佩戴角膜塑形镜后离焦环完整性及不同方向偏位对近视青少年眼轴增长的影响

目的探讨佩戴角膜塑形镜(OK镜)后离焦环完整性及偏位对近视青少年眼轴增(AL)长快慢的影响。方法回顾性病例对照研究。纳入佩戴OK镜的8~18岁儿童青少年110例(210只眼),按离焦环完整与否分成离焦环完整组、离焦环不完整组,对比两组基线参数(年龄、性别、眼别、屈光度)、及1年AL增长量的差异。按不同水平偏位方向分为颞侧组、鼻侧组、居中组,对比三组1年后AL增长量的差异。按照不同垂直偏位方向分为下方组、上方组、居中组,对比三组1年后AL增长量的差异。结果(1)离焦环完整与否组的对比:离焦环完整组(187只眼)与离焦环不完整组(23只眼),基线参数及1年AL增长量差异无统计学意义(均P>0.05);(2)OK镜偏位量与1年AL增长量的相关性分析:皮尔逊相关性分析显示,呈负相关(r=-0.16,P<0.05);(3)不同水平方向偏位对比:颞侧组(155只眼)、鼻侧组(10只眼)、居中组(22只眼)三组间1年AL增长量差异无统计学意义(P>0.05);(4)不同垂直方向偏位对比:上方组(27只眼)较下方组(93只眼)、居中组(67只眼)1年AL增长量较高(均P<0.05),下方组、居中组1年AL增长量差异无统计学意义(P>0.05)。结论近视青少年佩戴OK镜,离焦环不那么完整、轻度水平偏位对OK镜的近视防控效果影响不大,在垂直方向上应尽量避免上方偏位,更利于防控近视。

Analytic solution to the magnetotelluric response over anisotropic medium and its discussion

In the present paper,from the second order partial differential equations for solving the magnetotelluric(MT) fields of general anisotropic medium,we first obtained the second order partial differential equations for some anisotropic media with special conductivity(e.g.diagonal anisotropy,transverse anisotropy,azimuthal anisotropy,etc.) by simplifying the electrical conductivity tensor of anisotropic medium.And then we obtained the analytic solutions to MT fields for the case of transverse and azimuthal anisotropy through converting the conductivity parameter based on that of diagonal anisotropy.We further discussed the influence of the selection of integral limit and step length on precision in solving the analytic solutions for MT fields of isotropic medium.Finally,we presented the MT responses of two transverse and azimuthal anisotropic media as well as some applications of the analytic solutions to MT fields of anisotropic medium.