Methods for Making Lenses for Eyeglasses

All eyeglass lenses start out as a chunk of material, usually glass or plastic. Opticians use several processes for shaping the material into your prescription lenses. A lens first goes through surfacing, also called grinding or generating, the process that cuts down the material and puts optical power into the back of the lens. The next step is called finishing, which shapes lenses to fit in the frame. Other processes can also be done during lens-making.

Lens Blanks

• Optical lenses start out as chunks of either plastic or glass called lens blanks. The blanks have a specific magnification, also called optical significance, according to Opticianworks.com. A lens blank is about 4 inches in diameter and up to 1.5 inchesf thick, depending on the eyeglass prescription.

Surfacing

• The blank is put into a machine called a generator, or surfacing machine, that grinds and cuts down the material with a wheel or cutting bit on the back of the lens blank and creates curves in the lens. The lens is left semi-smooth and translucent. The lens is then put through a polishing process with abrasives to polish the lens and make it clear.

Finishing

• Once the lens is surfaced and polished, it is cut down to fit a frame with a machine called an edger. Edging used to be done manually, but now is computerized. Either way, the lens is mounted to the edger with by an adhesive method called blocking. The edger uses a pattern to cut the lens to the exact shape of the frame.

Additional Processes

• Some lenses are tinted after the lens is surfaced, finished and ready to be put into the frame. Other lens coatings, such as anti-reflective coatings and photochromic tints, that darken outdoors and lighten inside, are part of the original lens blank.