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List of soft contact lens materials
From Wikipedia, the free encyclopedia
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Soft contact lenses are one of several types of contact lenses for corrective vision eyewear as prescribed by optometrists and ophthalmologists.[1]
 | The examples and perspective in this deal primarily with the United States and do not represent a worldwide view of the subject. (November 2020) |
Background
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 | It has been suggested that this section be split out and merged into the article titled Contact lens#Soft lenses, which already exists. (Discuss) (January 2022) |
In the US market, soft contact lenses are approved by the US Food and Drug Administration.[2] The American Optometric Association published a contact lens comparison chart called Advantages and Disadvantages of Various Types of Contact Lenses on the differences between them.[3] These include:
- soft contact lenses
- rigid gas-permeable (RGP)
- daily wear
- extended wear
- disposable
- planned replacement contact lenses.
The US Food and Drug Administration (FDA) defines soft contact lenses as:
made of soft, flexible plastics that allow oxygen to pass through to the cornea. Soft contact lenses may be easier to adjust to and are more comfortable than rigid gas permeable lenses. Newer soft lens materials include silicone-hydrogels to provide more oxygen to your eye while you wear your lenses.[4]
History
The first contact lenses were made of glass, in 1888. Initially the glass was blown but soon lenses were made by being ground to shape. For the first fifty years, glass was the only material used. The lenses were thin, yet reports of injury were rare. In 1938 perspex (polymethylmethacrylate, or PMMA) began to replace glass in contact lens manufacture. PMMA lenses were easier to produce so the production of glass lenses soon ended. Lenses made of PMMA are called hard lenses.[5] Soft contact lenses were first produced in 1961 by Czech chemical engineer Otto Wichterle using polyhydroxyethylmethacrylate (pHEMA), a material that achieved long-term commercial application. Lenses made of polyacrylamide were introduced in 1971.[5]
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Types
The FDA classifies soft contact lenses into four groups for the US market. They are also subcategorized into 1st generation, 2nd generation, and 3rd generation lens materials.[6] These 'water-loving' soft contact lens materials are categorized as "Conventional Hydrophilic Material Groups ("-filcon"):
Note: Being ionic in pH = 6.0 – 8.0.[7]
The FDA has been considering updating soft contact lens group types and related guidance literature.[8][9][10]
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Contact lens polymers
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The materials that are classified in the 5 FDA groups include the ones listed in the next 5 sections:[11][12]
Hydrogel groups
Below is a list of most contact lens materials on the market, their water percentage, their oxygen permeability rating, and manufacturer brands.[14][15][16][17] Note that the higher the oxygen transmissibility rating, the more oxygen gets to the eye.
Low-water nonionic
High-water nonionic
Low-water ionic
High-water ionic
Silicone hydrogel polymers
Production generations
There are three generations of silicone hydrogel contact lens materials:[31]
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References
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