A Shack-Hartmann aberrometer for measuring ophthalmic wavefront aberrations having improved dynamic range is described. In one embodiment, a single lenslet only of the wavefront sensor microlens array is optically or physically altered. In another embodiment, a sub-array of immediately adjacent lenslets are altered. In an alternative embodiment, preferably only two non-adjacent lenslets are altered. The alteration provides for identification of the correspondence between spot images of the unknown wavefront formed by the microlens array and the respective lenslets forming the spot images. Once all the spot images are correctly identified, analysis of the incoming wavefront is simplified even when the magnitude of aberration is increased. Thus, the dynamic range and accuracy of the Shack-Hartmann aberrometer are no longer limited by the dimensions and optical properties of the lenslets.
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