Gas Permeable (GP)
What are Gas Permeable Contact Lenses?
Gas permeable contact lenses (GPs) are corrective lenses that are worn directly on the eye. GPs are the primary way to correct for irregular astigmatism, which may be the result of diseases like keratoconus or develop after a cornea transplant or other ophthalmic surgeries. Again the tears fill the space between the lens and the irregular cornea making for a smoother optical surface and crisper vision.
How Do I Clean and Disinfect Gas Permeable Contact Lenses?
Naturally occurring mucous, protein and lipids can accumulate on the lenses in the form of deposits, which can irritate the eyes and can also act as a depot for bacteria. Proper cleaning and disinfecting keeps the lenses free of deposits and bacteria.
There are two main types of lens care products, multi-purpose solution and hydrogen peroxide solution:
- Multi-purpose Solutions have a disinfectant and cleaner conveniently combined in one bottle. The solution is strong enough to kill the most common contact lens contaminants, but not so strong that it irritates the eye. Although multi-purpose solutions advertise that they do not require the wearer to rub the contacts, they do recommend rinsing each side of the contact with the solution for 5 seconds before storing the lenses in their case. Many eye doctors recommend rubbing the contacts because it is more effective and wastes less solution than rinsing. The wearer should put an ample amount of solution in the palm of one hand and gently rub the lens for about 10 seconds with the index finger of the other hand.
- Hydrogen Peroxide Solutions work differently than multi-purpose solutions. In this method, the lenses are disinfected and cleaned with 3‰ hydrogen peroxide. The lenses are stored in a special vial that is designed to neutralize the hydrogen peroxide. It is important to leave the contact lenses in the vial until the hydrogen peroxide has been neutralized. Inserting the contact lenses before the solution is neutralized can cause chemical burns to the eye. The lenses should not be rinsed with the hydrogen peroxide solution prior to insertion. The vials become less effective at neutralizing over time and need to be replaced with each purchase of solution. This method is a good alternative for patients who are sensitive to multi-purpose solutions because after the hydrogen peroxide is neutralized, it is free of disinfectants, preservatives and cleaners.
Advantages & Disadvantages
The advantages of GPs are the stable, astigmatic correction they provide, as well as the fact that they can be more economical over a person's wearing lifetime. The same pair of lenses may last a person several years, even though the initial cost may be a bit more than a soft lens. Additional advantages include:
- Durability –the lenses are not as likely to tear or develop deposits as a soft lens
- Easy to handle –process of getting them in and out of the eye is simple
- Extended wear options –special materials are available that permit up to thirty days of continuous wear
- Stop progression of myopia –data suggests that GPs can slow down the progression of nearsightedness in the developing eyes of children
The biggest disadvantage of a GP lens is its initial comfort. As you can imagine, a rigid piece of plastic in the eye takes more getting used to than a soft. It can take a couple of weeks of consistent wear to become accustomed to how this lens feels in the eye. A small number of patients never find them comfortable. Most patients adapt and can wear the lenses all their waking hours comfortably.
