Electroretinography (ERG) is an eye test used to measure the electrical potentials generated by light sensitive cells of the eye, the rods and cones and their connecting ganglion cells to detect function of retina. In ERG, an electrode is placed on the cornea at front of the eye to monitor changes in the electrical potential of the eye in response to specific stimuli. Careful manipulation allows the clinician to investigate different cell types and layers of the retina. The risk is that cornea may get a temporary scratch on the surface from the electrode and perform again only after 1 hour. It is useful in the evaluation of hereditary and acquired disorders of the retina and also useful in determining if retinal surgery or any other ocular surgery such as cataract extraction is required. The instrument used to conduct ERG is an electroretinograph and the resultant recording is called an electroretinogram