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目的研究眼外肌滑车系统在眼球大幅度内旋时的生物力学作用。方法结合文献报道的眼外肌坐标参数,根据眼球运动的力学平衡原理,建立主动滑车力学模型,并以无滑车模型作为对照,模拟眼球在30°~45°范围内的内旋运动。结果在内直肌对眼球内旋运动的贡献方面,无滑车模型的内直肌提供的作用力大于主动滑车模型,且内直肌力值明显大于生理安全极限值(约0.5 N)。在模拟眼球内旋的最大角度45°处,主动滑车模型和无滑车模型模拟得到的内直肌力分别为0.508、0.782 N,后者超过生理阈值约56%。在控制眼球运动方面,主动滑车模型消耗的能量远小于无滑车模型。结论滑车组织的存在,使得眼外肌能够以较低的耗能控制眼球运动,加强了眼外肌对眼球的牵引作用。而且,在眼球大幅度内旋运动时,主动滑车模型维持着内直肌的力学优势。
Objective To study the biomechanical effect of extraocular muscle block system on a large internal rotation of the eyeball. Methods According to the coordinate parameters of extraocular muscle reported in the literature, the dynamic model of the active pulley was established according to the principle of mechanics balance of the eye movement. The internal rotation motion of the eyeball in the range of 30 ° ~ 45 ° was simulated by using the non - pulley model as control. Results In the contribution of the medial rectus muscle to the rotational movement of the eye, the force exerted by the medial rectus without the pulley model provided more force than the active pulley model, and the force value of the medial rectus muscle was significantly greater than the physiological safety limit (about 0.5 N). At the maximal angle of 45 °, the maximal internal rotation of the eyeball was 0.508 and 0.782 N, respectively, for the active pulley model and the no-pulley model. The latter exceeded the physiological threshold by about 56%. In controlling the eye movement, the active pulley model consumes much less energy than the non-pulley model. Conclusion The existence of the pulley block makes the extraocular muscle can control the eye movement with lower energy consumption and enhance the traction of the extraocular muscle to the eyeball. Moreover, the active tackle model maintains the mechanical advantage of the medial rectus muscle with substantial internal rotation of the eye.