Electroretinography is a test to measure the electrical response of the eye's light-sensitive cells, called rods and cones. These cells are part of the retina (the back part of the eye).
ERG; Electrophysiologic testing
How the test is performed
While you are in a sitting position, the health care provider places numbing drops into your eyes, so you will not have any discomfort during the test. Your eyes are held open with a small device called a retractor. An electrical sensor (electrode) is placed on each eye.
The electrode measures the electrical activity of the retina in response to light. A light flashes, and the electrical response travels from the electrode to a TV-like screen, where it can be viewed and recorded. The normal response pattern has waves called A and B.
The doctor will take the readings in normal room light and then again in the dark, after allowing 20 minutes for your eyes to adjust.
How to prepare for the test
No special preparation is necessary for this test.
How the test will feel
The probes that rest on your eye may feel a little scratchy. The test takes about 1 hour to perform.
Why the test is performed
This test is done to detect disorders of the retina. It is also useful in determining if retinal surgery is recommended.
Normal test results will show a normal A and B pattern in response to each flash.
What abnormal results mean
The following conditions may cause abnormal results:
Cleary TS, Reichel E. Electrophysiology. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. Maryland Heights, Mo: Mosby Elsevier;2008:chap 6.9.
David C. Dugdale, III, MD, Professor of Medicine, Division of Medicine, Department of Medicine, University of Washington School of Medicine; and Franklin W. Lusby, MD, Ophthalmologist, Lusby Vision Institute, La Jolla, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.