What Contact Lenses Are Made Of
When it comes to contact lenses, it’s very important to know exactly what’s inside of them, or better yet, what they’re made of. Materials used have varied throughout the years. Earlier times called for more rigid materials that didn’t allow much oxygen to get to your eye. But as technology has improved, so has the availability of products. Based on current information on polymer technology as well as information from the U.S. Food and Drug Administration (FDA), lens polymers were divided into the filcon (hydrophilic) and the focon (hydrophobic) series, depending on their water content, which we will go over in the Silicone and Hydrogel section of this article. Still, we will also discuss what materials are in Soft, RGP and Intraocular lenses.
Soft Contact Lenses
Soft lenses are made from an oxygen permeable material and have a floppy structure that’s similar to an extra thick saran wrap. They are larger in size, as it covers the entire iris (colored part of your eye) and the edges rest on the sclera (the white part of your eye). Many wearers say soft contact lenses are much more comfortable to wear. This has made them the most popular lens on the market. Soft contacts can be used to change the color of your eye or add a special effect such as cat-eyes. Soft lenses also can be worn on a daily, biweekly, monthly or continuous basis thanks to the oxygen permeable material. Some of the different products available on the market for soft lenses are Acuvue and Acuvue 2 made by Johnson and Johnson, SofLens 38, , PureVision Multifocal , all made by Bausch and Lomb.
RGP Contact Lenses
RGP stands for rigid gas permeable, and is the material used to make them. They are much smaller lenses than soft lenses and have been around for much longer. The rigidness doesn’t allow as much oxygen to pass through, and many wearers say they take a lot longer to get used to. They are less then a centimeter across, and cover the entire pupil (black part of your eye) and the edges rest on the iris (the colored part of your eye). Doctors believe that even though they are tougher to get used to, they provide a more healthy option for your eye, as well as being more durable than soft contact lenses, lasting up to one year. Some of the products on the market today are OP-2 by Stellar Contact Lens, Inc. using the material Lotifocon A, and O Perm 30 made by Optical Polymer Research, using the material oxyflufocon A.
Silicone & Hydrogel Contact Lenses
Many people who hear silicone hydrogel lenses think that they’ve always gone together, when if fact that wasn’t the case until recently. Chemists came across this new material after they accidentally mixed a hydrophobic silicone with a hydrophilic PHEMA. This produced a copolymer that had improved oxygen transmissibility. Polymers and copolymers are a bunch of monomers linked together, and a monomer is a molecule that can be combined with others.
They difference between silicone hydrogel lenses and conventional hydrogel lenses is the high oxygen transmissibility of silicone hydrogel lenses. This oxygen transmissibility is not dependent on the water content of the lens material. Conventional hydrogel lenses are classified according to the water content. Low hydrogels range between 12-30% water; moderate hydrogels range from 40-70% water; high hydrogels range from 90-99.5% water and superabsorbant hydrogels have more than 99.5% water content.
Some of the different silicone hydrogel products on the market are Avaira lenses made by AQUAFORM technology, PureVision by Bausch and Lomb, and Focus Night and Day by Ciba Vision.
Intraocular Contact Lenses
Intraocular lenses are also known as IOL’s, and are lenses that are implanted into your eye. Traditionally they were made of an inflexible material known as PMMA. PMMA, or Polymethylmethacrylate, was the first material to be used successfully in intraocular lenses. However, over time chemists have found new ways to make them softer and healthier for your eyes. Nowadays they are small plastic lenses with plastic side struts called haptics, that can be made of silicone or acrylic, both of which are soft foldable materials, easily implanted into the eye.
Acrylic lenses are not the favorite yet though since they can be very expensive. Latest advances include IOL’s with square-edge design, non-glare edge design and yellow dye added to the IOL. Blue Light Filtering IOLs filter the UV and high-energy blue light present in natural and artificial light, helping to reduce future vision problems. Some of the different products on the market are Array Multifocal IOL’s made by Advanced Medical Optics, Clariflex by Advanced Medical Optics and Phacoflex II, also made by Advanced Medical Optics. All of these products are made of silicone optic material and PMMA haptic material.