Hard contact lenses are made of a hard plastic material. This material is called polymethyl methacrylate which is often known as PMMA. The material of hard contact lenses is different from that of soft contact lenses because soft contact lenses contain a lot of water while hard contact lenses does not. Therefore these hard contact lenses don't allow oxygen to reach the eyes, so many people find them uncomfortable to wear.
Hard contact lenses are made of PMMA (polymethyl methacrylate) polymer. The advantages of hard contact lenses are: difficult to change, longer life, easier cleaning and maintenance. The disadvantages are: less comfortable to wear, long adaptation period. The rigid gas-permeableï¼ˆRGPï¼‰is very common, it is made of flexible colloidal material, it has all the advantages of hard contact lenses, and has a higher rate of oxygen permeability, but the price is relatively high.