Agreement between corneal diameter measurements obtained with an optical biometer and a Placido-based topographer

The purpose of this study was to compare the white-to-white distance measurements of two devices (IOL Master 500 and Atlas corneal topographer) commonly used in clinical practice to determine if they were interchangeable. Providing information on instrument interchangeability could eliminate several unnecessary tests and consequently reduce the economic burden for the patient and society. In this prospective, comparative case series, the white-to-white distance was measured by independent examiners using the Atlas topographer (Carl Zeiss Meditec) and the IOL Master 500 (Carl Zeiss Meditec). One eye each of 184 patients was tested. Statistical analyses were performed using a paired t-test, Pearson correlation analysis, and Bland-Altman analysis to compare the measurement methods. The mean white-to-white distance measurements with the Atlas topographer and the IOL Master 500 were 12.20 ± 0.44 mm and 12.12 ± 0.41 mm, respectively (p