June 27, 2016
Is nearsightedness on the rise?
According to statistics the answer is yes. An article by Diana Kwon in the July/August edition of Scientific American Mind goes in depth into this common ailment. In the United States, the prevalence of myopia (nearsightedness) has doubled over the 30 year period from the decade of the 70s to the 2000s.
I was always taught that myopia was a result of excessive time reading and writing at close range of your eye to the paper/screen. Recent evidence is showing that the myopia prevalence increase is related more to excessive time spent away from the sun's light which is a by product of indoor excessive study/play.
Myopia occurs pathologically when the eyeball changes shape from spherical to oblong based on a combination of genetic predispositions and epigenetic environmental influences. This results in a different focal point for the visual image to hit our eye. If it happens to fall in front of the retina, then we see distant objects in a blur.
The environmental combination of time spent indoors away from the sun and excessive time in front of a screen/paper for play or work is the current recipe for visual disturbances that are currently rectified by glasses, contacts or laser surgery.
I clearly remember going up four levels of refraction for my glasses during medical school. Thus, being a bookworm had its drawbacks. Should we stop studying so much? Obviously not. If the research is correct though, spending more time outdoors may delay or postpone the myopic march.
One current theory for why being indoors causes myopia is based on research that shows that the eye's retina releases chemicals like the neurotransmitters dopamine and melatonin to slow eye growth in response to sunlight.
Globe elongation occurs when there is an excessive lack of sunlight. The research is pointing towards a multifaceted etiology including the time of day for exposure, length of exposure to light and host genetics.
"Environmental influences related to prolonged reading or near work as well as fewer hours spent outdoors are associated with a higher prevalence of myopia. A systematic review and meta-analysis to identify the association between time spent outdoors and myopia indicated a 2% reduced odds of myopia per additional hour of time spent outdoors per week after adjustment for covariates . In our study, the association between near work and myopia indicated a 2% increased odds of myopia per additional diopter-hour of time spent on near work per week" from Dr. Pei-Chang Wu PLOSone article.
Near work is defined as "the activities done at short working distance such as reading, studying (doing homework, writing), computer use/playing video games, or watching TV, etc"
Boiling it all down, we find that being outside everyday exposed to natural sunlight and reducing near work in children has a protective effect against the development of myopia.
How many ailments are benefited by being outdoors and getting adequate sunlight exposure?
1) Vitamin D deficiency - autoimmune/cancer precursor, bone health, infection defense
2) Dysthymia/mood disorder
3) Sleep cycle disorders
4) Hormonal balance
5) Visual function
6) General energy level
It is absolutely clear to me that we as a populace need to get our children outside daily. Let's begin by walking as a family daily and being a part of their lives while the sun fills their retinas with photons that stimulate the chemicals that protect their eyes. Nothing bad can come of this.
If you plan to be outside for more than a half hour for light skinned individuals, bring along sunscreen to apply at the 20 minute mark. This way you get vitamin D production through your skin, but also avoid burning your skin which is the route to skin cancer. See these previous articles about vitamin D: 1 and 2
We need the sun for many reasons!