PDF(Pubmed)
Abstract：
BACKGROUND: More than ~70% of the aqueous humor exits the eye through the conventional aqueous outflow pathway that is comprised of the trabecular meshwork (TM), juxtacanalicular tissue (JCT), the inner wall endothelium of Schlemm\'s canal (SC). The flow resistance in the JCT and SC inner wall basement membrane is thought to play an important role in the regulation of the intraocular pressure (IOP) in the eye, but current imaging techniques do not provide enough information about the mechanics of these tissues or the aqueous humor in this area.
METHODS: A normal human eye was perfusion-fixed and a radial wedge of the TM tissue from a high-flow region was dissected. The tissues were then sliced and imaged using serial block-face scanning electron microscopy. Slices from these images were selected and segmented to create a 3D finite element model of the JCT and SC cells with an inner wall basement membrane. The aqueous humor was used to replace the intertrabecular spaces, pores, and giant vacuoles, and fluid-structure interaction was employed to couple the motion of the tissues with the aqueous humor.
RESULTS: Higher tensile stresses (0.8-kPa) and strains (25%) were observed in the basement membrane beneath giant vacuoles with open pores. The volumetric average wall shear stress was higher in SC than in JCT/SC. As the aqueous humor approached the inner wall basement membrane of SC, the velocity of the flow decreased, resulting in the formation of small eddies immediately after the flow left the inner wall.
CONCLUSIONS: Improved modeling of SC and JCT can enhance our understanding of outflow resistance and funneling. Serial block-face scanning electron microscopy with fluid-structure interaction can achieve this, and the observed micro-segmental flow patterns in ex vivo perfused human eyes suggest a hypothetical mechanism.
METHODS: A normal human eye was perfusion-fixed and a radial wedge of the TM tissue from a high-flow region was dissected. The tissues were then sliced and imaged using serial block-face scanning electron microscopy. Slices from these images were selected and segmented to create a 3D finite element model of the JCT and SC cells with an inner wall basement membrane. The aqueous humor was used to replace the intertrabecular spaces, pores, and giant vacuoles, and fluid-structure interaction was employed to couple the motion of the tissues with the aqueous humor.
RESULTS: Higher tensile stresses (0.8-kPa) and strains (25%) were observed in the basement membrane beneath giant vacuoles with open pores. The volumetric average wall shear stress was higher in SC than in JCT/SC. As the aqueous humor approached the inner wall basement membrane of SC, the velocity of the flow decreased, resulting in the formation of small eddies immediately after the flow left the inner wall.
CONCLUSIONS: Improved modeling of SC and JCT can enhance our understanding of outflow resistance and funneling. Serial block-face scanning electron microscopy with fluid-structure interaction can achieve this, and the observed micro-segmental flow patterns in ex vivo perfused human eyes suggest a hypothetical mechanism.
摘要：
背景：超过70％的房水通过由小梁网（TM）组成的常规房水流出途径离开眼睛，耳旁组织（JCT），Schlemm管（SC）的内壁内皮。JCT和SC内壁基底膜中的流动阻力被认为在调节眼睛的眼内压（IOP）中起重要作用，但是目前的成像技术无法提供有关这些组织或该区域房水力学的足够信息。
方法：对正常人眼进行灌注固定，并从高流量区域解剖TM组织的径向楔形。然后将组织切片并使用连续块面扫描电子显微镜成像。选择并分割来自这些图像的切片以创建具有内壁基底膜的JCT和SC细胞的3D有限元模型。房水被用来代替小梁间隙，毛孔,和巨大的空泡，并且采用流体-结构相互作用将组织的运动与房水耦合。
结果：在具有开孔的巨大液泡下方的基底膜中观察到更高的拉伸应力（0.8-kPa）和应变（25％）。SC的体积平均壁切应力高于JCT/SC。当房水接近SC的内壁基底膜时，流速下降，导致流动离开内壁后立即形成小涡流。
结论：改进SC和JCT的建模可以增强我们对流出阻力和漏斗的理解。具有流体-结构相互作用的串行块面扫描电子显微镜可以实现这一点，在离体灌注的人眼中观察到的微段血流模式表明了一种假设的机制。
方法：对正常人眼进行灌注固定，并从高流量区域解剖TM组织的径向楔形。然后将组织切片并使用连续块面扫描电子显微镜成像。选择并分割来自这些图像的切片以创建具有内壁基底膜的JCT和SC细胞的3D有限元模型。房水被用来代替小梁间隙，毛孔,和巨大的空泡，并且采用流体-结构相互作用将组织的运动与房水耦合。
结果：在具有开孔的巨大液泡下方的基底膜中观察到更高的拉伸应力（0.8-kPa）和应变（25％）。SC的体积平均壁切应力高于JCT/SC。当房水接近SC的内壁基底膜时，流速下降，导致流动离开内壁后立即形成小涡流。
结论：改进SC和JCT的建模可以增强我们对流出阻力和漏斗的理解。具有流体-结构相互作用的串行块面扫描电子显微镜可以实现这一点，在离体灌注的人眼中观察到的微段血流模式表明了一种假设的机制。
