Corneal Gas Permeable (GP) or Rigid Gas Permeable (RGP) contact lenses are an alternative to soft contact lenses that are made from a hard, oxygen permeable material. GP lenses are currently less popular than soft lenses but offer a number of advantages and are continuing to improve as research and technology advance.
GP contacts are made of a firm plastic material which allows the passage of oxygen through the lens to your cornea and the front surface of your eye - essentially allowing your eye to “breathe”. This increases comfort, health and safety during contact lens wear.
Benefits of GP or RGP Contact Lenses
Because of the strong material and the ability to diffuse oxygen, GP lenses offer a number of advantages over soft contact lenses.
Health and Hygiene Benefits:
Unlike soft lenses, GPs don’t contain water which makes them less likely to attract and breed bacteria that can cause eye infections. Further protein deposits won’t build up on the lens, keeping them cleaner and healthier.
Because they are made with a strong durable material, GP lenses won’t tear and are easy to clean and disinfect. RGPs maintain their firm shape and will not dehydrate. Further GPs last longer than soft lenses - when cared for properly, a pair can last a year or more.
GP contact lenses are custom made for each patient based on the eye’s individual curvature, size, corneal shape. Their ability to transmit oxygen reduces eye problems such as dry eyes caused by reduced oxygen that are common in many brands of soft lenses or hard (non-GP) lenses.
Corneal GP lenses have a smaller diameter than soft contacts, meaning that they cover less of the surface of your eye. While this may take some time getting used to initially, ultimately many find that they are just as if not more comfortable than soft contacts.
Due to the rigid material, GPs have a smooth surface and maintain their shape, moving along with the eye to hold their place. This provides sharp and stable vision. Further they do not dehydrate, which is often a cause for reduced vision with other lenses.
Sometimes gas permeable lenses require soft contact lenses through "piggybacking" to increase visual comfort and clarity.
Because they last so long, GPs are much more cost effective than soft lenses, especially disposable lenses that require a constant supply. Because they are made to order, there is an initial cost investment and they will take up to a week to manufacture if you do need a replacement pair.
GPs for Astigmatism
GP lenses are ideal for individuals with astigmatism that may have been told that they cannot wear soft contacts. Because of the rigid nature of the lens, they hold their shape on the eye allowing for more clear and stable vision correction.
Adapting to GP lenses
One of the downsides of GP contact lenses is that they require an adaptation period, particularly if you are used to soft lenses with a larger diameter. One of the major differences is an experience of “lens awareness” in which you feel the edge of the lens when you blink. It could take up to a few weeks to get used to the lenses but many people report that after this initial period they find that GP lenses are just as if not more comfortable than soft lens varieties.
GP Lenses for Myopia Control and Ortho-K
Research shows that gas permeable lenses might be effective in slowing the progression or worsening of myopia or nearsightedness, particularly in children. They are also used in Orthokeratology (ortho-k), a vision correcting procedure in which you wear the lenses at night to reshape your cornea for improved vision during the day.