Research On Simulation Of Laser Cornea Thermo-keratoplasty Based On Virtual Reality Technology

With the development of society, people are taking more and more care of theireyes one of the most exact apparatus on the body. Many solutions, such as wearingredress glasses, PRK, artificial cornea, etc, are brought forward for hyperopia, myopia,aging eye and sundries immerging which indicates the attention to correlative illnesswith cornea. Ophthalmology is one of the most advanced research fields in the eyephysic and laser is widely used for the curing in the world. With the ripeness ofmyopia therapy, the hyperopia therapy becomes the focus. At present, however, thereis no good solution for hyperopia therapy, especially for the high hyperopia. So it isof great importance for both the research and application of seeking after how to curethe hyperopia with laser.With the combination of with VR, computer simulation, laser application,ophthalmology and biomedicine, the effect mechanism on cornea of Laser ThermoKeratoplasty is discussed; Finite Element Method (FEM) is used to make themedicine virtual analysis towards cornea characteristic and the qualitative analysis isgiven based on primary factors that effect the curvature change of cornea; inconjunction with the VR technology and virtual simulation system is established. Themain contents of this thesis are(1) the actualization principle of LTK is analyzed and the virtual analysis processof LTK based on FEM is studied; he differential equation for thermal conductiontheory and FEM model are researched, he thermal parameters of cornea is confirmedby referring to plentiful in and abroad data, he instantaneous temperature field on thecornea is discussed when diode laser, as an exterior hot center, acts on the corneaassuming that the thermal parameters of cornea does not change as the temperaturechanges and the temperature field distribution and the comparison betweenpenetration depths is given when the laser with different parameters acts on thecornea.(2) the change rate,η, of corneal refractive power D and the change rate of cornea curvature radius are analyzed according to the structure of human eye andcornea, the reason for ametropia and the principle of human eye's phototropism.Based on the FEM and constructing Geometry modal, with different constraints andloads, the shape changing quantity of cornea and the change rate of cornea curvatureradius are analyzed under different parameters. Through theory analysis andcomparison, the influence degree of each operation parameter to cornea curvaturechange in the operation is gained and the function effect of each operation parameterin diopter correction is confirmed.(3) According to the results of thermal analysis and mechanical analysis of thecornea, he qualitative analysis on the influence parameters in LTK is carried out, theexperiment precept is designed, the experiment design and anterior experiment aremade. Experimental results via slit-lamp and corneal topography are gained andaccomplishes the electron microscope pathology analysis is accomplished, All ofthese prove the security and effect of LTK, and provide a good foundation for theafter experiments.(4) Based on VR, the framework of physic simulation system of LTK isestablished; simulation system is developed with object-oriented design. The mainfunctions of the simulation, such as forecast, calculation, demonstration, etc., of LTKfor hyperopia therapy are realized. The correlative methods for distortion simulationof parenchyma are researched. According to the structure of eyeball and the principleof LTK, based on the idea of the Mass—Spring Method and the Pressure BasedMethod, the three-dimensional simulating distortion system for cornea is realized. Allthese results provide a good foundation for the realization of the interactive LTKsimulation.