To put it simply, we can start with the oxygen permeability of hard contact lenses. Generally, materials with a DK value greater than 90 are called high oxygen permeability materials:
1. High DK:
Advantages: More breathable and comfortable Disadvantages: Easy to accumulate sediment, the material is soft, so the scrub force should not be too strong
2. Low DK:
Advantages: More durable, not easy to deform Disadvantages: The lens is harder
