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Contact Lenses

Contact lenses are a popular alternative to the wearing of spectacles, and are now worn by 8% of those requiring an optical correction. Contact Lenses are worn in the main by the younger generation in the 18 to 40 age group for cosmetic purposes, and those who actively participate in sport, however Contact Lenses are now becoming increasingly more popular with those in the 40 plus age groups who desire the freedom from wearing spectacles frames.

Contact Lenses are virtually invisible whilst being worn as they effectively sit on a thin layer of tear covering the cornea. Because of the fact that they sit so close the surface of the eye they offer the wearer a much wider field of vision than do conventional spectacles because the contact lenses remain central to the filed of vision as the eye moves around and for many people this benefit alone is virtually a dream come true.

Contact lenses fall into two main categories:

Firstly -

Gas Permeable lenses, or as they are Known to the Profession, RGP. These are lenses made from a rigid Gas Permeable material, which allows oxygen to permeate through the tear film on the Contact lens front surface, through the lens material to the surface of the cornea via the tear film on which the lens is floating.

To further aid the flow of oxygen to the surface of the cornea the contact lens is allowed a certain amount of free movement to enable it to move slightly as the eye is closed thus forcing a flow of tear behind the back surface of the lens and across the surface of the cornea behind the Contact lens.

Gas Permeable lenses can be made to a wide specification range and are therefore suitable for Optical correction requirements. The Main disadvantage of “RGP” is that they can take time for the first time wearer to adapt to and they can become “uncomfortable” to wear due to the rigid nature of the lens. Gas Permeable lenses also require a very strict hygiene and cleaning routine and are not really suitable for the casual wearer.

Secondly -

The “Soft” Contact lens, these in themselves fall into many different categories, for example, daily wear disposable, Monthly disposable, Quarterly disposable, and annual replacement Lenses. They all however have one thing in common in that they are all made from special plastics which are known as “hydrophilic”, in other words they are a high water content plastic material which, when manufactured and “hydrated” take up a high content of water into the plastic, rather like a sponge, which effectively converts the material into “say” 39% water, (hence the term 39% soft contact lenses).

Soft contact lenses are now made to suit many types of optical requirements, however due to the inherent instability of the lens, because it is soft, there are limitations, however modern technology has in the past few years dramatically increased the range and availability of these types of lenses.

The Soft Contact Lens, when fitted, floats on a film of tear covering the cornea and also due to the High water content also “soaks up the tear fluid” from around the area of the cornea thus allowing the Free flow of water “and oxygen” to the cornea. As these types of lenses are “Soft” they offer a greater degree of comfort than other types of lenses and are consequently easier to “get used to".


It is important that you take the advise of the Contact Lens Practitioner when choosing Soft Contact Lenses because of the many different hygiene and cleaning regimes involved. It would for example not be advisable to try to extend the use of “Daily disposable” Lenses beyond 24 hours as they are not suitable for any kind of cleaning routines, similarly monthly and Quarterly Disposable should not be used beyond these periods as they are not designed to be durable or stable beyond these periods. The temptations may be great, but Contact Lens practitioners regularly see the results of Patients who have tried to “cheat the system” who present themselves to the practice with sore and red eyes.

There are now also many new types of “Cosmetic” Contact lenses which can be used to change the colour of the eye, or indeed for those of you who may be so inclined you can change the appearance of the eye to make them look like “cats” eyes, or even “happy face” eyes. These types of lenses are designed for casual wear and it is strongly advised to adhere to the very strict storage and cleaning regime with these lenses, as they are not usually recommended for daily use.

In all instances of Contact Lens wear it is “highly recommended” that the wearer stick to the hygiene and cleaning routine recommended by the Contact Lens Practitioner, and follow any advise given as to when to revisit for follow up checks as these visits can give the practitioner early warning of any impending problems related to wearing and the usage of the lenses.

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