ON THE RELATIONSHIP BETWEEN SOFT CONTACT-LENS OXYGEN TRANSMISSIBILITYAND INDUCED LIMBAL HYPEREMIA

The relationship between induced limbal hyperaemia and lens oxygen tra nsmissibility was investigated in a series of clinical studies in whic h subjects wore a range of soft contact lenses for eight hours each. D ata representing the degree of limbal hyperaemia induced in each case was extracted and subjected to non linear regression analysis with hyp eraemia as dependent, and oxygen transmissibility as independent varia bles, Strong, statistically significant associations were found, parti cularly when oxygen transmissibility in a 12 mm diameter annular zone at the lens periphery was considered. Best fitting functions were of a n inverse form for nasal (r(2) = 0.86 P = 0.008) and temporal (r(2) = 0 81, P = 0.014) quadrants and a logarithmic form for superior (r(2) = 0 .87, P = 0.007) and inferior (r(2) = 0.97, P < 0.005) quadrants. Th ese findings provide support for an hypoxic theory of soft contact len s induced limbal hyperaemia, Estimates based on the logarithmic model suggest a 95% confidence interval for the peripheral oxygen transmissi bility required to avoid limbal hyperaemia of 56-274 x 10(-9) (cm s(-1 )) (mlO(2) ml(-1) x mm Hg). (C) 1998 Academic Press.