The "L" in Dk/L.
We measured the Dk (oxygen permeability) of one specific hydrogel contact lens material (phemfilcon A, nominally 38% water content and ionic) by use of the conventional single chamber polarographic technique at 35 degrees C. When corrected for the boundary and edge effect, Dk was found to be 13 x 10(-11) cm2 ml O2/s ml mm Hg. (These units will be used for this term throughout the remainder of this report.) We also used the polarographic cathode as a model cornea to measure the Dk/L (oxygen transmissibility) of 7 powered contact lenses (-5 to +15 D) made from the same material by the same manufacturer. We found values ranging from 5 to 15 x 10(-9) cm ml O2/s ml mm Hg. (These units will also be used for this term throughout this report.) From analysis of these data, we found that any reasonable model (of the several previously proposed) for L could be used to predict the polarographically measured oxygen transmissibility of the low minus (-5 to -1 D) powered contact lenses, but that plus powered lenses, at least on this measurement apparatus, give Dk/L values that are closer to predictions based on the observed Dk and central thickness rather than any version of average thickness.
Weissman
B A
BA
Jules Stein Eye Institute, University of California School of Medicine, Los Angeles.
Pham
C
C
D003261:Contact Lenses; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D010100:Oxygen / Q000378:metabolism*; D011048:Polarography; D011092:Polyethylene Glycols
D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols; D010100:Oxygen