Contact Lens Fittings
Types of Contact Lenses
Hard (rigid) Lenses
- Conventional hard (polymethyl methacrylate, or PMMA) lenses are made of a fairly stiff plastic. They correct vision with no distortion, but they are the least comfortable type of contact lens.
- Rigid gas-permeable (RGP) lenses are more comfortable than conventional hard lenses. Some gas-permeable lenses are designed to be worn overnight and for up to 7 days.
- Daily-wear lenses are removed and cleaned at night and reinserted in the morning.
- Extended-wear lenses can be worn for up to a week at a time, day and night. But extended use may be uncomfortable, and it increases the risk of damaging the eye.
- Disposable lenses (daily and extended-wear) may be worn for up to several weeks and then discarded.
Contact lenses are small plastic discs shaped to correct an eyesight problem such as nearsightedness, farsightedness, presbyopia, or astigmatism. These are called refractive errors. They may also be used by people who have had surgery for cataracts.
Contacts are placed directly on the eye, where they float on a film of tears in front of the cornea. Correct design and fitting of the lenses are essential for comfort, safety, and accurate correction.
Improvements in contact lenses have made them more comfortable and easier to wear. In the United States, millions of people wear contact lenses, and most wear soft lenses. For these people, contact lenses offer a relatively safe and effective way of correcting vision problems.
With most hard contact lenses, there will be a 2- to 4-week break-in period during which you wear the lenses for increasingly longer periods of time each day. Soft contact lenses usually take less time to break in.