A method and an apparatus for extrapolating diagnostic data relating to one pupil diameter to another pupil diameter. Embodiments according to the invention are more particularly directed to extrapolating wavefront aberration data, for example, in the form of Zernike polynomial data, obtained from a smaller pupil diameter, d1, to a larger pupil diameter, d2. Data relating to the first pupil diameter d1 may be obtained in a diagnostic procedure. In the extrapolation, a conversion matrix M is utilized. The conversion matrix M can be generated from a static matrix and a dynamic matrix, the latter taking the pupil diameter d1 into consideration. Data relating the first pupil diameter d1 and wavefront aberration data can be ordered via a permutation matrix P. If necessary, Extrapolated data can be re-ordered via a transposed permutation matrix PT. The extrapolated data relating to the pupil diameter d2 can be processed to obtain an ablation profile, a shot file, or other data for a refractive vision correction treatment.