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Error distribution in toric intraocular lens calculation

Session Details

Session Title: Cataract I

Session Date/Time: Friday 14/02/2014 | 10:30-12:30

Paper Time: 11:28

Venue: Kosovel Hall (Level -2)

First Author: : NinoHirnschall AUSTRIA

Co Author(s): :    Peter C Hoffmann   Sophie Maedel   Peta Draschl   Maria Weber   Oliver Findl  

Abstract Details


To evaluate and quantify errors for residual astigmatism after implanting a toric intraocular lens (t-IOL).


VIROS, Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria


This multicenter study included patients who were scheduled for cataract surgery with implantation of a toric IOL. Optical biometry was performed as standard in each of all three centers in London (UK), Castrop-Rauxel (Germany) and Vienna (Austria). Three months after surgery subjective refraction was performed and the axis of the t-IOL was documented. For analysing purposes, the effect of t-IOL misalignment and the effect of post-operative ACD on the residual astigmatism were calculated. Different factors, such as surgically induced corneal astigmatism (SICA) and inaccuracy of keratometry were weighted regarding to their effect on residual astigmatism using Gaussian error propagation (GEP) and partial least squares regression (PLSR).


Twohundred-thirty eyes of 200 patients were included in this study. Mean pre- and post-operative corneal astigmatism was -2.24 D (SD: 0.87) and -0.61 D (SD: 0.52), respectively. Mean absolute misalignment of the t-IOLs was 4.5° (SD: 5.1) and the resulting loss of astigmatism reduction was 12.5% (SD: 11.5). The GEP and PLSR results will be presented at the meeting.


Residual astigmatism is related to t-IOL misalignment in some cases, but in the majority of cases the inprecise measurement of the cornea is the main source of error, especially in eyes with relatively low pre-operative corneal astigmatism. FINANCIAL INTEREST: NONE