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What Are Contact Lens Made Of

  Soft contact lenses are made of plastic, but not the type of plastic used in garbage bags or paper plates. Instead, soft lenses are made of hydrophilic plastics - a special type of water-absorbing plastic that stays soft and moist as long as it is absorbing lots of water, made of cast moulding technology . As long as that plastic stays nice and wet either inside our eye or in a case, the plastic stays pliable and soft. To our eyes, this soft flexibility spells comfort. When our eyes are dry, our lenses will begin to feel uncomfortable because they depend on moisture to keep them in place and pliable. Soft contact lenses are categorized by the amount of water they contain. They can be classified as either high water or low water. Most extended wear contact lenses are made out of silicone hydrogel - a material that combines the water-absorbing plastic of soft lenses with silicone. Adding silicone to the hydrogel plastic creates cast moulding contact lenses that stays moist a...
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What Is Silicone Hydrogel

  Silicone hydrogel contact lenses are advanced soft lenses that allow more oxygen to pass through the lens to the cornea than regular soft ("hydrogel") contacts. In fact, silicone hydrogel lenses enable up to five times more oxygen to reach the cornea than regular hydrogel lenses. Silicone hydrogel and regular hydrogel lenses both are made of plastics that are hard when dry but readily absorb water and become soft and gel-like when hydrated. If we have ever let a soft or silicone hydrogel lens dry out, we know that it becomes deformed, hard and fragile. But if we soak it for a few minutes in contact lens solution, it becomes soft and pliable again. Silicone hydrogel contact lenses sometimes are erroneously called silicon hydrogel lenses. Silicon is a very common mineral. In fact, ordinary sand is composed primarily of silicon dioxide (silica). And highly purified silicon is used to manufacture semiconductors, which is why the southern part of the San Francisco Bay area...
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