Contact Lens Solutions/ Cases

A contact lens (also known simply as a \"contact\") is a corrective, cosmetic, or therapeutic lens usually placed on the cornea of the eye. more...

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Contact lenses usually serve the same corrective purpose as conventional glasses, but are lightweight and virtually invisible — many commercial lenses are tinted a faint blue to make them more visible when immersed in cleaning and storage solutions. Cosmetic lenses are deliberately colored for altering the appearance of the eye.

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

People choose to wear contact lenses for various reasons. Many consider their appearance to be more attractive with contact lenses than with glasses. Contact lenses are less affected by wet weather, do not steam up, and provide a wider field of vision. They are more suitable for a number of sporting activities. Additionally, ophthalmological conditions such as keratoconus and aniseikonia may not be accurately corrected with glasses.

History

Leonardo da Vinci is frequently credited with introducing the general principle of contact lenses in his 1508 Codex of the eye, Manual D, where he described a method of directly altering corneal power by submerging the eye in a bowl of water. Leonardo, however, did not suggest his idea be used for correcting vision — he was more interested in learning about the mechanisms of accommodation of the eye.

René Descartes proposed another idea in 1636, in which a glass tube filled with liquid is placed in direct contact with the cornea. The protruding end was to be composed of clear glass, shaped to correct vision; however the idea was unworkable, since it would make blinking impossible.

In 1801, while conducting experiments concerning the mechanisms of accommodation, scientist Thomas Young constructed a liquid-filled \"eyecup\" which could be considered a predecessor to the contact lens. On the eyecup's base, Young fitted a microscope eyepiece. However, like da Vinci's, Young's device was not intended to correct refraction errors.

Sir John Herschel, in a footnote of the 1845 edition of the Encyclopedia Metropolitana, posed two ideas for the visual correction: the first \"a spherical capsule of glass filled with animal jelly\", and \"a mould of the cornea\" which could be impressed on \"some sort of transparent medium\". Though Herschel reportedly never tested these ideas, they were both later advanced by several independent inventors, seemingly unaware of Herschel's suggestion.

Read more at Wikipedia.org