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CA Westall, M Eizenman, H Lee; Effect of Scotoma Size on Disparity Vergence Eye Movements . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2876.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To study the effects of suppression scotomata on eye movement responses to disparity vergence stimuli. In response to disparity vergence stimuli, subjects with normal binocular vision show smooth symmetric vergence eye movements. In contrast, a study with 10 children with infantile esotropia showed a variety of responses including unequal saccades and asymmetric smooth eye-movements. Since children with infantile esotropia have suppression scotomata of varying sizes, we studied the effect of artificial scotomata on eye movement responses to disparity vergence stimuli, in subjects with normal binocular vision. Methods: Subjects were three young adults with normal binocular vision. Visual stimuli were presented with a stereoscopic display system comprising a 21" computer monitor and liquid crystal (LC) shutter glasses (StereoEyes, StereoGraphics Corp. San Rafael, California, USA). The LC glasses were integrated into a binocular head-mounted eye-tracking system (Vision 2000, EL-Mar Inc, Toronto, Canada). Subjects sat 50 cm from the display viewing a 45 * 35 degree cross that alternated between 0 disparity and crossed disparity of 1.5 degrees. The image to the right eye had a central scotoma varying in size from 0-15 degrees. Horizontal and vertical eye-movements were recorded. Vergence and saccadic eye-movements were detected and analysed within a time window of 600 msec following a change to a crossed disparity stimulus. Results: Crossed disparity visual stimuli with small scotomata (< one degree) elicited smooth, symmetrical vergence eye-movements with a mean amplitude of 1.32 degrees and no saccadic components. For progressively larger scotomata (1-10 degrees) the incidence of pure vergence eye-movements decreased, while the incidence of responses with combined saccadic and vergence eye-movements increased. Eye movement responses to disparity stimuli with large scotomata (15 degrees) were predominantly saccadic (70% of responses). Mean vergence amplitude decreased with larger scotomata. For 5,10,15 degree scotomata mean vergence amplitudes were 0.84, 0.60 and 0.25 degrees, respectively. Conclusion: Eye movement responses to vergence disparity stimuli with artificial scotomata had similar characteristics to those observed in children with infantile esotropia.
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