Types of Contact Lens
The first contact lenses were what have become known as ‘hard’ lenses. These are made of a perspex material which, while very durable, does not allow essential oxygen to pass through to the surface of the eye. Although still available for certain specialist needs, they have been largely replaced by gas permeable lenses which allow good oxygen flow and enable the eye to ‘breathe’.
Rigid gas permeable (RGP) lenses
Rigid gas permeable lenses allow oxygen to pass to the surface of the eye, but they are made of firmer plastics than soft lenses. This makes them more durable and gives them a longer life span.
These lenses are particularly suitable for certain prescriptions such as high degrees of astigmatism, where they give very good vision. Some people find rigid lenses easier to handle than soft lenses
and, although they take a little longer to get used to, regular wearers find them very comfortable.
Modern soft contact lenses are made from gel-like plastics, often with a high water content, that allow oxygen to pass freely to the eye. Because of this, soft lenses can be made much larger which
in turn makes them very comfortable and easy to adapt to. Some of the new ultra-thin soft lenses are so comfortable that new wearers can leave them in all day right from the start. New users usually
find that they are only mildly aware of standard thickness soft lenses and that tolerance can be built up fairly easily so that most people are able to wear them all day within a week.
All types of contact lenses are now available on a planned replacement programme. New manufacturing techniques have made it possible for users to have a fresh pair of lenses regularly for about the same cost over a period as non-disposable lenses. Daily disposable lenses are becoming increasingly popular as they eliminate the need for a lens care routine, but depending on the type of lens and the environment in which it will be worn, the replacement period can be anything from one day to two years.
Extended wear lenses
Most contact lenses are worn on a daily basis, being removed in the evening and put back in next morning. Special extended wear soft lenses are now available which may be recommended by your
practitioner, which allow you to sleep in them. Typically they are replaced weekly or monthly.
Exciting tinted contact lenses which can enhance or even change the colour of your eyes without affecting what you see are now widely available.