There are two types of contact lenses: soft contact lenses and hard contact lenses. Rigid contact lenses mainly achieve the purpose of correction by changing the cornea. Generally, they need to be worn at night when sleeping, and removed early the next morning. The correction effect can last all day. Soft contact lenses are the most common and well-known types of contact lenses on the market. Today, let's take a look at the materials of soft contact lenses.
One of the materials of soft contact lenses is hydrogel, which has strong hydrophilicity, good water retention and elasticity, and the texture of the lenses is very soft and moist. However, the main disadvantage of hydrogels is that the oxygen permeability is limited by water. To achieve high oxygen permeability, the water content must be increased. However, an excessively high water content will aggravate the problem of dryness. Therefore, hydrogels are currently mainly used to make long-term lenses such as annual and semi-annual lenses, and the water content is basically between 38% and 42%.
Silicon hydrogel, another material for soft contact lenses, is also a highly hydrophilic organic polymer material. Its biggest advantage is that it has a dual-phase material framework, which can ensure that the silicon channel and the water channel transmit oxygen at the same time, and the oxygen permeability can even reach 6-8 times that of the hydrogel. Because of its high water content and strong adsorption, it is more suitable for short-cycle disposable contact lenses. However, lenses made of silicone hydrogel are slightly harder, and people with sensitive eyes may feel a strong foreign body sensation when they first wear them.
Under the correct care and maintenance, wearing contact lenses during the service cycle will not cause eyeball deformation, but is superior to frame glasses in terms of correction effect and convenience.