Diagnostic Testing: Visually Evoked Potential (VEP)
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VISUALLY EVOKED POTENTIAL (VEP) TESTING
VEP is a painless, safe, non-invasive vision test used to objectively measure neurological responses of the entire visual pathway. VEP measures neurological responses by measuring the electrical activity in the vision system. When light from an image enters your eye, it is converted into electrical energy at the retina and travels through the optic nerve to the visual cortex of the brain which processes vision. The VEP test measures the strength of the signal reaching your visual cortex and how fast it gets there.
PATTERN ELECTRORETINOGRAPHY (ERG) TESTING
ERG measures the function of your retina – the light-sensitive layer at the back of your eye. When light from an image enters the eye, it is converted into electrical energy by specialized cells in the retina. These cells send electrical impulses through the optic nerve to the brain where the image is processed. The ERG records how well the cells of the retina are conveying electrical impulses within the eye.
Studies have shown that ERG results aid in the diagnosis and treatment planning of many vision-related disorders.
WHAT IS VISUAL EVOKED POTENTIAL (VEP)?
Visual Evoked Potential is a non-invasive testing method that provides objective information about the function of the entire vision system. VEP provides a means to measure the complete visual pathway, from the lens to the visual cortex, to detect mechanical or neural abnormalities related to vision. These problems are often subtle and difficult to detect.
HOW ARE THE VEP AND ERG TESTS DONE?
The technician will attach three small sensory pads to your head using a washable gel material. You will be seated in front of a screen and asked to focus on the center of the screen.
The screen will display different size patterns that quickly reverse. One eye may be covered while the other eye is tested. A computer records your responses. The testing time may vary depending on what tests your doctor orders.
WHAT ELSE DO I NEED TO KNOW?
You must sit still during the test. Relaxation is an important part of the test.
WHAT CAN I EXPECT AFTER THE TEST?
After the test the technician will remove the sensory pads and use a small amount of water to remove any gel residue. The test results will be provided to your doctor.
HOW SHOULD I PREPARE FOR THE TEST?
All medications should be taken as usual unless otherwise directed by the doctor. Hair should be clean, dry, and free of any gels, sprays, or oils.
It is important that you feel relaxed and comfortable so the test results are accurate.