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M. Day, N. C. Strang, D. Seidel, L. S. Gray; The Influence of Spatial Frequency on Accommodation Step Responses in Emmetropes and Myopes. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4005.
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© ARVO (1962-2015); The Authors (2016-present)
Inaccuracies in the myopic accommodation response may result from differences in their ability to interpret the effects of blur upon the spatial frequency information available in the target. The aim of this study is to investigate the effect of target spatial frequency upon dynamic accommodation response characteristics in emmetropes (EMMs) and myopes (MYOs).
Sixteen (8 EMMs/8 MYOs) young visually normal subjects participated with informed consent in the experiment. Monocular accommodation step responses were recorded while the subjects viewed high contrast sine wave targets (0.5cpd, 4cpd, 16 cpd) placed in a +5D Badal system. Two stimulus sizes were presented (2D-3D and 1D-4D) and a minimum of 10 near-far (N-F) and 10 far-near (F-N) accommodation steps were recorded for each condition. Accommodation responses were measured continuously at a sampling rate of 52 Hz using a modified open view Shin-Nippon SRW-5000 autorefractor.
Accommodation gain was significantly greater for both the MYOs (p<0.05) and EMMs (p<0.05) in all conditions where the 4cpd targets were viewed. Average and peak velocities were significantly greater for both MYOs (p<0.05) and EMMs (p<0.05) when viewing the 4cpd target. These findings were applicable to the 2-3D and 1-4D step sizes in both F-N and N-F directions. Accommodative response latency was found to be independent of target spatial frequency content. There was no significant difference between EMMs and MYOs in any of the parameters measured.
Dynamic accommodation response characteristics are most accurate when viewing mid spatial frequency targets. The characteristics of the accommodation step responses did not show any refractive error dependency. The accommodation system of both emmetropes and myopes is driven by mid spatial frequency target information when making 1D and 3D step responses.
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