Soft, Rigid Gas Permeable and Plano are all types of what?
Rigid gas permeable lens with keratoconus. However, they require a period of adaptation before full comfort is achieved. Rigid gas permeable lens A rigid gas permeable lens, also known as RGP lens or GP lens or colloquially, hard contact lens, is a rigid contact lens made of oxygen-permeable polymers. Initially developed in the late 1970s, and through the 1980s and 1990s, they were an improvement over prior 'hard' lenses that restricted oxygen transmission to the eye. Rigid lenses are able to replace the natural shape of the cornea with a new refracting surface. This means that a regular (spherical) rigid contact lens can provide
Semi-rigid airship able to achieve improvements in weight, aerodynamic, and structural performance. The boundary between semi-rigid and non-rigid airships is vague. Especially with small types, it is unclear whether the structure is merely an extended gondola or a proper structural keel. As in non-rigid airships, the hull's aerodynamic shape is maintained by an overpressure of the gas inside and light framework at the nose and tail. Changes in volume of the lifting gas is balanced using ballonets (air filled bags). Ballonets also may serve to provide pitch control. For small types the lifting gas is sometimes held in the hull itself, while