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Types of Contact Lenses:
PMMA lenses made from a rigid plastic material were the original contact lens. They are pretty much obsolete now due to their poor ability to allow oxygen to pass through to the cornea.
Gas-permeable lenses: These lenses are also known as "RGPs." They are newer rigid or "hard" lenses made of plastics combined with other materials, which allow oxygen in the air to pass directly through the lens. Different RGP materials allow varying amounts of oxygen through to the eye.
Replacement Schedule: RGP lenses are usually replaced on an annual basis. However if they are well cared for and maintained they can last for longer periods.
Soft contact lenses: These lenses are made of plastic materials that incorporate water and in some cases silicone. The addition of silicone to contact lens materials allows more oxygen to reach the cornea.
Soft Contact Lens Replacement : Soft contact lenses are available in the following replacement designs depending on the brand.
Daily
Two weekly
Monthly
Three monthly
Annual
Extended wear contact lenses are made of material that is so permeable to oxygen that they are safe to wear even with the eyes close i.e. while asleep.
Replacement schedules for extended wear lenses are usually on a weekly, two weekly or monthly basis depending on the material and manufacturer guidelines.
N.B. Sleeping in contact lenses should only ever be done with approval from your eye care practitioner
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Supplementary prescribing is a voluntary prescribing partnership between an independent prescriber and a supplementary prescriber, to implement an agreed patient-specific clinical management plan with the patient's agreement.
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