Research On The Model Of Wavefront Supported Corneal Ablation Profile And The Surgery Equipment

Modern corneal laser surgery has been one of the effective methods for refractive error correction and wavefront aberration correction in recent years. The model of wavefront supported corneal ablation profile and the surgery equipment are the key issues in the field. The model of wavefront supported corneal ablation profile and the surgery equipment have been studied and described in detail in this dissertation. The main research achievements are as following:1. A model for calculating ablation profile to correct refractive error is presented. The model used for the initial corneal surface is a torus, and the model used for the resultant corneal surface is a sphere, so the ablation profile is the intersection of the two surfaces. And wherein the two main meridian curvatures are used for the toric surface, and the refractive error are used to determine the radius of the sphere. The model can be used to correct myopia, hyperopia, and astigmatism.2. A model for calculating ablation profile to correct wavefront aberration is presented. The conception and Zernike representation of wavefront aberration of human eyes recommended by OSA are introduced first. The ablation profile is calculated based on the optical path difference. Because the ablation depth on the boundary is nonzero and irregular, we present a model for calculating ablation profile in a transition zone. And wherein the model is adapt to the change of size of the transition zone to assure the maximal ablation depth is not more than 1/3 of the total depth of corneal. The model can be used to correct wavefront aberration.3. A model for calculating ablation profile to precompensate for spherical aberration and the higher order astigmatism is presented. The basic ablation profile for myopic, hyperopic, and astigmatic correction is derived from the 2nd order Zernike representation of wavefront aberration. Based on the statistical data of the higher order aberration, the basic ablation allows precompensation for the expected amount of higher order aberration. The model can be used to improve the optical and visual outcomes of the refractive surgery.4. An ophthalmic excimer laser system used to correct refractive error and wavefront aberration is developed with the cooperation of Su Zhou 66 Vision Tech Co., Ltd. A small spot excimer laser and the models described above have been implemented in the system. And wherein the steps used to achieve a desired ablation profile include: Dividing the total ablation profile to many equal thickness layers, Overlapping in different locations in different layers, Determining the initial spot location on the bounder randomly, Scanning randomly for all calculated spot locations.5. The clinic data to correct refractive error and wavefront aberration with the ophthalmic excimer laser system is analyzed. Based on the analysis of the statistical data and reports several hospitals. the ophthalmic excimer laser system can be used to correct refractive error and wavefront aberration effectively and safely.