EOP and Dk/L: the quest for hyper transmissibility

The relationship between human equivalent oxygen percentage (human EOP) and oxygen transmissibility (Dk/L) was examined for 28 parallel- and nearly parallel-surfaced contact lenses having oxygen transmissibilities ranging from 14.2 to 134.4 Dk/L units as determined with a gas-to-gas method. EOP and Dk/L were positively related such that increases in Dk/L led to progressively smaller increases in human EOP, until Dk/L asymptoted at an EOP of approximately 20 percent. Human EOPs were semi-logarithmically correlated to Dk/L in a linear fashion (R2 = 0.95), though the semi-logarithmic linear equation didn't as closely predict the expected EOP vs. Dk/L curve at its extreme ends. Classifications of oxygen transmissibility and permeability were also standardized into ranges of equivalent oxygen percentage: contact lenses of low, medium, high, super, and hyper transmissibility and materials of low, medium, high, super, and hyper permeability were defined. While most available hydrogel lenses and materials are currently limited by their water contents to the low and medium Dk/L and Dk groups, some available rigid lenses and materials have attained super-Dk/L and hyper-Dk status. They should be better able to be fitted to the individual eye and to incorporate more complicated optical corrections, having partially alleviated dependency of corneal oxygen supply on lens design. The quest for hyper-permeable materials stable in thinner designs may produce lenses of hyper transmissibility with corneal oxygen supply nearly insensitive to lens design, as variation of thickness over lens apertures will then result in alterations of corneal oxygenation (EOP) having minimal clinical significance.(ABSTRACT TRUNCATED AT 250 WORDS)