You are scheduled for an electroretinogram, which is also called an ERG.

What is an ERG?

The ERG is a test that measures electrical impulses from the retina when stimulated by flashes of light. You will rest your chin on a chin-rest and look inside a globe to view lights while responses of the eye are recorded by the computer.

The ERG testing technician.  

A volunteer looking into the ColorDome globe during an ERG testing.


Why is your doctor recommending this test?

The ERG is important in the diagnosis and management of many eye diseases. ERG’s can tell how well the retina is functioning. Children as well as adults can have this test done.


What will happen during your test?

You will report to the eye clinic in the Duchossois Center for Advanced Medicine (DCAM) at 5738 South Maryland.

Drops will be put in your eyes to dilate them and then you will be brought to the Krill Retinal Clinic.

In preparation for the test, small clips will be attached to the ear lobes; please do not wear earrings.
A wire will be connected to one wrist.

A threadlike measuring device, called an electrode, will lie lightly across the cornea in each eye.
The "thread" is connected between two sticky pads that are put on each side of the eye. The thread should not feel uncomfortable in the eye; however, if there is any discomfort, a drop of numbing medicine can be put into the eye.


ERG electrode between two sticky pads with a nickel to show size.

  One volunteer with ERG electrode

The test takes about one hour and consists of two parts. The first part is in the dark and the second part is in the light. There will be a twenty minute wait in the dark at the beginning for dark adaptation. For the second part in the light, there will be ten minutes wait for light adaptation.

During the test you will rest your head on a chin rest and look into the testing globe at a red dot. You do not need to do anything during the test but look straight ahead. The computer will automatically record the signals from the retina. There will be a series of three short beeps and one long beep; then a flash of light or flickers of light will appear. You will need to try not to blink during a flash or while the light is flickering. For each trial, there will be three sweeps of the flash or flicker. There are five separate trials, each at different levels of light.


Short movie of an ERG testing procedure