Clear "picture" of reality
The first contact lenses made of plastic was invented in 1938, and in the early 60s of the last century was designed hydrogel, which became the basis for modern materials used in the manufacture of lenses. Today it is thermoplastic and hydrogel are the most popular materials for the manufacture of lenses.
Hydrogel contact lenses today constitute about 90 percent of the total produced lenses. Hydrogel lens material provides advantages such as the ability to retain and allow moisture is an important factor in comfort when wearing them, as well as smoothness and elasticity.
Smooth lenses have better interaction with the cornea and the upper eyelid does not create a sense of friction. The elasticity of the hydrogel minimizes mechanical stresses on the cornea and sclera. In addition, the use of hydrogel lenses minimizes the risk of infection if not properly stored or used. "Alignment" of such lenses can not move your eyes quickly get used to them. After hydrogel contact lens to the cornea receives six times more oxygen than traditional soft lens. These lenses are not only suitable for people who suffer from astigmatism, because having a high coefficient of gas permeability is not enough, they are not designed for the correction of this defect.
Contact lenses are made of thermoplastic differ permanently resilient and are rigid lenses. They are durable and easy to care for, but their disadvantage is airtight and fragility. The lenses are made of thermoplastic are also more susceptible to the formation of protein deposits. In contrast, hydrogel lenses, they can be adjusted into several diopters and astigmatism have a longer lifetime. Their size is larger in diameter than hydrogel lenses, facilitates donning and removal.