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Home » Eye Care Services » Eye Library & Vision Quiz » Contact Lenses » Gas Permeable (GP) Contact Lenses

Gas Permeable (GP) Contact Lenses

Gas permeable (GP) contact lenses, oxygen to pass through the lens material to the eye. GP lenses offer a number of advantages over soft lenses.

Advantages of gas permeable lenses

  • GP lenses allow your eyes to "breathe" better. GP lenses allow more oxygen to reach the front surface of the eye. This reduces the risk of eye problems caused by hypoxia (reduced oxygen supply). Gas permeable lenses provide a better oxygen supply than most soft lenses because:
    • The silicone-containing lens materials of GP lenses are more permeable to oxygen than many soft lens materials (though new "silicone hydrogel" soft lenses are comparable to GPs in oxygen transmission).
    • GP lenses are smaller in diameter than soft lenses, so they cover up less of the front surface of the eye (the cornea).
    • Gas permeable lenses hold their shape and move on the eye with each blink. This movement pumps oxygen-containing tears under the lens. Soft lenses conform to the shape of the cornea and have only minimal movement with blinks, so little or no tears circulate under soft lenses.
  • GP lenses provide sharper vision. Because they are custom-machined to a smooth surface and maintain their shape on the eye, GP lenses provide sharper vision than soft lenses, which can fluctuate in shape and clarity if they start to dry out. Gas permeable lenses also provide a more stable and accurate correction of astigmatism.
  • 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. And since they're long-lasting, GP can be less expensive than soft lenses in the long run.
  • GP lenses may slow the progression of nearsightedness. In addition to their other advantages, some research suggests that wearing gas permeable lenses may slow the progression of myopia (nearsightedness) in some children. GPs are also used for orthokeratology, where specially designed contacts are worn during sleep to reshape the cornea and improve vision.

The downside of GP contact lenses

Why doesn't everyone wear GP lenses?

  • Need for adaptation. Soft lenses have the advantage that they are comfortable right from the start.  It may take a few days to fully adjust to these lenses and once you do, you will realize that they are comfortable (some say even more comfortable than soft lenses because the gas permeable don't dry out as soft lenses will) and their vision is noticeably clearer.
  • Increased possibility of dislodging. Rarely, gas permeable lenses can dislodge from your eyes during contact sports or if you rub your eyes aggressively.
  • Higher lens replacement costs. Soft lenses come in limited parameters, essentially what the manufacturer chooses to make.  GP lenses are custom-made to the shape of your eye. This makes GP lenses slightly more expensive to replace if you lose them.  Since they are custom made for each individual's eyes as opposed to mass made, it will take several days to get them.  We can have them next day air, but many people find that it is a good idea to have a spare pair (like a tire in your trunk in case you get a flat) to avoid the inconvenience of being without your GP lenses if you lose or break one.

Best of both worlds?

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 that rivals that 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 trial fitting.