Equivalent oxygen percentage (EOP) technique: a standard calibration curve.

Between different oxygen concentrations (mixed with nitrogen) ranging from 0 to 21% were passed over the corneas of six subjects for 5 min. The resulting corneal oxygen responses were measured by polarography. The averages of these responses were used to calculate a "relative oxygen uptake response" (ROUR) value for each oxygen percentage. Analysis of these ordered pairs revealed a curvilinear relation which was best described by a third order equation; marked linearity was demonstrated in the middle of the oxygen range. The use of this third order equation as a "standard" or "average" equivalent oxygen percentage (EOP) calibration equation is suggested.