Soft Contact Lenses – Materials, Manufacturing, and Screening Practice Test

The main idea is how oxygen moves into the lens material. Oxygen transport through a polymer depends on two properties: how fast molecules diffuse (diffusion coefficient) and how much oxygen can dissolve into the material at a given partial pressure (solubility). The symbol K in this context represents that solubility: it’s the amount of oxygen that dissolves in the material per unit of ambient oxygen pressure. In practical terms, C_O2 = K × P_O2, where C_O2 is the concentration of dissolved O2 and P_O2 is the surrounding oxygen partial pressure. This solubility combines with diffusion to yield the overall permeability P = D × K. So K specifically reflects how soluble oxygen is in the lens material, not the rate of diffusion, the driving pressure, or a generic “coefficient of movement.”