Strabismus and amblyopia disrupt spatial perception but not the fidelity of cortical maps in human primary visual cortex

Amblyopia is a common disorder of spatial vision and is frequently associated with the presence of anisometropia, strabismus, or both, during visual development. For highly visible stimuli, subjects with strabismic amblyopia often report marked spatial distortions, but the neural basis of this supra-threshold deficit is not well understood. Here, we used a combination of behavioural measurements and visual field mapping with high spatial-resolution functional magnetic resonance imaging (fMRI) at 7 T to assess perceptual distortions in 12 participants with strabismic amblyopia and 9 control subjects. We measured both behavioural and cortical visual field maps monocularly through each eye. Although amblyopic subjects showed increased perceptual distortions, the layout of V1 maps, as measured through the eccentricity and size of population receptive fields, was largely unaltered compared to controls, with no discernible difference in cortical magnification between groups. This suggests that disruptions to V1 retinotopy do not explain the perceptual distortions experienced by amblyopes.