Chen Weiyi

An experimental study on collagen content and biomechanical properties of sclera after posterior sclera reinforcement.

BACKGROUND The development of pathological myopia is associated with reduced scleral collagen accumulation, scleral thinning, and loss of scleral tissue, in both humans and animal models. Posterior scleral reinforcement (PSR) was considered as an effective way for treating pathological myopia. Yet it is not well understood the possible role of collagen on the sclera reinforcement mechanisms in the PSR surgery. METHODS PSR surgery was performed on the normal adult New Zealand white rabbits eyes. Human sclera was used as reinforcement materials. At 1, 2, 3, 6, 9 months after the PSR surgery, scleral hydroxyproline (Hyp) synthesis and collagen fibers arrangement were determined by enzymolysic hydrolysis assay and histological morphology technique. An Instron test machine was used to investigate the elastic modulus of sclera. FINDINGS It was found that the elastic modulus and Hyp content of reinforced sclera were lower at first month after surgery, and then gradually up to physiological level in the following months. Those two indexes were close to that of the normal control groups at 9 months. INTERPRETATION These findings indicate that sclera elastic modulus was associated with both change of Hyp content and collagen fibers arrangement after PSR. The therapeutic effect of PSR surgery was confirmed not only from biological but also biomechanical aspects.

Derivation of the general form of elasticity tensor of the transverse isotropic material by tensor derivate

In the paper the elasticity tensor and the relation between stress and strain of transverse isotropic material and isotropic material are deduced by tensor derivate. From the derivation the reason why there are two independent elasticity co-efficients for isotropic elastic material and five for transverse isotropic elastic material can be seen more clearly.

Biomechanical Properties of Experimental Myopia in the Guinea Pig

A lens induce myopia model in 12 healthy guinea pigs was used in this study. For each guinea pig, one eye was selected randomly for myopia model, another served as a paired control. After 45 days, eye became myopic and elongated in myopia model. The alteration of eye volume with intraocular pressure was determined. Cornea and sclera strips were prepared for biomechanical properties measurement through uniaxial tension using Instron 5544 test machine. Our results showed that the ocular rigidity coefficient of myopia model eyeballs was lower than the control ones. Furthermore, under the physiological eye pressure, the elastic modulus of either sclera or cornea decreased significantly as compared to control ones. The ANSYS finite element simulation also confirmed that the maximal shape deformation of eyeball occurred in the polar of the post sclera and the maximal strain in the myopia model eyes was higher than the control ones.

Biomechanical Analysis of Odontoid Fracture with Different Loads by Finite Element Method

In this paper, a three-dimensional (3D) FE model of the healthy human axis was built considered cortical and cancellous bone. The model was validated using numerical results obtained by other authors. The stress distribution and potential fracture patterns of the anterior odontoid were analyzed under different loading direction within coronal plane and sagittal plane. The direction of loading is the main factor resulting in odontoid fracture. The results of FE analysis would be referenced by surgeon.