Lenses are optical articles made of glass or plastic that fit inside eyewear frames to correct the vision of the wearer. The first lenses were made from transparent quartz and beryl. To meet the growing demand for vision correction, quartz and beryl were later replaced with glass which remained dominant until 1952 when plastic lenses were introduced. Glass and plastic lenses are produced by successive series of fine grinding, polishing and shaping. The following article focuses on the manufacturing of plastic lenses which are placed in more than 80 percent of eyeglasses worn today.