Michelson G, Schmauss B
Department of Ophthalmology, University Erlangen-Nürnberg, Germany.
Br J Ophthalmol. 1995 Dec;79(12):1126-32. doi: 10.1136/bjo.79.12.1126.
To present a new non-invasive method of performing a high definition topography of perfused vessels of the retina and the optic nerve head with simultaneous evaluation of blood flow.
By a combination of a laser Doppler flowmeter with a scanning laser system the perfusion of the retina and the optic nerve head is visualised. The principles of measuring blood flow by laser Doppler flowmetry are based on the optical Doppler effect: laser light scattered by a moving particle is shifted in frequency by an amount delta f. Our data acquisition and evaluation system is a modified laser scanning tomograph. The technical data are retinal area of measurement 2.7 mm x 0.7 mm, 10 degrees field with 256 points x 64 lines, measurement accuracy 10 microns, wavelength 670 nm and 790 nm, light power 100 microW and 200 microW, data acquisition time 2.048 s. Every line is scanned 128 times by a line sampling rate of 4000 Hz. By performing a discrete fast Fourier transformation over 128 intensities of each retinal point the laser Doppler shift is calculated for each retinal point. With these data a two dimensional map with 256 x 64 points of the retinal perfusion is created. The brightness of the pixel is coded by the value of the Doppler shift. Offline capillary blood flow is estimated in arbitrary units according to the theory of laser Doppler flowmetry in every region of interest of the perfusion picture. We estimated the reliability and the validity of the method. Retinal blood flow was measured by scanning laser Doppler flowmetry (SLDF) while varying intraocular pressure by a suction cup of three healthy volunteers. Measurements of retinal blood flow performed in 47 eyes by the presented method (SLDF) were correlated with data gained by a commercially available laser Doppler flowmeter. Perfusion pictures of the superficial retinal layer and of deep prelaminar layers in the optic nerve head are presented.
The reliability coefficients r1 of 'flow', 'volume', and 'velocity' were 0.84, 0.85, and 0.84 respectively. We found a significant linear relation between SLDF flow and the ocular perfusion pressure (r = 0.84, p < 0.001). Comparative measurements of the retinal blood flow by SLDF and a commercially available laser Doppler flowmeter showed a linear and significant relation (flow r = 0.6, p < 0.0001, volume r = 0.4, p < 0.01). Capillaries of the retinal superficial vasculature or deep ciliary sourced capillaries of the optic nerve head became visible with a high resolution by the confocal technique dependent on the focus. Offline, the blood flow variables of areas of 100 microns x 100 microns were calculated.
SLDF enables the visualisation of perfused capillaries and vessels of the retina and the optic nerve head in high resolution by two dimensional mapping of perfusion variables which are encoded by the Doppler signal. This method achieves simultaneously qualitative and quantitative evaluation of capillary blood flow of distinct areas of the capillary meshwork.
提出一种新的非侵入性方法，用于对视网膜和视神经乳头的灌注血管进行高分辨率地形图绘制，并同时评估血流情况。
通过将激光多普勒血流仪与扫描激光系统相结合，可实现视网膜和视神经乳头灌注情况的可视化。激光多普勒血流测量法测量血流的原理基于光学多普勒效应：运动粒子散射的激光在频率上会发生Δf量的偏移。我们的数据采集和评估系统是一台经过改进的激光扫描断层扫描仪。技术参数为：视网膜测量面积2.7毫米×0.7毫米，10度视野，256点×64线，测量精度10微米，波长670纳米和790纳米，光功率100微瓦和200微瓦，数据采集时间2.048秒。每条线以4000赫兹的线采样率扫描128次。通过对每个视网膜点的128个强度值进行离散快速傅里叶变换，计算出每个视网膜点的激光多普勒频移。利用这些数据创建一个256×64点的视网膜灌注二维图。像素的亮度由多普勒频移值编码。根据激光多普勒血流测量理论，以任意单位离线估计灌注图像每个感兴趣区域的毛细血管血流。我们评估了该方法的可靠性和有效性。在三名健康志愿者中，通过吸盘改变眼内压的同时，用扫描激光多普勒血流测量法（SLDF）测量视网膜血流。用所提出的方法（SLDF）对47只眼睛进行的视网膜血流测量结果与商用激光多普勒血流仪获得的数据进行了相关性分析。展示了视网膜表层和视神经乳头深层板层前的灌注图像。
“流量”“体积”和“速度”的可靠性系数r1分别为0.84、0.85和0.84。我们发现SLDF流量与眼灌注压之间存在显著的线性关系（r = 0.84，p < 0.001）。SLDF与商用激光多普勒血流仪对视网膜血流的比较测量显示出线性且显著的关系（流量r = 0.6，p < 0.0001，体积r = 0.4，p < 0.01）。通过共聚焦技术，根据焦点不同，视网膜浅层脉管系统的毛细血管或视神经乳头深层睫状来源的毛细血管能够以高分辨率清晰可见。离线计算100微米×100微米区域的血流变量。
SLDF通过对由多普勒信号编码的灌注变量进行二维映射，能够高分辨率地可视化视网膜和视神经乳头的灌注毛细血管和血管。该方法可同时对毛细血管网不同区域的毛细血管血流进行定性和定量评估。
