Electrodes are placed on the surface of the cornea (DTL silver/nylon fiber string or ERG jet) or on the skin beneath the eye (sensor strips) to measure retinal responses.

Retinal pigment epithelium (RPE) responses are measured with an EOG test with skin-contact electrodes placed near the canthi.

[citation needed] If a dim flash ERG is performed on a dark-adapted eye, the response is primarily from the rod system.

[1] The pattern ERG (PERG), evoked by an alternating checkerboard stimulus, primarily reflects activity of retinal ganglion cells.

The study concludes that, if verified by further research, "ERG could provide the neurotransmitter specificity of PET at a much lower cost".

[12] Many of Ragnar Granit's observations became the basis of ERG understanding, for which he was awarded the 1967 Nobel Prize in Physiology and Medicine.