Optical Lens Finishing Process

Opticians use the term "finishing" to describe the second part of the lens-making process for eyeglasses. The first step is called surfacing. Finishing a lens is pretty much just what it sounds like; it is the last part of the laboratory work that turns chunk of plastic or glass into a prescription lens. Finishing is the process of cutting lens blanks into lenses to fit a frame.

Lens Blanks

• Opticians start the finishing process with a lens that has been surfaced, or made into a certain prescription, called a lens blank. Blanks are up to 2 inches thick and 4 or 5 inches in diameter. Most optical laboratories keep a large supply of lens blanks, but some types of specialty lenses have to be ordered. The lens blanks are put into a machine called a lensometer to verify that the lenses are the correct prescription.

Blocking

• The lens is "blocked" using a piece of material called a block and a tool called a blocker. The blocker stays on the lens throughout the finishing process and holds the lens in place in the cutting machine.

Edging

• The prescription information is entered into the edging machine, which does the actual cutting down of the lens. The lens blanks are attached to the cutting equipment with the block. A matching pattern for the finished lens shape and size helps trace the cutting edge of the machine. The optician turns on the machine and the edge cuts down the plastic or glass to the exact shape and size of the frame the lenses will go into.

Finishing the Finishing

• Once the machine has cut the lenses down to size, the optician removes the lenses from the edger. The blocks are removed and the lenses are inserted into the frame. The optician then puts the lenses back into the lensometer and checks the prescription to verify that the lenses were made properly and everything is correct.