不同电刺激水平下眼外肌的本构关系研究

The accuracy of the amount of extraocular muscle (EOM) surgery is the key to the successful strabismus surgery. Millions of people in our country suffer from strabismus, and they need to accept surgical treatment. Establishing an eye movement model with all EOMs will be theoretically and clinically important to determine the amount of EOM surgery and realize the personalized design of the surgery of EOM. The constitutive relations of passively stretched EOMs have been well studied at present. However，the constitutive relations of EOMs at different innervations, which are crucial to the accuracy of eye movement modeling, have not been reported. In this project, we will establish the constitutive relations of EOMs stimulated by different electric currents through animal experiment. The research contains the following three parts. Firstly, the anatomical data of the orbit of rabbit are obtained by using the magnetic resonance imaging. Secondly, the animal is anesthetized, and the afferent nerve of the single EOM is stimulated by electric currents with different intensities and different frequencies. Meanwhile, the relationship of elongation-tension of the EOM is tested. Then the constitutive relations of the EOMs, with different electrical stimulation, are obtained. Thirdly, the corresponding eye movement model with various electrical stimulation is established, and the relationship between the rotational angle of the eyeball and the external force torque is calculated. And the control eye of the animal is rotated while it was stretched. The constitutive relations of the EOMs and the corresponding eye movement model are verified by the comparison between the experiment results and the modeling results. The project can provide the theoretical significance for biomechanics of the eye and improve the precision of the surgical amount of the EOM clinically.

眼外肌手术量的准确性是斜视手术成功的关键，我国有成百万的斜视患者需要接受手术治疗。建立考虑全部眼外肌的眼球运动模型，对确定眼外肌手术量、实现眼外肌手术的个性化设计具有重要的理论价值和临床实际意义。目前只有眼外肌被动拉伸的本构关系，眼外肌在不同神经兴奋水平下的本构关系还未见诸报道，后者对眼球运动建模的精确性至关重要。本项目拟通过动物实验建立眼外肌在不同电刺激水平下的本构关系。研究内容包括，通过核磁共振技术获取兔眼眶的解剖学数据；麻醉动物，在对单条眼外肌的传入神经进行电刺激（不同强度、频率）的同时，测试其伸长-拉力关系，最终得到各眼外肌在不同电刺激下的本构关系；建立相应的眼球运动模型，计算不同电刺激下眼球的转角与外力转矩的关系并与动物对照眼被动牵拉转动的实测结果进行对照，对眼外肌的本构关系和相应的眼球运动模型进行验证。项目对眼生物力学有重要的理论意义并对精确化眼外肌手术量有重要的临床指导意义。

眼外肌手术量的准确性是斜视手术成功的关键。建立考虑全部眼外肌、眼眶悬挂组织、视神经及眼外肌与巩膜粘附作用的眼球运动模型，对确定眼外肌手术量、实现眼外肌手术的个性化设计具有重要的理论价值和临床实际意义。目前在眼球运动建模中，眼眶悬挂组织的刚度、视神经对眼球运动的作用、眼外肌与巩膜之间的粘附作用都还不清楚。本项目的研究内容分为三部分。第一部分通过动物实验研究眼球运动过程中含四条眼外肌和不含眼外肌的眼眶悬挂组织的阻力和刚度。结果表明含四条眼外肌和不含眼外肌的眼眶悬挂组织的阻力值没有统计学差异，而刚度值有显著性差异。说明以往被用在眼球运动建模过程中的含眼外肌的眼眶悬挂组织的刚度是不准确的。第二部分通过逆向重建方法建立包含巩膜、角膜、晶状体、玻璃体、6条眼外肌和视神经的眼球运动三维模型，将模型分为有、无视神经两组并对其进行了有限元分析。结果表明同等受力情况下，无视神经组比有视神经组眼球转动角度更大。研究表明当眼球在小范围内运动时，视神经对眼球运动起明显作用。第三部分用不同尺寸的球形压头对不同湿度的猪眼外肌条带做了离体压痕实验，测试了眼外肌的粘附行为，并用Kendall模型进行了理论分析。进一步将眼外肌的粘附行为包含在传统的眼球运动模型中，分析了眼外肌与巩膜之间的粘附行为对眼球外转的调节作用。结果表明随着眼球外转角度的不同，外直肌和巩膜之间的粘附力是一个常数值。表明外直肌和巩膜之间的粘附对眼球外转运动有调控作用。由于粘附作用的调控，巩膜在眼球运动过程中才能维持稳定的形态。研究结果对眼生物力学有重要的理论意义并对精确化眼外肌手术量有重要的临床指导意义。