Although contact lenses are made of a variety of plastics, they can be divided into two groups: soft or rigid gas permeable.
Soft contacts can comprise up to 80 percent water and as a result are comfortable to wear.
Rigid gas permeable (RGP) contact lenses take some getting used to, but last longer and are less susceptible to the build-up of deposits. While they’re more expensive initially, they tend to cost less because they last longer. Also, some people find their vision is crisper with RGP lenses.
Conventional soft contacts can last for about a year, while conventional RGP contacts can last for several years.
So-called replacement contacts need to be replaced every two months or so, while disposable lenses must be replaced every few days.
Other types of lenses available include:
- Bifocal lenses, which work in much the same way as bifocal glasses, allowing you to read as well as do things that require seeing further, such as driving;
- Toric lenses, which correct astigmatism;
- Novelty lenses, which feature a dazzling variety of designs, from sports team logos to cat’s eyes and radiation symbols.