Contact lenses are the thin lenses that are placed directly on the surface of the eye. They are medical devices used for the correction of eyesight. Contact lenses correct vision better as compared to conventional spectacles so they are preferred over spectacles. Contact lenses are made up of plastic polymer. Depending upon the type of lens the raw material differs. Like hard contact lenses are made of some variant of polymethyl methacrylate (PMMA) and soft contact lenses are made of a polymer such as poly hydroxyethyl methacrylate (pHEMA) which has hydrophilic qualities, means it can soak up water but still retain its shape and other optic functions.
There are two categories of contact lenses-soft and rigid contact lens. Soft contact lenses are soft and flexible which allow oxygen to pass through to the cornea. Soft contact lenses are easier to adjust and are more comfortable as compared to rigid gas permeable lenses. Soft lenses materials are made up of silicone-hydrogels that provide more oxygen to the eyes while wearing the lens. On the other hand rigid gas permeable contact lenses are very much durable and resistant to dust; also they give a clearer rand crisper vision. They last longer than soft lens so they tend to be less expensive over the life of the lens. Rigid gas permeable lenses are easier to handle and are less likely to tear. But despite of its several benefits, they are not as comfortable initially as soft contacts and it may take a few weeks to adjust to these lenses.
Last date updated on September, 2014