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Comparing the accuracy of spherical equivalent targeting in eyes undergoing cataract surgery and refractive lens exchange using monotoric and bitoric IOLs

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Session Details

Session Title: Interactive Free Paper Session: Pseudophakic IOLs/ Toric

Session Date/Time: Monday 15/09/2014 | 16:30-18:30

Paper Time: 16:42

Venue: Capital Hall B

First Author: : M.Pande UK

Co Author(s): :    A. Bourne   E. Proudfoot   A. Pande        

Abstract Details


Our spherical targeting data audit revealed that the spherical targeting in Monofocal Toric IOLs suffers in comparison to a non toric monofocal IOLs. Toric IOLs are designed in two ways, A Monotoric IOLs has the torus on a single surface (front or back) of the IOL while a Bitoric IOL has an equal amount of torus on both surfaces of the IOL. This difference in design has implications for the spherical equivalent targeting as the effective lens plane will change in a Monotoric IOL with each and every combination of sphere and toricity. In contrast the effective lens plane in a Bitoric lens does not change with the IOL spherical and toric power as the toricity is applied equally to both surfaces. This study reports on comparisions in the accuracy of Spherical equivalent targeting in eyes undergoing cataract surgery and refractive lens exchange using Monotoric and Bitoric IOLs.


Private Practice and Research Centre


Two consecutive single surgeon cohorts of 25 eyes undergoing cataract surgery or refractive lens exchange with preoperative corneal astigmatism more than 0.75 dioptres were enrolled into this study. There was no significant comorbidity in any eyes. A monofocal Monotoric IOL was used the first cohort while the other cohort had a monofocal Bitoric IOL. A manual markerless refercence meridian system was used to identify the steep meridian at surgery in all eyes. The steep meridian of the IOL aligned to the steep meridian of the cornea and this alignment was confirmed at the end of surgery after all instruments and viscoelastic were removed from the eye. 4-8 weeks after surgery all patients had a subjective refraction, uncorrected and distance corrected visual acuity as well as a full functional vision assessment. The absolute spherical equivalent targeting error was calculated and compared between the two cohorts. The correlation of the spherical equivalent targeting error to the IOL spherical equivalent power, was also examined in the two cohorts.


The visual results, astigmatism magnitude and meridian accuracy was similar in the two cohorts. There were significant difference in favour of the Bitoric IOLs in the spherical equivalent targeting error. The spherical equivalent targeting error correlated more strongly to the IOL spherical equivalent power in the Monotoric group compared to the Bitoric group.


The Spherical equivalent targeting error was significantly reduced in Bitoric IOLs compared to Monotoric IOLs and this error more strongly correlated with IOL spherical equivalent power in the Monotoric group.

Financial Interest:

One or more of the authors... receives nonNONEmonetary benefits from a company producing, developing or supplying the product or procedure presented.

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