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Prediction errors in corneal astigmatism measurements: a comparison between measured corneal astigmatism and the calculated true net total eye astigmatism

Session Details

Session Title: Assessment of Astigmatism

Session Date/Time: Saturday 05/10/2013 | 11:00-12:30

Paper Time: 11:47

Venue: Main Lecture Hall (Ground Floor)

First Author: : S.Ofir ISRAEL

Co Author(s): :    A. Abulafia   A. Levi   O. Reitblat   M. Rotenberg   G. Kleinmann   E. Assia

Abstract Details


To assess the accuracy of corneal astigmatism measured by dual-zone automated keratometry, automated keratometry and corneal topography


Ein-Tal Eye Center, Tel Aviv, Israel


Patient records were reviewed to identify those who had undergone Toric IOL implantation with post-operative Toric IOL axis measurements and post-operative anterior corneal measurements > 1month post-surgery, using the Lenstar LS 900, IOL Master 500 and ATLAS corneal Topographer devices. True net total eye astigmatism was calculated by vector analysis using the post-operative subjective refraction astigmatism and the Toric IOL astigmatic power at the corneal plane. Prediction Error for each device was calculated by subtracting the true net post-operative corneal astigmatic power from the post-operative astigmatic power measured by each device


Data for 70 eyes was available for analysis. Anterior corneal astigmatism measurements underestimated total corneal astigmatism by 0.57@180 (Lenstar), 0.58@176 (IOL-Master), 0.58@176 (ATLAS SimK) and 0.60@172 (ATLAS MeanK). No clinically significant differences were found between the different measuring devices. However, measurements gained by the Lenstar showed the lowest standard deviation


Astigmatism measured by dual-zone automated keratometry, automated keratometry and corneal topography showed a similar prediction error pattern. Selecting Toric IOLs based on these devices must take under consideration these consistent measuring errors

Financial Interest:


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