Narasimhan Anita, Tychsen Lawrence, Poukens Vadims, Demer Joseph L
Department of Ophthalmology, University of California, Los Angeles, CA, USA.
Invest Ophthalmol Vis Sci. 2007 Jun;48(6):2576-88. doi: 10.1167/iovs.06-0662.
Structural abnormalities of extraocular muscles (EOMs) or their pulleys are associated with some forms of human strabismus. This experiment was conducted to investigate whether such abnormalities are associated with artificial or naturally occurring strabismus in monkeys.
Binocular alignment and grating visual acuities were determined in 10 monkeys representing various species using search coil recording and direct observations. Four animals were orthotropic, two had naturally occurring "A"-pattern esotropia, two had concomitant and one had "V"-pattern esotropia artificially induced by alternating or unilateral occlusion in infancy, and one had "A"-pattern exotropia artificially induced by prism wear. After euthanasia, 16 orbits were examined by high-resolution magnetic resonance imaging (MRI) in the quasi-coronal plane. Paths and sizes of horizontal rectus EOMs were analyzed quantitatively in a standardized coordinate system. Whole orbits were then serially sectioned en bloc in the quasi-coronal plane, stained for connective tissue, and compared with MRI. Nerve and EOM features were analyzed quantitatively.
Quantitative analysis of MRI revealed no significant differences in horizontal rectus EOM sizes or paths among orthotropic or naturally or artificially strabismic monkeys. Histologic examination demonstrated no differences in EOM size, structure, or innervation among the three groups, and no differences in connective tissues in the pulley system. The accessory lateral rectus (ALR) EOM was present in all specimens, but was small, inconsistently located, and sparsely innervated. Characteristics of the ALR did not correlate with strabismus.
Major structural abnormalities of horizontal rectus EOMs and associated pulleys are unrelated to natural or artificial horizontal strabismus in the monkeys studied. The ALR is unlikely to contribute to horizontal strabismus in primates. However, these findings do not exclude a possible role of pulley abnormalities in disorders such as cyclovertical strabismus.
眼外肌（EOMs）或其滑车的结构异常与某些形式的人类斜视有关。进行本实验以研究此类异常是否与猴子的人工或自然发生的斜视有关。
使用搜索线圈记录和直接观察法，对代表不同物种的10只猴子进行双眼视轴对准和光栅视力测定。4只动物为正视眼，2只患有自然发生的“A”型内斜视，2只患有共同性斜视，1只因婴儿期交替或单侧遮盖人工诱发了“V”型内斜视，1只因佩戴棱镜人工诱发了“A”型外斜视。安乐死后，在准冠状平面上通过高分辨率磁共振成像（MRI）检查16个眼眶。在标准化坐标系中对水平直肌EOMs的路径和大小进行定量分析。然后将整个眼眶在准冠状平面上进行连续整块切片，对结缔组织进行染色，并与MRI结果进行比较。对神经和EOM特征进行定量分析。
MRI定量分析显示，正视眼或自然或人工斜视的猴子之间，水平直肌EOMs的大小或路径无显著差异。组织学检查表明，三组之间EOMs的大小、结构或神经支配无差异，滑车系统中的结缔组织也无差异。所有标本中均存在副外侧直肌（ALR）EOM，但体积小、位置不一致且神经支配稀疏。ALR的特征与斜视无关。
在所研究的猴子中，水平直肌EOMs及其相关滑车的主要结构异常与自然或人工水平斜视无关。ALR不太可能导致灵长类动物的水平斜视。然而，这些发现并不排除滑车异常在诸如旋转斜视等疾病中的可能作用。
