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Oren Yehezkel, Michael Belkin, Dov Sagi, Uri Polat; Adaptation to astigmatic lens: Effects on lateral interactions. Journal of Vision 2005;5(8):486. doi: 10.1167/5.8.486.
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© ARVO (1962-2015); The Authors (2016-present)
The visual system is capable of adapting to optical distortions caused by the eyes optics or by added lenses. Astigmatism is an optical error that distorts the visual input along one axis of the visual image due to the cylindrical shape of the lens (which is spherical in the standard eye). Here we ask if adaptation to cylindrically distorted visual inputs given to one eye affects spatial interactions. Subjects wore on one eye a cylindrical lens of +1.00 D, to create an optical distortion which changed the perceived sharpness along one direction and thus the directionality of the perceived pattern. The other eye was covered with translucent lens. Adaptation was tested using two sets of experiments: 1) A 10x10 dot matrix served as a target for testing grouping by proximity. Observers were asked to distinguish between horizontal and vertical groupings without feedback. Perceived grouping before, after, and throughout the adaptation period was measured. 2) Lateral interactions between a target Gabor Patch (GP) and two collinear GPs that improve detection at target-flankers separations of 2,3,4 and 6λ (wavelength). Initially, perceived proximity with the lens (N=6 Obs) showed a bias in accordance with the distortion axes. After 4 hours, observers' bias was reduced (adaptation). These results carried over to the next day when the lens was re-applied. A persisting opposite bias was observed without the lens after adaptation. Lateral facilitation at 2,3λ was observed with the lens when initially applied, but disappeared after 4 hours, with and without the lens, an effect that persisted to the next day. The results suggest that visual adaptation to astigmatic lens involves long term plasticity in the visual system. Both the geometrical recalibration, that corrects for spatial distortions, and the change in spatial interactions seem to involve obligatory processing stages, most likely at early stages of visual processing.
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