Comparison of Keratometric Measurements Obtained by the Verion Image Guided System with Optical Biometry and Auto-Keratorefractometer

Abstract

The aim of this study was to compare the keratometric measurements of Verion Image Guided System with an optical biometer (Zeiss IOLMaster 500, Carl Zeiss Meditec, Jena, Germany) and an automated keratorefractometer (AKR) (Topcon KR-8900, Topcon, Japan). In this prospective clinical trial, the right eyes of 52 patients with cataract were examined (mean age 62.25 +/- 12.16 years). The measurements were taken by the three systems in a random order. Keratometric data, magnitude of astigmatism, and astigmatic axis measurements from all three instruments were compared. The results were evaluated using, intraclass correlation coefficients (ICC), Bland-Altman plots, and paired samples t tests. 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 all 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 the AKR was 0.82 +/- 0.62D, less than the other two instruments (p < 0.001). Astigmatic axis measurements of Verion and AKR differed < 10A degrees in 38, between 10A degrees and 20A degrees in 5, and > 20A degrees in 9 eyes; the same difference was 30, 11, and 11 eyes, respectively, between Verion and IOLMaster. Although, keratometric and astigmatic results obtained from Verion were not completely interchangeable with IOLMaster and AKR, especially the agreement between Verion and IOLMaster was excellent with ICCs close to one. However, there were pronounced astigmatic axis measurement differences between three instruments.