Haugh L M, Linsenmeier R A, Goldstick T K
Department of Biomedical Engineering, Northwestern University, Evanston, IL 60208.
Ann Biomed Eng. 1990;18(1):19-36. doi: 10.1007/BF02368415.
To better understand oxygen utilization by the retina, a mathematical model of oxygen diffusion and consumption in the cat outer, avascular retina was developed by analyzing previously recorded profiles of oxygen tension (PO2) as a function of retinal depth. Simple diffusion modelling of the oxygen distribution through the outer retina is possible because the PO2 depends only on diffusion from the choroidal and retinal circulations and on consumption within the tissue. Several different models were evaluated in order to determine the best one from the standpoints of their ability to represent the data and to agree with physiological reality. For the steady state one-dimensional diffusion model adopted (the special three-layer diffusion model), oxygen consumption was constant through the middle layer and zero in the layers near the choroid and near the inner retina. On the average, the oxygen consuming layer, as found by nonlinear regression for each profile, extended from about 75% to 85% of the retinal depth from the vitreous. This is a narrow band through the mid-region of the photoreceptors. Oxygen consumption of the entire avascular retina, determined from fitting eight PO2 profiles measured in light-adapted retinas, averaged 2.7 ml O2(STP)/(100 g tissue.min), while the value determined from fitting thirty-two PO2 profiles measured in dark-adapted retinas averaged 4.4 ml O2(STP)/(100 g tissue.min). Consumption in the light was thus only 60% of that in the dark. This suggests that the outer retina is at greater risk of hypoxic injury in the dark than in the light, a finding of considerable clinical significance.
为了更好地理解视网膜对氧气的利用情况，通过分析先前记录的氧分压（PO2）随视网膜深度变化的曲线，建立了猫的无血管外层视网膜中氧气扩散和消耗的数学模型。通过外层视网膜对氧气分布进行简单扩散建模是可行的，因为PO2仅取决于脉络膜和视网膜循环的扩散以及组织内的消耗。为了从数据表示能力和符合生理现实的角度确定最佳模型，对几种不同的模型进行了评估。对于所采用的稳态一维扩散模型（特殊的三层扩散模型），氧气消耗在中间层是恒定的，而在靠近脉络膜和靠近视网膜内层的层中为零。平均而言，通过对每个曲线进行非线性回归发现，耗氧层从玻璃体算起延伸至视网膜深度的约75%至85%。这是一个穿过光感受器中间区域的窄带。根据对在明适应视网膜中测量的8条PO2曲线进行拟合确定的整个无血管视网膜的氧气消耗平均为2.7 ml O2（标准温度和压力）/（100 g组织·分钟），而根据对在暗适应视网膜中测量的32条PO2曲线进行拟合确定的值平均为4.4 ml O2（标准温度和压力）/（100 g组织·分钟）。因此，明视觉下的消耗仅为暗视觉下的60%。这表明外层视网膜在黑暗中比在明亮环境中面临更大的缺氧损伤风险，这一发现具有相当大的临床意义。
