Ophthalmic Electrophysiology

Ophthalmic electrophysiology is a series of tests that measure how different parts of your eyes and vision system respond to light. Ophthalmic electrophysiology tests are more involved than your usual eye exam. Talk to your healthcare provider or the test technician ahead of time to understand which type of test you’ll need and why.


What is this ophthalmic electrophysiology?

Ophthalmic electrophysiology is a series of tests used to diagnose conditions that affect your vision. They measure how different parts of your eyes and vision system respond to light.

These tests check how your eyes and brain process what you’re seeing by measuring the electrical activity in your retina and optic nerves.


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When is ophthalmic electrophysiology performed?

Your healthcare provider will use ophthalmic electrophysiology to diagnose conditions that affect your vision, including:

Ophthalmic electrophysiology can also help your healthcare provider diagnose more general symptoms like:

  • Inflammation.
  • Reactions to some medications.
  • Damage to your eyes.

Your healthcare provider might also use an ophthalmic electrophysiology test before recommending surgery on your eyes.

Who performs ophthalmic electrophysiology?

Trained technicians perform ophthalmic electrophysiology in a specially equipped lab.


Test Details

How does ophthalmic electrophysiology work?

Your healthcare provider will place electroencephalogram (EEG) disks on your face, eyes, head and scalp to read electric signals. Where EEG disks are placed depends on which type of ophthalmic electrophysiology test you’re having. The most common include:

  • Electroretinography (ERG): This test measures your retina’s response to light. In addition to the EEG leads, very thin wires will be placed over the front of your eye, directly above your bottom eyelid. The technician will flash bright lights in front of your eyes to measure your retina’s activity.
  • Visual evoked potential (VEP): This test measures how your optic nerve responds to light. EEG leads will be placed on your scalp or face and you’ll look at patterns on a computer screen.
  • Electro-oculography (EOG): This test measures the electrical potential across your retinal pigment epithelium, a single layer of cells that sits just behind your retina. The technician will place EEG leads on the inner and outside corners of your eyes. They’ll measure how well the pigmented epithelium cells in your retinas are functioning.

How do I prepare for the ophthalmic electrophysiology test?

On the day of your test, don’t wear or apply anything to your face or hair, including:

  • Makeup or cosmetics.
  • Lotion or other facial cleansers.
  • Hairstyling products like spray, gel or pastes.

Bring your prescription glasses with you to the test. If you usually wear contact lenses, you’ll need to take them out before the test.

Your eyes may be dilated for the test, which might make it unsafe for you to drive yourself home. Ask your healthcare provider ahead of time if your test requires dilation, and arrange for transportation if needed.


What should I expect during an ophthalmic electrophysiology test?

Ophthalmic electrophysiology tests are more involved than most tests your healthcare provider uses to check your eyes. Tests can take up to three hours from start to finish.

If the technician needs to put electrodes on your eyes themselves, they’ll numb your eyes with drops before applying the electrodes. The electrodes might feel scratchy or strange, but it shouldn’t hurt.

You usually won’t have to do anything during the test itself. Listen to the technician’s instructions and let them know if you’re feeling any pain or discomfort.

What should I expect after an ophthalmic electrophysiology test?

If you needed numbing drops in your eyes — or if your pupils were dilated — it might take a few hours for your vision to return to its usual level. Don’t drive, use tools or any equipment that might hurt yourself or others while your vision is impaired. Don’t rub your eyes for a few hours after your test either.

Talk to your healthcare provider or the test technician about how you should care for your eyes after your test.

What are the risks of ophthalmic electrophysiology tests?

There are usually no risks involved with an ophthalmic electrophysiology test.

It’s rare, but there’s a small chance an electrode applied directly to your eye can scratch your cornea.

Results and Follow-Up

What type of results will I get and what do the results mean?

Your healthcare provider will get the results after your ophthalmic electrophysiology. They’ll let you know if the test detected anything out of usual ranges in your vision system.

The test results will help your healthcare provider know what next steps you’ll need to correct any issues the test identified.

When should I call my doctor?

Visit your healthcare provider if you notice any changes to your vision, including:

  • Blurring.
  • Your vision is getting noticeably worse.
  • Dark spots.
  • Pain in your eyes.
  • Trouble focusing on something you’re looking at.

Go to the emergency room right away if you suddenly lose your vision.

A note from Cleveland Clinic

Your vision is precious to you, and it can be frightening to think something is wrong with your eyes. Needing an ophthalmic electrophysiology test doesn’t necessarily mean something is threatening your ability to see. The test will help your healthcare provider understand what’s causing any symptoms you’re experiencing, and what they need to do to help you maintain your eye health.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 02/16/2022.

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