The wavelength composition and temporal modulation of ambient lighting strongly affect refractive development in young tree shrews.
The wavelength composition and temporal modulation of ambient lighting strongly affect refractive development in young tree shrews.
复制标题
DOI：
10.1016/j.exer.2016.12.004
复制
发表时间：
2017-02
影响因子：
3.4
通讯作者：
Norton TT
中科院分区：
文献类型：
--
作者：
Gawne TJ;Siegwart JT Jr;Ward AH;Norton TT
出生后不久，大多数动物（包括人类）的眼睛都是远视眼，因为短的眼轴长度将视网膜置于焦平面的前面。在出生后的发育过程中，正视化机制使用与屈光不正相关的线索来调节眼睛的生长，将视网膜移向焦平面。一个可能的线索可能是纵向色差（LCA），如果眼睛变得太长（长[红色]波长比短[蓝色]更好地聚焦）或太短（短波长更好地聚焦），则发出信号。短波长敏感（SWS，“蓝色”）视锥细胞在视网膜上稀少且分布广泛，可能难以检测和发出短波长散焦的信号。我们假设SWS锥视网膜通路可以利用时间（闪烁）信息。因此，我们测试了仅暴露于长波长光是否会导致发育中的眼睛减慢其轴向生长并保持屈光性远视，以及闪烁的短波长光是否会导致眼睛加速其轴向生长并变得近视。四组幼年北方树鼩（Tupaia glis belangeri，与灵长类动物密切相关的二色视哺乳动物）在11天的视觉体验（DVE）开始13天的波长治疗。环境照明由放置在笼顶上的长波长（红色，626 ± 10 nm）或短波长（蓝色，464 ± 10 nm）发光二极管阵列提供。灯光要么稳定，要么以伪随机的步伐模式闪烁。笼底的近似平均照度（人勒克斯）为红色（稳定，527勒克斯;闪烁，329勒克斯）和蓝色（稳定，601勒克斯;闪烁，252勒克斯）。测量屈光状态和眼部组件尺寸，并与在广谱白色荧光菌落照明（100 - 300勒克斯）下饲养的一组年龄匹配的正常动物（n = 15用于屈光（第一天和最后一天）; 7用于眼部组件）进行比较。在13天的时间里，正常动物的屈光度从（平均值± SEM）5.8 ± 0.7屈光度（D）至1.5 ± 0.2 D，因为它们的玻璃体腔深度从2.77 ± 0.01 mm增加至2.80 ± 0.03 mm。（稳定和闪烁）在整个治疗期间保持远视，使得在波长治疗结束时眼睛显著远视（7.0 ± 0.7 D，稳态; 4.7 ± 0.8 D，闪烁）与正常动物比较（p <0.01）。稳定红色组玻璃体腔（2.65 ± 0.03mm）较正常组明显缩短（P <0.01）。平均而言，稳定的蓝光几乎没有影响;折射率超过正常折射率下降。相比之下，在闪烁的蓝光中饲养的动物增加了屈光下降的速度，因此与正常眼睛相比，眼睛变得明显近视（-2.9 ± 1.3 D），并且具有更长的玻璃体腔（2.93 ± 0.04 mm）。在恢复群体照明后，所有组的屈光逐渐恢复到正视。这些数据是一致的假设，LCA可以是一个重要的视觉线索，为出生后的屈光发展，短波长的时间闪烁提供了一个重要的线索，评估和信号散焦。
Shortly after birth, the eyes of most animals (including humans) are hyperopic because the short axial length places the retina in front of the focal plane. During postnatal development, an emmetropization mechanism uses cues related to refractive error to modulate the growth of the eye, moving the retina toward the focal plane. One possible cue may be longitudinal chromatic aberration (LCA), to signal if eyes are getting too long (long [red] wavelengths in better focus than short [blue]) or too short (short wavelengths in better focus). It could be difficult for the short-wavelength sensitive (SWS, “blue”) cones, which are scarce and widely spaced across the retina, to detect and signal defocus of short wavelengths. We hypothesized that the SWS cone retinal pathway could instead utilize temporal (flicker) information. We thus tested if exposure solely to long-wavelength light would cause developing eyes to slow their axial growth and remain refractively hyperopic, and if flickering short-wavelength light would cause eyes to accelerate their axial growth and become myopic. Four groups of infant northern tree shrews (Tupaia glis belangeri, dichromatic mammals closely related to primates) began 13 days of wavelength treatment starting at 11 days of visual experience (DVE). Ambient lighting was provided by an array of either long-wavelength (red, 626±10 nm) or short-wavelength (blue, 464±10 nm) light-emitting diodes placed atop the cage. The lights were either steady, or flickering in a pseudo-random step pattern. The approximate mean illuminance (in human lux) on the cage floor was red (steady, 527 lux; flickering, 329 lux), and blue (steady, 601 lux; flickering, 252 lux). Refractive state and ocular component dimensions were measured and compared with a group of age-matched normal animals (n=15 for refraction (first and last days); 7 for ocular components) raised in broad spectrum white fluorescent colony lighting (100-300 lux). During the 13 day period, the refraction of the normal animals decreased from (mean±SEM) 5.8±0.7 diopters (D) to 1.5±0.2 D as their vitreous chamber depth increased from 2.77±0.01mm to 2.80±0.03 mm. Animals exposed to red light (both steady and flickering) remained hyperopic throughout the treatment period so that the eyes at the end of wavelength treatment were significantly hyperopic (7.0±0.7 D, steady; 4.7±0.8 D, flickering) compared with the normal animals (p<0.01). The vitreous chamber of the steady red group (2.65±0.03 mm) was significantly shorter than normal (p<0.01). On average, steady blue light had little effect; the refractions paralleled the normal refractive decrease. In contrast, animals housed in flickering blue light increased the rate of refractive decrease so that the eyes became significantly myopic (−2.9±1.3 D) compared with the normal eyes and had longer vitreous chambers (2.93±0.04 mm). Upon return to colony lighting, refractions in all groups gradually returned toward emmetropia. These data are consistent both with the hypothesis that LCA can be an important visual cue for postnatal refractive development, and that short-wavelength temporal flicker provides an important cue for assessing and signaling defocus.