Soft contact lenses
Nowadays, soft contact lenses are most commonly used types of lenses. More than 90% of contacts wearers use soft contact lenses. This is mainly due to their perfect tolerability, simple handling, new material and still better price. In these days, soft contacts are able to correct almost any refractive error.
Hydrogel contact lenses
Hydrophilic gels are, in principle, polymers that contain a large percentage of water. Each macromolecule is combined in spatial lattice chemical bonds, which guarantee the dimensional stability and insolubility. Amount of hydrophylic monomers allow to create a range of gels with different properties.
How were silicone hydrogel contacts developed?
The difficulty of combining silicone rubber with a typical hydrogel-forming monomer was the first major obstacle in the development of the silicone hydrogel contact lenses. The first answer that springs to mind is to combine HEMA with TRIS, the monomer used in the preparation of RGP lens materials. However, combining hydrophobic TRIS with hydrophilic HEMA and then hydrating the product presents the same difficulty as trying to combine oil and water to form an optically clear product.
