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J. A. Bonanno, C. Clark, J. Pruitt, L. Alvord; Tear Oxygen Tension Under Silicone-Hydrogel Lenses in Human Subjects. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4846.
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To determine tear oxygen tensions and corneal oxygen flux under steady-state open and closed eye conditions in human subjects while wearing silicone-hydrogel contact lenses.
Tear PO2 was measured for Biomedics, Acuvue 2, Acuvue Advance, Purevision, O2Optix, Acuvue Oasys, Night & Day, and ultrathin Night & Day lenses (-0.50D) with central Dk/t of 17, 27, 85, 124, 137, 166, 226, and 329 x10-9•mlO2•cm-2•s-1•mmHg-1, respectively. The posterior surface only of each lens was coated with BSA-Pd-coproporphyrin, an oxygen quenching phosphorescent dye. Phosphorescent decay rates were measured: 1) in the open eye and 2) following five minutes of eye closure. O2Optix and Night & Day lenses were precoated with polyacrylic acid to allow for BSA binding. Quenching constants for each lens type was determined by coating the anterior surface only, placing on the eye and measuring decay rates with a goggle in place with perfusion of 6.7% O2. Fifteen subjects, who were not wearing contact lenses, participated in the study. O2 flux was calculated assuming ant PO2 of 155 and 55 torr in open & closed eye, respectively.
A plot of oxygen tension vs. contact lens oxygen resistance(t/Dk)indicated a y-intercept (equivalent to no lens) that is consistent with the expected 155 torr for open eye data.
At high Dk/t, in vivo tear oxygen tension under silicone-hydrogel lenses is significantly lower and oxygen flux is higher than that predicted from modeling using available EOP (Equivalent Oxygen Percentage) data.
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