Oh Sei Yeul, Clark Robert A, Velez Federico, Rosenbaum Arthur L, Demer Joseph L
Department of Ophthalmology, Jules Stein Eye Institute, University of California Los Angeles, 100 Stein Plaza, Los Angeles, CA 90095-7002, USA.
Invest Ophthalmol Vis Sci. 2002 Jul;43(7):2169-78.
Connective tissue pulleys serve as functional mechanical origins of the extraocular muscles (EOMs) and are normally stable relative to the orbit during gaze shifts. This study evaluated pulley stability in incomitant strabismus.
Contiguous 2- or 3-mm thick magnetic resonance images (MRIs) perpendicular to the orbital axis spanned the anteroposterior extents of 12 orbits of six patients with incomitant strabismus. Imaging was performed in central gaze, supraduction, infraduction, abduction, and adduction. Rectus EOM paths were defined by their area centroids and plotted in a normalized, oculocentric coordinate system. Paths of EOMs ran toward the pulleys. Sharp EOM path inflections in secondary gaze indicated pulley locations in three dimensions.
MRI revealed substantial inferior shift of the lateral rectus (LR) pulley of up to 1 mm during vertical gaze shifts in patients with axial high myopia and a posterior shift from abduction to adduction in simulated Brown syndrome. There was substantial LR pulley shift opposite the direction of vertical gaze in a subject with X-pattern exotropia who had undergone repeated LR surgery. The medial rectus (MR) pulley shifted inferiorly with gaze elevation in Marfan syndrome. Pulley instability was associated with significantly increased globe translation during gaze shifts.
Pulley instability, resulting in EOM sideslip during ductions, occurs in some cases of incomitant strabismus. Resultant patterns of strabismus may depend on static pulley positions, pulley instability, and coexisting globe translation that alters pulley locations relative to the globe. Translational instability of pulleys and the globe could produce abnormalities in actions of otherwise normal EOMs, and connective tissue disorders causing these instabilities should be considered as potential causes of strabismus.
结缔组织滑车作为眼外肌（EOMs）的功能性机械起点，在眼球注视转移过程中通常相对于眼眶保持稳定。本研究评估了非共同性斜视中滑车的稳定性。
对6例非共同性斜视患者的12个眼眶进行垂直于眼眶轴的连续2或3毫米厚的磁共振成像（MRI），覆盖前后范围。成像在中央注视、上转、下转、外展和内收时进行。直肌眼外肌路径通过其面积质心定义，并绘制在归一化的眼心坐标系中。眼外肌路径朝向滑车延伸。二级注视时眼外肌路径的急剧转折表明滑车在三维空间中的位置。
MRI显示，轴性高度近视患者在垂直注视转移过程中，外直肌（LR）滑车显著向下移位达1毫米；在模拟布朗综合征中，从外展到内收时滑车向后移位。一名接受过多次LR手术的X型外斜视患者，其LR滑车在垂直注视方向的相反方向有明显移位。在马凡综合征患者中，内直肌（MR）滑车随注视上抬向下移位。滑车不稳定与注视转移过程中眼球平移显著增加有关。
在某些非共同性斜视病例中，滑车不稳定会导致眼球运动时眼外肌侧滑。斜视的最终模式可能取决于滑车的静态位置、滑车不稳定以及同时存在的眼球平移，后者会改变滑车相对于眼球的位置。滑车和眼球的平移不稳定可能导致原本正常的眼外肌动作出现异常，应将导致这些不稳定的结缔组织疾病视为斜视的潜在病因。
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