Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1855 West Taylor Street, Chicago, IL 60612, USA.
Graefes Arch Clin Exp Ophthalmol. 2012 Mar;250(3):361-7. doi: 10.1007/s00417-011-1859-6. Epub 2011 Nov 19.
Oxygen delivery from the retinal vasculature plays a crucial role in maintaining normal retinal metabolic function. Therefore, measurements of retinal vascular oxygen tension (PO(2)) and PO(2) longitudinal gradients (gPO(2)) along retinal blood vessels may help gain fundamental knowledge of retinal physiology and pathological processes.
Three-dimensional retinal vascular PO(2) maps were generated in rats by optical section phosphorescence lifetime imaging. A major retinal artery and vein pair, and a smaller blood vessel (microvessel) between them were segmented, and PO(2) along each blood vessel was measured. In each blood vessel, an average PO(2) (mPO(2)) was calculated, and gPO(2) was determined by linear regression analysis. Reproducibility of measurements was assessed by calculating intraclass correlation coefficient (ICC) of repeated measurements. The correlations of mPO(2) and gPO(2) measurements with systemic arterial oxygen tension (P(a)O(2)) and carbon dioxide tension (P(a)CO(2)) was determined.
Measurements of mPO(2) and gPO(2) in retinal arteries, microvessels and veins were reproducible (ICC > 0.86; p < 0.01; N = 8), except for retinal arterial gPO(2). Retinal arterial, microvessel and venous mPO(2) were 41 ± 8, 32 ± 8 and 25 ± 7 mmHg, respectively (mean ± SD; N = 27). Retinal arterial mPO(2) was correlated with P(a)O(2) and P(a)CO(2) (R > 0.44; p < 0.03), while retinal microvessel and venous mPO(2) were only correlated with P(a)CO(2) (R > 0.68; p < 0.01). Retinal microvessel gPO(2) (-3.8 ± 1.5 mmHg/100 μm) was significantly steeper (more negative) than venous gPO(2) (0.02 ± 0.43 mmHg/100 μm) (p < 0.01; N = 27), and neither were significantly correlated with P(a)O(2) or P(a)CO(2).
Quantitative measurement of mPO(2) and gPO(2) in the retinal microvasculature was demonstrated. A significant decrease in PO(2) was observed along most retinal microvessels, indicative of substantial oxygen extraction by the retinal tissue. This method has the potential to help elucidate retinal microvascular oxygen transport in health and disease.
视网膜血管中的氧输送对维持正常视网膜代谢功能至关重要。因此，测量视网膜血管中的氧分压 (PO₂) 和 PO₂ 纵向梯度 (gPO₂) 可以帮助我们深入了解视网膜生理学和病理过程。
通过光学切片磷光寿命成像生成大鼠的三维视网膜血管 PO₂ 图谱。对主要的视网膜动脉和静脉对以及它们之间的较小血管（微血管）进行分段，并测量每条血管中的 PO₂。在每条血管中，计算平均 PO₂ (mPO₂)，并通过线性回归分析确定 gPO₂。通过计算重复测量的组内相关系数 (ICC) 来评估测量的可重复性。确定 mPO₂ 和 gPO₂ 测量值与全身动脉氧分压 (P(a)O₂) 和二氧化碳分压 (P(a)CO₂) 的相关性。
视网膜动脉、微血管和静脉中的 mPO₂ 和 gPO₂ 测量值具有可重复性（ICC>0.86;p<0.01;N=8），除了视网膜动脉的 gPO₂。视网膜动脉、微血管和静脉的 mPO₂ 分别为 41±8、32±8 和 25±7mmHg（平均值±标准差；N=27）。视网膜动脉的 mPO₂ 与 P(a)O₂ 和 P(a)CO₂ 相关（R>0.44;p<0.03），而视网膜微血管和静脉的 mPO₂ 仅与 P(a)CO₂ 相关（R>0.68;p<0.01）。视网膜微血管的 gPO₂（-3.8±1.5mmHg/100μm）明显比静脉的 gPO₂（0.02±0.43mmHg/100μm）陡峭（更负）（p<0.01；N=27），并且都与 P(a)O₂ 或 P(a)CO₂ 无显著相关性。
在视网膜微血管中定量测量 mPO₂ 和 gPO₂。在大多数视网膜微血管中观察到 PO₂ 显著下降，表明视网膜组织对氧的摄取量很大。这种方法有可能帮助阐明健康和疾病状态下的视网膜微血管氧运输。
