Definition of RGP Contact Lenses
There are three basic kinds of contact lenses which were developed for those who need vision correction in the following order:
1. The traditional hard contact lenses which were not gas-permeable and were the first type of contact lens produced.
2. The soft contact lens which was first used from 1971 onwards and is still used until the present day.
3. The rigid gas-permeable contact lens which were first introduced in the 1970s and have made the old type of contact lens in 1. above obsolete.
The focus here will be to define and describe the features of rigid gas permeable lenses which are a popular choice for those who need vision correction. They also have certain advantages over soft contact lenses for some users. These will be outlined as well.
A Definition and Description of RGP Contact Lenses
The main feature of rigid gas-permeable lenses is that even though they are made of hard plastic they allow oxygen to pass through them which is important for the health of the cornea of the contact lens user. If the cornea does not get enough oxygen it becomes swollen and cloudy which can lead to blurring of vision. This is not a risk when using rigid gas permeable lenses because as well as allowing oxygen to pass through them they also allow a film of oxygen-rich tears to pass over the cornea each time the RGP lenses wearer blinks. Therefore they ensure a healthy supply of oxygen to the eyes in these two ways.
RGP lenses are made of different materials. The more flexible the material it is made of the more oxygen can pass through it but the less durable it is. However RGP lenses can be made for individuals who wear them for long periods with no ill-effects to the cornea from lack of oxygen.
Advantages and Disadvantages of RGP Contact Lenses
RGP contact lenses have many advantages over soft contact lenses. First of all, RGP lenses last longer and are more durable than soft contact lenses. They are resistant to the build-up of deposits so they are more easily cleaned and maintained than soft lenses.Generally speaking, they give more clarity of vision and they are easier to work with.They are less expensive because they last longer than soft contact lenses.
For people with particular eyesight needs RGP lenses can often be tailored to these needs. For example,RGP lenses work particularly well for those with astigmatism, a condition in which the cornea of the eye is not completely round and the RGP lens can give the cornea a more round shape leading to better vision. This effect is not achieved with soft contact lenses.
RGP lenses can also be used in cases where bifocals are required much in the same way as glasses and they are becoming increasingly popular with those who previously did not need correction of their vision until the onset of presbyopia (natural deterioration of eyesight due to aging) and who do not wish to begin wearing glasses. Bifocal RGP lenses are indeed a practical alternative.
The main disadvantage of RGP lenses is that they are not as comfortable to start wearing as soft contact lenses and they take more time to get used to. More dust and debris is inclined to get under them as they are mobile on the eye causing irritation to the cornea. A third disadvantage is that because they are smaller, they are more easily dislodged from where they should be on the eye.
Although there are a few disadvantages of RGP lenses, the advantages far outweigh them and there are certain eye conditions for which they will be the only thing that works effectively.
Personally speaking, I have the same pair of RGP contact lenses now for about two years and they are still serving me well with little or no maintenance. I have much better vision with them than I have with glasses and because I am used to them (having worn RGP contact lenses full-time and regularly for nearly thirty years) I have no discomfort with them whatsoever except when a bit if dust or debris makes it's way under them which only happens occasionally .
An Innovation:Hybrid Lenses-Soft and RGP
In 2005 a contact lens company called Synergeyes launched an innovative hybrid contact lens which consists of a RGP lens in the middle surrounded by a soft contact lens fringe. This is a way of combining the clarity of vision available from RGP lenses with the comfort of soft contact lenses. There have been further advances in this company and in 2011 they developed a hybrid lens to correct astigmatism and they have also developed a hybrid lens for presbyopia and other eye conditions including lenses for post-surgery.
This is a further advance in the field of RGP contact lenses but many people can still tolerate the initial temporary discomfort of traditional RGP lenses for the long-term gain of improved clarity of vision in everyday use and the fact that RGP lenses have specific value in the management of specific eye conditions cannot be overlooked even in the context of this innovation of hybrid lenses.