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Michael J. Collins, Atanu Ghosh, Scott A. Read, Brett A. Davis, Robert Iskander, Payel Chatterjee; Influence of Accommodation and Gaze Angle on Primary and Secondary Spherical Aberration Over Time. Invest. Ophthalmol. Vis. Sci. 2011;52(14):829.
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To investigate the stability of wavefront aberrations between primary gaze and downward gaze with the same level of accommodation (2.5 D) over a period of time.
Twenty five young subjects (mean age 25 ± 4 years) were recruited. Subjects watched TV at 5 m distance in primary gaze for 10 mins duration prior to each trial and then performed a binocular near (40 cm) task (watching video on a portable LCD screen) in both primary (0°) and downward gaze (25°) in separate trials. Wavefront measurements were taken using a modified Shack-Hartmann aberrometer that allowed free space viewing of a target (high contrast Maltese cross) displayed on the LCD screen in both primary and downward gaze. Measurements were taken immediately (<1 min), 5 and 10 mins after the commencement of each trial from the subject’s left eye. Zernike coefficients up to the 8th radial order were analysed (fixed 3.0 mm pupil).
Repeated measures ANOVA revealed a significant effect of gaze (p=0.004) and a significant gaze by time interaction (p=0.046) for the changes in primary spherical aberration C(4,0) during accommodation. C(4,0) was significantly more negative in downward gaze, with the largest differences between primary and downward gaze (-0.013 µm) noted at the 10 mins measurement. A significant influence of gaze (p=0.02) was also found for secondary spherical aberration C(6,0) during accommodation. Refractive power analysis showed that the changes in primary and secondary spherical aberration resulted in more negative longitudinal spherical aberration with downward gaze that increased with time during the 2.5 D accommodation task. Defocus showed no obvious change between primary and downward gaze during the 10 mins near task (p=0.409).
Significant changes in primary and secondary spherical aberration occurred between primary and downward gaze for a moderate level of accommodation. The difference in spherical aberration between primary and downward gaze systematically increased over the 10 mins near task.
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