What are gas-permeable contact lenses?

Gas-permeable contact lenses, which differ from soft contact lenses, are made of durable, slightly flexible plastic. They allow oxygen to reach the cornea (the clear dome on the front of the eyeball). Because of improvements in materials used to make them, gas-permeable lenses have several advantages over soft lenses and are being prescribed more frequently.

The original 'hard' lenses, which were made of a plastic that did not allow oxygen to reach the cornea, are rarely prescribed today.

When are they used?

Gas-permeable contact lenses correct most of the vision problems for which glasses are prescribed. Gas-permeable lenses have the following advantages over soft lenses:

• They often correct vision better than soft lenses do, especially for people with severe astigmatism or irregular corneas.

• Allergic and toxic reactions to lens care solutions are less frequent. Unlike soft lenses, gas-permeable lenses do not absorb liquids.

• Gas-permeable contact lenses are easier to clean than soft contacts.

• Gas-permeable lenses are less expensive than soft lenses because:
  • They last longer because they are more durable.

  • They can be polished and reground when scratched or outgrown.

  • The materials used to make them are less expensive.

  • Gas-permeable lenses require fewer cleaning solutions than soft lenses do.

The main reason gas-permeable contacts are not more widely used is that many people need a break-in period to achieve a comfortable fit.

What are the types of gas-permeable contact lenses?

Gas-permeable lenses are available for daily wear and extended wear. However, many eye doctors recommend that you not wear contacts, even so-called extended-wear types, when you sleep. Ask your eye doctor how long you can safely leave in your lenses.

Two types of bifocal gas-permeable lenses are available. In one type, the reading prescription is a ring around the outside of the lens. The other type has the reading prescription and a weight at the bottom of the lens so it stays there when the lens is in your eye. Fitting these lenses can be difficult, and many people never adjust to them.

Tinted gas-permeable lenses are available for cosmetic reasons such as to change your eye color, or to use as sunglasses.

How can I get gas-permeable contact lenses?

You need to have a thorough eye exam with an ophthalmologist (a medical eye doctor) or an optometrist, who will:

• determine whether your eyes are suitable for contact lenses

• recommend either gas-permeable or soft lenses

• check your eyes once a year after you begin wearing your lenses full-time.

Slight discomfort when you first start wearing contact lenses is normal. However, if you have any pain in your eyes, see your eye doctor. Checkups of new lenses are recommended after 1 week, 2 weeks, 1 month, 6 months, and 1 year.

What precautions should I take with contact lenses?

• Be sure your hands are clean before you put in or take out your lenses.

• Do not wear your lenses while swimming because they may float out of your eyes.

• Use aerosol sprays, such as deodorant and hair spray, before you put in your lenses.

• Always insert your contact lenses before applying makeup. Use water-soluble makeup, and avoid lash-building mascara, which may drop particles into your eyes.

• Do not put contact lenses into your mouth to moisten or clean them because this may cause an eye infection.

• If there is a possibility that you may lose consciousness from seizures or other medical problems, include the fact that you wear contact lenses on your Medic Alert bracelet or card.

• See your eye doctor if you have burning, redness, pain, unusual light sensitivity, or blurry vision.

What are some problems with contact lenses?

You may find it difficult to wear contact lenses if you have:

• severely irritated eyes from allergies or exposure to dust or chemicals at your job

• an overactive thyroid, uncontrolled diabetes, or severe arthritis in your hands

• dry eyes because of pregnancy, birth control pills, diuretics, antihistamines, or decongestants.

Other possible problems include:

• allergic reactions to lens care solutions and contaminants on or in the lenses

• inflammation (redness) of the eye

• scratching of the cornea.