The Accuracy Of Intraocular Lens Calculation Formulas In Cataract Patients With Short Axial Length

Objective: To evaluate the accuracy of 8 intraocular lens(IOL)calculation formulas(Kane,EVO,Barrett Universal II,Olsen,Haigis Optimized,Hoffer Q,Holladay 1,SRK/T)in predicting refractive error in eyes with age related cataract and axial length(AL)equal to or less than 22.5mm,and analysis of related factors contributing to refractive prediction errors.Methods: Retrospective case-control study.313 eyes of 313 patients who underwent modern conventional cataract surgery combined with intraocular lens implantation(SN60WF,ZCB00)into the capsule in our hospital from November 2017 to November 2019 were included.Divided them into two groups: short axial length group(AL≤22.5mm)and normal axial length group(22.5mm < AL < 26mm).Preoperative biological parameters were measured using OA2000 or IOL Master 700.Using the eight IOL calculation formulas(Kane,EVO,Barrett Universal II,Olsen,Higis Optimized,Hoffer Q,Holladay 1,SRK/T)to calculate the predicted refractive diopter and the refractive prediction error,and the mean error(ME),mean absolute error(MAE),median absolute error(Med AE).The Wilcoxon rank sum test was used for comparing the median values between groups for the same formula.The Friedman nonparametric test was chosen to compare the differences between different formulas within groups.The Chi-square test was needed to compare the percentages of different formulas in different refractive error intervals,and multiple linear regression was applied to analyse the relevant influencing factors of different formulas,and the differences were considered statistically significant when p values less than 0.05.Results:In this study,126 eyes were implanted with SN60 WF and 187 eyes with ZCB00.The average age of the patients was 66.44±8.45 years old.When AL less than or equal to 22.5mm,in SN60 WF lens group,ME was between-0.16±0.37D(EVO)and 0.4±0.33D(Olsen),and Med AE was at least 0.25D(EVO).Maximum was 0.41D(Haigis Optimized).The highest percentage of refractive error within ±0.5D was81.10%(Kane)and the lowest was 65.32%(Olsen),there was no statistical significance in the comparison of MAE of all formulas.In the ZCB00 lens group,there was a little myopia drift in all the 8 formulas,and the ME was between-0.06±0.54D(Barrett Universal II)and-0.39± 0.58D(Hoffer Q).The minimum value of Med AE was 0.24D(Barrett Universal Ⅱ)and the maximum was 0.39D(SRK/T).The proportion of postoperative refractive error within ± 0.5D was 81.10%(Barrett Universal II)and 65.32%(Hoffer Q).When AL less than 26 mm and greater than22.5mm,in the SN60 WF lens group,except EVO formula(-0.05±0.36D),the other seven formulas showed significant hyperopia drift,ME was between 0.23±0.36D(Kane)and 0.32±0.39D(Olsen).The minimum value of Med AE was 0.24D(EVO)and the maximum was 0.35D(Olsen).The highest and lowest values of refractive error within ±0.5D were 83.56%(EVO)and 71.56%(Olsen),respectively.In ZCB00 lens group,all of the 8 formulas produced slightly hyperopia drift.The range of ME was 0±0.37D(Kane)to 0.13±0.40D(Barrett Universal II),and the minimum of Med AE was 0.22D(EVO).Maximum was 0.27D(Haigis Optimized).The highest percentage of refractive error within ±0.5D was 84.56%(Kane),followed by 83.22%(EVO),and the lowest was 71.56%(Hoffer Q).Multiple linear regression analysis indicated that AL,ACD,LT,K and IOL type were the influencing factors of refractive error of most formulas in this study.Conclusion:For the short eyes,both of the SN60 WF and ZCB00 groups,there was no statistical difference between the eight formulas.Comparing the values of ME,MAE and Med AE,the new generation formulas(including EVO and Barrett Universal Ⅱ)showed the better performance,followed by the Kane formula.In the normal eyes,the ME,MAE and Med AE of EVO and Kane formulas of the two lens groups are lower than Hoffer Q,Haigis Optimized and Olsen formulas.In addition,in the short eyes,all of eight formulas show hyperopia drift in SN60 WF lens group.However,in the ZCB00 lens group,myopia drift was observed,while in the normal eyes,both of them showed hyperopia drift.AL,ACD,LT,K and IOL type are the common factors affecting the accuracy of the prediction of IOL power.