Raw Materials
The raw materials for contact lenses differ depending on the type. Manufacturers use hydroxyethyl methacrylate to craft soft contact lenses. They use a stiffer material called polymethyl methacrylate to make hard contact lenses. Both are plastic polymers that are malleable but quite sturdy.
Contact Molding
The most common technique used to manufacture contact lenses is molding. The raw material for the contact lenses are injected or poured into a mold. The lens is then formed in the mold to a specific power, diameter, curvature and edge shape. The contact lens is also cooled, spinned, and polished to form the finished product.
Contact Lathing
Another process used to manufacture contact lenses is lathing. Contact lens blanks are punched out of strips of solidified raw material. They are then placed on a lathe and spun around at high speed. The shape, power, and curvature are then cut into the blank with a laser or diamond. The contact lens is polished while the lathe spins.
Contact Spin Casting
Another process used to manufacture contact lenses is spin casting. The liquid raw materials are spun at high speed until they form the desired shape. They are then cooled until they solidify. The spin casting technique allows more water to be stored inside the contact lens. Up to half of a contact lens made this way will be water.
Contact Finishing
Fine detail work is performed on each contact lens before it leaves the manufacturer. Each lens is "finished" by grinding it to fit specific characteristics of the eye. The contact lens is placed on a grinding machine where emery paper or a razor blade is used to trim it down. This work is often done by a computer.
Contact Sterilizing
Manufacturers boil contact lenses in salt water for several hours to sterilize them. This liquid is very similar to the composition of saline solution and human tears. The contact lenses must be completely germ and bacteria free before they leave the factory.
Contact Packaging
Manufacturers package contact lenses in sterile glass jars or plastic sleeves with peel away tops. All contact lenses are floating in a saline solution that is gentle on the human eye. This keeps the contact lens soft and hydrated during shipping and while it sits waiting to be used.
