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Comparison of methodologies for considering posterior corneal astigmatism in toric intraocular lens power calculation

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Session Details

Session Title: Pseudophakic IOLs: Toric

Session Date/Time: Tuesday 10/10/2017 | 08:30-10:30

Paper Time: 09:00

Venue: Room 4.4

First Author: : T.Ferreira PORTUGAL

Co Author(s): :    P. Ribeiro   F. Ribeiro   J. O'Neill              

Abstract Details


To compare the prediction error in the calculation of toric intraocular lenses (IOLs) associated with methods that mathematically estimate the power (Barrett Toric Calculator and Abulafia-Koch formula) with that of methods that consider real measures of the posterior corneal surface (corneal curvature evaluated with Scheimpflug imaging and IOL calculated in Panacea Toric Calculator software and a ray tracing software – PhacoOptics)


Hospital da Luz, Lisbon, Portugal


In a retrospective case series of 107 eyes of 107 patients undergoing cataract surgery with toric IOL implantation (Alcon Acrysof IQ Toric), predicted residual astigmatism by each calculation method was compared with manifest refractive astigmatism. Prediction error in residual astigmatism was calculated by vector analysis


All calculation methods resulted in overcorrection of with-the-rule astigmatism and undercorrection of against-the-rule astigmatism. Both estimation methods resulted in lower astigmatic prediction error than methods considering real measures (p < .001). For Barrett toric calculator centroid prediction error (CPE) was 0.07 D @ 172º, for the Abulafia-Koch formula (combined with Holladay toric calculator) CPE was 0.13 D @ 174º. For the methods using real posterior corneal surface measurements, CPE was 0.24 D @ 173º for the Panacea software and 0.29 D @ 171º for the ray tracing software


The Barrett toric calculator and Abulafia-Koch formula yielded the lowest astigmatic prediction errors. Directly evaluating the total corneal power is not superior to estimating it for toric IOL calculation. The outcomes of toric IOL implantation may be improved by using one of these calculation methods

Financial Disclosure:

receives consulting fees, retainer, or contract payments from a competing company, travel has been funded, fully or partially, by a competing company

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