青年近视患者角膜前表面Q值规律及特性分析

Analysis of the Q-values and characteristics of the anterior corneal surface in young myopes

目的运用正切曲率半径结合曲线拟合计算，推算角膜半子午线Q值并进行区间整合，对青年近视角膜前表面Q值规律及特性进行分析。方法横断面研究。16～30岁近视受检者90例（90眼）行OrhscanII角膜地形图检查，均取右眼，受检者平均等效球镜度为（-5．45±2．75）D。采集并导出角膜前表面间隔0．1mm的360条半子午线正切曲率值Ft。将所需计算半子午线截痕上的所有Ft值代人正切曲率半径公式．应用线性回归方法结合MatlabR2009b（矩阵实验室MatrixLaboratory）系统拟合计算并通过计算机编程的模型处理系统计算得到各半子午线Q值．并进行区间整合、分析。结果90眼水平方向鼻侧和颞侧2个区间平均Q值分别为-0．32±0．11、-0．30±0．12，差异有统计学意义（t=2．009，P〈0．05）。72眼经过Matlab系统进行拟合计算得到的曲线决定系数R^2均大于0．9。拟合前后水平鼻侧、颞侧区间平均Q值差异无统计学意义（鼻侧t=1．299，P〉0．05；颞侧t=0．848，P〉0．05）。拟合后垂直上方、下方区间Q值平均值为-0．26±0．12、-0．21±0．23。结论采用线性回归方法结合拟合计算可以由角膜地形图正切曲率半径推算角膜前表面Q值和区间Q值。近视青年角膜前表面形态趋向于长椭圆，垂直方向较水平方向更趋向于圆形。

Objective To calculate the Q-values of the meridian sections of the anterior corneal surihce based on the tangential radius and curve-fitting calculations; to analyze the distribution of the Q-values and the characteristics of the anterior corneal surface in young myopes. Methods This was a cross-sectional study. Ninety right eyes of 90 myopia subjects with an age range of 16-30 years and mean spherical equivalent of -5.45±2.75 D underwent corneal topography examinations using the Orbscan II system. The tangential curvatures along the meridian section at 0.1 mm intervals from the apex to the periphery of the anterior surface were calculated and the Q-values of the semi-meridian section were calculated by linear regression of the tangential radius. Matlab R2009h （Matrix Laboratory） was used for curve fitting calculations. Results The average calculated Q-values on the nasal and temporal horizontal intervals were -0.32±0.11 and -0.30±0.12, with a significant difference between them （t=2.009, P〈0.05）. The coefficients of determination for curve fitting＇calculations in all the semi-meridians were over 0.9 based on Matlab R2009b （Matrix Laboratory） for 72 eyes. There were no significant differences before and after cmwe fitting calculations （nasal： t=1.299, P〉0.05; temporal： t=0.848, P〉0.05）. The average calculated Q-values along the superior and inferior intervals were -0.26＋0.12 and -0.21±0.23, respectively. Conclusion This study analyzes the calculated Q-values of the semi-meridian section in myopes based on the linear regression of the tangential radius using tangential topography and curve-fitting calculations. The anterior corneal surface proved to be a prolate elliptical shape in subjects with myopia. The vertical meridians were more round.