There are many commonly held beliefs about eye glasses and eyesight that are not proven facts. For instance, some people believe that wearing glasses too soon weakens the eyes. But there is no evidence to show that the structure of eyes is changed by wearing glasses at a young age. Wearing the wrong glasses, however, can prove harmful. Studies show that for adults there is no danger, but children can develop loss of vision if they have glasses inappropriate for their eyes. We have all heard some of the common myths about how eyesight gets bad. Most people believe that reading in dim light causes poor eyesight, but that is untrue. Too little light makes the eyes work harder, so they do get tired and strained. Eyestrain also results from reading a lot, reading in bed, and watching too much television. However, although eyestrain may cause some pain or headaches, it does not permanently damage eyesight. Another myth about eyes is that they can be replaced, or transferred from one person to another. They are close to one million nerve fibers  that connect the eyeball to the brain, so it is impossible to attach them all in a new person. Only certain parts of the eye can be replaced. But if we keep clearing up the myths and learning more about the eyes, some day a full transplant may be possible. If a child wears appropriate glasses,   _  .
the structure of his eyes will keep the same as before it is harmful the structure of his eyes will be changed he will lose sight