Manufacturing of Contact Lenses
Typically, soft contact lenses are mass produced while rigid lenses are made-to-order. This is because the size and shape of a rigid lens is made to exact specifications for each and every patient.
- Spin-cast lenses – A spin-cast lens is a soft contact lens manufactured by whirling liquid silicone in a revolving mold at high speed.
- Diamond turning – A diamond-turned contact lens is cut and polished on a CNC lathe. The lens starts out as a cylindrical disk held in the jaws of the lathe. The lathe 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. In order to hold the delicate lens in reverse manner, wax is used as an adhesive. The convex (outer) surface of the lens is thus cut and polished by the same process. This process can be used to shape rigid lenses, but can also be used to make soft lenses. In the case of soft lenses, 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 centrifugal forces. Injection molding and computer control are also used to create nearly perfect lenses. The contact lens is kept moist throughout the entire molding process and is never dried then rehydrated.
Although many companies make contact lenses, in the US there are four major manufacturers:
- Bausch & Lomb: Makers of Boston rigid lens materials and care system as well as various soft lens brands and the ReNu line of multipurpose solutions.
- Ciba Vision: Owned by Novartis; when Novartis purchased Alcon in August 2010, Ciba Vision was absorbed by Alcon, though products continue to carry the Ciba name.
- CooperVision: Makers of Biofinity and Proclear brand lenses.
- Vistakon: Makers of Acuvue brand lenses, and a subsidiary of Johnson & Johnson
Read more about this topic: Contact Lens
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