In some areas of the world, such as Hong Kong and Singapore, the number of students passing out of secondary school with myopia is well over 50% and sometimes as high as 80-90%. In the US the number of people with myopia has increased by 60% since the 1970s. A recent article raises the question whether exposure to daylight at school may reduce the likelihood of myopia in children.
Myopia, or nearsightedness, is the inability to see or read distant objects clearly. Symptoms include eye strain, headaches and squinting. The article by Richard Hobday in the journal Perspectives in Public Health, discusses how attitudes have changed regarding the link between sunlight and myopia, and how a similar story played out with regards to rickets.
Rickets, a bone disease, is like myopia in that it is a seasonal ailment that worsens in the colder months. Rickets became a common condition in the 1600s and became widespread in Norther Europe and America. Rickets was believed to be a hereditary disease until research in the 1920s finally showed that lack of exposure to sunlight, and a resulting vitamin D deficiency, was the cause.
Similarly, says Hobday, it was first believed that myopia was a genetic condition, although the astronomer Johannes Kepler observed 400 years ago that young people who were involved a lot of close work (reading and writing, for example) were more often short-sighted. Up to a hundred years ago, there was a debate whether myopia was caused by environmental factors or by genetics.
In the late 1860s a German ophthalmologist name Hermann Cohn observed a correlation between the number of years spent in school, the amount of sunlight in the classrooms and the rates of myopia in the students. As this research became widely known, it led to a change in school building design over the next few decades. Classrooms were constructed with large windows to let in higher levels of natural light. By the 1950s in Britain it was required by law to allow sunlight into classrooms.
However, myopia rates did not go down, and without sufficient proof, the emphasis on sunlight died down in the 1960s. The prevailing opinion again went back to the idea myopia was a genetic ailment and, hence, somewhat unpreventable. Bad design choices had also led to classrooms with large windows that overheated in the summer and were not warm enough in the winter. It was believed that artificial light was a good enough substitute.
Changing teaching methods and philosophies in the 1970s and the increased use of air-conditioning led to smaller classrooms with smaller windows. Then the increase in global oil prices again renewed interest in building schools with sunlight access.
All these changes have made it unclear what effect sunlight has on students’ vision.
“It has not been investigated properly since the connection was first made in the 1860s,” said article author Hobday, an independent researcher, as quoted in the Business Standard. “But, given the rapid increase in myopia among school children worldwide, this should be revisited.”
While a conclusive link between sunlight and myopia may be elusive, many recent studies indicate that sunlight may have a protective effect against myopia. There are other benefits to children being exposed to daylight as well. Vitamin D deficiency is still a concern when children do not play much outdoors. Sunlight is also valued psychologically by students and teachers and appears to improve academic performance. That in itself is a good reason to let the sunshine in.