The visual information processing of human starts at retina. We developed a population model for retinal ganglion cells(RGC) whose receptive field sizes grow with eccentricity. We generated visual metamers, stimuli that are perceptually the same but physically different, to test the model. We developed a spatial-variant filtering method for approximation of linear shift-variant systems based on an idea of warped Fourier transform. Detailed procedure and results are discussed. The model provides a basis for building metamers of cascaded models of the visual pathway.