Contact lenses can be manufactured in a variety of ways.

Soft contact lenses are most commonly “cast molded.” In this process, the polymer that the lens is made from is injected in liquid state into a two-part mold. The parts are pressed together to form a specifically determined lens power, diameter, curvature and edge. The lens is then cured into a solid though soft and pliant state. It is stored in sterile saline (the consistency of human tears) in a foil-topped plastic pack. Soft lenses also can be lathe-cut in a solid state and then hydrated. A third method is spin-casting, in which the liquid polymer is spun into a prescribed shape and then firmed into a soft lens. When finished, soft lenses are made up of about one-third to one-half water.

Oxygen permeable contact lenses are made differently. The liquid polymer used in the lens is solidified into rods, which are cut into buttons, from which a finished lens is cut on a computer-driven lathe. In some cases, the inside curve (called a “base curve”) is molded and then finished. The computer-generated lathing process allows for an oxygen permeable lens to be “custom made” to the exact corneal curvature of your eyes.