Oxygen permeability of contact lens materials: a 1993 update

Oxygen permeability of currently marketed hydrogel contact-lens materials is predictable from water content, asituation that has not changed for 30 years. Experimental hydrogels with greater oxygen permeability than expected from their water content have been tested but none are currently marketed. Rigid gas permeable (RGP) materials are very different. In 1993, RGP lenses manufactured from materials of permeability 10E-11 (cm²/sec) (ml O₂/ml × mmHg) up to 200E-11 (cm²/sec) (ml O₂/ml × mmHg) are available to practitioners. The RGP permeability data are more reliable than in previous years because the measurement methods have become standardised and reference materials are available.