Rigid Gas Permeable Contact Lenses
Although the most common type of contact lenses worn are soft contact lenses, there are other types of contact lenses available which in some cases may be more suitable. Gas permeable (GP) contact lenses (also known as rigid gas permeable or oxygen permeable lenses) are more rigid than the soft lenses but should not be confused with the original hard contact lenses which were made of PMMA and are now obsolete. The old PMMA lenses did not allow oxygen to reach the eye, which is essential for good eye health.
What Makes GPs Different?
Gas permeable lenses were first introduced in the late 1970s and most now incorporate some silicone in the material. This makes them more flexible than the old PMMA type and, as silicone is oxygen-permeable, oxygen can pass through the new GP lenses making them more comfortable and healthier for the eye. The newest developments now allow more oxygen to pass through the GP lenses than through the soft contact lenses, making them a better option for some patients.
The Pros of Gas Permeable Lenses
GP lenses provide crisper vision overall and can correct some corneal abnormalities which soft lenses cannot. They also retain their shape when you blink and reduce the need to refocus. They do not tear easily like soft contact lenses; in fact they are very durable and are generally only broken if they are stepped on. GP lens materials do not contain water, so proteins and debris from tears do not adhere to gas permeable contact lenses as easily as to soft lenses, making them easier to clean and maintain.
With regular care and cleaning gas permeables will last for several years or until a prescription change becomes necessary, making them a more cost-effective option for some people.
The Cons of Gas Permeable Lenses
GP lenses can be uncomfortable at first and take some time to get used to. You may need to wear your lenses only part-time until you adapt to them. Once the eyes have adjusted, the GP lenses must be worn regularly to maintain comfort levels, or some readjustment time will again be necessary to get comfortable again. Since GP lenses are not available as disposables, they must be cared for consistently to avoid a build up of deposits or an eye infection.
Hybrid Contact Lenses
Hybrid lenses combine a rigid, gas-permeable center with a soft outer ring. This type of lens is thought by many to be the best of both worlds: giving the crisp vision of GP contacts with greater comfort. Versions of this type of lens are now available for a variety of conditions including presbyopia, keratoconus and post surgical use.
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