| Summary: | Purpose: To measure the effects of contact lens correction and accommodation upon SA in myopia and hyperopia. Methods: Eleven myopes (Average MSE −3.22±2.21D; mean age 20.7±1.1 years) and eleven hyperopes (Average MSE 4.20±2.20; mean age 20.1±1.5) participated. Subjects were corrected with daily disposable contact lenses and pupil dilation was induced with 2.5% phenylephrine hydrochloride. SA was measured at accommodation stimulus levels of 0D and 4D, using the Zywave Aberrometer while subjects viewed a high contrast letter target array in a +5D Badal system, aligned perpendicularly to the measurement axis of the instrument via a semi-silvered mirror. Results: For 0D of accommodation, the hyperopic group had significantly ( p < 0.01) greater positive SA. Contact lens correction produced a positive shift in SA in the hyperopic group ( p < 0.01), whereas there was a negative shift in SA in the myopic group ( p < 0.01). Negative shifts in SA were found with accommodation in both myopic ( p < 0.01) and hyperopic ( p < 0.01) groups, with the shift being greater in the hyperopic group ( p < 0.01). Conclusions: The net effect of contact lens correction and accommodation result in SA for near visual tasks, which is predominantly negative in myopia and positive in hyperopia.
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