A contact lens, or simply contact, is a thin lens placed directly on

the surface of the eye. Contact lenses are considered medical

devices and can be worn to correct vision, or for cosmetic or

therapeutic reasons.[1] In 2004, it was estimated that 125 million

people (2%) use contact lenses worldwide, including 28 to 38

million in the United States.[2] In 2010, worldwide contact lens

market was estimated at $6.1 billion, while the U.S. soft lens market

was estimated at $2.1 billion.[3] Multiple scientists estimated that

the global market would reach $11.7 billion by 2015.[3] As of 2010,

the average age of contact lens wearers globally was 31 years old,

and two thirds of wearers were female.[4

People choose to wear contact lenses for many reasons.[5]

Aesthetics and cosmetics are often motivating factors for people

who would like to avoid wearing glasses or would like to change

the appearance of their eyes.[6] Other people wear contacts for

functional or optical reasons. When compared with spectacles,

contact lenses typically provide better peripheral vision, and do not

collect moisture such as rain, snow, condensation, or

perspiration(extreme weather); this makes them ideal for sports

and other outdoor activities. Contact lens wearers can also wear

sunglasses, goggles, or other eyewear of their choice without

having to fit them with prescription lenses or worry about

compatibility with glasses. Additionally, there are conditions such

as keratoconus and aniseikonia that are typically corrected better

by contacts than by glasses