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 _c was 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 _IOL calculations (Δ P _IOL) using keratometric and Gaussian P _c values were evaluated. Preliminary clinical validation of a P _IOL algorithm using P _kadj was performed in 13 keratoconus eyes.

Results:

P _IOL underestimation was present if P _c was overestimated, and vice versa. Theoretical P _IOL 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 n _kadj was used, maximal Δ P _IOL was ±1.1 D, with most of the values ≤±0.6 D. Clinically, P _IOL under- and over-estimations ranged from −1.1 to − 0.4 D. No statistically significant differences were found between P _IOL obtained with P _kadj and Gaussian equation ( P > 0.05).

Conclusion:

The use of the keratometric P _c for P _IOL calculations in keratoconus can lead to significant errors that may be minimized using a P _kadj approach.