- The way contact lenses are made depends on the condition of your eyes and your particular vision problem. For instance, if you have myopia--nearsightedness--you'll need a contact lens that is thinner in the middle and thicker on the edges to allow the retina to correctly process light. Your optometrist measures your cornea so your lens will properly fit your ey and determines which vision problem or problems you have in order to prescribe the proper lens.
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Soft contact lenses are made up of 1/3 to 1/2 water. They can be made in one of three ways, the most common of which is cast molding. In this method, liquid polymer is injected into a two-part mold. The two parts are then pressed together to form a predetermined lens power, diameter, curvature and edge. The lens sets up into a solid yet pliable form and is stored in sterile saline solution in a foil-topped plastic pack as in the photograph above.
The two other methods are lathe-cut and spin-casting. Lathe-cut contact lenses are cut in a solid polymer and then hydrated. Spin-cast lenses are made as liquid polymer is spun into a prescribed shape and then firmed into a soft lens. - To make oxygen permeable contact lenses, liquid polymer is formed into solid rods. The rods are cut into buttons and then finished lenses through a computer-directed lathe. This custom lathing process allows an oxygen permeable contact lens to be made to fit the eye's exact corneal curvature.
