There are three types of contact lens materials:
- Soft lenses – made from soft gel-like plastic, known as either hydrogel or silicone hydrogel
- Hard (PMMA) – the original lenses, which are not readily used these days
- Gas permeable lenses
Gas permeable contact lenses are known as GP contact lenses. They are firm or rigid and made from durable plastic that transmits oxygen.
Benefits of GP lenses:
- A sharp and clear vision for all prescriptions
- Retain shape when you blink
- Easy to care for
- Less chance of infection – They don’t contain water like soft lenses, so more resistant to deposits and bacteria
- Healthy for your eyes
- Don’t tear easily like soft contact lenses
- Good value – if you look after them, they can last over a year
GP contact lenses are also particularly good for people with high astigmatism. If you have keratoconus, which is when you have a cone-shaped cornea, GP lenses are very effective at correcting your vision.
Specially designed GP lenses are also used to wear whilst sleeping, with the aim of gently reshaping your cornea a process called OrthoK. You remove these lenses in the morning, leaving you lens and glasses-free all day.
Both soft and rigid contact lenses, like GP lenses, provide long term comfort. However soft lenses provide better initial comfort and therefore seem to be more popular than GP lenses. GP contact lenses require regular wear and time for adaptation.