A Shack-Hartmann wavefront sensor was modified to allow measurement of ocular aberrations in downward gaze with binocular fixation. Subjects first performed a control task prior to four different trials involving a distance task or a near task (accommodative demand of 2.5 D) performed in primary and downward gaze (25°). Immediately after beginning and then again 5 and 10 min after the commencement of each trial, ocular aberrations were measured. To observe the recovery in ocular aberrations following each test condition, subjects again viewed a distance target in primary gaze and aberration measurements were taken at 0, 5, and 10 min. During the distance task, small but significant changes in refractive power and higher order aberrations were observed in downward gaze compared to primary gaze. The changes in ocular aberrations that occurred in downward gaze recovered almost immediately after shifting gaze from downward back to primary gaze. During the accommodation tasks, there was a significant influence of gaze for changes in primary spherical aberration C(4, 0) [p=0.004] and secondary spherical aberration C(6, 0) [p=0.02]. There was also a significant gaze by time interaction (p=0.04) for changes in C(6, 0). These findings show that ocular aberrations change from primary to downward gaze, particularly during accommodation.
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