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1. The time course of accommodation and vergence adaptation following exposure to a stereoscopic display Laura Sweeney , Lyle S. Gray, Dirk Seidel , Mhairi Day and Stewart Stanger Department of Life Sciences, Glasgow Caledonian University, Glasgow, Scotland, UK Aim Introduction Tonic accommodation and tonic vergence have been shown to be stable over both short and long time periods.1 Previous experimental data has shown adaptive changes to the vergence system2 and alterations in the crosslinks between the accommodation and vergence systems after viewing a virtual stereoscopic stimulus3. To determine the time course of tonic accommodation and vergence changes after viewing a stereoscopic (3D) stimulus. Methods • A pilot study was carried out on 3 subjects to determine duration of stereoscopic stimulus exposure necessary to produce adaptive changes. • 18 emmetropic, binocularly normal subjects (mean age =20.4±1.9 years). • Subjects viewed 3D stimulus for 20 minutes created using Crystaleyes shutter goggles synchronised with CRT monitor. • Vergence stimulus varied from 1 to 5MA and the accommodation stimulus was fixed at 3D. • Measurements taken at baseline and up to 50 minutes post exposure. • Accommodation measured using Shin Nippon SRW-5000 autorefractor in static mode (average of 20 readings). • Eye movements measured continuously using the Iota Eye-trace 300X infrared limbal reflection eyetracker . • Mean tonic vergence was calculated for each subject over 6.5 minute intervals. • Mean shifts calculated as change in tonic vergence ,at each time point, compared to baseline. Results Figure Fig 2: Tonic accommodation did not vary significantly during the experiment. Fig 1: Significant post task vergence shifts were observed, although these shifts varied widely between subjectsand were not related to baseline tonic vergence p<0.05 p<0.01 p<0.01 P> 0.05 P> 0.05 Fig 3: Vergence shift observed immediately post exposure was not correlated with baseline tonic vergence Fig 4 : Correlation graphs comparing the shift from baseline to T1 to the shift from baseline at other time points. Vergence up to 36.5 minutes post exposure showed a significant correlation with the initial post exposure vergence shift. Conclusions • Tonic vergence shifted to become more converged in some subjects and less converged in other subjects. The direction of the shift was not related to baseline tonic vergence. • Shifts immediately post exposure were sustained for over 30 minutes and tonic vergence failed to return to baseline values in around 50% of subjects by the end of the 50 minute measurement period. • Tonic accommodation was not significantly affected by viewing a virtual stereoscopic stimulus. • Wolf KS, Ciuffreda KJ, Jacobs SE. Time course and decay of effects of near work on tonic accommodation and tonic vergence. Ophthalmic Physiol Opt. 1987;7(2):131-5. • Fisher SK, Ciuffreda KJ. Adaptation to optically-increased interocular separation under naturalistic viewing conditions. Perception. 1990;19(2):171-80. • Eadie AS, Gray LS, Carlin P, Mon-Williams M. Modelling adaptation effects in vergence and accommodation after exposure to a simulated virtual reality stimulus. Ophthalmic Physiol Opt. 2000 May;20(3):242-51.