Drexel University College of Medicine

Tests

Electroretinography

Definition

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).

Alternative Names

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 Values

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:

• Arteriosclerosis with damage to the retina
• Congenital night blindness
• Congenital retinoschisis (splitting of the retinal layers)
• Giant cell arteritis
• Medications (chloroquine, hydroxychloroquine)
• Mucopolysaccharidosis
• Retinal detachment
• Rod-cone dystrophy (retinitis pigmentosa)
• Trauma
• Vitamin A deficiency

What the risks are

The cornea may get a temporary scratch on the surface from the electrode. Otherwise, there are no risks with this procedure.

Special considerations

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 it means for you.

References

Odom JV, Leys M, Weinstein GW. Clinical visual electrophysiology. In: Tasman W, Jaeger EA, eds. Duane's Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins;2009:chap 5.

Cleary TS, Reichel E. Electrophysiology. In: Yanoff M, Duker JS, eds. Ophthalmology. 3rd ed. Maryland Heights, Mo: Mosby Elsevier;2008:chap 6.9.

Physician Reference

Current Procedural Terminology (CPT)

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

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 2009 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.