Contact lenses are one of the most popular forms of eyesight correction. It has been estimated that there are greater than 3.3 million people in the UK alone wearing contact lenses (The Association of Contact Lens Manufacturers). Contact lenses are used to correct short sightedness (myopia) and long sightedness (hypermetropia), and there are also lenses available for astigmatism and presbyopia. After an eye examination you will be checked to see if your eyes are suitable for contact lenses, and all being well will fit the lenses. The optician will check to see if your tears are good quality to ensure that the lenses are kept lubricated. The optician will also measure the size of your cornea, the pupil and the position of your eyelids to ensure the correct size lenses are fitted.
Contact lenses generally fall into two categories, hard and soft. The contact lenses themselves are held in place by the tears in the eye between the lens and the cornea, the front of the eye. Most contact lenses are worn on a daily basis and should not be worn overnight. Your optician may advise you whether it is safe to wear lenses when sleeping but always check if you are not sure.
Soft Contact Lenses
Soft contact lenses are made from oxygen permeable plastics. They contain between 30 and 40 per cent water and are very pliable, comfortable to wear, as well as being easy to fit.
Astigmatism (the shape of the cornea causes distorts the 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.
The first contact lenses that were developed were hard lenses. These lenses didn’t allow for oxygen to pass through the lens to the cornea. These lenses needed to be very small to leave as much cornea uncovered as possible so they could easily fall out especially when blinking. These lenses are still available for certain specialist needs, however they have largely been replaced by rigid gas permeable lenses.
Rigid Gas Permeable (RGP)
These lenses combine the functions of both hard and soft lenses. These lenses are firmer than soft lenses, but are made of an oxygen permeable plastic. RGP lenses last longer than soft lenses and are quite 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.
Disposable contact lenses have become very popular these days, 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 comparable to other lenses. They are usually not 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.