The Pattern Electroretinogram (PERG)

For many years the electrical output of the retina has been recorded wtth being a bright flash of light. The retina responds to light flashes (or changes In luminance) with a rather simple response consisting of an Initial negative a-wave and a second poshive b-wave. Since a single flash of light, no matter how long tt is Induration, will produce only a single response, this standard ERG Is sometimes called a luminance ERG (LERG). Clinical studies, begun in the 1940s and animal studies for many years previously, showed that the cells responsible for those responses were the photore captors (a-wave) and the Muller cells via connections to the bipolar cell region (b-wave). Ganglion cells played no role at all and Indeed, animals with transection of the nerve and humans with optic nerve trauma showed a normal ERG