Kagemann L, Harris A, Chung H S, Evans D, Buck S, Martin B
Department of Ophthalmology, Indiana University School of Medicine, Indianapolis 46202, USA.
Br J Ophthalmol. 1998 Feb;82(2):131-6. doi: 10.1136/bjo.82.2.131.
To evaluate factors affecting Heidelberg retinal flowmeter (HRF) measurements of retinal and optic nerve head blood flow in human subjects.
The angle of incidence between laser beam and fundus, and camera distance from the eye, were evaluated for their effect upon measures of blood volume, velocity, and flow in a single 100 x 100 x 400 microns volume of temporal peripapillary retinal tissue in normal volunteers. Both intra and intersession reproducibility of these measures were studied. Intersession data were obtained by taking one image per week for 4 weeks. Finally, the intersession haemodynamic data were examined in the entire image (640 x 2560 x 400 microns), using histograms of pixel by pixel blood flow.
Measures of blood volume, velocity, and flow from a single anatomical site were unaffected by laser beam to fundus angle of incidence (n = 12). As camera distance from the eye was increased (from 2 to 5 to 7 cm), flow measurements showed increasing individual changes, despite unaltered measured vessel lengths and constant overall mean flow (n = 14). The coefficient of variation for two intersession images of optic nerve head blood flow averaged 7% (n = 20); in contrast, the 4 week intersession coefficient of variation averaged 30% (n = 15). Intersession reproducibility was increased by using flow histograms from the entire image: the coefficients of variation averaged 16% for total flow and 17% for flow in the pixel of median flow.
HRF measures of flow are independent of the laser beam to fundus angle of the incidence and dependent upon camera distance from the eye. Intersession reproducibility is best using pixel by pixel analysis of the entire image.
评估影响人体视网膜和视神经乳头血流的海德堡视网膜血流仪（HRF）测量的因素。
在正常志愿者的颞侧视乳头周围视网膜组织的单个100×100×400微米体积中，评估激光束与眼底之间的入射角以及相机与眼睛的距离对血容量、速度和血流测量的影响。研究了这些测量的组内和组间重复性。组间数据通过连续4周每周拍摄一张图像获得。最后，使用逐像素血流直方图在整个图像（640×2560×400微米）中检查组间血流动力学数据。
来自单个解剖部位的血容量、速度和血流测量不受激光束与眼底入射角的影响（n = 12）。随着相机与眼睛的距离增加（从2厘米增加到5厘米再到7厘米），尽管测量的血管长度未改变且总体平均血流恒定，但血流测量显示个体变化增加（n = 14）。视神经乳头血流的两张组间图像的变异系数平均为7%（n = 20）；相比之下，4周组间变异系数平均为30%（n = 15）。通过使用来自整个图像的血流直方图提高了组间重复性：总血流的变异系数平均为16%，中位数血流像素处的血流变异系数平均为17%。
HRF血流测量与激光束与眼底的入射角无关，而取决于相机与眼睛的距离。使用整个图像的逐像素分析时组间重复性最佳。
