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Peter Bex, Anna Kosovicheva, Adriana Ferreira, Fuensanta Vera-Diaz; Effects of temporal frequency on binocularity and contrast sensitivity in amblyopia. Journal of Vision 2017;17(10):1055. doi: 10.1167/17.10.1055.
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Amblyopia is associated with a range of visual deficits, including reduced contrast sensitivity, interocular suppression, and impaired stereopsis. Binocular interactions are modulated by temporal frequency in normally-sighted observers; for example continuous flash suppression can be induced by monocular flicker. We examined the effects of temporal frequency on contrast sensitivity and binocular interactions in adults with amblyopia (n = 5) and normally-sighted control subjects (n = 16). For each observer, we estimated the temporal contrast sensitivity function (tCSF) monocularly in each eye using a modified quick CSF procedure (Lesmes et al., 2010) with bandpass-filtered letters at four spatial frequencies (1, 2, 4, and 8 cpd). Results showed greater interocular differences in the area under the tCSF in amblyopes compared to controls, but only at high (4 and 8cpd) spatial frequencies (F = 2.82, p = .047), indicating that amblyopes have a preserved ability to process temporal information at low spatial frequencies. We also evaluated binocularity by measuring interocular suppression and stereoacuity thresholds across four temporal (0, 4, 7.5, and 12 Hz) and spatial (1, 2, 4, and 8 cpd) frequencies. Interocular suppression was estimated by varying the contrast ratio of two dichoptic letters to produce perceptual reports of each letter with equal frequency (Kwon et al., 2014). Stereoacuity thresholds were measured by determining the minimum disparity at which subjects identified a front-depth target with 75% accuracy in a 3AFC task. Across both groups, interocular suppression was lower at higher temporal frequencies (F = 3.50, p = .02), whereas stereoacuity thresholds were unaffected by temporal frequency (F = 0.43, p = .73). Our results point to a temporal dependence of amblyopic deficits, a dissociation between the effects of flicker on interocular suppression and stereopsis, and suggest that temporal modulation may be used to attenuate interocular suppression.
Meeting abstract presented at VSS 2017
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