Amblyopia is a developmental visual disorder of the cerebral cortex that compromises contrast sensitivity, spatial resolution, and shape perception (Kiorpes \& Movshon, 1996; Holmes \& Clarke, 2006). Based on recent studies (Pons et al., 2019; Najafian et al. 2022), we hypothesize that amblyopia differently affects ON and OFF visual pathways and their sampling of visual space in the cortex. We test this hypothesis with a computational model that simulates visual distortions in humans with amblyopia, reported as drawings of grating patterns (Barrett et al., 2003). The grating distortions are simulated by sampling visual space with grating-like population cortical receptive fields with their weights calculated as the average convolutions with the stimuli. The population cortical filters are then adapted and saturated to generate filter percepts with different line thicknesses and ON-OFF asymmetries. The final visual percept is calculated as a weighted sum of the filter percepts (optimized with the Nelder-Mead algorithm). The model generates accurate perceptual distortions by decreasing the responses of matched filter percepts (and matched/mismatched filter ratio) while combining just 2-6 filters. The average perceptual distance (normalized Laplacian pyramid distance, Laparra et al., 2016) between simulations and drawings decreases by 48\%, from 2.61 ± 0.26 when using the best filter match to 1.24 ± 0.29 when using all filters (7 subjects and 35 visual percepts). The results also reveal a strong correlation between the magnitude of filter distortions and deficits in contrast sensitivity (r=0.93, p=0.003). They also demonstrate an amblyopia shift in the spatial frequency distribution of the filter percepts that resembles a shift in the spatial frequency tuning of thalamocortical inputs when contrast decreases (measured in recordings from the cat Lateral Geniculate Nucleus). Taken together, these results indicate that visual distortions and contrast deficits in amblyopia are both the result of weakened cortical responses to stimuli.