Why myopia? New surprising research

In Hong Kong, Taiwan and Singapore more than 80% of the population is near sighted. Compare that with Western Europe and North America which have about 20% of the population near sighted. What causes near sightedness and why the difference?

For years it was thought to be genetic or inherited. But that was ruled out in the mid 60’s with research done with Eskimos in Alaska. Nearsightedness went from almost nothing to 45% among the children in one generation when the society adopted to the western world and children started to go to school. Genetics do not change from one generation to the next so the gene theory is not the main cause of myopia.

Then there is the use-abuse theory which stipulates that myopia occurs because of to much near work. This theory feels intuitively correct. Most people have felt eyestrain after reading for a long time.

Graph

tIn fact here is a very interesting study of myopia among young Israelies. It turns out that there is a much higher rate and more severe cases of myopia among the boys attending religious schools than girls. Why the difference? The girls don’t have to read as many scriptures so their eyesight is better.

On the graph you can see that its only the boys in religious schools that develops higher degree of near sight. 90% of the children are less than 2 diopters near sighted, which is typical except in cultures where children are required to spend a lot of time doing near work, such as practising to write Chinese from the age of four.

Most children are actually born far sighted

Infants are typically between +2 and +3 diopters far sighted. As the eye develop over the first 5 to 10 years the eyes become normal. The medical term for this process is “emmetropization.”

The body’s natural intelligence knows when to stop growing through a concept known as homeostacis where organs grow to the appropriate size and no more. If you implant a liver from a small dog into a big dog, the liver will grow to fit the size of the dog in which it was implanted. This is homeostacis by which the implanted liver found its appropriate balance.

When we talk about eyes this process is called emmetropization – a balancing of vision to normal clear eyesight. Emmetropic vision, in other words, is perfect vision. The point of least effort is looking in the distance. When you are doing a lot of near work such as studying, then your eyes are turned in and down as well as focused one the book or paper your are writing on. In order to see the book clearly your eyes also has to adjust – 3 diopters in order to keep the book in sharp focus. Doing this for hours, days, weeks, months even years causes the visual system to adjust itself towards the near. In other words the body’s natural homeostasis adapt to the environment. In this case as a nearsighted book worm.

The usual way to deal with nearsightedness is to fit minus lenses. Now, there is a huge problem with this approach. Josh Wallman and Jonathan Winawer, University of New York, (2004) have shown that the growth of eyes is guided by visual imput, in animals as divergent as fish, birds, rodents, monkeys and by extension humans.

If minus lenses are fitted on young monkeys then their eyeballs grow longer in order to adjust their vision. If you fit plus lenses the eyeball grows shorter. In other words the glasses are creating more myopia or hyperopia depending on the type of lens worn. This was tested with just one lens over one eye and that eye only elongated in order to adapt and achieve homeostasis. The other eye remained normal. So there is not much doubt about the effect of wearing glasses.

This emmetropization (homeostasis) is understood to be driven by blur. That is the retina is moved in a direction that will bring the eye to a point where it has clear vision.

The two researchers write: “In contrast to the usual view of the retina as the input stage of vision, in the control of eye growth the retina encompasses an entire sensiomotor apparatus. Because lens compensation occur in eyes with a severed optic nerve, the retina is clearly able to both decode the blur and to move itself forward and backward within the eye by inflating and defalting the choroids and also by controlling the growth of the posterior sclera.”

Concerning the reading or near work activity they write:

“The risk factor most discussed as the intervening variable is reading, because the nearness of the page presents the eye with hyperopic defocus. Although the accommodation system reduces this hyperopic defocus, it cannot eliminate it, because accommodation is under negative feedback control, with defocus being the error signal that drives the accommodation output. Therefore, it is plausible that continuous hyperopic defocus during reading drives the emmetropization mechanism to correct refractive errors by making the eye myopic.

The negative lenses in fact reimpose the original error that caused the myopia in the first place.”

Wow, this study is amazing it validates the experience most people have when they start wearing glasses they feel that their vision gets worse when wearing them. This is also explains why so many Chinese children become near sighted.

The conclusion is – better try the natural vision training approach. It has no known side effects and the results are lasting.