Modeling Corneal Metabolism and Oxygen Transport During Contact Lens Wear
Modeling Corneal Metabolism and Oxygen Transport During Contact Lens Wear
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DOI：
10.1097/opx.0b013e31819f9e70
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发表时间：
2009-05-01
影响因子：
1.4
通讯作者：
Radke, Clayton J.
中科院分区：
文献类型：
--
作者：
Chhabra, Mahendra;Prausnitz, John M.;Radke, Clayton J.
目的.为角膜-接触透镜系统开发了一个代谢模型，以阐明葡萄糖代谢在角膜氧合中的作用，并评估接触透镜氧透过率在避免长期佩戴应用中缺氧诱导的角膜异常中的作用。通过角膜和接触透镜系统的氧输送通常通过具有反应性损失的氧扩散来描述。然而，角膜中的氧通过有氧糖酵解（Krebs或三羧酸循环）和厌氧糖酵解与其他代谢物质相互作用，特别是葡萄糖、乳酸根离子、碳酸氢根离子、氢离子和二氧化碳。在这里，角膜有氧和无氧代谢反应被纳入一个六层（内皮，基质，上皮，后透镜泪膜，接触透镜，和前透镜泪膜）稳态连续反应扩散模型，以量化氧运输。我们还定义了一个新的指标，缺氧因子（ODF），用于衡量角膜氧合。与其他现有的缺氧指标不同，ODF是一种局部的、敏感的角膜缺氧程度和严重程度的指标。我们不仅计算了角膜的氧合，还计算了其耦合的葡萄糖、乳酸盐和酸中毒行为。第一次，从有氧到无氧糖酵解的代谢转变被明确地纳入到闭眼接触透镜佩戴时角膜中的氧运输和消耗中。采用酶促Monod动力学的代谢反应允许现实的评估当地物种的浓度在整个角膜。我们发现厌氧产生的乳酸盐从角膜运输到前房，而缓冲性的碳酸氢根离子从前房运输到角膜。角膜代谢中氧与其他活性物质的偶联为了解角膜-接触透镜系统中氧的转运提供了有用的信息。具体地说，我们发现，除了氧气消耗和酸中毒的角膜，乳酸浓度增加，而葡萄糖和碳酸氢盐浓度从内皮细胞向上皮细胞减少。与其他角膜氧合指标不同，ODF对局部缺氧的角膜区域特别敏感。因此，ODF是评估角膜缺氧程度和严重程度的有用生理指标。（Optom维斯科学2009; 86：454 - 466）
Purpose. A metabolic model is developed for cornea-contact-lens system to elucidate the role of glucose metabolism in oxygenation of the cornea and to gauge the role that contact lens oxygen transmissibility plays in avoiding hypoxia-induced corneal abnormalities for extended wear applications.Methods. Oxygen transport through the cornea and contact lens system is typically described by oxygen diffusion with reactive loss. Oxygen in the cornea, however, interacts with other metabolic species, specifically glucose, lactate ion, bicarbonate ion, hydrogen ion, and carbon dioxide via aerobic glycolysis (Krebs or tricarboxylic acid cycle) and anaerobic glycolysis. Here, corneal aerobic and anaerobic metabolic reactions are incorporated into a six-layer (endothelium, stroma, epithelium, postlens tear film, contact lens, and prelens tear film) steady-state continuum reaction-diffusion model to quantify oxygen transport. We also define a new index, the oxygen deficiency factor (ODF), for gauging corneal oxygenation. As opposed to other current gauges of hypoxia, ODF is a local and sensitive measure of both the extent and severity of corneal oxygen deprivation.Results. We calculate not only oxygenation of the cornea but also its coupled glucose, lactate, and acidosis behavior. For the first time, the metabolic shift from aerobic to anaerobic glycolysis is explicitly incorporated into the transport and consumption of oxygen in the cornea on closed-eye contact lens wear. Adoption of enzymatic Monod kinetics for the metabolic reactions permits realistic assessment of local species concentrations throughout the cornea. We find that anerobic-produced lactate transports out of the cornea into the anterior chamber, whereas buffering bicarbonate ion transports into the comea from the anterior chamber.Conclusions. The coupling of oxygen with other reactive species in corneal metabolism provides useful insight into the transport of oxygen in cornea-contact-lens system. Specifically, we find that in addition to oxygen depletion and acidosis in the cornea, lactate concentration increases while glucose and bicarbonate concentrations decrease from the endothelium toward the epithelium. Unlike other indices of corneal oxygenation, ODF is sensitive specifically to regions of cornea with local oxygen deficiency. Accordingly, ODF is a useful physiologic index to assess the extent and severity of hypoxia in the cornea. (Optom Vis Sci 2009;86:454-466)