Bringmann Andreas
Department of Ophthalmology and Eye Hospital, Medical Faculty, University of Leipzig, Leipzig, Germany.
Anat Histol Embryol. 2019 May;48(3):177-200. doi: 10.1111/ahe.12432. Epub 2019 Feb 7.
The cellular structure and functional relevance of the bird fovea are still incompletely understood. This review gives an overview of the cellular composition of the bird fovea, with special regard to Müller glial cells that provide the mechanical stability of the foveal tissue. A survey of previous data shows that the visual acuity of different bird groups (with the exception of owls) depends on the eye size, while the shape of the foveal pit does not correlate with the visual acuity. Among various bird groups, the foveal pit may have two depths, shallow (80-120 µm) or deep (190-240 µm). There is a long-lasting debate whether the bird fovea acts as a local image enlarger or as a focus indicator and movement detector. These functions are supported by the refraction of the incoming light at the tissue surface. However, it was shown that Müller cells form highly refractive layers in the centre and walls of the deep avian fovea (Nature, 1978, 275, 127). Analysis of the light path through the tissue may suggest that Müller cell layers serve at least two optical functions: magnification of the image in the foveal centre and light focusing into a point within and/or a ring around the foveal centre. It is suggested that Müller glial cells contribute to various optical functions of the bird fovea.
鸟类中央凹的细胞结构及其功能相关性仍未完全明确。本综述概述了鸟类中央凹的细胞组成，特别关注提供中央凹组织机械稳定性的米勒胶质细胞。对先前数据的调查表明，不同鸟类群体（猫头鹰除外）的视力取决于眼睛大小，而中央凹坑的形状与视力无关。在各种鸟类群体中，中央凹坑可能有两种深度，浅（80 - 120微米）或深（190 - 240微米）。关于鸟类中央凹是作为局部图像放大器还是焦点指示器和运动探测器，一直存在长期争论。这些功能受到入射光在组织表面折射的支持。然而，研究表明米勒细胞在深层鸟类中央凹的中心和壁上形成高折射层（《自然》，1978年，第275卷，第127页）。对穿过组织的光路分析可能表明，米勒细胞层至少具有两种光学功能：放大中央凹中心的图像以及将光聚焦到中央凹中心内的一个点和/或围绕中央凹中心的一个环上。有人认为米勒胶质细胞对鸟类中央凹的各种光学功能有贡献。
