Abstract: Lens for eye glasses are formed by a method in which a lens is selected having a finished front face and a rear face to be finished to provide a required curvature. The rear face is firstly cut on a Generator machine and is then polished on a cylinder machine. In the invention the conventional metal tool of the cylinder machine is replaced by a tool formed from a plastics material. The tool is mounted on a tool holder by a cooperating shape of the tool holder and a contact surface of the tool including wedge-shaped members and side shoulders which locate the tool without the necessity for a clamping action. The tool is formed by selection of a tool having a curvature approximating to the required curvature following which the approximate tool is cut on the Generator machine to form the required curvature.