Gas permeable contact lenses are rigid lenses made of durable plastic that transmits oxygen. These lenses also are called GP lenses, rigid gas permeable lenses, RGP lenses and oxygen permeable lenses. For many patients, they offer outstanding benefits over soft lenses. For one, because GP lenses are made from a firm plastic material, they retain their shape when you blink, which tends to provide sharper vision than pliable soft lenses.
GP lenses also are extremely durable. Although you can break them (for instance, if you step on them), you can't tear them easily, like soft lenses. In addition, they are made of materials that don't contain water (as soft contact lenses do), so protein and lipids from your tears do not adhere to GP lenses as readily as they do to soft lenses.
There are some disadvantages of RGP lenses for patients with irregular corneas and most of these deal with discomfort and poor fit. Because of the shape and curvature of more keratonic corneas, the RGP lens has a difficult time centering, thus creating movement of the lens, and therefore blurring vision and making the lens uncomfortable.
