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B.A. Fink, A. Barber, G.L. Mitchell, R.M. Hill; Effect of Rigid Gas Permeable Contact Lens Transmissibility and Wearing Duration on Corneal Oxygen Uptake . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3677.
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Purpose: When the human cornea is hypoxically stressed by the wear of polymethylmethacrylate contact lenses, two modes of oxygen uptake are demonstrated—a rapid increase in oxygen uptake with increasing duration of wear up to 90 s of lens wear, followed by a more gradual increase in oxygen uptake with increasing duration of wear for longer wearing durations. After 300 s of lens wear, oxygen uptake rate is 6.5x that of the normal open eye. The purpose of this study is to determine the extent and time course for the increase in corneal oxygen uptake associated with the wear of rigid gas permeable contact lenses. Methods: Corneal oxygen uptake rates were measured for the central cornea of nine human subjects with a Clark-type polarographic electrode. Measurements were made for the normal open eye, as well as following the static (non-blinking) wear of a rigid gas permeable contact lens (Dk = 30) for the following periods of time: 90, 180, 270, 360, 450, and 540 seconds. Measurements were randomized and repeated twice. Repeated measures ANOVA with appropriate adjustment for multiple comparison was performed to compare the means. Results: There was a significant jump in oxygen uptake relative to that of the normal open eye between time 90 s and 180 s (p<0.0001). There was also a significant increase between time 180 s and times 450 s (p=0.04) and 540 s (p=0.0006). The oxygen uptake rate following 540 s of lens wear was 2.9x that of the normal open eye. Conclusions: The increase in corneal oxygen uptake with duration of contact lens wear is less rapid and reaches lower final values than that associated with the wear of polymethylmethacrylate contact lenses. Proximal tissue, tear, and contact lens reservoirs appear to play a role in moderating the hypoxic stress following periods of rigid gas permeable contact lens wear.
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