Oxygen Permeability of the contact lenses is a very important figure especially in continuous wear contact lenses.
The permeability of oxygen through the lens to the cornea is abbreviated Dk (diffusion coefficient), where “D” is the ability of gas molecules to move within the material and “k” is the amount of gas that will fit in a particular volume. If Dk is less than 20, the permeability is low, between 20 – 49 medium, 49 to 99 is high and over 100 is very high. Material with a medium value of Dk has optimal properties. High oxygen permeability is achieved by silicone-hydrogel contact lenses.