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P. J. Knox, A. J. Simmers, L. Gray; Binocular Interactions in Childhood Amblyopia. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4758.
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Recent evidence in adult amblyopes suggests that binocular mechanisms are intact in amblyopia, but unused. The purpose of this study was to investigate whether children with no clinically demonstrable binocular vision could achieve binocularity using a novel method of dichoptic stimulation.
8 amblyopic children with a mean age of 9.5±1.5 years were recruited. Routine optometric and orthoptic evaluation revealed no clinically demonstrable binocularity. A novel method of measuring interocular suppression using a global motion coherence task was then employed to assess binocularity in these subjects (Mansouri et al, Vis. Res 2008 48, 2775-84). Stimulus presentation was dichoptic, with the signal dots viewed by the amblyopic eye and noise presented to the fellow eye. The binocular threshold was identified as the number of signal dots necessary for detection in the amblyopic eye at high contrast. Using this threshold, the contrast of the noise was then varied making it possible to measure the extent of binocular interaction present.
All subjects’ demonstrated binocular interaction with a mean interocular contrast threshold of 0.36±0.06. No relationship was found between the binocular contrast threshold and clinical measures of the area or density of suppression. There was a significant correlation between the level of visual acuity in the amblyopic eye and both the binocular coherence threshold (p=0.01) and the interocular contrast threshold (p=0.05).
These results psychophysically verify the presence of binocular interaction in amblyopic children under optimal viewing conditions, which cannot be identified by standard clinical tests. These findings may have implications for proposed future treatments of amblyopia, aimed at strengthening dormant binocular interactions (Mansouri et al, Soc for NeuroSci. 2008 Washington 454.5).
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