Toric intraocular lens calculation post corneal refractive surgery: method, description, and outcomes

Session Details

Session Title: IOL Power Calculations, Post-LASIK & Extreme Eyes

Session Date/Time: Tuesday 25/09/2018 | 14:00-16:00

Paper Time: 14:44

Venue: Room A2

First Author: : B.LaHood NEW ZEALAND

Co Author(s): :    S Beheregaray   M. Goggin                 

Abstract Details

Purpose:

Intraocular lens (IOL) power calculation for cataract surgery following corneal refractive procedure is challenging as the relationship between anterior and posterior corneal curvatures is altered and the prediction of the effective lens position is compromised. Although successful results for calculating spherical IOL power post refractive surgery have been achieved using different formulas and nomograms, no standard method has been described for toric IOL power calculation. Our aim is to describe a method for toric intraocular lens power calculation post corneal refractive surgery and report our outcomes in a series of cases.

Setting:

Publicly funded hospital and a private practice

Methods:

The IOL calculator post keratorefractive surgery available on www.iolcalc.ascrs.org was used, and IOL sphere and cylinder power calculation was based on the power of two hypothetical spherical IOLs, one for the flattest and one for the steepest corneal meridian, the difference between these values being the required cylinder power, and the lower value being the required sphere power. Microincision cataract surgery and toric IOL implantation was performed in eyes which had prior LASIK (n=5) and PRK (n=3). Biometry was obtained using IOLMaster 500 / 700 (Carl Zeiss Meditec AG). Refraction outcomes and vector analyses were evaluated.

Results:

Unaided and best corrected visual acuities were logMAR 0.15 ± 0.19 and 0.07 ± 0.18. Target and postoperative spherical equivalent refraction (spectacles plane) were -0.11±0.10 D, and 0.08±0.43 D respectively, with resulting absolute prediction of error of 0.36±0.34 D. Six out of 8 eyes were within ±0.50 D of the target. All eyes were within ±1.0 D of the target. Vector analysed mean target induced astigmatism and surgically induced astigmatism of 1.44 ± 0.61 D and 2.14 ± 0.74 D, respectively yielding mean absolute astigmatism prediction error of 0.69 ± 0.26 D. No eyes had remaining astigmatism greater than 1D.

Conclusions:

We describe a method for calculation of toric IOL power post refractive surgery which relies on basic optical concepts and uses online resources with which most cataract surgeons are familiar. Although our sample is small, our results suggests that this method could be used with accuracy in this group of patients.

Financial Disclosure:

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