Editing Contact lens (section)

==Manufacturing==
[[File:Siliconehydrogel.svg|thumb|left|Molecular structure of silicone hydrogel used in flexible, oxygen-permeable contact lenses.<ref>{{Cite book |title=Kirk-Othmer Encyclopedia of Chemical Technology |year=2000 |isbn=9780471484943 |editor-last=John Wiley & Sons, Inc |doi=10.1002/0471238961}}</ref>]]
Typically, soft contact lenses are mass-produced, while rigids are custom-made to exact specifications for the individual patient.
* Spin-cast lenses – A soft lens manufactured by whirling liquid silicone in a revolving mold at high speed.<ref name="Cassin">Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company, 1990.</ref>
* [[Diamond turning]] – This type is cut and polished on a CNC [[lathe]].<ref name="Cassin" /> The lens starts out as a cylindrical disk held in the jaws of the lathe that is equipped with an industrial-grade [[diamond]] as the cutting tool. The CNC lathe may turn at nearly 6000 RPM as the cutter removes the desired amount of material from the inside of the lens. The concave (inner) surface of the lens is then polished with some fine abrasive paste, oil, and a small polyester cotton ball turned at high speeds. To hold the delicate lens in reverse manner, wax is used as an adhesive. The lens' convex (outer) surface is thus cut and polished by the same process. This method can be used to shape rigid as well as soft lenses. In the case of softs, the lens is cut from a dehydrated polymer that is rigid until water is reintroduced.
* Molded – Molding is used to manufacture some brands of soft contact lenses. Rotating molds are used and the molten material is added and shaped by centripetal forces. Injection molding and computer control are also used to create nearly perfect lenses.<ref>Manufacture of soft contact lenses. [http://www.lensfinder.co.uk/information/contact-lens-manufacturing-process/ "Manufacture of soft contact lenses".]</ref> The lens is kept moist throughout the entire molding process and is never dried and rehydrated.