<unk> , abbreviated<unk> , is a parameter of a contact lens.  Another parameter,  the transmissibility level, abbreviated <unk> /t; the<unk>  per thickness of the lens, is generally more used.  Typical values are from 25 to 50.  The<unk>  expresses the ability of the lens to let<unk>  reach the eye by diffusion.  In soft contact lenses, it is dependent on the thickness of the lens and the material of the lens, especially concerning the water content.
Oxygen permeability
Blood flow
Ventilation/perfusion ratio
Electrochemical gradient
Volumetric flow rate
Diffusion capacity
Microcirculation
Ammonia production