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Refractive outcomes after cataract surgery using Wang-Koch optimised axial lengths for intraocular lens power calculations

Poster Details

First Author: W.Khor SINGAPORE

Co Author(s):                  

Abstract Details



Purpose:

Even with modern intraocular lens (IOL) power calculation formulas, patients with long axial lengths may experience a hyperopic surprise after cataract surgery. The purpose of this study was to review the refractive outcomes of cataract surgery using IOL calculations performed with axial lengths optimised with equations described by Drs Wang and Koch. The Wang-Koch equations adjusts the measured axial length so as to improve the accuracy of IOL power calculation formulas in eyes >25.00mm.

Setting:

Singapore National Eye Centre, a tertiary ophthalmic centre

Methods:

This was a retrospective single-surgeon case series. The study included patients with long axial lengths (>25.0 mm) as determined by optical coherence biometry (IOL Master, Carl Zeiss Meditec, Inc) and who had IOL power calculations performed using optimised axial lengths (calculated with the Wang-Koch equations). Power calculations were made with the SRK/T formula, using the IOL Master-measured axial length and the optimised axial length. The target refraction for each eye (typically emmetropia or -1.00D) as well as the final IOL selected for implantation was recorded. Pre- and post-operative visual acuity and the automated refraction at 4-6 weeks after surgery were also documented.

Results:

Ten eyes of 6 patients were included in the study. There were 4 females, and the mean age was 60 years old (range 40-78). The mean axial length measurement with the IOL Master was 27.25+/-0.95mm. All eyes had the Acrysof SA60AT IOL (Alcon Laboratories, Inc) implanted during uncomplicated phacoemulsification with a 2.65mm clear cornea incision placed on the steep axis of existing corneal astigmatism. After axial length optimisation, the IOL power selected to achieve the target refraction was increased by a median of +0.75D (range 0.00D - 1.00D) over the original IOL power calculation. At 4-6 weeks after surgery, the difference between the actual spherical error versus the target refraction was a median of 0.00D (range +0.75D to -1.00D). One eye was left hyperopic (+0.75D) while another was more myopic (-1.00D) then intended; both eyes had unaided visual acuity of 6/6 after surgery. The remaining eyes were all within +/-0.50D of the target refraction.

Conclusions:

This study demonstrates that use of the Wang-Koch-optimised axial length with the SRK/T formula can reduce the risk of hyperopic surprise after cataract surgery in eyes with long axial lengths. FINANCIAL INTEREST: NONE

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