There are many commonly held beliefs about eyeglasses 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 the wrong glasses. We have all heard some of the common myths about how eyesight gets bad. Most people believe that reading in dim light causes pool eyesight, but that is unique. 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. But, 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. There are close to one million nerve fibers that connect the eyeball to the brain .and as if yet it is impossible to attach them all in a new person. Only certain parts of the eye—the cornea and the retina—can be replaced. But if we keep clearing up the myths and learning more about the eyes, someday a full transplant may be possible! This passage is mostly about______.