Rigid gas permeable lens are made of-: (A) Plymethymethacrylate, (B) Hydroxymethylmethacrylate, (C) Co polymer of PMMA, Silicon containing monomer & cellulose acetyl butyrate, (D) Cellulose acetae Butyrate
Answer is C. 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)