We appreciate Savini and associates’ interest in our study. They raised several issues about the calculation of the goal diopter, statistics, and vector analysis.
As for the statistical analysis, we performed the Kruskal-Wallis test. In comparing IQ SN60WF and AcrySof T3, T4, and T5, there were significant differences of spherical equivalents between the groups postoperatively. Then, we undertook Wilcoxon matched-pairs signed rank test and Mann-Whitney U test as post hoc test. Because the study variables were nonparametric, we did not consider the ANOVA test as an appropriate statistical method in our study.
As mentioned, Hoffer Q and Holladay 1 methods are proven to be accurate methods of calculation in patients with short eyes. However, the eyes included in this study had axial lengths between 22 and 25 mm. A previous study with 8108 eyes showed no significant differences among Hoffer Q, Holladay 1, and SRK/T in axial lengths between 22 and 25 mm. Also, another study with 643 eyes comparing different formulas (Hoffer Q, Holladay 1, Holladay 2, SRK/T) showed the same result.
Mean axial length was 23.88 mm (range 22.33-24.95) in the IQ SN60WF lens group, 23.63 mm (range 22.86-24.31) in the T3 group, 23.38 mm (range 22.32-24.89) in the T4 group, and 23.72 mm (range 22.19-24.97) in the T5 group. Mean corneal power was 43.37 diopter (D) (range 41.63-46.00) in the IQ SN60WF lens group, 44.51 D (range 41.44-47.50) in the T3 group, 44.03 D (range 41.63-46.13) in the T4 group, and 44.39 D (range 41.00-47.00) in the T5 group. Since there were no outliers in the axial lengths and corneal powers in the subjects included in the study and there were no significant differences between the lens groups, it is unlikely that errors in the intraocular lens (IOL) power arose from these values.
As mentioned about the Alcon online calculator, it does not take into consideration the influence of anterior chamber depth. This online calculator may have limitations in estimating the proper toric power of toric IOLs, but it does not determine the IOL power itself. In this study, IOL power of toric IOLs was predetermined using optical coherence biometry (IOLMaster; Carl Zeiss Meditec, Dublin, California, USA) using the SRK-T formula, then the predetermined power was applied to the online toric IOL calculator. Other online calculation programs for toric IOLs, such as TECNIS or HOYA toric calculators, also suggest toric power of toric IOLs without adjusting for the IOL power.
Finally, vector analysis was not shown in the manuscript. However, we performed vectorial analysis for measurement of astigmatism using various methods in our previous study. Based on the result, we assume that there was no significant difference among the techniques for measuring keratometric values.
In conclusion, our data showed IOLs with higher-cylinder toric IOL led to a more myopic outcome after cataract surgery. As this correspondence indicated, it is hard to elucidate the proper reason for this disparity. However, based on this observation, we would like to bring up the need for a new calculation program for toric IOLs, taking into consideration the effect of toric power on IOL power.