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Sho C. Takatori, Clayton J. Radke; A Quasi-2D Model For Oxygenation Of The Cornea With Contact-lens Wear. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6523.
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The peripheral cornea is about 40% thicker than at the center; soft-contact-lens (SCL) thickness may vary over 100 micrometers across its lateral dimension. To quantify the significance of cornea/SCL thickness variations on local oxygen demand, we develop a quasi-two-dimensional (2D) oxygenation model that accounts for aerobic and anaerobic metabolism and bicarbonate buffering.
Since metabolism is critical to corneal respiration, we extend the one-dimensional (1D), six-layer oxygen-metabolic model of Chhabra et al. (2009). About 99.6% of diffusion flux occurs normal to the cornea/SCL surfaces with essentially no lateral diffusion. Accordingly, we adopt the 1D reactive-diffusion metabolic model but apply it locally along the cornea/SCL extent. This "quasi-2D" approximation permits 2D assessment of oxygen consumption including the effects of respiratory metabolites carbon dioxide, glucose, and lactate, bicarbonate, and hydrogen ion.
Figure 1 illustrates the importance of the quasi-2D respiration model to provide quantitative spatial resolution of corneal hypoxia. For a SCL with harmonic Dk/L of 56.4 hBarrer/cm, the open-eye, peripheral stroma is anoxic, whereas central and harmonic mean locations have 25 mmHg and 15 mmHg of oxygen supply available, respectively. These results accentuate the shortcomings of previous 1D models that neglect both respiration kinetics and radial-thickness variations. Our quasi-2D model not only predicts 2D oxygen concentration profiles but also profiles of carbon dioxide, glucose, and lactate, bicarbonate, hydrogen-ion for any cornea/SCL shape or transmissibility with minimal computation time.
The new quasi-2D respiration model indicates that both radial-thickness variations and respiration kinetics are critical for assessing the physiological performance of SCLs, especially near the lens periphery.
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