Contact lenses come in various material types, replacement schedules and wear schedules. There are two general types of contact lenses: hard and soft The hard lenses most commonly used today are rigid gas permeable lenses. Soft lenses are comfortable and come in many versions, depending on how you want to wear them. Daily-wear lenses are the least expensive, are removed nightly and are replaced on an individualized schedule. Extended-wear lenses are worn overnight but are removed at least weekly for thorough cleaning and disinfection. Disposable-wear lenses are more expensive, but convenient. They are removed nightly and replaced on a daily, weekly, biweekly, or monthly basis. Disposable lenses are sometimes recommended for people with allergies