Gas Permeable Contact Lenses
Today, most hard contact lenses are made of a rigid, gas permeable material, sometimes abbreviated as r-g-p. Unlike the original hard contacts, which did not allow air to pass through, gas permeable lenses do permit some exchange of air. This is important, because the cornea, where your contacts sit, has no direct blood supply of its own. It must take vital oxygen directly from the air, and your tears. Therefore, circulation is crucial. However, the same materials that let air flow through gas permeable lenses also make them difficult to get wet. To make the lenses more wettable, manufacturers may add extra ingredients, or specially treat the surface. Even so, dryness can sometimes be a problem with r-g-p contacts.
Benefits of gas permeable contact lenses
But gas permeable lenses do have their advantages: they are more useful in correcting astigmatism and certain corneal problems than soft lenses. What’s more, they can be rinsed in plain tap water, and typically require no special cleaning solution. For more details on gas permeable lenses, consult an eye care specialist.