Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A contact lens is a lens placed on the eye for medical purposes, for cosmetic reasons or for therapeutic reasons. In 2004, it was estimated that 125 million people 2% of people used contact lenses worldwide, including 28 to 38 million in the United States. The worldwide contact lens market was estimated at $6.1 billion in 2010 and in that same year the average age of contact lens wearers was 31 years old while two thirds of wearers were female...