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 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.
