Comparison of Corneal Powers Obtained from 4 Different Devices

Purpose

To assess the repeatability and comparability of anterior corneal power values obtained from the Galilei Dual Scheimpflug Analyzer (Ziemer, Port, Switzerland), Humphrey Atlas corneal topographer (Carl Zeiss, Jena, Germany), IOLMaster (Carl Zeiss), and a manual keratometer (Bausch & Lomb Inc, Rochester, New York, USA).

Design

Prospective, comparative study.

Methods

Prospectively, 20 subjects were enrolled. Three sets of corneal power measurements were obtained by a single observer using the Galilei, Atlas topographer, IOLMaster, and manual keratometer. Repeatability of the 3 measurements from each device was evaluated by means of coefficient of variation, standard deviation (SD), and intraclass correlation coefficient. An analysis of variance was used to compare the differences in corneal powers among devices. The Bland and Altman method also was performed to assess agreement in measurements between devices. Vector analysis was used to compare the astigmatism values obtained from different devices.

Results

For each device, the coefficient of variation of repeated measurements was lower than 0.22%. The SD of 3 repeated measurements ranged from 0.042 to 0.096 diopters (D). The intraclass correlation coefficients were higher than 0.99 in all devices. Mean central corneal powers were 43.80 D, 43.88 D, 43.92 D, and 43.76 D for the Galilei, Atlas, IOLMaster, and manual keratometer, respectively. SDs of the differences between devices ranged from 0.07 D for Galilei and IOLMaster to 0.14 D for Galilei and Atlas. For astigmatism, the mean astigmatism values for the Galilei, Atlas, IOLMaster, and manual keratometer were 0.54 D at 84 degrees, 0.51 D at 88 degrees, 0.62 D at 88 degrees, and 0.52 D at 87 degrees, respectively.

Conclusions

The corneal power measurements from these 4 devices were highly reproducible, comparable, and correlated.