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 for 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:
The cornea may get a temporary scratch on the surface from the electrode. Otherwise, there are no risks with this procedure.
You should not rub your eyes for an hour after the test, as this could injure the cornea. Your doctor will discuss with you the results of the test and what they mean for you.
Baloh RW, Jen J. Neuro-ophthalmology. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 432.
Brodie SE, Leys M. Clinical visual electrophysiology. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 2013 ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013:chap 5.
Cleary TS, Reichel E. Electrophysiology. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. St. Louis, MO: Elsevier Mosby; 2008:chap 6.9.
Reviewed By:Franklin W. Lusby, MD, ophthalmologist, Lusby Vision Institute, La Jolla, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
The information provided herein should not be used during any medical emergency
or for the diagnosis or treatment of any medical condition. A licensed medical professional
should be consulted for diagnosis and treatment of any and all medical conditions. Call 911
for all medical emergencies. Links to other sites are provided for information only -- they
do not constitute endorsements of those other sites. © 1997-A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.
The Agency for Health Care Administration (Agency) and this website do not claim the information on, or referred to by, this site is error free. This site may include links to websites of other government agencies or private groups. Our Agency and this website do not control such sites and are not responsible for their content. Reference to or links to any other group, product, service, or information does not mean our Agency or this website approves of that group, product, service, or information.
Additionally, while health information provided through this website may be a valuable resource for the public, it is not designed to offer medical advice. Talk with your doctor about medical care questions you may have.