Abnormal electroretinogram Abnormal full-field electroretinogram The full-field electroretinogram (ffERG) is an ophthalmologic test that provides non-invasive objective quantitative measures of the electrical activity in the retina. The ffERG represents an electrical response from the retina to a flash of light and measures global retinal function. UMLS:C4072956 An anomaly observed by full-field electroretinogram (ffERG). The ffERG measures the light-induced electrical activity of the retina at the corneal surface. Specifically, the ffERG records the global or total retinal electrical response to a full-field (Ganzfield) light stimulus. Isolation of the rod and cone components has important diagnostic value in differentiating between various retinal diseases. Modifying the properties of the light-stimulus (wavelength, strength, and flicker rate) as well as the adaptive state of the retina can separate the rod and cone functions of the ffERG.