Monthly lenses - Contact lenses with the most common wearing period
Monthly lenses can be worn for a month. It exists one difference of this monthly lenses between the material: hydrogels and silicone hydrogels and affects on the number of hours of possible daily wearing time.
Hydrogels as monthly lenses consist of water and hydrophilic polymer. The most well-known are Omafilcon oder Ocufilcon. In contrast to the silicone hydrogels, polymer are not oxygen permeable. The monthly lenses carry oxygen through water by diffusion. It follows that in the monthly lenses of hydrogel lenses, the oxygen permeability is higher, the more water fraction contains the monthly lens. Among the best known monthly lenses of this type include inter alia Focus Visitint from Alcon (formerly Ciba Vision), SofLens 59 from Bausch+Lomb or Biomedics 55 UV from Cooper Vision.
Monthly lenses as silicone hydrogels a re suitable for multi-day wearing (overnight). This requires a high oxygen permeability. Balafilcon ist f.E. a silicone hydrogels material. In contrast to hydrogel lenses silicone hydrogel containing hydrophobic highly oxygen-permeable silicone polymers, which allow a continuous wearing of up to 30 days and nights. Monthly lenses with silicone hydrogels material are inter alia Pure Vision 2 HD from Bausch+Lomb, Air Optix Aqua from Ciba Vision or Biofinity from Cooper Vision.