Preliminary validation of an optimized algorithm for intraocular lens power calculation in keratoconus

Abstract

Purpose: This study aimed to evaluate the theoretical influence on intraocular lens power (P_IOL) calculation of the use of keratometric approach for corneal power (P_c) calculation in keratoconus and to develop and validate an algorithm preliminarily to minimize this influence. Methods: P_cwas calculated theoretically with the classical keratometric approach, the Gaussian equation, and the keratometric approach using a variable keratometric index (n_kadj) dependent on r_1c(P_kadj). Differences in P_IOLcalculations (ΔP_IOL) using keratometric and Gaussian P_cvalues were evaluated. Preliminary clinical validation of a P_IOLalgorithm using P_kadjwas performed in 13 keratoconus eyes. Results: P_IOLunderestimation was present if P_cwas overestimated, and vice versa. Theoretical P_IOLoverestimation 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 n_kadjwas used, maximal Δ P_IOLwas ±1.1 D, with most of the values ≤±0.6 D. Clinically, P_IOLunder- and over-estimations ranged from −1.1 to − 0.4 D. No statistically significant differences were found between P_IOLobtained with P_kadjand Gaussian equation (P > 0.05). Conclusion: The use of the keratometric P_cfor P_IOLcalculations in keratoconus can lead to significant errors that may be minimized using a P_kadjapproach.