Shinozaki Aya, Hosaka Yoshinao, Imagawa Tomohiro, Uehara Masato
The United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi 753-8515, Japan.
J Comp Neurol. 2010 Jun 15;518(12):2305-15. doi: 10.1002/cne.22333.
Retinal topographies of some cell types and distribution of the tapetum lucidum in the sheep's eye were investigated in this study. The tapetum was observed macroscopically in the fundus. The topographical distributions of retinal ganglion cells (RGCs), cones, and rods were simultaneously analyzed in retinal whole mounts stained with cresyl violet. Short-wavelength-sensitive (S) cones were immunocytochemically identified in retinal whole mounts. The tapetum was located dorsal to the optic disc, with the nasal part elongated horizontally and the temporal part expanded dorsally. RGCs were distributed densely in the area centralis, horizontal visual streak, and anakatabatic area. The highest density in the area centralis was approximately 18,000 RGCs/mm(2). Cones showed high density in the horizontal area crossing the optic disc and dorsotemporal area, whereas rods showed high density in the horizontal area, which was greater in height than the horizontal area of high cone density. S cones showed high density in the dorsotemporal retina. The rod/cone ratios were high horizontally in the dorsal retina to the optic disc, with a mean value of 11:1. The cone/RGC and rod/RGC ratios were lower in the horizontal and dorsotemporal retina, and the rod/cone/RGC ratio was lowest in the area centralis (9:1:1). The retinal topographies and distribution of the tapetum were specialized in the horizontal and dorsotemporal fundus. This suggests that sheep have better visual acuity in horizontal and anteroinferior visual fields and that this specialization is related to the visual ecology of sheep.
本研究调查了绵羊眼中某些细胞类型的视网膜地形图以及反光层的分布。在眼底肉眼观察到了反光层。用甲酚紫染色的视网膜全层标本中，同时分析了视网膜神经节细胞（RGCs）、视锥细胞和视杆细胞的地形图分布。在视网膜全层标本中通过免疫细胞化学方法鉴定了短波敏感（S）视锥细胞。反光层位于视盘的背侧，鼻侧部分水平伸长，颞侧部分背侧扩展。RGCs密集分布于中央凹、水平视觉带和下行区域。中央凹的最高密度约为18,000个RGCs/mm²。视锥细胞在穿过视盘的水平区域和背颞区域密度较高，而视杆细胞在水平区域密度较高，该区域的高度大于视锥细胞高密度的水平区域。S视锥细胞在背颞视网膜中密度较高。在视盘背侧的视网膜水平方向上，视杆/视锥细胞比值较高，平均值为11:1。在水平和背颞视网膜中，视锥细胞/RGC和视杆细胞/RGC比值较低，在中央凹区域视杆/视锥细胞/RGC比值最低（9:1:1）。视网膜地形图和反光层的分布在水平和背颞眼底具有特殊性。这表明绵羊在水平和前下视野具有更好的视力，并且这种特殊性与绵羊的视觉生态有关。
