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We could answer your question with just one word, à la The Graduate. That word would be "plastics." Contact lenses are made of thin, clear, curved plastics, specifically polymers. In the 1960s, the first contact lenses that became commonly available were made of poly(methyl methacrylate) (PMMA). PMMA is used in Plexiglas and Lucite and for things like aquariums and hockey rink barriers. It's even found in latex paints. PMMA lenses are hard, rigid, and not very comfortable. These lenses don't allow oxygen to pass directly to the cornea, which can be detrimental to the eye. Hard lenses are
not very popular anymore. In 1971, the first soft contact lenses were introduced commercially in the United States. These were also made of a polymer, but this time it was a polyacrylamide, which contains nitrogen. This polymer dissolves in water, and it's similar to polymers used to make acrylic fibers for fabric. Crosslinked polyacrylamide actually absorbs water, so it's a good material for contact lenses. Anywhere from 38% to 79% of a soft contact lens is water, and the water keeps the lens soft and flexible. Over 75% of contact lens wearers in the U.S. use soft lenses. In 1979,
the first rigid gas-permeable lenses (also known as RGPs) hit the market. These lenses combine PMMA with silicone and fluoropolymers so oxygen can pass directly through the lens to the eye. This makes the lens more comfortable for the wearer. Plus, the rigidity of RGPs can make vision crisper, and RGPs are better suited to correcting astigmatism and bifocal needs. Hope this provides some insight for you.
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