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Contact lenses may be grouped into two main types; hard gas permeable contact lenses, and soft hydrogel contact lenses.
Leonardo da Vinci is frequently credited with introducing the general principle of hard contact lens. He described a method of directly altering corneal power by submerging the eye in a bowl of water. Leonardo, however, did not suggest his idea be used for correcting vision as he was primarily concerned with learning about the mechanisms of accommodation of the eye.
Soft contact lenses were first commercially available in the late 1960s. They were quickly prescribed more often than the original hard contact lenses, due to their increased comfort and shorter adaptation time. The original soft contact lenses were designed to be removed nightly and lasted 12 to 24 months.
The 1980s saw the introduction of the next generation of contact lenses - soft disposable hydrogel contact lenses. By adhering to a regular replacement regime, these lenses had the advantage of lower complication rates due to the lenses developing less surface deposits and lower infection rates. medical8.com
The late 1990s saw silicon-hydrogel launched. Silicon-hydrogel lenses such as PureVision and Focus night & Day contact lenses have the advantage of increased oxygen permeability, enabling them to be worn on an extended wear or overnight basis. They also result in a whiter, healthier eye.
In the 2000s a new range of silicon-hydrogel disposable contact lenses were released. These lenses such as Acuvue Oasys and O2 Optix have a hydrophilic coating resulting in a lens that wets better on the eye, leading to increased comfort and greater hydration.
Contact lenses are now available with many wearing schedules, ranging from one day or daily disposable contact lens, to monthly disposable and conventional contact lens.
