Posters

Evaluating the 'refractive surprise' outcomes after using A-scan to predict lens power needed for lens insertion during cataract surgery

Poster Details

First Author: R. Jones UNITED KINGDOM

Co Author(s):    A. Baneke   G. Vakros                 

Abstract Details

Purpose:

To assess the accuracy of A-scan ultrasound lens estimation by using refractive outcomes in patients undergoing phacoemulsification cataract surgery. To assess the possibility of using contralateral eye’s measurement to predict the most accurate intraocular lens (IOL).

Setting:

Data collected from electronic patient records at the Department of Ophthalmology, Royal Free Hospital, London.

Methods:

A retrospective audit comparing post-operative refractive outcome with predicted refractive outcome from A-scan ultrasound (calculated using the SRK-T formula) was conducted. The Zeiss IOLMaster® printout was used to predict spherical equivalent (SE) for both eyes when possible. In cases where optical biometry was not possible, A-scan ultrasound was used. The accuracy of A-scan was also evaluated by comparing the refractive outcome of those eyes on which both ultrasound and optical biometry were conducted. Data was collected on 32 eyes from 01/01/2014 to 31/12/2014 with dense cataract requiring A-scan ultrasound to estimate axial length and therefore the lens power required.

Results:

The mean actual SE for inserted IOL was -1.10±1.26, making the average refraction difference between A-scan predicted and actual outcome -1.01D. The mean IOL power suggested was 22.5D, which was similar to mean IOL ultimately inserted of 22.0D. The difference between lens suggested and actually inserted ranged from -2D to +2.5D. When both methods were used, the IOLMaster® predicted SE was more myopic than A-scan SE for the same lens power (mean difference -0.52±0.49). A positive correlation of difference between A-scan predicted and actual SE, and between predicted SE for A-scan and IOLMaster® in the contralateral eye, was demonstrated.

Conclusions:

Our results suggest a post-operatively myopic shift more than predicted by A-scan ultrasound, indicating the need of a less convergent lens. IOLMaster® and A-scan ultrasound of the contralateral eye could be used to estimate the correction factor needed to achieve emmetropia, as there is a positive correlation between datasets. However, due to the limited sample a larger dataset is required.

Financial Disclosure:

NONE