Electroretinography (ERG) is an eye test accustomed to detect abnormal function with the retina. Specifically, on this test, the light-sensitive cells with the eye, the fishing rods and cones, and their connecting ganglion cells from the retina are screened. Electroretinography measures the electrical responses of assorted cell types from the retina, including your photoreceptors, inner retinal cells (bipolar and amacrine cells), plus the ganglion cells.