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K.A. Morrison, N.C. Strang, L.S. Gray, D. Seidel, M. Day; The Effect Of Perceived Proximity Cues Upon Accommodation Response Dynamics . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3893.
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© ARVO (1962-2015); The Authors (2016-present)
Accommodation responses are generated by a combination of retinotopic and spatiotopic stimuli. Previous work shows that perceived proximity can affect the steady–state accommodation response, particularly under open loop conditions when retinotopic input to the accommodation controller is reduced. This study investigates the capacity for perceived proximity cues to produce accommodation step responses and their ability to influence the steady–state accommodation response.
The stimuli were two computer generated black and white illustrations both of which contained a wide range of spatial frequency information. They were presented on photographic slides in a Badal optical system, one containing predominantly distance cues and one containing mainly near cues. Changes in accommodation were recorded continuously in ten young visually normal subjects at a sampling rate of 52Hz using a modified Shin Nippon SRW 5000 optometer. Subjects viewed the targets monocularly in 3 different conditions:
1) Both targets were presented in random order (distance–near (D–N) and near–distance (N–D)) at a stimulus vergence of 2.3D in closed and open loop (Maxwellian view) conditions.
2) The distance target was presented at 0D and the near target at 2.3D (coherent depth stimulus and target vergence) under closed loop conditions.
3) The near target was presented at 0D and the distance target at 2.3D (conflicting depth stimulus and target vergence information) under closed loop conditions.
In condition 1 a significant shift in the mean steady–state response level was found in both open (D–N=0.32D (p<0.05), N–D=–0.36D (p<0.05)) and closed loop viewing (D–N=0.32D (p<0.05), N–D=–0.46D (p<0.05)). In condition 2 no significant change in mean step response gain was found in comparison to non–proximal target step responses (D–N=0.06D (p>0.05), N–D=–0.12D (p>0.05)). In condition 3 no significant change in mean step response gain was found in comparison to non–proximal target step responses (D–N=–0.09D (p>0.05), N–D=0.15D (p>0.05)). The reaction and response times of the accommodative step responses were not significantly affected by the presence of perceived proximity targets (p>0.05).
Perceived proximity cues can significantly alter both the open–loop and steady–state closed–loop accommodation response level. However, the dynamic gain of the accommodation response and step response times in closed loop viewing are unaffected by proximity cues. Perceptual (spatiotopic) stimuli significantly alter the accommodation response but only in the absence of retinotopic stimuli.
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