Department of Anatomy and Cell Biology, Wayne State University, Detroit, MI 48201, United States.
Exp Eye Res. 2013 Oct;115:87-95. doi: 10.1016/j.exer.2013.06.025. Epub 2013 Jul 6.
It was recently demonstrated that refractive errors in mice stabilize around emmetropic values during early postnatal development, and that they develop experimental myopia in response to both visual form deprivation and imposed optical defocus similar to other vertebrate species. Animal studies also suggest that photopic vision plays critical role in emmetropization in diurnal species; however, it is unknown whether refractive eye development is guided by photopic vision in the mouse, which is a nocturnal species. We used an infrared mouse photorefractor and a high-resolution MRI to clarify the role of photopic visual input in refractive eye development in the mouse. Refractive eye development and form-deprivation myopia in P21-P89 C57BL/6J mice were analyzed under 12:12 h light-dark cycle, constant light and constant darkness regimens. Animals in all experimental groups were myopic at P21 (-13.2 ± 1.6 D, light-dark cycle; -12.5 ± 0.9 D, constant light; -12.5 ± 2.0 D, constant dark). The mean refractive error in the light-dark-cycle-reared animals was -0.5 ± 1.3 D at P32 and, and did not change significantly until P40 (+0.3 ± 0.6 D, P40). Animals in this group became progressively hyperopic between P40 and P89 (+2.2 ± 0.6 D, P67; +3.7 ± 2.0 D, P89). The mean refractive error in the constant-light-reared mice was -1.0 ± 0.7 D at P32 and remained stable until P89 (+0.1 ± 0.6 D, P40; +0.3 ± 0.6 D, P67; 0.0 ± 0.4 D, P89). Dark-reared animals exhibited highly hyperopic refractive errors at P32 (+5.2 ± 1.8 D) and became progressively more hyperopic with age (+8.7 ± 1.9 D, P40; +11.2 ± 1.4 D, P67). MRI analysis revealed that emmetropization in the P40-P89 constant-light-reared animals was associated with larger eyes, a longer axial length and a larger vitreous chamber compared to the light-dark-cycle-reared mice. Constant-light-reared mice also developed 4 times higher degrees of form-deprivation myopia on average compared to light-dark-cycle-reared animals (-12.0 ± 1.4 D, constant light; -2.7 ± 0.7 D, light-dark cycle). Dark-rearing completely prevented the development of form-deprivation myopia (-0.3 ± 0.5 D). Thus, photopic vision plays important role in normal refractive eye development and ocular response to visual form deprivation in the mouse.
最近的研究表明，在早期的产后发育过程中，小鼠的屈光不正会稳定在正视值附近，并且它们会像其他脊椎动物一样对视觉形态剥夺和施加的光学离焦产生实验性近视。动物研究还表明，在昼行性物种中，光觉在正视化中起着关键作用；然而，尚不清楚在作为夜行性物种的小鼠中，屈光眼发育是否由光觉指导。我们使用红外小鼠光折射仪和高分辨率 MRI 来阐明光觉输入在小鼠屈光眼发育中的作用。在 12:12 小时明暗循环、持续光照和持续黑暗条件下，分析了 P21-P89 C57BL/6J 小鼠的屈光眼发育和形态剥夺性近视。在所有实验组中，P21 时的动物均为近视（13.2±1.6 D，明暗循环；12.5±0.9 D，持续光照；12.5±2.0 D，持续黑暗）。明暗循环饲养的动物在 P32 时的平均屈光误差为-0.5±1.3 D，直到 P40 时，其值并未发生明显变化（0.3±0.6 D，P40）。该组动物在 P40 至 P89 之间逐渐远视（2.2±0.6 D，P67；3.7±2.0 D，P89）。在持续光照饲养的老鼠中，P32 时的平均屈光误差为-1.0±0.7 D，直到 P89 时仍保持稳定（0.1±0.6 D，P40；0.3±0.6 D，P67；0.0±0.4 D，P89）。黑暗饲养的动物在 P32 时表现出高度远视的屈光误差（+5.2±1.8 D），并且随着年龄的增长，远视程度逐渐增加（+8.7±1.9 D，P40；+11.2±1.4 D，P67）。MRI 分析显示，P40-P89 持续光照饲养的动物在正视化过程中眼睛更大、眼轴更长、玻璃体腔更大，与明暗循环饲养的动物相比。持续光照饲养的老鼠还平均发展出高出 4 倍的形态剥夺性近视（-12.0±1.4 D，持续光照；-2.7±0.7 D，明暗循环）。黑暗饲养完全阻止了形态剥夺性近视的发展（-0.3±0.5 D）。因此，光觉在小鼠正常屈光眼发育和视觉形态剥夺的眼反应中起着重要作用。
