Maier Felix M, Howland Howard C, Ohlendorf Arne, Wahl Siegfried, Schaeffel Frank
Section of Neurobiology of the Eye, Ophthalmic Research Institute, Calwerstraße 7/1, 72076 Tübingen, Germany.
Dept. of Neuroscience and Behavior, Cornell University, Ithaca, NY 14853, USA.
Vision Res. 2015 Apr;109(Pt A):68-76. doi: 10.1016/j.visres.2015.02.002. Epub 2015 Feb 18.
Primate eyes display considerable oblique off-axis astigmatism which could provide information on the sign of defocus that is needed for emmetropization. The pattern of peripheral astigmatism is not known in the chicken eye, a common model of myopia. Peripheral astigmatism was mapped out over the horizontal visual field in three chickens, 43 days old, and in three near emmetropic human subjects, average age 34.7years, using infrared photoretinoscopy. There were no differences in astigmatism between humans and chickens in the central visual field (chicks -0.35D, humans -0.65D, n.s.) but large differences in the periphery (i.e. astigmatism at 40° in the temporal visual field: humans -4.21D, chicks -0.63D, p<0.001, unpaired t-test). The lack of peripheral astigmatism in chicks was not due to differences in corneal shape. Perhaps related to their superior peripheral optics, we found that chickens had excellent visual performance also in the far periphery. Using an automated optokinetic nystagmus paradigm, no difference was observed in spatial visual performance with vision restricted to either the central 67° of the visual field or to the periphery beyond 67°. Accommodation was elicited by stimuli presented far out in the visual field. Transscleral images of single infrared LEDs showed no sign of peripheral astigmatism. The chick may be the first terrestrial vertebrate described to lack oblique astigmatism. Since corneal shape cannot account for the difference in astigmatism in humans and chicks, it must trace back to the design of the crystalline lens. The lack of peripheral astigmatism in chicks also excludes a role in emmetropization.
灵长类动物的眼睛表现出相当大的斜轴外散光，这可能提供有关正视化所需散焦符号的信息。鸡的眼睛是近视的常见模型，其周边散光模式尚不清楚。使用红外视网膜检影法，在三只43日龄的鸡和三名平均年龄为34.7岁的正视化程度接近的人类受试者的水平视野中绘制了周边散光图。在中央视野中，人类和鸡的散光没有差异（小鸡-0.35D，人类-0.65D，无显著性差异），但在周边有很大差异（即颞侧视野40°处的散光：人类-4.21D，小鸡-0.63D，p<0.001，未配对t检验）。小鸡缺乏周边散光并非由于角膜形状的差异。也许与它们优越的周边光学系统有关，我们发现鸡在极周边也有出色的视觉表现。使用自动视动性眼球震颤范式，当视觉仅限于视野中央67°或67°以外的周边时，在空间视觉表现上未观察到差异。通过在视野远处呈现的刺激引发调节。单个红外发光二极管的经巩膜图像未显示周边散光的迹象。小鸡可能是所描述的第一种缺乏斜散光的陆生脊椎动物。由于角膜形状不能解释人类和小鸡散光的差异，这一定可以追溯到晶状体的设计。小鸡缺乏周边散光也排除了其在正视化中的作用。
