Gas permeable contact lenses are small, curved pieces of durable, slightly flexible plastic shaped to fit your eyes. They float on the tear film in front of the cornea (the clear outer layer on the front of the eye). Contact lenses correct most of the vision problems for which glasses are prescribed.
The plastic used for gas permeable lenses allows oxygen to reach the cornea. The original hard contact lenses, which were made of a plastic that did not allow oxygen to reach the cornea, are rarely prescribed today. Although gas permeable lenses are not the same as the hard lenses of the past, people sometimes still refer to gas permeable lenses as "hard" or "rigid" lenses. This is because they are harder and more durable than soft contact lenses.
Because of improvements in materials used to make them, gas permeable lenses have several advantages over soft lenses and are being prescribed more often.
Gas permeable lenses have the following advantages over soft lenses:
The main reason gas permeable contacts are not more widely used is that they are harder to get used to.
Gas permeable lenses are available for daily wear and extended wear. However, eye care providers recommend that you not wear contacts, even so-called extended-wear types, when you sleep. Ask your eye care provider 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 the reading position stays at the bottom when the lens is in your eye. Fitting these lenses can be difficult, and some people never adjust to them.
Tinted gas permeable lenses are available that can change your eye color, or be used as sunglasses.
You need to have a thorough eye exam with an eye doctor, who will:
Slight discomfort when you first start wearing contact lenses is normal. If you have any pain in your eyes, see your eye care provider. You should have checkups of your eyes and lenses 1 week, 2 weeks, 1 month, 6 months, and 1 year after you first get them. If you have any problems, you may need to go for checkups more often.
You may find it difficult to wear contact lenses if you have:
Other possible problems include: