Higher order aberrations in normal eyes measured with three different aberrometers

PURPOSE: To assess the repeatability of measurements of higher order aberrations using three different aberrometers and to compare higher order aberration measurements between optical path difference (OPD) scanning and the Hartmann-Shack method. METHODS: Wavefront aberration data obtained using the NIDEK OPD-Scan, Bausch & tomb Zywave wavefront aberrometer, and VISX CustomVue wavefront analyzer were compared. A total of 19 subjects were included in the study. The repeatability in each machine was assessed by calculating the difference between measurements, and the mean of three consecutive measurements in the same eye. Subsequent 'analysis of the distribution of these differences yields the mean difference, the standard deviation of the differences, and the 95% confidence interval for repeated measurements, also termed the "repeatability coefficient." RESULTS: Repeatability errors in all three machines were found to be low, suggesting that all three mac ins are reliable in their repeated measurements. Significant differences were demonstrated between OPD scanning and Hartmann-Shack aberrometers. All three machines showed statistically significant differences in several higher order aberration parameters when compared to each other. CONCLUSIONS: The three different aberrometers provided repeatable measurements but statistical differences were noted in the measurement of higher order aberrations when comparing the machines. No instrument was superior over the other and all three were reliable.