Gas Permeable Lenses
These are today’s most state-of-the-art “hard” contact lenses.
Hard lenses were made of a material known as PMMA, and before 1971, when soft lenses were introduced, just about all contact lenses were PMMA.
PMMA lenses were difficult to get used to and hence uncomfortable to wear. They also did not allow oxygen to pass through them and hence caused long term complications.
What makes GPs different?
Introduced in the mid 1980s, they are actually a newer technology than soft lenses. They incorporate silicone, which makes them more flexible then PMMA whilst also being more oxygen permeable. This results in greater comfort and better eye health.
GPs can also provide better vision, more durability, and increased deposit resistance than soft lenses. They are also easier to clean, are longer lasting and less expensive in the long term than soft lenses.
The need to adapt.
Soft lenses are more instantly comfortable to wear and so this is why GPs are not everybody’s first choice lens.
Advantages of GPs
Crisper vision than soft lenses due to increased stiffness of material (it retains its shape well when you blink).
Extremely durable (though they can break!!!)
Low deposit adhesion- GP material does not contain water as soft contact lenses do, hence deposits (protein and lipids) from your tears do not bind to the lens material.
Disadvantages of GPs
They take a lot longer to adapt to (compared with soft lenses). Unlike soft lenses, to achieve maximum comfort with GPs, you have to wear them every day.
This is when lenses are removed, vision is a little blurry (temporarily) even while wearing glasses. This can necessitate full time GP wear. Not suitable for many sports due to their rigid nature.