A Mathematic model to correct myopic astigmatism

The corneal surface was modeled as a torus before ablation, and the corneal surface was modeled as a sphere after ablation in the myopic astigmatism eye. So the mathematic model to determine the ablation profile in LASIK or PRK was deduced according the two surfaces. The two different-radii of curvature of the torus along its orthogonal meridians were determined by the deepest and flattest section of the corneal measure by topographic observation. The mathematic model was applied in the software to correct refractive error in the ophthalmic excimer laser system produced by Su Zhou 66 Vision Tech Co., Ltd. The results showed the mathematic model is safe and effective to correct myopic astigmatism.