Contacts are thin discs of clear plastic that float on the tear film of the cornea and correct for the same vision errors as glasses. There are basically two main types of contact lenses -- hard lens and soft lens.

Hard lens contacts include the PMMA contacts that were invented in the 60's and are rarely used today, and RGP or rigid gas permeable contacts. RGP contacts are a combination of plastics and other materials like silicone and fluoropolymers that help the lens hold its shape while still allowing oxygen to freely flow through the lens to the cornea. The new RGP contacts are more "wettable," easier to adjust to, and more comfortable to wear than the old PMMA hard lens contacts. RGP contacts may be your best choice if your cornea has enough astigmatism -- egg-shaped instead of spherical -- that a soft lens cannot provide sharp vision. They may also be a good choice if you tend to have allergies or form protein deposits on your contacts.

Soft lens contacts are the first choice of more than 75% of all contact lens wearers, because they are the most comfortable to wear and offer the widest range of choices in lens features.

Daily Wear Lenses -- The least expensive contacts, must be removed nightly and replaced on an individualized schedule. They should not be used as extended wear lenses.

Extended wear lenses -- These contacts are worn overnight, but must be removed at least weekly for a thorough cleaning and disinfection. They are, however, being recommended less and less frequently due to a greater risk of corneal infection with overnight wear.

Disposable wear lenses -- These contacts are the most expensive, but are also very convenient. They must be removed nightly, and replaced on a daily, weekly, or monthly basis. Disposable lenses are sometimes recommended for patients with allergies, or if they tend to form protein deposits on their lenses. Disposable contacts also come in colored and toric versions as well.

Colored contact lenses -- These contacts can be used to change your appearance by changing your eye color in varying degrees.

Toric contact lenses -- These contacts can sometimes correct for astigmatism. But depending upon the severity of your astigmatism, they may or may not be as successful as RGP lenses. They are also more expensive than most other contact lenses.

If you have presbyopia and want to wear contacts, you have several options, which are somewhat different from correcting for other types of refractive errors with contacts. You can: 

* Wear your distance correction in contact lenses, and wear reading glasses when you need them.

* Wear one contact for distance vision in one eye, and one for near vision and reading in the other eye. This is called monovision and works well for many, but is not for everyone. A trial testing period may be helpful for you if you are considering this option.

* Wear bifocal contacts, which work like bifocal glasses in that they allow both distance vision and near vision in the same lens. They are, however, somewhat more expensive to fit just right, and may not provide acceptable vision correction for all patients.