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N. C. Strang, D. Seidel, V. Manahilov, S. Mucke, L. S. Gray; Accommodation Suppression of High Spatial Frequency Information. Invest. Ophthalmol. Vis. Sci. 2007;48(13):978.
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© ARVO (1962-2015); The Authors (2016-present)
Little is known about visual sensitivity during the dynamics of an accommodation step response. The aim of this experiment was to measure perceptual visual performance during the dynamic portion of an accommodation response.
Throughout the experiment contrast thresholds were measured for spatial frequencies of 1, 2, 4, 8 cpd using a monitor at 1.75m. The stimulus was a 2 degree Gabor patch, presented for 26ms, at a distance of 1 degree to the left or right of the accommodation target and thresholds were established using a 2 AFC technique. Contrast thresholds were measured in conditions where the accommodation response was a) static or b) dynamic. In the static condition the accommodative stimulus was a Maltese cross target (vertical spokes only) positioned between 1D and 3D in 0.5 D intervals. In the dynamic condition the same accommodative target was movied between 1D and 3D in a stepwise fashion. Contrast thresholds were then measured at selected time intervals (0, 200ms, 400ms, 600ms, 800ms, 1000ms) after the initiation of the accommodation response. Accommodation responses were measured using a Shin-Nippon optometer in continuous recording mode (mean latency (±SD) = 291±56ms, mean step response time (±SD) = 453±79ms). Subjects were allowed to respond to a stimulus presentation only if an appropriate accommodation response had been made. Two young visually normal emmetropic subjects (VA better than 0.0 logMAR) participated with informed consent in the experiment.
Contrast thresholds for 8cpd at 400 and 600ms after the initiation of a dynamic accommodation response were found to be significantly elevated compared to the static baseline level. At the other spatial frequencies no significant differences (p<0.05) between the dynamic contrast threshold and the static threshold (defocus equivalent) were found at all time intervals.
High spatial frequency information is suppressed during accommodation step responses from 1 to 3 D. This suggests that high spatial frequency information does not provide defocus feedback during the accommodation step response.
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