Contact Lenses
Gas contact lenses.
HARD LENSES
Hard Lenses
When contact lenses were first developed they were hard lenses. These lenses didn’t allow for oxygen to pass through the lens to the cornea. As they needed to be very small to leave the cornea uncovered as much as possible, they could easily fall out especially when blinking. Although these are still available for certain specialist needs they have largely been replaced by rigid gas permeable lenses.
DISPOSABLE LENSES
Disposable lenses are very popular especially with those who have a busy lifestyle. There is no need to look after the lenses as they are replaced each day with new lenses and the old lenses are thrown away. It is also means you do not have to worry about losing a lens. The cost of disposable lenses is very comparable to other lenses. They are often not any more expensive than non-disposable lenses. Your optician will advise you how often you need to replace the lenses. This can vary from daily replacement to a much longer period
RIGID GAS PERMEABLE (RGP)
Rigid Gas Permeable (RGP)
These lenses combine the functions of both hard and soft lenses. These are firmer than soft lenses but are made of oxygen permeable plastic. RGP lenses usually last longer than soft lenses and are very hard-wearing. Some prefer to wear these lenses as they are easier to handle than soft lenses. People with a high level of astigmatism are often prescribed RGP lenses. Once a person has got used to the lenses they are generally just as comfortable to wear as soft lenses.
SOFT CONTACT LENSES
Soft Contact Lenses
Soft lenses are made from oxygen permeable plastics which become pliable during manufacturing. They contain between 30 and 40 per cent water and are very comfortable to wear, as well as being easy to fit.
Astigmatism, where the shape of the cornea causes distorted eyesight, can be treated with ‘toric’ contact lenses. Bifocal contact lenses are used to treat presbyopia, when a person has difficulty seeing close up particularly when reading. This condition was traditionally treated by wearing reading glasses for close up tasks but now bifocals ensure the person can see objects in the distance and as well as for reading.