Purpose:This study aimed to evaluate the theoretical influence on intraocular lens power (PIOL) calculation of the use of keratometric approach for corneal power (Pc) calculation in keratoconus and to develop and validate an algorithm preliminarily to minimize this influence.Methods:Pc was calculated theoretically with the classical keratometric approach, the Gaussian equation, and the keratometric approach using a variable keratometric index (nkadj) dependent on r1c(Pkadj). Differences in PIOL calculations (ΔPIOL) using keratometric and Gaussian Pc values were evaluated. Preliminary clinical validation of a PIOL algorithm using Pkadj was performed in 13 keratoconus eyes.Results:PIOL underestimation was present if Pc was overestimated, and vice versa. Theoretical PIOL overestimation up to −5.6 D and −6.2 D using Le Grand and Gullstrand eye models was found for a keratometric index of 1.3375. If nkadj was used, maximal Δ PIOL was ±1.1 D, with most of the values ≤±0.6 D. Clinically, PIOL under- and over-estimations ranged from −1.1 to − 0.4 D. No statistically significant differences were found between PIOL obtained with Pkadj and Gaussian equation (P > 0.05).Conclusion:The use of the keratometric Pc for PIOL calculations in keratoconus can lead to significant errors that may be minimized using a Pkadj approach.