Feldkaemper M, Diether S, Kleine G, Schaeffel F
University Eye Hospital, Experimental Ophthalmology, Roentgenweg 11, Tuebingen, 72076, Germany.
Exp Eye Res. 1999 Jan;68(1):105-15. doi: 10.1006/exer.1998.0590.
Degrading the retinal image by frosted eye occluders produces elongated eyes and 'deprivation myopia' in a variety of animal models. The postulated retinal 'deprivation detector' is quite sensitive to even small changes in image contrast or spatial frequency composition. Because psychophysical experiments have shown that a decline in luminance shifts the contrast sensitivity function to lower spatial frequencies, it is likely that only a reduced spatial frequency range is available for image analysis to control eye growth. It is even possible that the compression might be sufficient to promote deprivation myopia. We have tested this hypothesis, using the animal model of the chicken. (1) At an ambient illumination of 550 lux (about 76 cd m-2), neutral density (ND) filters placed in front of the eye with 0.0, 0.5 or 1.0 log unit attenuation did not change refractive development. However, monocularly or binocularly attached filters with 2 log units attenuation produced 5-7 D of myopia relative to normal eyes. Black occluders were not more effective. Frosted eye occluders with little effect on image brightness (about 0.5 log units attenuation) produced much more myopia (about 16 D compared with the controls). (2) The effects of the ND filters on refractive development could not be reproduced if the ambient illumination was reduced by 2 log units. Probably, minor effects on image quality were introduced by optical imperfections of the ND filters which were more critical at low retinal image brightness. (3) In an optomotor experiment (spatial frequency 0.2 cyc deg-1, stripe speed 57 deg sec-1), it was shown that the chickens' contrast sensitivity was severely reduced when the eyes were covered by 2.0 ND filters. (4) Since there is evidence that changes in dopamine release from the retina may be one of the factors affecting the development of myopia, we have tested how selective these changes were for spatial information. It was found that dopamine release was controlled by both spatial and luminance information and that the inputs of both could be scarcely separated. (5) Because the experiments show that the eye becomes more sensitive to image degradation at low light, the human eye may also be more prone to develop myopia if the light levels are low during extended periods of near work.
在多种动物模型中，用磨砂眼罩使视网膜图像退化会导致眼睛变长并出现“剥夺性近视”。假定的视网膜“剥夺探测器”对图像对比度或空间频率组成的微小变化都相当敏感。由于心理物理学实验表明，亮度下降会使对比度敏感度函数向较低空间频率偏移，因此很可能只有缩小的空间频率范围可用于图像分析以控制眼球生长。甚至有可能这种压缩足以促进剥夺性近视。我们使用鸡的动物模型对这一假设进行了测试。（1）在550勒克斯（约76坎德拉每平方米）的环境光照下，置于眼前的中性密度（ND）滤光片，其衰减为0.0、0.5或1.0对数单位时，不会改变屈光发育。然而，单眼或双眼佩戴衰减为2对数单位的滤光片会相对于正常眼睛产生5 - 7屈光度的近视。黑色眼罩效果并不更好。对图像亮度影响很小（约0.5对数单位衰减）的磨砂眼罩会产生更多近视（与对照组相比约为16屈光度）。（2）如果环境光照降低2对数单位，ND滤光片对屈光发育的影响就无法再现。可能是ND滤光片的光学缺陷对图像质量产生了微小影响，而在低视网膜图像亮度下这种影响更为关键。（3）在一个视动实验中（空间频率0.2周/度，条纹速度57度/秒），结果表明当眼睛被2.0的ND滤光片覆盖时，鸡的对比度敏感度会严重降低。（4）由于有证据表明视网膜多巴胺释放的变化可能是影响近视发展的因素之一，我们测试了这些变化对空间信息的选择性如何。结果发现多巴胺释放受空间和亮度信息两者控制，且两者的输入几乎无法区分。（5）因为实验表明眼睛在低光照下对图像退化变得更敏感，所以如果在长时间的近距工作期间光照水平较低，人眼也可能更容易发展为近视。
