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Ana Fernandez, Dirk Seidel, Laura E. Sweeney, Lyle S. Gray; Accommodation response to step changes in disparity vergence when viewing stereoscopic displays. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3968.
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© ARVO (1962-2015); The Authors (2016-present)
Stereoscopic displays require fixed levels of accommodation while the vergence system responds to maintain single vision. The aim of the present study was to measure the closed loop accommodation response to isolated step changes in disparity vergence presented upon a stereoscopic display
10 emmetropic subjects(mean age 21.8±2.6years) with normal visual and binocular function participated with informed consent. The stereoscopic display (Zalman ZM215W 21.5" 1920x1080) presented a high contrast(86%) Maltese cross target at 40cm. Step changes in disparity vergence of 6Δ convergent or divergent were presented randomly at 10s intervals over a period of 6 min. Vergence eye movements were monitored continuously using an infrared limbal reflection eyetracker (Skalar IRIS 6500) with resolution of 2’at sampling frequency of 62.5Hz, while accommodation responses were recorded continuously and simultaneously with a specially modified infrared, open field autorefractor (Shin-Nippon SRW-5000) with 0.125D resolution at sampling frequency of 62.5Hz. This experimental paradigm requires the right eye to remain stationary with the total vergence response occuring in the left eye. 10 vergence and accommodation traces for both convergent and divergent steps were analysed for each subject
A significant initial step accommodation response (mean±sd = 0.48 ±0.12D p=0.01 convergent stiumulus and 0.27±0.070D p=0.01 for divergent stimulus) was observed. During the subsequent 10s fixation period the accommodation response drifted back to the original level in both conditions. A significant increase in the root mean square of the steady-state accommodation response was also observed during this period (mean±sd rms 0.31±0.22D no disparity stimulus; 0.42±0.21D p<0.01 convergent stimulus; 0.46±0.24D p<0.01 divergent stimulus) Fourier analysis showed that this increase in variability of the accommodation response could be attributed to changes in the 0.1-0.6Hz temporal frequency range
Disparity vergence stimuli produce closed-loop phasic accommodation responses, which are limited by the ocular depth of focus. The steady-state accommodation response demonstrates increased variability which may be due to the asymmetry in stimulus demand between accommodation and vergence.This instability in the accommodation response could be a key factor in the asthenopia experienced when using stereoscopic displays
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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