Snodderly D M, Weinhaus R S, Choi J C
Neuroscience Unit, Eye Research Institute, Boston, Massachusetts 02114.
J Neurosci. 1992 Apr;12(4):1169-93. doi: 10.1523/JNEUROSCI.12-04-01169.1992.
The relationship of the vasculature to the neuronal layers was studied in whole-mounts and in sections of macaque retinas. Like other central nervous structures, primate retinas have local variations in vascularity that reflect local variations in metabolism, rather than simply tissue thickness or volume. A special feature of the retina is a dense vascular plexus in the nerve fiber layer, which is unmyelinated and hence must generate a substantial metabolic demand for ion pumping. Much of the retinal vasculature is laminated and located at specific layer boundaries. Throughout the central retina, two planes of capillaries bracket the inner nuclear layer to form a sclerad capillary network. In some regions, especially near the fovea, a second, more vitread network brackets the ganglion cell layer with another pair of capillary planes. Wherever the nerve fiber layer is thick, the vitread network becomes less planar and is multilayered. When surrounded by nerve fibers, capillaries tend to orient parallel to the fibers; when adjacent to ganglion cell bodies, the capillaries are less systematically oriented. At the border between the nerve fiber layer and the ganglion cell layer, rows of ganglion cells often interdigitate with nerve fiber bundles, resulting in local perturbations of capillary orientation. The volume of the sclerad capillary network is relatively constant at different locations, but the volume of the vitread network increases dramatically where the nerve fiber layer is thick. As a result, the vascularity of the retina is greatest in the peripapillary region near the optic disk, even though the total thickness of the peripapillary retina is comparable to the retinal thickness near the foveal crest. As many as 60-70% of the photons passing through the retina in the peripapillary region will encounter one or more capillaries before reaching a photoreceptor. Median capillary diameter increases with retinal depth from 4.5-4.7 microns in the nerve fiber layer to 5.0 microns at the sclerad border of the inner nuclear layer. Capillary diameter in the nerve fiber layer also increases near the optic disk.
在猕猴视网膜的整装标本和切片中研究了脉管系统与神经元层的关系。与其他中枢神经结构一样，灵长类动物视网膜的血管分布存在局部差异，这些差异反映了局部代谢的变化，而不仅仅是组织厚度或体积的变化。视网膜的一个特殊特征是神经纤维层中有密集的血管丛，该层无髓鞘，因此必须产生大量的离子泵代谢需求。视网膜的许多脉管系统是分层的，并位于特定的层边界处。在整个中央视网膜中，两层毛细血管包围内核层，形成一个巩膜侧毛细血管网络。在一些区域，特别是在中央凹附近，第二层更靠近玻璃体的网络通过另一对毛细血管平面包围神经节细胞层。在神经纤维层较厚的地方，玻璃体网络变得不那么平面，而是多层的。当被神经纤维包围时，毛细血管倾向于与纤维平行排列；当与神经节细胞体相邻时，毛细血管的排列则不太规则。在神经纤维层和神经节细胞层的边界处，一排排神经节细胞常常与神经纤维束相互交错，导致毛细血管排列的局部扰动。巩膜侧毛细血管网络的体积在不同位置相对恒定，但在神经纤维层较厚处玻璃体网络的体积显著增加。因此，视网膜的血管分布在视盘附近的视乳头周围区域最为丰富，尽管视乳头周围视网膜的总厚度与中央凹嵴附近的视网膜厚度相当。在视乳头周围区域，多达60% - 70%穿过视网膜的光子在到达光感受器之前会遇到一根或多根毛细血管。毛细血管的中位直径随着视网膜深度的增加而增大，从神经纤维层的4.5 - 4.7微米增加到内核层巩膜侧边界处的5.0微米。神经纤维层中的毛细血管直径在视盘附近也会增大。
