Formerly they were called spectacles. They were small lenses mounted in a metal rim with side or ear temples. They were used, mainly, by older persons to read smaller print. Later, when some spectacles were made without temples they were called Eye-glasses. In the early 19th century, when younger adults began to wear spectacles constantly, a nose piece was developed which held them firmly on the nose. These were called "Nose-glasses." In recent years, when plastic frames became popular and nose-glasses almost disappeared, the name glasses came into popular use.
Glasses, at present, is the popular name for spectacles. Glasses is a meaningless word; it has nothing to differentiate it from beer-glasses or colored-glasses. The dictionary will not help us because the name "Glasses" is not to be found in the old or new dictionaries. The lack of knowledge about spectacles is widespread. It includes not only the ordinary person but also our educators, our legislators, and most of the medical profession. A proper name for spectacles would be Focus-glasses.
Formerly, when they were called spectacles it was believed that they were, more or less, spectacular and fictitious. Now, they are believed to be mystic, some mystery in the glass or about the glass that makes you see better or worse. Lately, I asked a medical doctor, (a pathology professor in a large eastern medical college): "What is it in glasses that makes you see better or worse?" First he tried to give me a meaningless answer. When I insisted on a clear answer, he said: "It is the molecular structure of the glass." His answer proved his confusion about spectacles and glasses.
It is important that we know and understand that it is the curvature in the lenses that gives it the optical power. It is the curvature in the spectacles or glasses that changes the focus in our eyes.