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RM Hill, BA Fink, TJ Brunstetter, GL Mitchell; Hypoxic Stress with Contact Lenses; Response Differences to the Limiting Case of Dk/t = 0 . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3081.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Since 1981, a range of individual differences centered around the mean oxygen uptake rate first reported by Hill and Fatt (1963) has been known for human corneas under normoxic (N) conditions. Asked here: 1. Does a similar range of individual differences exist for anoxic (A) conditions as well? 2. If so, then does the normoxic (N) condition response of a given cornea predict its anoxic (A) condition response? Methods: Oxygen uptake rates were measured polarographically for 10 right eye corneas, each in response to normoxic (155 mm Hg) and to anoxic (0 mm Hg) oxygen partial pressure conditions for a total of 30 normoxic trials, each paired with 30 anoxic trials (300 sec of on-K static wear with Dk/t = 0 contact lenses). Means and standard deviations for each cornea's response to each condition were calculated, and regression analysis applied to test if the (N) versus (A) slope of this function was significantly different from zero. In addition, a four cell frequency representation analysis of high versus low rating categories was established based on the (A) and (N) response means of the total sample. Agreement (balance of individual cornea responses ) among those categories was compared using an exact McNemars test. Results: 1. A range of anoxic (A) response means was found among human corneas of 19.6 to 27.0 mm Hg/sec; 2. The regression slope for (N) versus (A) rates was not found to be significantly different from zero (p = 0.6766); 3. The four response cells of high and low (N) and (A) combinations were not found to be significantly different in their frequency representations. Conclusion: Human corneas do have a substantial range of mean oxygen uptake rates demonstrable among them to the same oxygen deprivation (here, Dk/t = 0) conditions, but the mean (N) response of a given cornea does not predict its (A) response. Further, Chi square analysis indicated no association (p = 0.6874) or useful predictability for anoxic and normoxic frequency distributions among high versus low response categories.
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