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Vienna 2018 Delegate Registration Programme Exhibition Virtual Exhibition Satellites 2018 Survey


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Assessing the variability of keratometry readings in preoperative cataract patients

Poster Details

First Author: U.Khan UK

Co Author(s):    Z. Estephan                    

Abstract Details


Keratometry measures central corneal curvature. This determines the power of the cornea and differences across this results in astigmatism. Keratometry readings are used in IOL power calculation (this can be a large source of error). Disruption of the ocular surface also affects measurements. Different devices are currently being used in our department for these measurements. A previous large study in the The Netherlands looked at the sources of error in IOL power calculations. Errors in measurements are matched 1:1 to refractive outcomes. If you’re 1.00 D off in your K readings, you will have a 1.00 D refractive surprise.


Eye clinic at Huddersfield Royal Infirmary, UK.


Pre-operative cataract patients were included over a 2 month period of March and April 2018. The patients were seen in the pre-assessment clinic and the procedure was explained and consent obtained. The patients had central corneal curvature (K) readings taken on an IOL master machine first. They then had measurements taken with a Nidek and Orb scanner also. A slit lamp examination with fluorescein was done finally and a proforma completed. There was a total of 40 patients overall. They were classfied into three groups: Group A (<0.5D), Group B (0.5-1.0D) and Group C (>1.0D)


Of the patients included in the study 33% were found to have ocular surface disease with none having previous diagnosis of dry eye. IOL master and Nidek measurements were within 0.5D of each other in 67% of patients, with the other 33% of patients having their measurents between 0.5D-1.0D None of the readings taken on IOL master and Nidek differed 1.0D. IOL master and Orbscanner measurements were within 0.5D of each other in 33% of patients, whilst 25% of patients having their measurents between 0.5D-1.0D. 42% of measurements taken on IOL master and Orbscanner differed >1.0D.


Recommendations from this study: • Ensure 3 readings are taken for each measurement. • To stop using Orb Scanner for Keratometry readings. • Consider measuring K readings on 2 devices for ALL patients. – If >0.5D difference examine patient with fluorescein and consider repeating measurements. – If >1.0D difference repeat measurements and delay surgery till investigated further.

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