RGP Contact Lenses
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 eyeball). Contact lenses work the same way that glasses do to improve your vision.
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 frequently.
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.