The use of a single nk for estimating the corneal power in eyes that underwent a laser myopic refractive surgery can lead to significant errors. These errors can be minimized by using a variable nk dependent on r1c.

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Purpose:To evaluate the predictability of the refractive correction achieved with a positional accommodating intraocular lenses (IOL) and to develop a potential optimization of it by minimizing the error associated with the keratometric estimation of the corneal power and by developing a predictive formula for the effective lens position (ELP).Materials and Methods:Clinical data from 25 eyes of 14 patients (age range, 52–77 years) and undergoing cataract surgery with implantation of the accommodating IOL Crystalens HD (Bausch and Lomb) were retrospectively reviewed. In all cases, the calculation of an adjusted IOL power (PIOLadj) based on Gaussian optics considering the residual refractive error was done using a variable keratometric index value (nkadj) for corneal power estimation with and without using an estimation algorithm for ELP obtained by multiple regression analysis (ELPadj). PIOLadj was compared to the real IOL power implanted (PIOLReal, calculated with the SRK-T formula) and also to the values estimated by the Haigis, HofferQ, and Holladay I formulas.Results:No statistically significant differences were found between PIOLReal and PIOLadj when ELPadj was used (P = 0.10), with a range of agreement between calculations of 1.23 D. In contrast, PIOLReal was significantly higher when compared to PIOLadj without using ELPadj and also compared to the values estimated by the other formulas.Conclusions:Predictable refractive outcomes can be obtained with the accommodating IOL Crystalens HD using a variable keratometric index for corneal power estimation and by estimating ELP with an algorithm dependent on anatomical factors and age.

Purpose. To validate clinically a new method for estimating the corneal power (P c) using a variable keratometric index (n kadj) in eyes with previous laser refractive surgery. Setting. University of Alicante and Medimar International Hospital (Oftalmar), Alicante, (Spain). Design. Retrospective case series. Methods. This retrospective study comprised 62 eyes of 62 patients that had undergone myopic LASIK surgery. An algorithm for the calculation of n kadj was used for the estimation of the adjusted keratometric corneal power (P kadj). This value was compared with the classical keratometric corneal power (P k), the True Net Power (TNP), and the Gaussian corneal power (P cGauss). Likewise, P kadj was compared with other previously described methods. Results. Differences between P cGauss and P c values obtained with all methods evaluated were statistically significant (p < 0.01). Differences between P kadj and P cGauss were in the limit of clinical significance (p < 0.01, loA [−0.33,0.60] D). Differences between P kadj and TNP were not statistically and clinically significant (p = 0.319, loA [−0.50,0.44] D). Differences between P kadj and previously described methods were statistically significant (p < 0.01), except with P cHaigisL (p = 0.09, loA [−0.37,0.29] D). Conclusion. The use of the adjusted keratometric index (n kadj) is a valid method to estimate the central corneal power in corneas with previous myopic laser refractive surgery, providing results comparable to P cHaigisL.