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Uma Shahani, Velitchko Manahilov, William A. Simpson; New insights into amblyopia from classification images. Journal of Vision 2006;6(6):379. doi: 10.1167/6.6.379.
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© ARVO (1962-2015); The Authors (2016-present)
The amblyope's view of the world is scrambled compared to that of a normal observer, with deficits in processing global motion and orientation. The Classification Image technique was applied here to reveal the strategies used by normal and amblyopic eyes in tasks that required the global integration of information over large areas of the visual field. Two tasks were used: (1) an orientation task requiring a global judgement of an array of Gabor patches having some average orientation, (2) a motion direction task requiring a judgement of global motion direction of moving discs. Each element had an orientation or direction that varied randomly about the mean. Observers judged whether the near-threshold global orientation or motion direction were to the left or right of vertical. Classification images were calculated by adding (element-by-element) noise samples eliciting correct responses and subtracting noise samples producing incorrect responses. The results showed that normal observers had a surprisingly narrow “perceptive field”, using motion or orientation information from the central 1–2 deg of their visual fields. A similar picture was seen in amblyopes for the global orientation task with both amblyopic and fellow eyes. However, amblyopic eyes could integrate global motion BETTER than normal eyes: their performance was higher and perceptive fields wider than that of normal or fellow eyes, with sparse sampling of stimulus elements. This sparse sampling over a wider area of the visual field is actually an advantage in global motion judgement tasks and may reflect reduced inhibition in motion processing mechanisms.
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