Effects of pupil center shift on ocular aberrations

We investigated effects of pupil shifts, occurring with changes in luminance and accommodation stimuli, on refraction components and higher-order aberrations.

Participants were young and older groups (n = 20; 22 ± 2 years; age range, 18-25 years; and n = 19, 49 ± 4 years, 45-58 years, respectively). Aberrations/refractions at 4- and 3-mm diameters were compared between centered and decentered pupils for low (background, 0.01 cd/m(2), 0 diopters [D]), and high (6100 cd/m(2), 4 or 6 D) stimuli. Decentration was the difference between pupil centers for low and high stimuli. Clinical important changes with decentration were: M at ± 0.50 or ± 0.25 D, J180 and J45 at ± 0.25 or ± 0.125 D, HORMS at ± 0.05 μm, C(3, 1) at ± 0.05 μm, and C(4, 0) at ± 0.05 μm.

Because of small pupil shifts in most participants (mean 0.26 mm), there were few important changes in most refraction components and higher-order aberration terms. However, M changed by >0.25 D for a third of participants with 4-mm pupils. When determining refractions from second to sixth order aberration coefficients, the more stringent criteria gave 76/534 (14%) possible important changes. Some participants had large pupil shifts with considerable aberration changes. Comparisons at the high stimulus were possible for only 11 participants because of small pupils. When refractions were determined from second order aberration coefficients only, only 35 (7%) had important changes for the more stringent criteria.

Usually pupil shifts with changes in stimulus conditions have little influence on aberrations, but they can with high shifts. The number of aberrations orders that are considered as contributing to refraction influences the proportion of cases that might be considered clinically important.