A contact lens is a thin, curved lens placed directly on the surface of the eye to correct vision problems. They can be made from soft or rigid materials and are designed to fit comfortably on the eye. Contact lenses are often used as an alternative to eyeglasses for people with nearsightedness, farsightedness, or astigmatism. These lenses come in various types, including daily disposables, which are worn for a single day, and extended wear lenses, which can be worn overnight. Proper care and hygiene are essential to prevent eye infections and ensure the longevity of the lenses.