Rigid gas permeable lens are made of-
1. Hard lenses: Made of pokymethylmethacrylate (PMMA) 2. Rigid gas permeable (RGP) lenses: Copolymer of PMMA, silicon containing vinyl monomer & cellulose acetate butyrate (CAB) are used to manufacture RGP lenses. 3. Soft lenses: These are made up of hydroxymethymethacrylate (HEMA)
Plymethymethacrylate
Hydroxymethylmethacrylate
Co polymer of PMMA, Silicon containing monomer & cellulose acetyl butyrate
Cellulose acetae Butyrate