Posters

Comparison of corneal astigmatism and axis location measurements of Verion image-guided system with optical biometry and automated keratorefractometer

Poster Details

First Author: A.Akman TURKEY

Co Author(s):    S. Gur Gungor                    

Abstract Details

Purpose:

Correct measurement of corneal astigmatism and axis location is key to astigmatism correction during the cataract surgery by either toric intraocular lenses or astigmatic keratotomies. The Verion Image Guided System (Verion) (Alcon Laboratories, Ft. Worth, Texas, USA) is a preoperative measurement device that determines the corneal curvatures, limbal position, pupil diameter and corneal reflex positions. In this study, we aimed to compare the keratometric measurements of Verion with an optical biometer (Zeiss IOLMaster 500, Carl Zeiss Meditec, Jena, Germany) and automated keratorefractometer (AKR) (Topcon KR-8900, Topcon, Japan).

Setting:

The study was performed at Başkent University Eye Clinic, Ankara, Turkey

Methods:

The right eyes of 52 patients with cataract were examined prospectively (mean age: 62.25±12.16 years).  The measurements were taken by the three systems in a random order without pupillary dilatation. Keratometric data, magnitude of astigmatism and astigmatic axis measurements from all three instruments were compared.

Results:

The mean flat/steep K of Verion, IOLMaster and AKR were 43.22±1.38D/44.23±1.46D, 43.07±1.26D/44.05±1.34D and 43.07±1.31D/43.89±1.42D respectively. Flat K readings of Verion were higher than IOLMaster and AKR (p<0.05 for both). Steep K readings were different for both three (p<0.05). The magnitude of astigmatism by Verion and IOLMaster were 0.98±0.65D and 0.98±0.59D (p=0.88). The mean astigmatism measured by AKR was 0.82±0.62D, less than other two instruments (p<0.001). Astigmatic axis measurements of Verion and AKR differed <10° in 38, between 10°-20° in 5 and >20° in 9 eyes; the same difference was 30, 11 and 11 eyes respectively between Verion and IOLMaster.

Conclusions:

Although, keratometric and astigmatic results were obtained from Verion is not completely interchangeable with IOLmaster and AKR, the final differences were quite small (mean difference less than 0.20D) and do not expected to effect final astigmatic correction. Differences in measurement zone diameter and data points of these 3 instruments probably cause the difference. On the other hand, astigmatic axis measurement differences between three instruments can be more detrimental on final astigmatic corrections. Patient head tilt during the measurements can be the underlying reason and the caution of the technician can contribute to decrease these differences.

Financial Disclosure:

NONE