Biomechanical Behavior Of Extraocular Muscles And The Visualized Analysis Of The Model Of Eye Movement

The coordination of the eyeball is controlled by the brain center in order to keep the consistent function of the two eyeballs.But the disorder of the brain center or the function of the extraocular muscles could lead to the result that the two eyeballs can not fix the target synchronously with the separated visual axises.The main function of extraocular muscles (EOMs) is controlling eye movement, thus they are the indispensable components in the study of eye modeling. EOMs contain six muscles, i.e., superior rectus (SR), inferior rectus (IR), lateral rectus (LR), medial rectus (MR), superior oblique (SO), and inferior oblique (10). The main objectives of this work are investigating the mechanical behaviors of EOMs and modeling the3D finite element model for eye tissues, and then analyzing EOMs controlling eye rotation using this finite element model.The so-called strabismus surgery is that the anatomical factors and the neural factors are changed by reinforcing or weakening the strength of the extraocular muscles to correct the abnormal eye and restore the two eyeballs as a single view.Gennerally,the strabismus can be corrected by shortening or strengthening the extraocular muscles.Because of the complicated mechanism of the extraocular muscles movement,most of the judgements of the surgical operation quantity are based on the clinical experience and the effect of the operation is difficult to predict. In recent years,a model interpreting the coordination mechanism of the two eyeballs is gradually used to the treatment of the strabismus,which could predict the effect of the surgery accurately. As an important component of the orbital tissues,the biomechanical properties of the extraocular muscles are essential to the3D modeling and the qualitative and quantitative analysis of the correction effect of the strabismus surgery.In this paper,the uniaxial tensile experiment of the extraocular muscle of the swine in vitro is conducted to detect the mechanical behavior of the extraocular muscles. The3D finite element model of the orbital tissues is established based on the experimental data.And the relationships between the extraocular muscles and rotational angles of the eyeball are analyzed which could provide the theoretical basis and the guidance for the clinical strabismus surgery.The main contents and conclusions of the paper are as follows.1.The porcine extraocular muscles were selected to test. All the porcine extraocular rectus muscles were obtained in vitro from a local abattoir.And the uniaxial tensile experiment was conducted so that the stress-strain relationships of the porcine extraocular muscles were obtained.2.The hyperelastic model of the Mooney-Rivlin constitutive model and the Ogden constitutive model were used to fit the experimental data,respectively.The parameters of the hyperelastic properties of the extraocular muscles were analyzed and imported into the ABAQUS of the numerical modeling software to establish the finite element model.Therefore,the rationality of the passive behavior of the extraocular muscles described by the hyperelastic model was verified.Compared with the experimental results,it showed that the hyperelastic constitutive model could describe the passive behavior of the extraocular muscles well.And the small deformation of the extraocular muscles could be described better by the Mooney-Rivlin constitutive model than by the Ogden constitutive model.3.Referring to the relevant geometric parameters of the eyeball and the extraocular muscles obtained from the data of the orbital anatomy,the finite element model of the orbital tissues was established. The eyeball and the geometric dimention of the six extraocular muscles could be reflected better by the model.The eyeball was considered as the linear elastic material.And the extraocular muscles were considered as the hyperelastic material and the hyperelastic parameters which was obtained from the fitting of the porcine experimental data were used.The relationships between the eye movements and the forces of the extraocular muscle were analyzed by applying the load and the displacement to the obove finite element model.The simulation results had good match with the clinical data.