Contact lenses are plastic corrective disks that cling to the |cornea| with the aid of the |eye|'s fluid layer, which cushion the |lenses| and hold them in place. Although there are hundreds of brands and types and some very specialized |lenses|, there are three main types of contact lenses on the market: rigid gas permeable |lenses| and soft |lenses| (both intended for daily wear only), and extended-wear |lenses| (designed to be worn for longer periods, including overnight). Recently a new type of extended-wear |lens| became available, the disposable |lens|.
