These cells are known as rods and cones. They form part of the retina at the back of the eye. These cells connect to other cells, called the retinal ganglion cells, and carry the light signals to our brain. ERG's can measure different retinal responses specific to our macula or our optic nerves. These signals are very sensitive and are measured in millionths-of-a-volt and can be used to diagnose diseases such as glaucoma and macular degeneration up to 7 years earlier than more traditional tests!
For more in depth information on this testing procedure, please feel free to go to the main Diopsys web page below:
Diopsys® ERG Testing: https://www.diopsys.com/advanced-patient-care/pattern-erg-vision-test/