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Influence of posterior astigmatism on the estimation accuracy of residual astigmatism after toric lenses implantation

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Session Details

Session Title: Cataract Surgery Outcomes

Session Date/Time: Tuesday 16/09/2014 | 08:00-10:30

Paper Time: 09:14

Venue: Capital Hall A

First Author: : Q.De Bosredon FRANCE

Co Author(s): :    G. Mello   M. Santhiago   T. de Castro   D. Smadja     

Abstract Details


To determine whether the consideration of the posterior astigmatism in the toric iol calculation provides a more accurate estimation of the postoperative residual astigmatism (RA).


Bordeaux Hospital University


A total of 30 eyes of 20 patients candidates for toric lense implantation were prospectively enrolled in this study. The thirty lenses were calculated with two different calculations methods. The standard method, using the simulated anterior astigmatism (SimAA) measured with a Dual Scheimpflug system (Galilei, Ziemer) and the alternative method that uses the total corneal astigmatism (TCA) measured with ray tracing. The achieved residual astigmatism (magnitude and axis) at 3 month postoperatively was compared to the estimated residual astigmatism calculated with the standard method or the ray tracing method.


The average preoperative corneal astigmatism was measured at 1.8D with the SimAA, and at 1.46D with TCA (p< 0.05). The mean magnitude of achieved residual astigmatism at 3 months was 0.16 +/- 0.24 D, whereas the mean estimated residual astigmatism was expected to be 0.5 +/- 0.32 D when using the SimAA and 0.28 +/- 27D when using the TCA. The mean difference between the estimated and the achieved RA was significantly greater (p< 0.05) when using the SimAA (0.25 +/- 0.3D) than that with TCA (0.08 +/- 0.16D).


The use of the simulated anterior astigmatism rather than the total corneal astigmatism in the toric lenses calculation is less accurate and leads to an overestimation of the expected residual astigmatism, which might ultimately flip the cylinder axis in some cases.

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