Before the invention of the Gutenbergs' printing press, visual aids were used only by religious monks and scholars. After the widespread distribution of manuscripts and books among the general public, the demand for eyeglasses increased. By 1500, spectacle peddlers were a common sight. They carried baskets of single wire German made spectacles which people would rummage through in order to find the right pair. The image is from Wikimedia Commons and is free to use.