Contact lenses are usually used as an alternative to spectacles. They are placed directly on the cornea. They can be classified as hard or soft contact lenses. Soft contact lenses are made of flexible hydrophilic ("water-loving") plastics called hydrogels[1].
Hydrogel contact lenses
Hydrogel contact lenses are made from polymers. These polymers contain chains of monomers linked together by cross-linking agents to form a polymer network. Since the cross-linking agents are few, there will be absorption of water and that is why they called hydrophilic. The first and commonest hydrogel contact lenses are made of polyHEMA (2-hydroxy-ethyl methacrylate) cross-linked with ethylene glycol dimethacrylate (EDMA)[2]. PolyHEMA is cheap to produce, highly flexible, stable to changes in pH and temperature. Hydrogels absorb water to keep the lens soft and elastic. Since they are hydrophilic, the water content of various hydrogel lenses can range from approximately 38 to 70 percent. Poly HEMA lenses have a low water content of 38% and this will limit their ability to dissolve and …show more content…
Technological advances permit opportunities for expanding the use of contact lenses in areas that have limited use before. The challenges with these lenses like corneal staining and lipid depositions associated with the incompatibility with contact lens polymers should be eliminated in the future. Contact lens companies are looking for developing novel silicone hydrogel contact lenses and the apparent future for this group of lens materials looks promising. In future, the market will be dominated by the release of silicone hydrogels from all manufacturers. Ideally, such materials would consist of polymers that would resist contamination with pathogenic organisms and reduced inflammatory complications compared with currently available materials and would have a significant impact on growing the contact lens
Hydrogel contact lenses
Hydrogel contact lenses are made from polymers. These polymers contain chains of monomers linked together by cross-linking agents to form a polymer network. Since the cross-linking agents are few, there will be absorption of water and that is why they called hydrophilic. The first and commonest hydrogel contact lenses are made of polyHEMA (2-hydroxy-ethyl methacrylate) cross-linked with ethylene glycol dimethacrylate (EDMA)[2]. PolyHEMA is cheap to produce, highly flexible, stable to changes in pH and temperature. Hydrogels absorb water to keep the lens soft and elastic. Since they are hydrophilic, the water content of various hydrogel lenses can range from approximately 38 to 70 percent. Poly HEMA lenses have a low water content of 38% and this will limit their ability to dissolve and …show more content…
Technological advances permit opportunities for expanding the use of contact lenses in areas that have limited use before. The challenges with these lenses like corneal staining and lipid depositions associated with the incompatibility with contact lens polymers should be eliminated in the future. Contact lens companies are looking for developing novel silicone hydrogel contact lenses and the apparent future for this group of lens materials looks promising. In future, the market will be dominated by the release of silicone hydrogels from all manufacturers. Ideally, such materials would consist of polymers that would resist contamination with pathogenic organisms and reduced inflammatory complications compared with currently available materials and would have a significant impact on growing the contact lens