Hydrogel contact lenses, also known as soft contact lenses, consist of superabsorbent, interconnected polymers. As of 2010, there are two main types of these lenses on the market: traditional or HEMA lenses, which contain the compound 2-hydroxyethyl methacrylate, and silicone hydrogel lenses, which use silicone instead. Both types of hydrogel lenses have advantages over their hard counterparts, known as RGP (rigid gas permeable) contact lenses. However, they also have several disadvantages.
