickets.

Myopia, like rickets, is a seasonal condition which seems to get worse in the winter. Recent research on myopia has revived an old theory that school children who spend more time outdoors have lower levels of myopia, the study noted.

"However, unlike rickets, low ambient light levels rather than low vitamin D levels seem to be the deciding factor in myopia," it said.

"It has not been investigated properly since the connection was first made in the 1860s," said study author Richard Hobday, an independent researcher.

"But, given the rapid increase in myopia among school children worldwide, this should be revisited," Hobday added.

A century ago, it was widely believed that high daylight levels in schools could prevent myopia. Education departments built classrooms with large windows to try to stop children becoming short-sighted.

Then in 1960s, medical thinking changed.

Myopia was thought to be an inherited condition; so less was done to prevent it. Today, it is known that children's education has a far greater impact on their sight than genetic factors, the study pointed out.