Mori Takafumi, Matsuura Kazuki, Zhang Bin, Smith Earl L, Chino Yuzo M
College of Optometry, University of Houston, Houston, Texas 77204-2020, USA.
Invest Ophthalmol Vis Sci. 2002 Apr;43(4):1262-9.
To determine how the duration of early strabismus influences the severity of loss of disparity sensitivity in V1 neurons and the effects of extensive poststrabismus visual experience on the maintenance of functional binocular connections.
Concomitant strabismus was optically simulated in 10 rhesus monkeys using a prism-rearing procedure. The onset of strabismus was kept constant at 4 weeks of age and the duration was maintained for 2, 4, or 8 weeks. In one group of monkeys (infants), the neurophysiological experiments were conducted immediately after the period of rearing with prisms. In another group (adults), after the termination of the prism-rearing regimen at either 8 or 12 weeks of age, the monkeys were kept in a normal housing environment until maturity and behavioral testing was conducted before the recording experiments to determine the animal's monocular and binocular visual capacities. To assess the effects of the period of early strabismus on binocular interactions in V1, extracellular single-unit recording methods were used in anesthetized and paralyzed monkeys, and dichoptic sine-wave gratings were used as stimuli.
In all strabismic monkeys, the sensitivity of V1 units to interocular spatial phase disparity (disparity sensitivity) was significantly reduced, and the prevalence of binocular suppression was higher than that found in age-matched control animals. Although 8 weeks of strabismus resulted in a slightly larger loss of disparity sensitivity, the overall effects of the duration of strabismus were surprisingly small in infant strabismic monkeys. After poststrabismus visual experience, a small but significantly higher degree of disparity sensitivity was noted in V1 if prism-rearing was terminated after 4 weeks of strabismus (i.e., at 8 weeks of age), but not after 8 weeks of strabismus (i.e., at 12 weeks of age).
A brief period (2 weeks) of misalignment after the emergence of stereopsis is sufficient to drastically reduce the functional binocular connections in V1, and longer periods of strabismus result in little additional loss in disparity sensitivity. Clinically, these results suggest that taking corrective measures for infantile esotropes before the known onset age for stereopsis may be important for maintaining better binocular sensory function and better interocular alignment at later stages of development.
确定早期斜视的持续时间如何影响V1神经元中视差敏感性丧失的严重程度，以及斜视后广泛的视觉经验对功能性双眼连接维持的影响。
使用棱镜饲养程序在10只恒河猴中光学模拟共同性斜视。斜视的起始时间保持在4周龄不变，持续时间维持2、4或8周。在一组猴子（幼猴）中，在棱镜饲养期结束后立即进行神经生理学实验。在另一组（成年猴）中，在8周或12周龄时终止棱镜饲养方案后，将猴子饲养在正常环境中直至成熟，并在记录实验前进行行为测试以确定动物的单眼和双眼视觉能力。为了评估早期斜视期对V1中双眼相互作用的影响，在麻醉和麻痹的猴子中使用细胞外单单位记录方法，并使用双眼正弦波光栅作为刺激。
在所有斜视猴子中，V1单位对两眼间空间相位视差（视差敏感性）的敏感性显著降低，双眼抑制的发生率高于年龄匹配的对照动物。尽管8周的斜视导致视差敏感性的损失略大，但在婴儿斜视猴子中，斜视持续时间的总体影响出人意料地小。斜视后视觉经验后，如果在斜视4周后（即8周龄）终止棱镜饲养，V1中视差敏感性会有轻微但显著更高的程度，但在斜视8周后（即12周龄）则没有。
立体视觉出现后短暂的（2周）眼位不正足以大幅减少V1中的功能性双眼连接，更长时间的斜视对视差敏感性的额外损失很小。临床上，这些结果表明，在已知立体视觉开始年龄之前对婴儿内斜视采取矫正措施，对于在发育后期维持更好的双眼感觉功能和更好的眼间对齐可能很重要。
