Friedman M H
Biophys J. 1973 Sep;13(9):890-910. doi: 10.1016/S0006-3495(73)86033-3.
The unsteady response of the rabbit cornea to the normal periodic variations in tear tonicity which accompany the sleep-wake cycle is examined quantitatively in terms of a physical description of corneal mechanics and transport. Two different sets of experimental epithelial and endothelial flow conductivities and reflection coefficients are used, and the effect of variations in epithelial solute permeability and sodium pump rate is examined. The use of a set of experimental corneal parameters chosen earlier provides good agreement between calculated and observed in vivo corneal thickness dynamics when the tear tonicity is within the physiologic range. The factors affecting the time-course of corneal thickness dynamics are discussed, including the osmometric quality of the corneal stroma, the role of the epithelial sodium pump, the flow resistance of the limiting corneal layers, and cyclic changes in aqueous tonicity. The unsteady solutions presented here are related to the steady-state solutions given in earlier papers through the concept of the time-average steady state. Any realistic description of the normal in vivo cornea must recognize its unsteady character and the potential for transepithelial flow. On the average, the hypertonicity of the tears relative to the stromal fluid can be sufficient to account for rabbit corneal deturgescence. The absence of endothelial "pumping" from the in vivo rabbit cornea cannot be proven; neither is there any certain need to postulate such transport in the normal state.
根据角膜力学和物质运输的物理描述，对兔角膜在睡眠-觉醒周期中伴随的泪液张力正常周期性变化的非稳态反应进行了定量研究。使用了两组不同的实验性上皮和内皮流动传导率及反射系数，并研究了上皮溶质通透性和钠泵速率变化的影响。当泪液张力处于生理范围内时，使用一组先前选择的实验性角膜参数，计算得到的和观察到的体内角膜厚度动态变化之间具有良好的一致性。讨论了影响角膜厚度动态变化时间进程的因素，包括角膜基质的渗透性质、上皮钠泵的作用、角膜限制层的流动阻力以及房水张力的周期性变化。这里给出的非稳态解通过时间平均稳态的概念与早期论文中给出的稳态解相关。对正常体内角膜的任何现实描述都必须认识到其非稳态特征和跨上皮流动的可能性。平均而言，相对于基质液，泪液的高渗性足以解释兔角膜的消肿。无法证明体内兔角膜不存在内皮“泵吸”作用；在正常状态下也没有必要假定这种运输。
