Introduction
When dealing with vision problems, you are usually faced with the decision of wearing glasses or contacts. If you choose contacts, you may wonder how a device so small can be worn to correct your vision without damaging the corneal tissues of your eyes. The tissues of the eyes are fragile, and contacts are carefully crafted to correct the vision of their wearer. This crafting process occurs in a variety of ways, depending on the type of contact being made.
Cast Molding
One of the first ways in which contact lenses are made is through cast molding. In the cast molding process, a contact lens polymer is injected into a two half contact lens mold. Each mold corresponds to a different prescription strength contact lens shape. The molds can also differ based on the contact lens' diameter, edging and curve structure. Once the mold has set, the contact lens is removed from the mold, polished, sterilized and packaged.
Spin Casting
Another method in which contact lenses are made is spin casting. Spin casting involves the use of a monomer material which is spun into the shape of the contact lens. This process is mostly used for soft lenses, and the final product contains between one-third and one-half water. By manipulating the speed in which the contact mold is rotated, the lens qualities such as lens power and diameter can be changed. Different molds can also be used to create different qualities of contact lenses.
Computer Generated
The most advanced way in which contacts are made is through computer generated molding. This is mostly done with oxygen permeable contact lenses. Computer assisted contact lens production involves using a computer operated lathe to shape buttons of polymer into contact lenses. This allows exact specifications and prescriptions to be input into the computer program, to create more precise and comfortable lenses. It also allows for the production of more intricate contact lenses, especially for those that need custom lenses made because of abnormalities of the cornea or other parts of the eye.
