Yu Dao-Yi, Townsend Russel, Cringle Stephen J, Chauhan Balwantray C, Morgan William H
Centre for Ophthalmology and Visual Science, The University of Western Australia, Perth, Australia.
Invest Ophthalmol Vis Sci. 2005 Jan;46(1):166-74. doi: 10.1167/iovs.04-0772.
To improve the interpretation of Heidelberg Retina Flowmeter (HRF; Heidelberg Engineering GmBH, Dosselheim, Germany) flow maps by examining the influence of specific vascular structures and focus depth in the presence and absence of retinal blood flow.
HRF flow maps were recorded from the inferior retina of anesthetized Brown Norway rats over a wide range of focus levels, before and after laser occlusion of the retinal circulation. Analysis of the resultant flow maps showed that the sample window was positioned on a retinal artery, arteriole, or vein, or in a retinal capillary area, with or without a visible underlying choroidal vessel. The relationship between HRF-measured flow (arbitrary units) and focus depth was determined for each location. At the conclusion of each experiment, the effect of reduction of systemic blood pressure on the choroidal circulation and the level of background signal in the HRF flow map with no ocular blood flow were assessed.
The strongest flow signals came from the retinal arteries, veins, and arterioles and were reduced to choroidal background level after occlusion of the central retinal artery. Larger choroidal vessels also contributed strong flow signals. In contrast, the flow signal from the retinal capillary area was weak and unaffected by retinal artery occlusion. Changing the depth of focus significantly altered the contribution from the major retinal arteries, arterioles, and veins, but no significant depth effect was seen for retinal capillaries or choroidal vessels. The HRF flow signal remaining when systemic blood pressure was reduced to zero was not significantly different from the capillary sampling location when the eye was normally perfused.
In the pigmented rat eye, the HRF signal from retinal capillaries is not significantly different from the background noise unrelated to blood flow. Strong flow signals can be obtained from the retinal arteries, retinal arterioles, retinal veins, and choroidal vessels. Current HRF flow maps in the rat therefore reflect blood flow in the larger elements of the microvasculature rather than the capillary network.
通过研究特定血管结构和聚焦深度在有或无视网膜血流情况下的影响，改进对海德堡视网膜血流计（HRF；德国多塞尔海姆海德堡工程有限公司）血流图的解读。
在麻醉的棕色挪威大鼠视网膜下，于视网膜循环激光闭塞前后，在广泛的聚焦水平范围内记录HRF血流图。对所得血流图的分析表明，样本窗口位于视网膜动脉、小动脉或静脉上，或位于视网膜毛细血管区域，有无可见的脉络膜血管。确定每个位置的HRF测量血流（任意单位）与聚焦深度之间的关系。在每个实验结束时，评估全身血压降低对脉络膜循环的影响以及无眼血流时HRF血流图中背景信号水平。
最强的血流信号来自视网膜动脉、静脉和小动脉，在视网膜中央动脉闭塞后降至脉络膜背景水平。较大的脉络膜血管也贡献了较强的血流信号。相比之下，视网膜毛细血管区域的血流信号较弱，不受视网膜动脉闭塞的影响。改变聚焦深度显著改变了主要视网膜动脉、小动脉和静脉的贡献，但视网膜毛细血管或脉络膜血管未见明显的深度效应。当全身血压降至零时，HRF血流信号与正常灌注眼时的毛细血管采样位置无显著差异。
在有色大鼠眼中，来自视网膜毛细血管的HRF信号与与血流无关的背景噪声无显著差异。可从视网膜动脉、视网膜小动脉、视网膜静脉和脉络膜血管获得强血流信号。因此，目前大鼠的HRF血流图反映的是微血管较大成分而非毛细血管网络中的血流。
