Eyeglasses cause light from things we see to come to a focus on the retina.  This creates clear vision. Just like focusing a camera lens makes a distant object  appear sharp on a film plane.  Eyeglasses will not change the anatomy or the physiology of your eyes.  If glasses are worn, things you see will be clearer.  If not worn, they will be blurrier.  Glasses will not cause any damage to your eyes.  If one puts on glasses that have the wrong prescription, vision may be blurry, your eyes may feel strained and tired and you may even suffer from mild headaches.  However, no permanent, negative consequences will ensue.  Often, when patients wear glasses and get used to seeing clearly, they perceive increased blurry vision when the glasses are removed, giving the impression that the glasses made their vision worse.