Influences of luminance and accommodation stimuli on pupil size and pupil center location.

PURPOSE We investigated effects of luminance and accommodation stimuli on pupil size and pupil center location, and their implications for progressive addition lens wear. METHODS Participants were young and older adult groups (n = 20; 22 ± 2 years; age range, 18-25 years; and n = 19; 49 ± 4 years; age range, 45-58 years). A wave aberrometer included a relay system to allow a 12.5° × 11° background for the internal fixation target. Participants viewed the target under a matrix of conditions with luminance levels 0.01, 3.7, 120, and 6100 cd/m(2), and with accommodation stimuli up to 6 diopters (D) in 2 D steps. Pupil sizes and their centers, relative to limbus centers, were determined from anterior eye images. RESULTS With luminance increase, reduction in pupil size was accentuated by increase in accommodation stimulus in the young, but not in the older, group. As luminance increased, pupil center location altered. This was nasally in both groups with an average shift of approximately 0.12 mm. Relative to the lowest stimulus condition, the mean of the maximum absolute pupil center shifts was 0.26 ± 0.08 mm for both groups with individual shifts up to 0.5 mm, findings consistent with previous studies. There was no significant effect of accommodation on pupil center locations for either age group, or evidence that location was influenced by the combination of luminance and accommodation stimulus that resulted in any particular pupil size. CONCLUSIONS Variations in luminance and accommodation influence pupil size, but only the former affects pupil center location significantly. Pupil center shifts are too small to be of concern in fitting progressive addition lenses.