Demer Joseph L
Department of Ophthalmology, Jules Stein Eye Institute, University of California at Los Angeles, Los Angeles, California 90095-7002, USA.
Invest Ophthalmol Vis Sci. 2008 Nov;49(11):4858-64. doi: 10.1167/iovs.08-2069. Epub 2008 Jul 3.
Paths of inactive lateral rectus (LR) muscles were studied to investigate putative roles of orbital fat and intrinsic muscle stiffness suggested to be alternatives to connective tissue pulleys as determinants of pulling direction.
Surface coil orbital magnetic resonance imaging was performed in axial planes in adult humans: seven with chronic unilateral LR paralysis, three with nonparalytic concomitant esotropia of similar angle, and 15 healthy controls. Fixation was controlled using targets placed at a broad range of horizontal positions.
Paralyzed LRs exhibited marked atrophy compared with functional contralateral LRs and LRs of orthotropic and esotropic subjects without LR paralysis. The normal LR exhibited a gradual 18.8 degrees +/- 4.5 degrees (mean +/- SD) lateral inflection 14.4 +/- 2.6 mm posterior to the globe center, bowing the LR away from the orbital center. The paralyzed LR exhibited a significantly (P < 0.002) larger and typically more discrete 29.2 degrees +/- 8.8 degrees lateral inflection, similar to that observed in concomitant esotropia in maximal adduction. Average position of this inflection was 11 to 14 mm posterior to the globe center in all three subject groups, but in LR palsy only the inflection of the paralyzed LR-0.17 mm further posterior per degree of abduction (linear fit, R = 0.85)-depended on horizontal gaze. The behavior of the paralyzed LR inflection was consistent with LR pulley anatomy.
Sharper lateral inflection in the flaccid rather than the tense LR seems inconsistent with intrinsic muscle stiffness or diffuse orbital fat pressure but suggests the influence of discrete connective tissue.
研究静止状态下外直肌（LR）的走行路径，以探讨眼眶脂肪和肌肉固有僵硬度的假定作用，它们被认为是决定牵拉方向的结缔组织滑车的替代因素。
对成年人进行表面线圈眼眶磁共振成像，扫描轴面：7例慢性单侧LR麻痹患者、3例类似角度的非麻痹性共同性内斜视患者和15例健康对照者。通过放置在广泛水平位置的目标来控制注视。
与对侧功能正常的LR以及无LR麻痹的正视和内斜视受试者的LR相比，麻痹的LR表现出明显萎缩。正常LR在眼球中心后方14.4±2.6mm处有一个逐渐的18.8°±4.5°（平均值±标准差）的外侧弯曲，使LR向远离眼眶中心的方向弯曲。麻痹的LR表现出明显更大（P<0.002）且通常更离散的29.2°±8.8°外侧弯曲，类似于在最大内收时共同性内斜视中观察到的情况。在所有三个受试者组中，该弯曲的平均位置在眼球中心后方11至14mm，但在LR麻痹中，仅麻痹LR的弯曲——每外展一度向后0.17mm（线性拟合，R=0.85）——取决于水平注视。麻痹LR弯曲的行为与LR滑车解剖结构一致。
松弛而非紧张的LR出现更明显的外侧弯曲，这似乎与肌肉固有僵硬度或弥漫性眼眶脂肪压力不一致，但提示离散结缔组织的影响。
