label: Abnormal pattern electroretinogram
label_lc: abnormal pattern electroretinogram
description: "An anomalous response to a pattern electroretinogram (PERG), a particular kind of ERG obtained in response to contrast modulation of patterned visual stimuli at constant mean luminance-typically contrast-reversing gratings or checkerboards-whose characteristics are fundamentally different from those of the traditional ERG in response to diffuse flashes of light."