Information on Different Types of Contact Lenses
Since the initial discovery of contact lenses by Leonardo da Vinci, many varieties of contact lenses have been developed and marketed. Today the lens wearers, together with the eye specialist, have many varieties to choose from.
HARD CONTACT LENSES
Made from polymethylmethacrylte (PMMB), commonly known as Plexiglas, hard contact lenses were the first type of contacts commercially available. Hard contacts can be easily inserted and removed. They do not often cause infections, because the material they are made from is resistant to contamination. Hard contacts are relatively inexpensive and easy to care for. So why aren’t they used much today?
Hard contacts are uncomfortable, and they risk damage to the cornea. The cornea is the clear dome in front of the eyeball and it requires oxygen to function properly. Plexiglas lenses do not allow much oxygen to flow to the cornea. Most contact lens wearers and providers seek other options.
GAS PERMEABLE CONTACT LENSES
Gas Permeable contact lenses were introduced in the 1970’s and remained popular through the ‘80’s and ‘90’s. Known as Rigid Gas Permeable (RGP) lenses, these lenses allow greater oxygen flow to your cornea. Due to their rigid nature, there is a period of adjustment before the wearer can feel truly comfortable with RGP lenses. Some Rigid Gas Permeable lenses have been manufactured for extended wear, but it is not recommended by most clinicians. Rigid lenses are easier to care for than soft contact lenses, however soft contact lenses area the most popular type of contact lens.
SOFT CONTACT LENSES
Otto Wichterle invented the hydogel lens in 1951, made of hydroxethyl methacrylyte, a water absorbing plastic. Bausch and Lomb first marketed soft Contact lenses in 1971.
Soft contact lenses are more comfortable than hard lenses. However, they are more difficult to take care of, requiring special cleansers, as they are more susceptible to contamination. People who have dry eye disease cannot wear soft contact lenses. Soft contact lenses are more expensive and less durable than other lenses are. It is the increase comfort that makes them so popular.
DISPOSABLE CONTACT LENSES
Disposable contact lenses are soft contact lenses that are used for a period of time and, as the name implies, are thrown away. These comfortable lenses offer a decrease chance of infection and protein deposits as they are thrown away before contamination occurs. Disposable contact lenses are beneficial to people who are allergic to lens solutions as they are unnecessary. Disposable contact lenses are more costly than other lenses.
BIFOCAL CONTACT LENSES
As the name implies, bifocal contact lenses are prescribed for people who need vision correction for both near and far vision, a condition known as presbyopia. These are available in gas permeable and soft lenses, offered as extended wear and daily wear.
OTHER TYPES OF CONTACT LENSES
Toric lenses treat astigmatism, a change in the normal shape of the eye. Extended wear lenses are available in gas permeable and soft contact lenses and are meant to be worn over night. Contacts are also available in colors for cosmetic purposes.