Contact Lenses

• A contact lens is a small lens that is placed on the cornea of the eye. These lenses are used for a variety of purposes, from visual correction to cosmetics. Corrective contact lenses serve the same basic purpose as glasses, but instead of resting in front of the eye, are placed on the eye itself. The end result is a nearly invisible lens that provides greater versatility and a greater field of vision.
  
  

Types

• There are a variety of lenses available that are used for different purposes. The most common is visual correction. Lenses can be created and modified to suit an individual's needs, just like regular glasses. Cosmetic lenses are designed to alter the appearance of an eye, most commonly by altering the color itself. Cosmetic lenses can also assist in correcting vision, but are not as effective.
  
  Some lenses are created from rigid materials, some early lenses being constructed of polymethyl methacrylate. Newer lenses allow the passage of air through the lens, preventing lack of oxygen to the eyes. Softer lenses, which are commonly made of hydroxyethylmethacrylate, are more comfortable and increase the oxygen permeability of the lenses themselves. These types of lenses are the most recent.
  
  

Creation

• Lenses are first created by shaping plastics into specific forms and curvatures. Lenses are created to fit two specific curves, one being the overall size of the lens itself, the other being the curve needed to correct the vision of the patient. In the molding method of creation, the plastics are injected into a mold under pressure, then when cooled, are sometimes finished on a lathe, but this is not always necessary. In a lathe creation process, plastic is attached to a steel button, which rotates at high speeds. A laser or a diamond cutting tool is used to create the curves of the lenses. The lens is then smoothed and measured for accuracy against specific dimensions for individual eyes. To finish, lenses are cut to an appropriate diameter and polished.