Polymers in contact lens applications. V. Design and calibration of a technique for “dissolved” oxygen permeability measurements

The importance of ‘ in vitro ’ measurements of ‘dissolved’ oxygen permeabilities of polymers for use in contact with the cornea (as in contact lenses) is discussed and a description given of the design and calibration of a technique suitable for the measurement of oxygen permeabilities in both the ‘dissolved’ (i.e. the transport of oxygen across a membrane separating two aqueous phases) and ‘gaseous’ (in which the membrane separates two gas phases) states. By the use of a thin film of hydrophobic but highly oxygen permeable polymer even very fragile high water content hydrogels can be supported and studied. Sources of error are discussed together with the conflicting literature values for the oxygen permeability of poly(2‐hydroxyethyl methacrylate) hydrogels. On the basis of the present work a value of 75 × 10 −10 cm 3 (STP) mm cm −2 s −1 cm −1 Hg is suggested for the ‘dissolved’ oxygen permeability of this polymer at 25 °C.