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  • Publicado : 27 de febrero de 2012
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A contact lens is a corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye. Leonardo da Vinci is credited with describing and sketching the firstideas for contact lenses in 1508, but it was more than 300 years later before contact lenses were actually fabricated and worn on the eye. Modern soft contact lenses wereinvented by the Czech chemist Otto Wichterle and his assistant Drahoslav Lím, who also invented the first gel used for their production.
Contact lenses usually serve thesame corrective purpose as glasses, but are lightweight and virtually invisible—many commercial lenses are tinted a faint blue to make them more visible when immersed incleaning and storage solutions. Some cosmetic lenses are deliberately colored to alter the appearance of the eye. Some lenses now have a thin surface treatment which is a UVcoating; this helps to reduce UV damage to the eye's natural lens.

It has been estimated that 125 million people use contact lenses worldwide (2%), including 28 to 38 millionin the United States and 13 million in Japan. The types of lenses used and prescribed vary markedly between countries, with rigid lenses accounting for over 20% ofcurrently-prescribed lenses in Japan, the Netherlands and Germany but less than 5% in Scandinavia.

People choose to wear contact lenses for many reasons, often due to theirappearance and practicality. When compared with spectacles, contact lenses are less affected by wet weather, do not steam up, and provide a wider field of vision. They aremore suitable for a number of sporting activities. Additionally, ophthalmological conditions such as keratoconus and aniseikonia may not be accurately corrected with glasses.
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