Oxygen permeability (OP) is a parameter of a contact lens. OP expresses the ability of the lens to let oxygen reach the eye by diffusion. Another parameter is the transmissibility level (abbreviated DK/t), the Dk per thickness of the lens, and is generally more used. Typical values are from 25 to 50. In soft contact lenses, it is dependent on the thickness of the lens and the material of the lens, especially concerning the water content.
D being diffusivity (cm2/sec)--a measure of how fast the oxygen moves through the material. Note, different sources may use different units: contact package inserts often use cm2/sec, while academic papers may use other values for distance such as mm2/sec.
k being the solubility (ml O2/ml of material x mm Hg)--a measure of how much oxygen is contained in the material. Once again, various sources may use units of different sizes. Do not assume that they're the same unless specified by the source.
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