Error induced by the estimation of the corneal power and the effective lens position with a rotationally asymmetric refractive multifocal intraocular lens

AIM : To evaluate the prediction error in intraocular lens(IOL) power calculation for a rotationally asymmetric refractive multifocal IOL and the impact on this error of the optimization of the keratometric estimation of the corneal power and the prediction of the effective lens position(ELP).METHODS: Retrospective study including a total of 25 eyes of 13 patients(age, 50 to 83y) with previous cataract surgery with implantation of the Lentis Mplus LS-312 IOL(Oculentis Gmb H, Germany). In all cases, an adjusted IOL power(P IOLadj) was calculated based on Gaussian optics using a variable keratometric index value(n kadj) for the estimation of the corneal power(P kadj) and on a new value for ELP(ELP adj) obtained by multiple regression analysis.This P IOLadj was compared with the IOL power implanted(P IOLReal) and the value proposed by three conventional formulas(Haigis, Hoffer Q and Holladay Ⅰ).RESULTS: P IOLReal was not significantly different than P IOLadj and Holladay IOL power(P 】0.05). In the Bland and Altman analysis, P IOLadj showed lower mean difference(-0.07 D) and limits of agreement(of 1.47 and-1.61 D)when compared to P IOLReal than the IOL power value obtained with the Holladay formula. Furthermore, ELP adj was significantly lower than ELP calculated with other conventional formulas(P 【0.01) and was found to be dependent on axial length, anterior chamber depth and P kadj. CONCLUSION: Refractive outcomes after cataract surgery with implantation of the multifocal IOL Lentis Mplus LS-312 can be optimized by minimizing thekeratometric error and by estimating ELP using a mathematical expression dependent on anatomical factors.

非球面人工晶状体度数计算的最优化

目的：通过评价非球面人工晶状体（intraocular lens,IOL）屈光度的可预测性,初步开发一种计算屈光度（PIOL）的优化算法。方法：本研究纳入植入非球面IOL（LENTIS L-313,Oculentis Gmb H）65眼,并分为2组：A组8例12眼,PIOL≥23.0D;B组35例53眼,PIOL〈23.0D。术后3mo进行屈光度可预测性评价。参考角膜屈光力估计所致的可变性屈光指数计算出校正的IOL度数（PIOLadj）及屈光结果,根据年龄和解剖学因素得出校正的有效晶状体位置（adjusted effective lens position,ELPadj）。结果：术后A、B两组等效球镜度数分别为-0.75~＋0.75D、-1.38~＋0.75D。A、B两组的PIOLadj和实际晶状体屈光度（PIOLReal）之间无统计学差异（P=0.64、0.82）。BlandAltman分析显示A、B两组PIOLadj和PIOLReal之间的一致性区间分别为＋1.11^-0.96D和＋1.14^-1.18D。Hoffer Q公式和Holladay I公式计算PIOLadj和PIOL之间存在临床和统计学上的显著差异（P〈0.01）。结论：植入非球面IOL白内障手术的屈光可预测性可通过平行轴光学联合线性法则使角膜屈光力及晶状体位置相关误差最小化。