近视个体人眼角膜曲面方程的探讨

The establishment of an individual myopic cornea surface equation

目的拟合建立一种角膜面形方程,为后续角膜生物力学研究奠定基础。方法通过截痕法判断近视个体人眼角膜形态,创用网格法划分角膜表面,Orbscan角膜地形图系统测量角膜前、后表面各特定点与最适球面的径向距离差值及中央角膜厚度值,计算各点坐标,SAS软件非线性回归拟合角膜前、后表面曲面方程,SPSS软件检验结果。结果该近视人眼角膜前、后表面均为椭球面,前表面曲面方程:X2/8.97882+Y2/8.87792+(Z+9.9601)2/9.96012=1(Residual=0.0184,R2=0.9995),方程预测Z坐标值与实测值相关性较好(r=1.000),差异无统计学意义(t=0.456,P>0.05);后表面:X2/7.60942+Y2/7.51642+(Z+9.5758)2/9.03682=1(Residual=0.0360,R2=0.9993),方程预测Z坐标值与实测值相关性较好(r=1.000),两者差异无统计学意义(t=-0.930,P>0.05)。结论本研究用较为合理的截痕法、网格划分及非线性回归拟合算法使得最终求出的角膜前、后表面的曲面方程具有较高精确性,可较好地描述真实角膜面形,为其它相关研究提供方法。

Objective To establish a more accurate corneal surface equations for further study. Methods Mesh cross section were used to fit the myopic corneal surface equations, Orbscan corneal topography system was used to measure central corneal thickness values and the radial distances of the specific points between the cornea surface and the best fit sphere, which were incorporated into the mathematical formula into the 3D coordinates of the special points. SAS statistical software was applied to fit the cornea surface equations through non-linear regression method, and SPSS was used to inspect and compare the forecast results with the actual values. Results The anterior and posterior surfaces of myopic individual cornea were the type of ellipsoid. The anterior cornea surface equation： X^2 / 8.97882＋Y^2 / 8.87792＋ （Z ＋ 9.9601 ）2 / 9.96012=1 （Residual=0.0184, R^2=0.9995）. The paired-samples T-test results~ of the forecast results and the actual value： r=-1.000, t=-0.456, P〉0.05 ; The posterior surface equation： X2 / 7.60942＋Y^2 / 7.51642＋ （Z ＋ 9.5758 ）2 / 9.03682= 1 （Residu- al=0.0360, R^2=0.9993）. The paired-samples T-test results of the forecast results and the actual value： r=-1.000, t=-0.930, P〉0.05. Conclusion This study uses a more reasonable way to mesh, using cross section and nonlinear regression algorithm makes the cornea eventually obtained surface equations have high accuracy, the equations are used to describe true corneal surface. The study will be able to provide other relevant basic information.