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Behzad Mansouri, Robert Hess; A disrupted retinotopic map in amblyopia. Journal of Vision 2006;6(6):543. doi: https://doi.org/10.1167/6.6.543.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The amblyopic visual system exhibits both positional uncertainty and distortion. Animals whose visual input in early life has been disrupted also exhibit severe deficits in positional coding (Gingras 2005). We studied the quality of the retinotopic map by measuring the perceived position of stimuli presented to various parts of the amblyopic visual field.
Methods: Using a polarization method, we have tested 15 amblyopes and 5 normals. The stimuli were Gaussian blobs, which were presented within a circle of 30 degrees diameter. Each blob was seen only by the amblyopic eye. Moving a mouse and a marker seen only by the fellow-fixing eye, each subject had to localize the position of this previously presented target. This was repeated 50 times in each of 32 field positions. Refraction and alignment of the eyes were corrected before data collection.
Results: Our results confirm previous findings that there are significant degrees of distortion in the maps of the central visual field in amblyopic subjects (Fronius 1989). However, the variability was not correlated with the measured distortion in amblyopic maps. The distortion/variability index was significantly larger in amblyopic maps, showing that the higher distortion in amblyopia could not be simply explained by higher variability in localization. Also, regional analysis of the data showed that the distortion occurred heterogeneously in different parts of the visual field.
Conclusions: Our results show that amblyopes are not only uncertain as to where objects are but also they experience stable distortions that may only affect circumscribed regions of the visual field.
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