Comparing Laser Ray Tracing, the Spatially Resolved Refractometer, and the Hartmann-Shack Sensor to Measure the Ocular Wave Aberration

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Abstract
To compare quantitatively three techniques to measure the optical aberrations of the human eye: laser ray tracing (LRT), the Hartmann-Shack wavefront sensor (H-S), and the spatially resolved refractometer (SRR). LRT and H-S are objective imaging techniques, whereas SRR is psychophysical. Wave aberrations were measured in two normal subjects with all three techniques implemented in two different laboratories. We compared the experimental variability of the results obtained with each technique with the overall variability across the three methods. For the two subjects measured (RMS wavefront error 0.5 μm and 0.9 μm, respectively), we found a close agreement; the average standard deviation of the Zernike coefficients within a given method was 0.07 μm, whereas the average global standard deviation across techniques was 0.09 μm, which is only slightly higher. There is a close match between the Zernike coefficients obtained by LRT, H-S, and SRR. Thus, all three techniques provide similar information concerning wave aberration when applied to normal human eyes. However, the methods are operationally different, and each has advantages and disadvantages depending on the particular application.