MedlinePlus Medical Encyclopedia: Electroretinography

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Electroretinography

Contents of this page:
Illustrations Alternative names Definition How the test is performed How to prepare for the test How the test will feel	Why the test is performed Normal Values What abnormal results mean What the risks are Special considerations

Illustrations

Contact lens electrode on eye

Alternative names Return to top

ERG

Definition Return to top

Electroretinography is a test to measure the electrical response of the eye's light-sensitive cells (rods and cones). Electrodes are placed on the cornea and the skin near the eye.

How the test is performed Return to top

While you are comfortably seated in a chair, anesthetic drops are placed in your eyes, causing them to become numb. Your eyes are then propped open and an electrode is placed on each eye. The electrode measures the electrical activity of the retina in response to light. The information from the electrode goes to a monitor, 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. A light is flashed, and the electrical response to the flash is recorded.

How to prepare for the test Return to top

No special preparation is necessary for this test.

For infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics:

infant test or procedure preparation (birth to 1 year)
toddler test or procedure preparation (1 to 3 years)
preschooler test or procedure preparation (3 to 6 years)
schoolage test or procedure preparation (6 to 12 years)
adolescent test or procedure preparation (12 to 18 years)

How the test will feel Return to top

The probes that rest on your eye may feel like an eyelash. The test takes about one hour to perform.

Why the test is performed Return to top

Both hereditary and acquired disorders of the retina can be evaluated with this test. It is also useful in determining if retinal surgery is recommended.

Normal Values Return to top

Normal test results will show a normal A and B pattern in response to each flash.

What abnormal results mean Return to top

Decreased electroretinography values may indicate any of the following:

What the risks are Return to top

The cornea may get a superficial scratch from the electrode. Otherwise, there are no risks associated with this procedure.

Special considerations Return to top

You should not rub your eyes for an hour after the test, or you may injure the cornea.

Update Date: 7/21/2003

Updated by: Raymond S. Douglas, M.D., Ph.D., Department of Ophthalmology, UCLA Medical Center, Los Angeles, CA. Review provided by VeriMed Healthcare Network.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician 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. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.