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E.M. Rislove, E.C. Hall, L. Kiorpes; Global Form Perception in Human Amblyopia Studied Using Glass Patterns . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3593.
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Purpose:Our aim was to examine whether a history of strabismic amblyopia is related to higher–order form processing deficits that are qualitatively different from those predictable from low–level visual tasks. Studies in animal models provide evidence for deficits in the primary visual cortex, area V1, but V1 deficits alone may not account for the performance of amblyopes on higher–order visual perceptual tasks. Methods:6 adults participated in this experiment; 2 had normal vision, while 4 had a history of strabismic amblyopia. We measured Glass pattern sensitivity at a range of spatial scales and contrast sensitivity over a range of spatial frequencies using a 2AFC MOCS procedure, We tested each eye separately with best optical correction in place. Glass patterns are random dot stimuli in which the local orientation of dot pairs (dipoles) must be integrated to yield a global form percept. We used translational (having the appearance of parallel lines) and concentric (having the appearance of a series of concentric circles) pattern types. The observer’s task was to identify which of two simultaneously presented fields of dipoles contained the structured pattern. We assessed Glass pattern sensitivity by varying pattern coherence, the proportion of dot pairs with orientations determined by the underlying pattern structure. Results:Adults with a history of strabismic amblyopia showed deficits in the perception of both concentric and translational Glass patterns compared with controls. While control observers showed no consistent difference in sensitivity to the two pattern types, amblyopic observers were particularly impaired with translational patterns. Interocular deficits were largest for patterns of fine spatial scale. These deficits were not qualitatively predictable from contrast sensitivity losses. Conclusions:Higher–order form processing deficits are associated with amblyopia. Although amblyopes are not generally impaired on orientation discrimination tasks, deficits are apparent in tasks using stimuli that require integration of orientation information over space. These losses may be related to deficient processing beyond V1.
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