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Cristina Llerena Law, Benjamin Backus, Alexander Yuan; An Efficient Objective Measure of Binocular Suppression in Adult Amblyopia. Journal of Vision 2012;12(9):1367. doi: 10.1167/12.9.1367.
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Binocular mechanisms affect monocular loss of visual function in amblyopia. Evidence of intact but suppressed binocular cortical mechanisms in adult amblyopes have been found in animal and human subjects. Binocular stimuli may therefore be more effective than monocular stimuli to treat suppression in adult amblyopes (Hess et al, 2010; Li et al, 2011). A measure of suppression is interocular contrast ratio (ICR), which estimates the relative signal strengths of the two eyes after combination (Hess). We tested a new, direct method to measure ICR using a protocol adapted from Mansouri et al (2008) in normally sighted and amblyopic subjects. Like Mansouri we used motion coherence displays, but we measured contrast thresholds at fixed motion coherence, rather than motion coherence thresholds at fixed contrast. The direction (up or down) of 12% coherently moving dots in random dot kinematograms was detectable when signal (coherent) dots had sufficient contrast. The signal dots and noise (random motion) dots were presented either to the same eye or dichoptically. Stimuli lasted 500ms. Noise dots had 0%, 10%, 20% or 30% contrast. A staircase procedure was used to measure contrast threshold for signal dot motion direction. Conditions were presented twice, the first being for practice. Sessions lasted 45 minutes. The contribution of the amblyopic eye became measurable as contrast in that eye increased. Threshold ratios (ICRs) were higher by a factor of 2 when signal dots were presented dichoptically to the dominant eye in amblyopic subjects as compared to normally sighted controls. This method was efficient and results are consistent with Mansouri et al. to quantify binocular suppression. This measure of ICR is convenient to use for binocular approaches to perceptual learning in the treatment of adult amblyopia.
Meeting abstract presented at VSS 2012
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