Vision is the result of electrical signals that travel between the retina and the part of the brain involved with vision (occipital cortex).
Electrophysiology tests check to see how well this visual nerve pathway sends the electrical signals needed for vision. These tests measure electrical activity that occurs in your eye when you look at something.
Electrophysiology includes different tests that measure how well the retina works. It can help check for diseases of the retina. The tests may also help diagnose and evaluate different kinds of vision and health problems.
Why It Is Done
The different electrophysiology tests are done for different reasons.
How To Prepare
You don't need to do anything special to prepare for the tests. Follow any instructions your doctor gives you about what to do before your test.
For visual evoked response (VER):
- Follow your doctor's instructions about eating to avoid low blood sugar.
- Avoid caffeine within 12 hours of the test.
- Wash your hair well.
- Don't wear any jewelry, such as earrings, near your head.
How It Is Done
The way each electrophysiology test is done varies.
How It Feels
These tests most often cause little or no discomfort. Tests include electroretinography (ERG), electro-oculography (EOG), and visual evoked response (VER). The electrode used for an ERG test may feel like having an eyelash stuck on your eye.
Risks
There are usually no risks from these tests. Tests include electroretinography (ERG), electro-oculography (EOG), and visual evoked response (VER). After an ERG test, avoid rubbing your eyes for at least an hour. Rubbing your eyes may scratch the front of your eye (cornea).
Results
Electroretinography (ERG). This test measures the amplitude (height) of certain brain waves (A-waves and B-waves) to detect vision problems. The time it takes for the eye to respond to light stimulus is called latency.
Normal
- You have normal A-waves and B-waves and a normal latency response time.
Abnormal
- You have abnormal A-waves and B-waves or an abnormal latency response time.
Electro-oculography (EOG). Test results use a number measurement called the Arden ratio. This is the ratio of the eye's maximum electrical activity in light to the minimum electrical activity in the dark.
Normal
- The Arden ratio is within a normal range.
Abnormal
- The Arden ratio is lower than the normal range.
Visual evoked response (VER).
Normal
- There is no delay in neural conduction in the brain's visual pathway. (Your results are compared with baseline norms for the lab where the test is given.)
Abnormal
- There is a delay between the eye's stimulation and the nerve's response. Abnormal results may be a sign of problems in the visual pathway between the eye and brain.
Credits
Current as of: January 22, 2026
Author: WebMD Ignite Staff
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