Troilo D, Wallman J
Department of Biology, City College of New York, NY 10031.
Vision Res. 1991;31(7-8):1237-50. doi: 10.1016/0042-6989(91)90048-a.
During growth the vertebrate eye achieves a close match between the power of its optics and its axial length with the result that images are focused on the retina without accommodative effort (emmetropia). The possibility that vision is required for the regulation of eye growth was studied experimentally in chicks made myopic or hyperopic by different visual manipulations. After discontinuing these visual manipulations, the eyes returned quickly to emmetropia mainly by adjusting the growth of their vitreous chambers; growth stopped in eyes recovering from myopia and continued in eyes recovering from hyperopia. Because both hyperopic and myopic eyes were already larger than normal controls, the difference in growth indicates that refractive error, rather than eye size per se, guides the eye toward emmetropia. Evidence is also presented for nonvisual shape-related control of eye growth, but this is slow-acting and cannot explain the emmetropization from induced refractive errors. Both the visually guided and shape-related mechanisms work even in eyes with the optic nerve cut, indicating that the two mechanisms are local to the eye. Although the optic-nerve-sectioned eye can sense the sign of a refractive error and initially adjust growth accordingly, it eventually overshoots emmetropia and reverses the sign of the initial refractive error. Whether this is due to loss of feedback from the central nervous system or retinal ganglion cells is unclear.
在生长过程中，脊椎动物的眼睛使其光学能力与眼轴长度达到紧密匹配，结果是无需调节努力（正视）图像就能聚焦在视网膜上。通过不同的视觉操作使小鸡近视或远视，以此对视觉是否是调节眼球生长所必需的进行了实验研究。在停止这些视觉操作后，眼睛主要通过调节玻璃体腔的生长迅速恢复到正视状态；从近视恢复的眼睛生长停止，而从远视恢复的眼睛生长继续。由于远视和近视的眼睛都已经比正常对照大，生长的差异表明屈光不正，而非眼睛大小本身，引导眼睛趋向正视。也有证据表明存在非视觉的与形状相关的眼球生长控制，但这种控制作用缓慢，无法解释由诱导性屈光不正导致的正视化。视觉引导机制和与形状相关的机制即使在视神经被切断的眼睛中也起作用，这表明这两种机制都局限于眼睛局部。虽然视神经切断的眼睛能够感知屈光不正的迹象并最初相应地调节生长，但它最终会超过正视状态并逆转初始屈光不正的迹象。这是由于中枢神经系统或视网膜神经节细胞的反馈丧失尚不清楚。
