Raw Material
Hard contact lenses are made of a plastic polymer called polymethyl methacrylate. This is often abbreviated as PMMA. This substance differs from the plastic polymer used to make soft contact lenses in that it does not soak up liquids to the same degree. Soft contacts are made up of a lot of water while hard contacts are not.
Hard Contact Molding
Hard contact lenses can be molded into shape. The PMMA is poured or sprayed in a liquid form into a mold. The hard contact lens then hardens inside the custom made mold that determines the hard contact lens power, diameter, curvature and edge shape. The hard contact lens is later cooled, polished, and sterilized.
Hard Contact Lathing
Hard contact lenses can also be made on a lathe. Strips of hard contact lens material is made out of PMMA. Hard contact lens blanks are then cut or punched out of the PMMA strips. Each blank is then attached to a lathe and rotated at high velocity. A laser or diamond is used to craft the hard contact lens and adjust its power, curvature, and shape. After that, the hard contact lens is polished on the spinning lathe. Some hard contact lenses that are initially made with the molding method are later polished using the lathing method.
Hard Contact Finishing
Hard contact lenses made with both the molding method and lathing method must be "finished" to be ready to wear. This is fine detail work to adjust for very minute specifications. Finishing is accomplished by grinding the hard contact lens. It is attached to a grinding machine where emery paper or a razor blade is used to trim the hard contact lens. Most of this work is performed by computers since it requires a great deal of attention to detail in a very small space.
Hard Contact Cleaning
All hard contact lenses must be cleaned and sterilized before they can be worn. This is done by boiling them in a solution of saline. Boiling kills all bacteria that could infect the eye. Since hard contact lenses do not adsorb liquid the same way soft contact lenses do, it is especially important that they be manually cleaned every night. It is not good enough to simply soak them in multi-purpose solution.
