In vivo and in vitro repeatability of Hartmann-Shack aberrometry

Purpose: To assess the in vivo and in vitro repeatability of objective refraction and higher-order aberrations (HOAs) measured by a commercially available Hartmann-Shack wavefront sensor. Setting: Department of Ophthalmology, Johann-Wolfgang-Goethe University, Frankfurt am Main, Germany. Methods: After pupil dilation of 40 myopic or myopic, astigmatic eyes of 20 patients, wavefront measurements were performed 6 times in each eye and in a test object provided by the manufacturer by 2 experienced examiners using a Hartmann-Shack wavefront sensor (Zywave ®, software version 3.21, Bausch & Lomb). The mean standard deviation (SD) and the coefficient of variation (CV) for sphere, cylinder, and each Zernike polynomial were computed for a 7.0 mm pupil diameter. Vector analysis was performed for the astigmatism. After the data were subdivided into 2 groups with 3 measurements in each, one measurement that best matched the subjective manifest refraction was chosen in each group and the difference between them was calculated. Results: The mean SD (CV) was 0.15 diopter (D) (7%) for the sphere value of the predicted phoropter refraction and 0.16 D (22%) for astigmatism. Thirty-two eyes had an axis deviation of at least 10 degrees. Vector analysis revealed a mean SD of 0.24@109.8. Other results for mean SD and mean CV were as follows: total in vivo higher-order RMS, 0.097 μm, 13.4%; sphere in myopic test device, 0.034 D, 0.65%; sphere in hyperopic test object, 0.035 D, 0.72%. The difference between the 2 best-matched refractions was significantly different from zero (0.11 D, P