subject: Materials of contacts [print this page] Materials of contacts Materials of contacts
Contacts are available in a wide variety of selections in the market that even make customers hard to choose. Although contact lens comes in colorful choices, it has some categories. Mainly, contacts can be grouped in four ways according to different aspects. One of the elements is the material. According to different materials, there are three types of contacts.
The first type is hard contact lens. This kind of lenses is generally made of a rigid material abbreviated as PMMA, which is also known as Plexigas or Lucite. Hard contacts are mainly provided under sizes of 8 to 18mm with the center thickness of 100um. The material makes this type of lenses durable and blocks oxygen from reaching the cornea directly. In order to achieve this function, hard contact lens also uses other plastics. Is this way, oxygen can only reaches the cornea indirectly through eye blinking, which dissolves the oxygen. Nevertheless, hard contacts are the least comfortable so that people rarely use them now.
The second type is soft contact lens, which is the most common one. These kinds of lenses are made of gel-like, water containing plastics. These contacts constitute of 38% to 70% water. This type of plastic can absorb water in nature. Soft contact lens is more comfortable to wear than hard one. Other advantage of soft contacts is that they are disposable so that you can simply throw them away after using for designated period of time.
The third type is GP contact lens, which is made from rigid and waterless plastics. GP contacts are particularly helpful for people with presbyopia and high astigmatism. This kind of lenses is usually about 8mm in diameter. GP contacts offer excellent eye heath because they do not contain water so that are deposits-resistant.
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