Pournaras C J, Roth A, Munoz J L, Abdesselem R
Clinique Universitaire d'Ophtalmologie, H.C.U. Genève.
Klin Monbl Augenheilkd. 1990 Jun;196(6):475-80. doi: 10.1055/s-2008-1046227.
Transretinal pO2 profiles were recorded during normoxia and hyperoxia in normal and ischemic retinal regions in anesthetized miniature pigs, using double-barrelled recess-type microelectrodes. In normoxia and hyperoxia, pO2 in the normal region decreased from the inner retina and the choroid toward the midretina, indicating that the choroid cannot supply O2 to the entire normal retina. Preretinal and transretinal pO2 measurements in ischemic regions following laser occlusion of a retinal branch vein showed that in normoxia the direction of pO2 gradients prevents O2 diffusing from the choroid to reach the inner retina. This explains why the ischemic regions remain hypoxic. On the contrary, during hyperoxia the intraretinal pO2 gradient indicates an O2 flux from the choroid to the inner retina, resulting in a marked increase in preretinal pO2 in the affected regions. Hence hyperoxia could be a useful tool for restoring the oxygen supply to the inner, hypoxic retinal layers; unfortunately it cannot be used in clinical practice. Parabulbar injections of dexamethasone induce a transitory increase in preretinal pO2, probably by reducing the outer retinal consumption of O2 and thus allowing O2 which diffuses through the choroid to reach and restore the inner retinal hypoxia; clinical experience has shown that parabulbar dexamethasone injections may be effective in the treatment of venous branch occlusion.
使用双管凹型微电极，在麻醉的小型猪的正常和缺血视网膜区域，记录常氧和高氧状态下的经视网膜氧分压（pO₂）分布。在常氧和高氧状态下，正常区域的pO₂从视网膜内层和脉络膜向视网膜中层降低，这表明脉络膜不能为整个正常视网膜提供氧气。视网膜分支静脉激光闭塞后，对缺血区域进行视网膜前和经视网膜pO₂测量显示，在常氧状态下，pO₂梯度方向阻止氧气从脉络膜扩散至视网膜内层。这就解释了为什么缺血区域会持续缺氧。相反，在高氧状态下，视网膜内pO₂梯度表明有氧气从脉络膜流向视网膜内层，导致受影响区域的视网膜前pO₂显著增加。因此，高氧可能是恢复缺氧视网膜内层氧气供应的有用工具；不幸的是，它不能用于临床实践。球周注射地塞米松可使视网膜前pO₂短暂升高，可能是通过减少视网膜外层的氧气消耗，从而使通过脉络膜扩散的氧气能够到达并缓解视网膜内层缺氧；临床经验表明，球周注射地塞米松可能对治疗视网膜分支静脉阻塞有效。
