STATISTICAL DISTRIBUTION OF FOVEAL TRANSVERSE CHROMATIC ABERRATION, PUPIL CENTRATION, AND ANGLE-PSI IN A POPULATION OF YOUNG-ADULT EYES

Subjective transverse chromatic aberration (sTCA) manifest at the fove a was determined for a population of 85 young adults (19-38 years old) by means of a two-dimensional, two-color, vernier alignment technique . The statistical distribution of sTCA was well fitted by a bivariate Gaussian function with mean values that were not significantly differe nt from zero in either the horizontal or the vertical direction. We co nclude from this result that a hypothetical, average eye representing the population mean of human eyes with medium-sized pupils is free of foveal sTCA. However, the absolute magnitude of sTCA for any given ind ividual was often significantly greater than zero and ranged from 0.05 to 2.67 arcmin for the red and the blue lights of a computer monitor (mean wavelengths, 605 and 497 nn, respectively). The statistical dist ribution of the absolute magnitude of sTCA was well described by a Ray leigh probability distribution with a mean of 0.8 arcmin. A simple dev ice useful for population screening in a clinical setting was also tes ted and gave concordant results. Assuming that sTCA at the fovea is du e to decentering of the pupil with respect to the visual axis, we infe r from these results that the pupil is, on average, well centered in h uman eyes. The average magnitude of pupil decentration in individual e yes is less than 0.5 mm, which corresponds to psi = 3 deg for the angl e between the achromatic and the visual axes of the eye. (C) Optical S ociety of America