Siegwart J T, Norton T T
Department of Physiological Optics, School of Optometry, University of Alabama at Birmingham, AL 35294-4390, USA.
Vision Res. 1998 Nov;38(22):3505-15. doi: 10.1016/s0042-6989(98)00053-4.
To examine the susceptible period for deprivation-induced myopia, six groups of tree shrew pups (Tupaia glis belangeri) were monocularly deprived for 12 days with an opaque occluder starting 7, 15, 21, 33, 48, or 63 days after natural eyelid opening. Compared to the untreated fellow control eye, significant myopia and vitreous chamber elongation were produced by the deprivation in all six groups. The effect was greater in the middle three groups in comparison with the youngest and the two oldest groups and the amount of induced myopia and axial elongation was not proportional to the normal rate of axial growth. The peak period of susceptibility was between approximately 15 and 45 days after eye opening during the juvenile, slow-elongation phase of ocular development when the eye is within 7% of its adult axial length. Significant myopia and axial elongation were also induced in adult animals by 70 days of monocular deprivation. To examine recovery from deprivation-induced myopia, the occluder was removed at the end of the 12 day deprivation period. After an additional 48 days of binocular visual experience, no significant myopia was present in the previously deprived eyes in any experimental group. During the recovery period, the elongation rate of the previously deprived eyes was reduced in comparison with the control eyes while normal corneal flattening and lens development continued, thus reducing the myopia. No difference in corneal curvature, relative to the untreated control eyes, was found after deprivation or after the recovery period. Data are presented which suggests that changes in the thickness of the choroid may occur in this mammal during deprivation and recovery that are in the same direction, but of smaller magnitude, than those reported in the chicken. The results of this study provide evidence that visually guided emmetropization occurs in this mammalian species during a period of ocular development analogous to the juvenile period in humans.
为了研究剥夺性近视的易感期，将六组树鼩幼崽（Tupaia glis belangeri）在自然睁眼后7、15、21、33、48或63天开始用不透明眼罩单眼剥夺12天。与未处理的对侧对照眼相比，所有六组的剥夺均产生了显著的近视和玻璃体腔延长。与最年幼和最年长的两组相比，中间三组的效果更明显，诱导性近视和眼轴伸长量与正常眼轴生长速率不成正比。易感高峰期大约在睁眼后15至45天，处于眼发育的幼年、缓慢伸长阶段，此时眼睛的轴长在其成年轴长的7%以内。成年动物单眼剥夺70天也会诱导显著的近视和眼轴伸长。为了研究剥夺性近视的恢复情况，在12天剥夺期结束时移除眼罩。经过另外48天的双眼视觉体验后，任何实验组中先前被剥夺的眼睛均未出现显著近视。在恢复期，与对照眼相比，先前被剥夺的眼睛的伸长速率降低，而角膜正常变平和晶状体发育继续，从而减轻了近视。在剥夺后或恢复期后，相对于未处理的对照眼，角膜曲率没有差异。所呈现的数据表明，在该哺乳动物的剥夺和恢复过程中可能会发生脉络膜厚度的变化，其方向与鸡中报道的相同，但幅度较小。本研究结果提供了证据，表明在与人类幼年时期类似的眼发育阶段，该哺乳动物物种会发生视觉引导的正视化。
