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Rigid gas permeable lenses

Soft contact lenses are the most commonly used, but there is another, lesser-known category of contact lens materials: rigid gas permeable (RGP) contact lenses, or oxygen permeable lenses.

RGP contact lenses are rigid, but are not the same as old-style "hard" contact lenses, which were not gas permeable, and are now obsolete. Healthy eyes need plenty of oxygen from the air, hence the need for gas (oxygen) permeability.

RGP lenses can provide better vision, durability, and deposit resistance than soft contact lenses. They can be easier to clean, and since they are long lasting, they can be less expensive in the long term than soft lenses.

Unlike soft lenses, which are instantly comfortable to wear, even after a week of non-use, RGP lenses require an adaptation period before they are comfortable. This means that you will need to wear them regularly, to avoid having to re-adapt after each non-use period.

Some people also experience blurry vision when RGP lenses are removed, even while wearing glasses. This effect is temporary, but it can mean full-time RGP wear is preferable. This can make RGP lenses an all-or-nothing proposition, which some people will find inconvenient.

A small percentage of patients, however, find that they prefer RGP lenses to soft contacts. Because rigid lenses retain their shape on the cornea better than soft lenses, they tend to provide crisper vision to people who have astigmatism. This degree of difference in crispness is not noticeable for most contact lens wearers, but if you're particularly fussy about your vision, you may appreciate it.

Other people for whom RGP lenses can be the answer include:  

• People with presbyopia, because RGP lenses come in numerous bifocal and multifocal designs. Different bifocal designs work well for different people; so having many choices is beneficial. Many people find that the best combination of near and distance acuity is obtained with RGP bifocals.
• People with keratoconus, where the cornea is cone-shaped and causes extreme visual distortion.