STUDY OF THE TRANSVERSAL DEFORMATION OF CORNEAL STRIP UNDER UNIAXIAL LOADING

Uniaxial test is easy to access and to obtain accuracy data, but it is difficult to acquire two-dimensional deformation information. We investigated the relationship between the two strain components of corneal strip in uniaxial tests, which is the basis for determining of anisotropic strain energy function of cornea via uniaxial tests. Nine rabbits were taken. The left and right corneas were cut along superior-inferior (SI) and nasal-temporal (NT) direction, respectively. For each strip the uniaxial test was carried out, and the tensile displacements, strip images and loads were recorded. Then the stretching strain, the transversal strains and stress were obtained. Optimization based inverse analysis was utilized to find the best among six fitting models that characterizes the relationship between two strain components in uniaxial tests. All models fitted well the experimental data gathered for corneal strips (R-2 > 0.91). According to the model selection index, the power model achieved the best performance index: 0.1268 for SI strips and 0.1063 for NT strips versus 0.151 (SI strips) and 0.107 (NT strips) found at most by other models. Thus, it is the most suitable one for describing the relationship between the two strain components of corneal strip during uniaxial stretching.