Crewther Sheila G, Barutchu Ayla, Murphy Melanie J, Crewther David P
School of Psychological Science, La Trobe University, Plenty Rd, Bundoora, Melbourne, Vic. 3086, Australia.
Exp Eye Res. 2006 Aug;83(2):322-8. doi: 10.1016/j.exer.2005.12.016. Epub 2006 Mar 31.
Emmetropization, the process by which ocular growth of young animals adapts to ensure focussed retinal images, can be disrupted by high frequency flicker, causing a hypermetropic shift. Emmetropization can also be disrupted differentially, in a sign dependent manner, by pharmacological alteration of the balance of activation of the ON and OFF retinal sub-systems in normal light or by rearing in an environment with a moving spatiotemporally varied diamond pattern (yielding local sawtooth illumination on the retina). Thus the aim of this experiment was to determine whether low frequency temporal modulation alone was sufficient to cause defocus sign-dependent interference with compensation. Chicks were reared for 6 or 7 days with monocular +/-10 D, 0 D, or No Lenses in a 12h light/dark cycle. Luminance of the environment was temporally modulated during the light cycle with a non-square wave profile pulse of 250 msec duration, with the illumination fluctuating between 1.5 and 180 lux at 1 Hz, 2 Hz, 4 Hz or with no flicker (0 Hz-180 lux). Final refractive state and ocular dimensions, measured using retinoscopy and A-scan ultrasonography, demonstrated that in the absence of temporal luminance modulation (0 Hz), chicks compensated to induced defocus in the expected sign-dependent manner. However, under 1, 2 and 4 Hz flickering light conditions, there was an overall myopic offset of approximately 6D across lens groups with refractive compensation to positive lenses more strongly inhibited. This myopic offset was reflected by increases in the depth of both vitreous and anterior chambers. However, luminance modulation had no effect on refraction or ocular parameters in the No Lens conditions. This is a hitherto unreported strong interaction between lens wear and low frequency temporally modulated light, with the refractive compensation mechanism being overridden by a generalized myopic shift.
正视化是幼小动物眼睛生长以确保视网膜图像聚焦的过程，高频闪烁会干扰这一过程，导致远视性偏移。正视化也可能以一种与信号相关的方式受到不同程度的干扰，在正常光照下，通过药理学改变视网膜ON和OFF子系统激活的平衡，或者在具有时空变化的移动菱形图案（在视网膜上产生局部锯齿状照明）的环境中饲养动物。因此，本实验的目的是确定仅低频时间调制是否足以引起与补偿相关的散焦信号依赖性干扰。将雏鸡在12小时光照/黑暗周期中，单眼佩戴+/-10 D、0 D或不戴镜片饲养6或7天。在光照周期内，环境亮度通过持续250毫秒的非方波脉冲进行时间调制，光照在1赫兹、2赫兹、4赫兹下在1.5至180勒克斯之间波动，或无闪烁（0赫兹 - 180勒克斯）。使用检影法和A超超声检查测量最终屈光状态和眼部尺寸，结果表明，在没有时间亮度调制（0赫兹）的情况下，雏鸡以预期的信号依赖性方式对诱导的散焦进行了补偿。然而，在1赫兹、2赫兹和4赫兹闪烁光条件下，各镜片组总体近视偏移约6D，对正镜片的屈光补偿受到更强抑制。这种近视偏移表现为玻璃体腔和前房深度增加。然而，在不戴镜片的情况下，亮度调制对屈光或眼部参数没有影响。这是迄今为止未报道的镜片佩戴与低频时间调制光之间的强烈相互作用，屈光补偿机制被普遍的近视偏移所取代。
