Most extended wear (EW) contacts are thinner than daily wear lenses and are made of silicone hydrogel. This advanced soft lens material enables EW lenses to "breathe" better than daily wear lenses, allowing more oxygen to reach the cornea. This is especially important when lenses are worn continuously for extended periods of time.
Hard Contact Lenses. Hard contact lenses are generally known as semi-rigid gas permeables (RGPs)and they are now made of plastic-like material, although originally they were in fact made of glass. For many years, hard contact lenses were made out of a material called polymethyl methacrylate (PMMA).
Types of Contact Lenses: There are two general categories of contact lenses – soft and rigid gas permeable (RGP). All contact lenses require a valid prescription Types of Contact Lenses: There are two general categories of contact lenses – soft and rigid gas permeable (RGP).
Multifocal and bifocal contact lenses are designed for people with presbyopia who have trouble focusing on close-up objects. They work by combining correction for distance and near vision into the same contact lens. Multifocal lenses have improved significantly in recent years due to better technology.
Gas permeable contact lenses are also called RGP (Rigid Gas Permeable) contact lenses, and oxygen permeable lenses. GP designs are differentiated primarily by size. For many years virtually all GP lenses were fitted significantly smaller than the corneal diameter, typically 9 to 10 mm in diameter.
Spherical contact lenses have the same lens power throughout the entire optical part of the lens to correct myopia (nearsightedness) or hyperopia (farsightedness). Toric soft contact lenses have different powers in different meridians of the lens to correct astigmatism as well as nearsightedness or farsightedness.