Materials for different contact lenses

... Materials for different contact lenses There are three main types of contact lenses. They are hard contact lenses, soft lenses and gas permeable lenses. Contact lenses were invented a century ago. At the beginning, there are only hard contact lenses which are made out of glass, then soft contact lenses were invented and gas permeable lenses have only started the development in the last decade. They are trying new material for gas permeable lenses. Hard contact lenses Hard contact lenses nowadays are made of Polymethylmethacrylate (PMMA) which is generally known as Perspex. It is the second stage of hard contact lenses. The advantage of hard contact lenses is that it doesn't pull moisture from eyes. The hardness of the material cause it to retain shape better which make the vision crisper. Also, more different kind of lenses could be made out of it. They also tend to last longer than soft contact

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