Use of dichoptic random dot kinematograms to assess amblyopic suppression
33.44, Sunday, May 12, 8:30 am - 12:30 pm, Orchid Ballroom
Cristina Llerena Law1, Benjamin Backus1, Alexander Yuan1, Oksana Natanelova1, Lisa Steele1, Ivan Tseng1, Lanya Cai1; 1SUNY State College of Optometry
Binocular mechanisms affect monocular visual function in amblyopia. Human and animal amblyopes show evidence of intact binocular mechanisms, but interocular suppression is chronic. Measuring suppression is therefore important for understanding amblyopia and for designing binocular stimuli for treating amblyopes (e.g. Hess et al, Optom Vis Sci, 2010; Li et al, IOVS, 2011). A measure of suppression is interocular contrast ratio (ICR), which estimates the relative signal strengths of the two eyes after combination. Following Hess, Thompson, and colleagues we used dichoptic random-dot kinematograms with signal dots in one eye and noise dots in the other. Amblyopes reported dot direction on each trial and interocular contrast ratio was under the control of a staircase procedure. We tested the robustness of this measure to changes in stimulus size and percent coherence within displays. Fourteen amblyopes and 8 control subjects ran in one to four sessions. Stimuli lasted 300 ms and contained 100 moving dots, presented using either a mirror stereoscope or a rear projection screen and stereo shutter glasses. ICR was highly robust to changes in percent coherence between 18 and 36 percent, and to stimulus size between 5 and 10 deg diameter. Suppression as measured by ICR was maximum in central vision and fell with eccentricity. Thus, use of this method to measure binocular suppression in amblyopes is robust to changes in stimulus size (and thus viewing distance from a display) and to changes in percent coherence (and thus individual differences in percent coherence threshold), increasing its relevance for use as a clinical tool. Across subjects it correlated with a binocular pattern contrast adjustment task (Ding and Sperling, Proc Natl Acad Sci, 2006). It may therefore be convenient to use for binocular approaches to the treatment of adult amblyopia.