Hirata Yuya, Nishiwaki Hirokazu
Department of Ophthalmology, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan.
Prog Retin Eye Res. 2006 Mar;25(2):129-47. doi: 10.1016/j.preteyeres.2005.08.001. Epub 2005 Oct 12.
The choroid plays an important role in supplying nutrients to and removing waste products from the outer region of the retina. Abnormal choroidal blood flow can disrupt normal retinal function and lead to alterations in visual function. Visualization of the choriocapillaris in vivo is a great challenge to understanding its normal physiology and involvement in the disease process. Laser-targeted angiography (LTA) is a relatively new method used to visualize and analyze the choroidal circulation. Carboxyfluorescein (CF), encapsulated in heat-sensitive liposomes, is released locally in the choroid through the application of a heat beam provided by an infrared laser. Video angiograms are generated with excitation illumination provided by an argon laser. Obtained images are highly selective to the choriocapillaris and are sharply contrasted against underlying and overlying structures. The images can be obtained repetitively, during which period the circulating liposome concentration is sufficient to generate adequate angiograms. These high-quality images have revealed three distinct phases (filling, plateau, and draining) of the choriocapillaris. In the plateau phase, a cluster of lobules fed by a common arteriole has been uniformly illuminated. This defined cluster area does not change in size while an infrared laser is continuously applied to the same spot, which demonstrates that each cluster is functionally independent and no physiological communication exists between them. Only in posterior regions do the angiograms demonstrate during the filling and draining phases that each lobule is filled from a central spot and drained along a peripheral ring, showing honeycomb flow patterns. The regional differences in choriocapillaris flow patterns revealed by LTA suggests that the choriocapillaris provides a more highly efficient system of outflow in posterior regions than in peripheral regions. LTA is useful in analyzing choroidal circulation in vivo and has the potential for clinical application in the future. Additionally, LTA has a unique capability to image choroidal neovascularization in animal models and it promises potential application in age-related macular degeneration (AMD).
脉络膜在为视网膜外层区域供应营养物质和清除代谢废物方面发挥着重要作用。脉络膜血流异常会干扰正常的视网膜功能，并导致视觉功能改变。在体内可视化脉络膜毛细血管对理解其正常生理学以及在疾病过程中的作用是一项巨大挑战。激光靶向血管造影术（LTA）是一种用于可视化和分析脉络膜循环的相对较新的方法。包裹在热敏脂质体中的羧基荧光素（CF）通过应用红外激光提供的热光束在脉络膜局部释放。视频血管造影通过氩激光提供的激发照明生成。获得的图像对脉络膜毛细血管具有高度选择性，并且与下层和上层结构形成鲜明对比。这些图像可以重复获取，在此期间循环脂质体浓度足以生成足够的血管造影图像。这些高质量图像揭示了脉络膜毛细血管的三个不同阶段（充盈、平台期和排空）。在平台期，由一条共同小动脉供血的一簇小叶被均匀照亮。当红外激光持续照射同一点时，这个确定的簇区域大小不变，这表明每个簇在功能上是独立的，它们之间不存在生理连通性。只有在后部区域，血管造影在充盈期和排空期显示每个小叶从一个中心点充盈并沿外周环排空，呈现蜂窝状血流模式。LTA揭示的脉络膜毛细血管血流模式的区域差异表明，脉络膜毛细血管在后部区域提供了比周边区域更高效的流出系统。LTA有助于在体内分析脉络膜循环，并且在未来具有临床应用潜力。此外，LTA具有在动物模型中对脉络膜新生血管成像的独特能力，有望在年龄相关性黄斑变性（AMD）中得到潜在应用。
