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Originally, hard contact were made of a material called PMMA. Although still available, the more common types of contact are listed below:Rigid gas-permeable (RGP) daily-wear lenses are made of plastic that does not absorb water but allows oxygen to get from the atmosphere to the cornea. (This is important because the cornea has no blood supply and needs to get its oxygen from the atmosphere through the film of tears that moves beneath the lens.) They must be removed and cleaned each night. Rigid gas-permeable (RGP) extended-wear lenses are made from plastic that also does not absorb water but is more permeable to oxygen than the plastic used for daily-wear lenses. NEARSIGHTED? NEED READING GLASSES? New developments in lens technology ensure a solution to almost every vision problem. Talk to your ocularsciencecontacts eye doctor ocularsciencecontacts about what''s available (costs vary).Rigid gas-permeables Recommended for those with high degrees of corneal astigmatism, RGPs are firm plastic lenses with microscopic slits that allow more oxygen to reach the eye. RGPs have a greater resistance to bacteria because they don''t contain water. Improved ocularsciencecontacts extended-wear materials also guarantee greater durability, sharper vision, comfort and cheaper maintenance costs. Allow yourself a week or two to get used to these slightly stiff lenses.Bifocals These contact correct presbyopia, ocularsciencecontacts a kind of farsightedness that usually occurs around age 40. There are two types: Rimless frames are the least noticeable type, and they are lightweight because the nosepiece and temples are attached directly to the lenses, eliminating the weight of the rims. They tend to not be as sturdy as frames with rims, so they are not a good choice for people who frequently remove their glasses and put them on again. They are also not very suitable for lenses that correct a high degree of farsightedness, because such lenses are thin at the edges.Metal frames are less noticeable than plastic, and they are lightweight. They are available in solid gold, gold-filled, anodized aluminum, nickel, silver, stainless steel, and now titanium and titanium ocularsciencecontacts alloy. Until the late 1980s, when titanium-nickel ocularsciencecontacts alloy and titanium frames were introduced, metal frames were, in general, more fragile than plastic frames. The titanium frames, however, are very strong and lightweight. An alloy of titanium and nickel, called Flexon, is not only strong and lightweight, but returns to its original shape after being twisted or dented. It is not perfect for everyone, though, because some people are sensitive to its nickel. Flexon frames are also relatively expensive.
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