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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 is sending 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 is working. It can help check for diseases of the retina. The tests may also help diagnose and evaluate different kinds of vision and health problems.
Electroretinography (ERG)measures the retina's electrical response while you look at different patterns or flashes of light. AnERG test can check for diseases and problems of the retina.
A full-field ERG can check how well your entire retina is working.A multifocal ERG (mfERG) tests just part of the retina. This can check for diseases of the macula and for central vision loss.
An electro-oculogram (EOG) tests how well electrical currents are working in the entire eye. It is done to check for certain eye and retina problems.
Visual evoked response (VER) tests the electrical activity in the entire visual pathway, from the eyes to the parts of the brain involved with vision.
Like ERG, this test measures electrical activity when the eye responds to looking at something. A VER test can find problems by showing how brain waves respond to certain things you look at during the test.
A full-field ERG measures how well rod and cone cells are working. These cells help you detect light and color. This test also looks at other cells in the retina. It may be used to check for problems such as:
A full-field ERG may help find the cause of certain retina problems, such vitamin A deficiency or metabolic disorders.
A multifocal ERG (mfERG) tests the electrical response in the central part of the retina. It may be used to help check for:
An electro-oculogram is used to help diagnose problems of the retina. It may be used to help check for problems such as:
Visual evoked response (VER) measures how well the entire visual pathway between the eye and the brain is working. The test may be used to check for or evaluate conditions such as retina problems, optic nerve problems, and multiple sclerosis.
VER can be used to check vision problems in people who can't take other eye tests. This includes infants or patients who can't respond to or follow instructions.
You don't need to do anything special to prepare for the test.Follow any instructions your doctor gives you about what to do before your test.
For visual evoked response (VER):
During the test:
A computer records changes in your brain waves while you look at patterns. Electrical signals are measured in the visual pathway, the area of the brain involved with vision (primary visual cortex).
These tests usually cause little or no discomfort. The electrode used for an ERG test may feel like having an eyelash stuck on your eye.
There are usually no risks from these tests.
After an ERG test, avoid rubbing your eyes for at least an hour. Rubbing your eyes may scratch the front of your eye (cornea).
The 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 A-wave and B-wave; normal latency response time
Abnormal A-wave or B-wave, or abnormal latency response time
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.
Arden ratio is within a normal range.
Arden ratio is lower than the normal range.
There is no delay in neural conduction in the brain's visual pathway.
Results are compared to baseline norms for the lab where the test is given.
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.
You may not be able to have the tests, or the results may not be helpful, if:
Talk to your doctor about the reasons for having this test and what the results mean.
Current as of:
December 18, 2019
Author: Healthwise StaffMedical Review: Adam Husney MD - Family MedicineChristopher J. Rudnisky MD, MPH, FRCSC - Ophthalmology
Current as of: December 18, 2019
Adam Husney MD - Family Medicine & Christopher J. Rudnisky MD, MPH, FRCSC - Ophthalmology
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