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Algorithm for minimizing the IOL power error induced by the keratometric power

Session Details

Session Title: Biometry

Session Date/Time: Tuesday 08/10/2013 | 08:00-10:30

Paper Time: 08:18

Venue: Elicium 2 (First Floor)

First Author: : D.Pińero Llorens SPAIN

Co Author(s): :    V. Camps   V. Mateo   R. Pérez-Cambrodķ   D. De Fez   P. Ruiz-Fortes  

Abstract Details


To evaluate theoretically in normal eyes the influence on IOL power (PIOL) calculation of the use of a keratometric index (nk) as well as to analyse and validate preliminarily the use of an adjusted keratometric index (nkadj) in the IOL power calculation (PIOLadj)


Oftalmar, Medimar International Hospital, Alicante, Spain University of Alicante


A model of variable keratometric index (nkadj) for corneal power calculation (Pc) was used for IOL power calculation (named PIOLadj). Theoretical differences (?PIOL) between the new proposed formula (PIOLadj) and which is obtained through the Gaussian optics (PIOLgauss) were determined using Gullstrand and Le Grand eye models. The proposed new formula for IOL power calculation (PIOLadj) was pre-validated clinically in 81 eyes of 81 candidates for corneal refractive surgery comparing with the Haigis, HofferQ, Holladay and SRK/T formulas.


A theoretical PIOL underestimation > 0.5 D was present in most of cases when nk=1.3375 was used. If nkadj was used for Pc calculation, a maximal calculated error in ?PIOL of ±0.5 D at corneal vertex in most of cases was observed independently from the eye model, r1c and the desired postoperative refraction. The use of nkadj in IOL power calculation (PIOLadj) was found to be valid with ELP optimization nondependent of the corneal power.


The use of a single value of nk for Pc calculation can lead to significant errors in PIOL calculation that may explain some IOL power overestimations with conventional formulas. These inaccuracies can be minimized by using the new PIOLadj based on the algorithm of nkadj

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