To ensure that your contacts remain healthy, you should always replace them as required by the manufacturer or type of contacts you are using. Most types of contacts need to be replaced every 2 weeks, and replaced with a fresh pair. If you are using daily disposable lenses, you should always throw them away before you go to sleep, then wake up to a fresh new pair in the morning. This material is very rigid, and doesn t contain near as much water as soft contacts. With that in mind, taking care of and cleaning hard lenses is very different that cleaning and maintaining soft contact lenses. Before you purchase a pair of hard or rigid contacts, you should know how to take care of them and how to clean them. You can buy them online, through your local optician, or anywhere else that sells contacts. They are available in virtually every subscription, which is perfect for anyone who needs a dependable pair of lenses. The Acuvue advance lenses are unlike any other type, for the simple fact that they are very comfortable, dependable - and easy to take care of. Although they are relatively new, they are specifically made for those who work or live in dry environments. These contacts contain a special agent for re-wetting purposes, which enables the contact lens to remain moist, even if your eyes aren t producing enough tears. They are daily wear contacts, and should be soaked in solution at night and replaced every two weeks or so. You should also make sure that you dry your hands thoroughly with a clean towel, as soap residue or chemicals may get on the contacts, causing them to be very uncomfortable and possibly even burning your eyes when you put them in. If you can t seem to get your contacts to go in your eyes, you shouldn t force them. These two adjustments in the contact lens are very distinct, with a sharp line between them. Even though they may sound hard to use, most people find that they are easy use with a little bit of practice. One type of bifocal lens is the aspheric lens, which have a more gradual change of focus. Both power are in the central area of the pupil, and similar to the concentric lens, your eye will immediately adjust to these lenses and decide on the focus that is best to use.