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Predictability of different calculators to minimise postoperative astigmatism after the implantation of a toric intraocular lens

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Session Details

Session Title: Toric IOL Calculations & Alignment

Session Date/Time: Sunday 23/09/2018 | 08:00-10:00

Paper Time: 08:18

Venue: Room A5

First Author: : F.Ribeiro PORTUGAL

Co Author(s): :    T. Ferreira   C. Relha   C. Esteves   S. Gaspar           

Abstract Details


To assess the efficacy of five different calculators for toric intraocular lens (IOL) power calculation by evaluating the mean absolute error (MAE) and the predicted residual astigmatism (PRA).


Hospital da Luz, Lisbon, Portugal


Retrospective comparative case series in cataract patients undergoing implantation of trifocal toric IOLs (PhysIOL FineVision POD FT). Inclusion criteria were age-related cataract and a corneal astigmatism between 0.90 and 4.50 D. Five different calculators were compared. Furthermore, two groups were differentiated according to the type of astigmatism: with the rule (27 eyes) and against the rule (16 eyes). The MAE and the centroid errors in the PRA from each calculator were evaluated.


Fifty-one eyes of 43 patients were included. For the standard toric calculator using anterior keratometry values only, the centroid prediction error was 0.39 D ±0.41@166º, which was reduced by the application of the PhysIOL toric calculator that includes the Abulafia-Koch formula and adjustment for the effective lens position (0.05 D ±0.34@167º) and also by the application of the Barrett toric calculator (0.07 D ±0.28@160º). Regarding the techniques that directly evaluate the posterior corneal surface, the using total corneal power provided by a color-LED topographer generated better results (0.10 D ±0.44@156º) than those using Scheimpflug camera data (0.23 D ±0.56@158º).


The PhysIOL and the Barrett toric calculators taking into account the posterior corneal astigmatism by regression formulas, yielded lower astigmatic prediction errors compared to a standard toric calculator based on anterior keratometry data only. When total corneal power measurements were used, prediction errors were lower with color-LED than with Scheimpflug based topography.

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