Contact lenses are thin, curved lenses worn directly on the surface of the eyes to correct vision or change the appearance of the eyes. They can help people with nearsightedness, farsightedness, astigmatism, or presbyopia. Some contact lenses are also cosmetic and are used to change eye color. They are available as daily, bi-weekly, monthly, or extended-wear lenses and should be cleaned and used according to the manufacturer's instructions."