Gas permeable contact lenses are rigid lenses made of durable plastics that allow oxygen to pass through the lens. These lenses are called GP lenses, rigid gas permeable lenses, RGP lenses, and oxygen permeable lenses.
Scleral contact lenses get their name from the fact that, unlike regular contacts, they vault over the entire corneal surface and rest on the white part of the eye, which is called the sclera. This makes them larger than standard contacts, which in turn provides a variety of benefits. Their size makes them easier to handle and more stable when on the eye, which in turn provides the patient with sharper and more reliable vision. They are also less likely to become dislodged and come out.