Apr 10 2016

Scientists shed light on the rise of Myopia

Published by at 12:33 pm under Personal Care

Scientists shed light on the rise and cure for short sightedness.
Myopia is on the rise and the cure might be as simple as going outside.

 

Last week we talked about the importance of being outside in order to be exposed to a healthy diversity of microbes. Scientists are finding they have another important reason for us to be out in the sunshine and fresh air. It has to do with the dramatic rise in myopia in children all over the world.  “…According to the American Academy of Opthalmology, Myopia or short sightedness is a refractive error, which means that the eye does not bend light properly to a single focus to see images clearly, which causes light to refract images so that they don’t come to a single focus…”1 It is caused by “…a slightly elongated eyeball, in which the lens focuses light from far objects slightly in front of the retina, rather than directly on it. In severe cases, the deformation stretches and thins the inner parts of the eye, which increases the risk of retinal detachment, cataracts, glaucoma and even blindness. Because the eye grows throughout childhood, myopia generally develops in school-age children and adolescents. …”2 When a person has myopia, far away images are blurry, and close up objects are clear. (1,2)*

 

Myopia has been particularly prevalent in East Asia where up to 90% of teenagers and young adults are short sighted. Sixty years ago, the percentage was only 10-20% . In Seoul, it is estimated that 96.5% of all men aged 19 have myopia. There has also been a dramatic increase in this condition in other parts of the world as well. It is affecting approximately half of young adults in both the US and Europe which is twice as many as were affected 50 years ago. Scientists estimate that one-third of the world’s population could be affected by myopia by the end of this decade. (1,2)*

 

Myopia can be corrected by glasses, contact lenses and even surgery, but they don’t  address the underlying defect. With approximately one-fifth of university-aged people in East Asia having such an extreme form of myopia that half of them are expected to develop irreversible vision loss., researchers are intent on understanding the causes of this eye disorder. Fortunately, they are beginning to find answers.2*

 

Besides genetics, the most obvious underlying factor seemed to be too much time reading up close. This theory was broached by Johannes Kepler, a German astronomer and optics expert over 400 years ago when he connected his own short-sightedness with his extensive studying. “…On a biological level, it seemed plausible that sustained close work could alter growth of the eyeball as it tries to accommodate the incoming light and focus close-up images squarely on the retina…” 1*

 

The rise in myopia in today’s world seems to correspond with increased time spent studying, reading and most recently, the unrelenting use of computer screens and smart phones, amongst our children and adolescents. This is particularly the case in East Asia where a very high value is placed on educational performance. “…A report last year from the Organization for Economic Co-operation and Development showed that the average 15-year-old in Shanghai now spends 14 hours per week on homework, compared with 5 hours in the United Kingdom and 6 hours in the United States…” (1,2)*

 

In the early 2000s, researchers began to examine more specific behaviors, such as number of books read per week and hours spent reading or using a computer. But none of these seemed to be the major contributor to myopia risk. In 2007, a study headed by Donald Mutti at the Ohio State University College of Optometry in Columbus tracked more than 500 eight and nine year olds in California, all with healthy vision. Mutti and his colleagues examined how the children spent their days, and by accident, began exploring how much time these children spent on “sports and outdoorsy stuff.” (1,2)*

 

They discovered the missing link. After five years, one in five of the children had developed myopia, and “…the only environmental factor that was strongly associated with risk was time spent outdoors...”  Similar findings were discovered in Australia after observing 4,000  children  for three years. They found that those students who spent less time outside were at greater risk of developing myopia. Continued research and observation ruled out physical activity and other factors. The one underlying factor that seemed to make a difference in not developing myopia was these children’s exposure to bright light. “…The leading hypothesis is that light stimulates the release of dopamine in the retina, and this neurotransmitter in turn blocks the elongation of the eye during development…” (1,2)*

 

“…Retinal dopamine is normally produced on a diurnal cycle — ramping up during the day — and it tells the eye to switch from rod-based, nighttime vision to cone-based, daytime vision. Researchers now suspect that under dim (typically indoor) lighting, the cycle is disrupted, with consequences for eye growth…” 2*

 

It is estimated that children need to spend about three hours per day under “light levels of at least 10,000 lux “ to be protected against myopia. This is equivalent to what you would experience under a shady tree, wearing sunglasses on a sunny day. This is based on epidemiological studies, according to Ian Morgan, a myopia researcher at the Australian National University in Canberra. 2*

 

Being outdoors is so important for us all as it encourages physical activity, exposes us to Vitamin D and microbes and allergens that boost our immune system. And now, we are seeing evidence that it can also benefit our eyesight. 2*

Healthiest wishes,

Kelli

 

 

Resources:

  1. http://jonbarron.org/childrens-health/myopia-epidemic#.Vwe-paQrLIU
  2. http://www.nature.com/news/the-myopia-boom-1.17120


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