We appreciate the comment by Wallerstein et al. on our original article.1

We would like to point out that their study, “Angle kappa influence on multifocal IOL outcomes,” was omitted because it was published after our submission and after our final revision.2 More importantly, their study and ours are incomparable for 2 main reasons: (1) We intended to evaluate intraocular lens (IOL) power calculation, and therefore, our outcomes were prediction error (PE) and absolute PE. At no point along the study, we evaluated visual acuity or raw postoperative refraction. On the other hand, the study by Wallerstein et al. intended to evaluate the visual results, and their outcomes were visual acuity and subjective refraction metrics.2 These depend not only on IOL power calculation but also on the surgeon’s choice for target refraction, the available IOL power steps, and so on. Unfortunately, they did not evaluate PE. (2) Our sample was limited to a monofocal aspheric IOL with −0.2 μm spherical aberration. The sample by Wallerstein et al. included 2 different multifocal IOLs with −0.1 μm spherical aberration.2 The different IOL designs (less aspheric in their cases) may alone justify some immunity to angle kappa as the IOL power changes less from the center to the periphery. Therefore, the studies are not mutually opposed.

Regarding the other points raised by the comment, (1) the “importance of large-scale studies” is applicable when proofing the inexistence of effects. However, larger does not always mean better. Studies with samples too large are less sustainable and will move statistical significance away from clinical significance. Sample size should be calculated and not larger. In fact, a 67-patient study may have a role as a 26 000-patient study has. (2) “Eyes with higher angle kappa are more likely to be hyperopic (short eyes).” In our sample, we observed no association between axial length or magnitude of astigmatism and PE (both in univariate and multivariate analyses) probably because we had average size eyes. May the higher angle kappa be a further reason for error in short eyes? (3) It was not our purpose to evaluate the clinical and subjective effect of angle kappa; our protocol and sample were not appropriate. Still, we may add that for every mm in nasal offset of the pupillary center in relation to Purkinje-Sanson image 1, we observed a 0.370 diopters (D) increase in absolute PE, with quite a large CI (0.046 to 0.693 D). It is not enough to change the current practice in IOL power calculation, but we advocate that future formulas should contemplate more variables.

1. Marques JH, Baptista PM, Ribeiro B, Menéres P, Beirão JM. Intraocular lens power calculation: angle κ and ocular biomechanics. J Cataract Refract Surg 2024;50:345–351 2. Wallerstein A, Ridgway C, Gatinel D, Debellemanière G, Mimouni M, Albert D, Cohen M, Lloyd J, Gauvin M. Angle kappa influence on multifocal IOL outcomes. J Refract Surg 2023;39:840–849