接触镜光学特性和后顶焦度测量分析

An analysis of contact lens optical properties and the back vertex power measurement

目的 :探讨接触镜的球差特征以及后顶焦距测量的实质。方法 :应用光学理论分析接触镜光学特性和聚焦情况。采用光线追迹公式计算球差量和像方交点弥散斑分布值。结果 :接触镜基弧曲率半径小导致大球差 ,在入瞳为 5mm时球差约为近轴后顶焦距的 8.5 %～ 11.8% ;接触镜后顶焦距测量 ,实质是测量实际焦点位置———像方光轴截面弥散斑最小处 ,它与近轴光焦点位置偏差很大 ,离焦量约为 76 %。同时实际焦点位置与入瞳大小紧密相关。结论 :焦度仪的入瞳 2h与人眼瞳孔相匹配时 ,测量的接触镜后顶焦度就是接触镜实际后顶焦距———带高 0 .87h光线的像方截距L0 .87h′的倒数。

Objective:To analyze the aberration properties of contact lens and its central back vertex power measurement.Methods:The optical properties and focusing situation of contact lens were analyzed by the applied optics. The aberration and the distribution value of blur spot on the intersection point of the orientation of image were calculated by the light focus formula.Results:The contact lens has a bigger aberration. When the incident pupil is 5mm, the value of aberration is about 8.5%～11.8% of back vertex power. The central point for measuring the back vertex power is measuring the position of real focus minimum blur spot, which is the section on the orientation of image going along light axis. It has large deviation to focus position of axial ray, the value is about 76%. The real focus position is much affected by the size of incident pupil.Conclusion:When the incident pupil 2h of focimeter is corresponding with human pupil, the measuring value of the back vertex power is the real back vertex power of contact lens the reciprocal of distance on the orientation of image L0.87h′of band height 0.87h light.