http://www.myopia.org/08chapter3.htm
WHY THE USUAL TREATMENT FOR MYOPIA IS HARMFUL
Assume that a child has just begun to become nearsighted. This means that the ciliary muscle spasm, which has been useful in reducing the infantile farsightedness to zero, is now threatening to cause the eye to continue to elongate and become permanently myopic. The most natural way to relax the spasm, return the vision to normal, and prevent overelongation is to have the child give up all close work and take up activities which only require distance vision.[snip]
[The concave lense glasses] make the eye feel (with regard to focusing effort, at least) that the viewed object is actually closer than it is. In fact, if you follow the dotted lines, you will see that point F is where the viewed object appears to be. In this example, F is also the focal point of the lens. Minus lenses thus move the world closer to the eyes. Note that with these lenses, there is no longer any way that the eye can receive parallel rays. All light rays are diverging to a greater or lesser extent. Since the cause of myopia is too much close work, it is obvious that such glasses, by moving everything closer, will aggravate the condition.
Most of the damage occurs when such glasses are used for reading. Many people use their distance glasses for reading even though they could read without them, merely because the eye specialist has never advised against it. There are also many people who must use their glasses for reading because their myopia has progressed to the point that if they take their glasses they will find that even the book is blurred. Their far point or limit of clear vision is not far enough to reach the book.
A vicious cycle now develops. The minus glasses bring everything closer, making increased accommodation necessary. The increased accommodation causes further lengthening of the eye with the resulting need for even stronger glasses. Many children find they need stronger glasses as often as once a year.
The present, almost universal, practice of allowing a child to read with concave "distance" glasses is ruining the vision of millions of children. Imagine going to a dentist with a toothache and being given medication to remove the symptom (pain) so that you again felt fine. Imagine also that the medication not only failed to stop the decay but even made the decay get worse faster. Each time the pain would begin again, you would return to the dentist for more of the same kind of treatment until finally the tooth became permanently damaged and perhaps useless. This is similar to what we are doing on a regular basis to our children's vision, merely because the errors of the past are being handed down from generation to generation.
It is the old story of treating symptoms and ignoring causes, a situation that has always prevailed in the "healing professions." Prevention is the highest form of health care. The second highest form is treatment of existing problems by removing the cause. A poor third is the treatment or removal of symptoms but ignoring the cause. The fourth, and by far the worst form, is ignoring causes and treating symptoms in a manner that causes the basic problem to get worse. It is in this fourth category that we must place the prescription of concave lenses for acquired myopia. [snip]
The harmful effect of minus lenses is often easy to demonstrate. If a myopic child is given minus lenses to read with for, say, one-half hour, the distance vision after removing the glasses is often found to be appreciably worse than before. The vision can be tested before and after the experiment by using an ordinary wall chart. In other words, the eyes have adapted to the minus lenses by temporarily becoming more myopic. If this type of eye abuse is continued long enough, the distance vision will be permanently damaged.
Concave lenses have been called a poison. They are worse than that. They are more like an addictive drug. With a little imagination, it is possible to see some similarity between putting concave lenses on a beginning myope and giving such a drug to the child. Both the lenses and the drug can be considered addictive insofar as their use results in an ever-increasing dependency and a need for stronger and stronger doses to get the same effect. Both can cause permanent damage to the body if their use is continued for too long. However, it is possible to overcome a dependency on drugs. By going through a withdrawal period, the drug addict can overcome the addiction and begin a new life free from symptoms. The concave lens addict is not so fortunate. The abnormal lengthening of the eye that these lenses cause is permanent. Trying to withdraw from this addiction is futile since the eye will not return to its original shape. The drug pusher is none other than your eye doctor.