High Myopic Strbismus Study Based On Mechanical And Finite Element Modeling And Analysis

High myopic strabismus is one of many complications of high myopia. With the progression of the disease, strabismus fixus will appear and the affected eyeball will be limited to the nasal and inferior corner. With the severely limited visual field, life quality of the patients will be vehemently affected. Base on the observed features from MRI imaging, some hypotheses of the etiology are proposed, but the etiology still can’t be confirmed due to the limited imaging and observation conditions. At present, the treatment of high myopic strabismus is based on operation, which can be divided into traditional oextraocular muscular operation and Yokoyama operation. The specific choice of operation style is still to be studied, but Yokoyama operation has been proved effective. Generally, the necessity of Yokoyama operation is judged by the angle measurement.To study the general pattern of eye movement, a new 3-dimensional coordinate system is put forward to simplified the expression of Listing’s Law. An new algorithm of eye torsion measurement is therefore proposed. On this basis, a simplified theoretically mechanical model is constructed to simulate the effect of an oblique lateral rectus on the formation of strabismus. The results confirmed the rectus obliquity as a minor pathogenic factor.To study other pathogenic factors, the 3-dimensional finite element analysis (FEA) models based on clinical MRI imaging are constructed. By simulating the eye rotation directly caused by forces on the eyeballs, the rationality of the models is confirmed. The judging criterion of necessity of Yokoyama operation is applied and proved to be effective. Simultaneously, the rationality of the model is confirmed again.Based on the 3-D FEA model, the muscular characteristics of normal,high myopic and high myopic strabismic eyes are simulated respectively. By comparing and analyzing the results, the etiology of high myopic strabismus is concluded. The nasal deviation of eyeball and increasing friction and pression between intraorbital tissues caused by eyeball displacement are the main pathogeneses. Additionally, the distorted lateral rectus is related with esotropia. And the pressure from other tissues may play a role in the formation process of hypotropia.It’s the first time that FEA model of eye with high myopic strabismus is built and used to study the etiology. The resultant hypotheses are supported strongly by the clinical observationdata.