No! Poorly fitted glasses don't have any long-term effect on the health of your eyes. However, we should distinguish between the eyes of an adult and the eyes of a child, the latter of which are still developing. If a pair of glasses is poorly fitted, then this can definitely impair the vision of children and young adults. Children are not emmetropic, meaning their vision is not ideal. A child's vision develops progressively: starting in its immediate vicinity, such as when looking at its mother, through the close-up range required later for painting or reading right up to 3D distance vision. In other words: this slight hyperopia is actually advantageous at first and is something which children ultimately gets used to with age. A pair of glasses can help children develop optimum vision. Visual defects don't damage adults' eyes – no matter if they're near-sighted, far-sighted, or if they wear the wrong glasses. Instead, your eyes 'learn' to correctly focus on different distances and to modify their visual performance, as well as possible, to accommodate the particular situation. If this happens over a longer period of time and requires greater effort from your eyes, then noticeable symptoms occur.