Khoobehi B, Shoelson B, Zhang Y Z, Peyman G A
LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans 70112-2234, USA.
Ophthalmic Surg Lasers. 1997 Nov;28(11):937-47.
Quantitative assessment of choriocapillaris circulation has proven difficult. Although the fluorescent vesicle system provides a means of quantifying the retinal circulation, the attempts at imaging fluorescent liposomes in the choroidal microcirculation have been largely unsuccessful. The authors introduce a new tool, fluorescent microsphere imaging, and examine its utility for evaluating the hemodynamics of the retina and choroidal microcirculation. The usefulness of fluorescent microsphere imaging is demonstrated through the examination of the retinal and choroidal circulations of three rhesus monkeys.
Fluorescent microsphere imaging uses polystyrene latex microspheres that incorporate one or more dyes. These microspheres are injected intravenously into an animal and are excited in the eye through the resident lasers of a scanning laser ophthalmoscope. The excited particles are detected by the ophthalmoscope, and its output is then digitized directly or recorded on a videocassette recorder for subsequent image analysis. Multiple-dye microspheres use the principle of resonance energy transfer for the activation of the final dye in a non-radiative cascade. These microspheres enable the investigator to tailor the excitation and emission spectra of the particles for the investigation of different ocular tissues.
Using 488/515 microspheres (excitation and emission peaks at 488 nm and 515 nm, respectively), the authors captured images of particles circulating in the perimacular retinal circulation. Shifting excitation and emission spectra toward the red and infrared enabled the imaging of blood flow in progressively deeper tissue. Using 633/825 microspheres, the authors recorded and tracked particles in the microcirculation of the choroid.
The authors' findings suggest that fluorescent microsphere imaging provides images useful for studying the retinal circulation and for evaluating previously inaccessible choroidal hemodynamics.
脉络膜毛细血管循环的定量评估已被证明具有难度。尽管荧光囊泡系统提供了一种量化视网膜循环的方法，但在脉络膜微循环中对荧光脂质体进行成像的尝试大多未成功。作者引入了一种新工具——荧光微球成像，并研究其在评估视网膜和脉络膜微循环血流动力学方面的效用。通过对三只恒河猴的视网膜和脉络膜循环进行检查，证明了荧光微球成像的有用性。
荧光微球成像使用包含一种或多种染料的聚苯乙烯乳胶微球。这些微球通过静脉注射到动物体内，并通过扫描激光检眼镜的固有激光在眼中被激发。激发后的粒子由检眼镜检测，其输出然后直接数字化或记录在盒式录像机上以便后续图像分析。多染料微球利用共振能量转移原理在非辐射级联中激活最终染料。这些微球使研究者能够调整粒子的激发和发射光谱，以研究不同的眼组织。
使用488/515微球（激发峰和发射峰分别在488纳米和515纳米），作者捕捉到了在黄斑周围视网膜循环中流动的粒子的图像。将激发和发射光谱向红色和红外方向移动，能够对更深组织中的血流进行成像。使用633/825微球，作者记录并追踪了脉络膜微循环中的粒子。
作者的研究结果表明，荧光微球成像提供了有助于研究视网膜循环和评估以前难以获取的脉络膜血流动力学的图像。
