Gas Permeable (GP) Contact Lenses
Gas Permeable (GP) Contact Lenses
Gas permeable (GP) contact lenses, also known as rigid gas permeable (RGP) lenses, are rigid contacts made of silicone-containing compounds that allow oxygen to pass through the lens material to the eye. Though not as popular as soft contact lenses, GP lenses offer a number of advantages.
Advantages of Gas Permeable Lenses
GP lenses allow your eyes to “breathe.” Getting oxygen to the eye reduces the risk of problems caused by hypoxia (reduced oxygen supply). Because GP lenses are made with oxygen-permeable silicone, they allow more oxygen to reach the front surface of the eye than traditional hydrogel soft contact lenses. (However, many of the new silicone hydrogel soft contact lenses are comparable to GPs for oxygen delivery.)
GP lenses provide sharper vision. Because they maintain their shape on the eye, GP lenses provide sharper vision than soft lenses, which can fluctuate in shape. And gas permeable lenses don’t contain water, so they are not prone to drying out. Many soft lenses contain a large percentage of water and will compromise vision if they start to dry out.
GP lenses last longer. GP lenses are rigid, so there’s no worry about ripping or tearing them. They are also easier to keep clean and don’t need to be replaced frequently like soft lenses. With proper care, a single pair of GP lenses can last a year or longer. Since they’re long-lasting, GP lenses can be less expensive than soft lenses in the long run.
GP lenses can slow the progression of nearsightedness. GPs used for overnight orthokeratology – also called corneal reshaping, or ortho-k – have been shown to reduce the progression of myopia (nearsightedness) in some children. Overnight ortho-k also enables clear daytime vision without the use of glasses or contacts.
GPs are great for multifocal designs and problem corneas. Many wearers feel that GP multifocals offer superior vision to soft bifocals. GPs are also the most common choice for eyes that have been compromised by corneal diseases, or for people who still need vision correction after refractive surgery such as LASIK.
The Downside of GP Contact Lenses
So why doesn’t everyone wear GP lenses? Potential disadvantages of GP lenses (compared with soft lenses) include:
Need for adaptation. Unlike wearing soft lenses, which are immediately comfortable, you may need a few weeks before you can wear GP lenses comfortably all day. Initially, you may be able to wear the lenses only a few hours daily until your corneas adapt to them. But if you can tough it out for those first few days, you may be pleasantly surprised at how comfortable GP lenses become.
Inability to wear part-time. To fully adapt to GP lenses and to stay comfortable wearing them, you have to wear them every day. If you stop wearing them for several days, you will be more aware of the lenses on your eyes and you’ll have to re-adapt to the lenses.
Increased possibility of dislodging. Because they are smaller than soft lenses, gas permeable lenses can dislodge from your eyes during contact sports or if you rub your eyes aggressively.
Vulnerability to sand and dust. GP lenses don’t conform to the shape of your eye like soft lenses do, so it’s possible for sand or dust to get under your lenses at the beach or on a windy day. (You can minimize this risk by wearing wrap-style sunglasses outdoors.)
Higher initial and replacement costs. Unlike soft lenses, which come in off-the-shelf sizes, GP lenses are always custom-made to the shape of your eye. This makes GP lenses more expensive to purchase, and to replace if you lose them. Also, it can take up to a week to get a GP lens replaced. So it’s a good idea to purchase a spare pair to avoid the inconvenience of being without your GP lenses if you lose or break one.
Hybrid Contact Lenses
Since comfort is the primary barrier to GP use, an interesting innovation is the hybrid contact lens. These lenses have a GP center, surrounded by a soft lens “skirt.” The goal of hybrid lenses is to provide the clarity of a gas permeable lens and wearing comfort of a soft lens.
Call for More Information and a Trial Fitting
To see if gas permeable lenses are right for you, call our office for more information and to schedule a trail fitting.