Mechanisms mediating avian eye growth

当眼睛长得太长而不适合它们的光学功能时，近视就会发生。 除了某些视觉线索，调节，聚焦在附近物体上的行为也被认为是人类近视发展的驱动力。 透镜是眼睛中控制聚焦的结构，视网膜是控制眼睛生长的结构。 长期的目标是确定透镜和视网膜如何相互作用来控制眼睛的生长。 短期目标是首先确定视网膜和透镜功能的细胞机制。 这项工作将在两个方面进行，1）通过检查视网膜改变的眼睛如何对环境生长信号作出反应，2）通过检查透镜的细胞如何控制或通过聚焦控制。 小鸡将用于这些研究，因为它们和人类一样，是昼夜活动的，具有色觉，并通过使透镜变形来聚焦。 1)视网膜的细胞变化-通过切断视神经将眼睛与大脑断开，不仅会消除聚焦的动力，还会导致眼睛比正常眼睛短，这表明眼睛生长发生了变化。 视神经切除也会导致视网膜中一些细胞的损失，因此视神经切除的眼睛将被用来探测视网膜的哪些细胞以及如何控制眼睛对视觉信号的反应。 2)调节晶状体的细胞变化-研究表明，透镜内的亚细胞结构蛋白可能赋予透镜收缩活性。 此外，机械应力已被证明会诱导其他细胞内的生化活性，但对影响变形（机械应力）透镜和受其影响的细胞变化的研究却被忽略了。 一个调节模型，它允许直接测量的透镜在神经刺激聚焦，将被用来调查的亚细胞结构的透镜是如何受到自然引起的机械应力和其他生长相关的变化的眼睛。

Near-sightedness (myopia) develops when eyes grow too long for their optics.  In addition to certain visual cues, accommodation, the act of focussing on nearby objects has been implicated  as a driving force for myopia development in humans.  The lens is the structure in the eye that controls focussing and the retina is the structure that controls eye growth.  The long-term aim is to determine how the lens and retina interact to control eye growth.  The short term goals are to first determine the cellular mechanisms underlying how the retina and lens function.  The work will be carried out on two fronts, 1) by examining how eyes with altered retinas respond to environmental growth signals and 2) by examining how the cells of the lens control, or are controlled by focussing.  Chicks will be used for these studies because, like humans, they are diurnal, have colour vision and focus by deforming the lens.  1) CELLULAR CHANGES TO THE RETINA - Disconnecting the eye from the brain by severing the opitc nerve not only removes the drive to focus but also results in a shorter than normal eye, indicating altered eye growth.  Optic nerve-section also results in loss of some cells in the retina therefore optic nerve-sectioned eyes will be used to probe how and which cells of the retina control eye growth in response to visual signals.  2) CELLULAR CHANGES TO THE ACCOMMODATING LENS - Studies suggest that subcellular structrual proteins within the lens might impart contractile activity to the lens.  In addition, mechanical stress has been shown to induce biochemical activity within other cells, yet studies of the cellular changes that affect and are affected by a deforming (mechanically stressed) lens have been neglected.  An accommodation model, which allows direct measurement of the lens during nerve-stimulated focussing, will be used to investigate how the subcellular structures of the lens are affected by naturally-induced mechanical stress and other growth-related changes to the eye.