What is the difference between ERG and VEP?
Objective. Electroretinography (ERG) examines the functional integrity of the retina. Visual evoked potentials (VEP) are electrical responses recorded from occipital cortex which provides information about central visual pathways.
What is a VEP ERG test?
Visual Evoked Potential Test A Visual Evoked Potential (VEP) test measures 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.
How do you interpret VEP?
A normal VEP response to a pattern-reversal stimulus is a positive peak that occurs at a mean latency of 100 ms. There are three separate phases in the VEP waveform: an initial negative deflection (N70), a prominent positive deflection (P100), and a later negative deflection (N155).
How do you do visual evoked potential?
Visual evoked potentials (VEP): You sit in front of a screen and watch an alternating checkerboard pattern. Brainstem auditory evoked potentials (BAEP): You hear a series of clicks in each ear. Somatosensory evoked potentials (SSEP): You get short electrical pulses on one of your arms or legs.
How is an ERG performed?
ERGs are often recorded using a thin fiber electrode that is placed in contact with the cornea or an electrode that is embedded within a corneal contact lens. These electrodes permit the electrical activity generated by the retina to be recorded at the corneal surface.
What is full field ERG?
The full-field electroretinogram (ffERG) is an ophthalmologic test that provides non-invasive objective quantitative measures of the electrical activity in the retina. The ffERG represents an electrical response from the retina to a flash of light and measures global retinal function.
Where is VEP test done?
The VEP/VER is performed in the Clinical Neurophysiology department, located in D-wing on the main floor, East of the old main entrance.
What does an abnormal VEP mean?
Any abnormality that affects the visual pathways or visual cortex in the brain can affect the VEP. Examples are cortical blindness due to meningitis or anoxia, optic neuritis as a consequence of demyelination, optic atrophy, stroke, and compression of the optic pathways by tumors, amblyopia, and neurofibromatosis.
What are the types of ERG?
There are 3 main types of ERGs: full-field flash ERG (ffERG), pattern ERG (PERG), and multifocal ERG (mfERG). Each has different applications and benefits.
What is ERG and EOG?
Electroretinography (ERG) and Electro-oculography (EOG) are two of the tests conducted in the Ophthalmic Electrophysiology Laboratory. The primary objective of the electrophysiologic examination is to assess the function of the visual pathway from the photoreceptors of the retina to the visual cortex of the brain.
How does signal averaging work?
Signal Averaging Relies on the Noise Randomness For example, the noise coming from the power line can create a non-random noise component. Assume that the power line frequency is 50 Hz (a period of 20 ms) and we trigger our measurements every 40 ms.
What is VEP stand for?
Visual Evoked Potential/Response (VEP/VER) measures the electrical signal generated at the visual cortex in response to visual stimulation. The visual cortex is primarily activated by the central visual field and there is a large representation of the macula in the occipital cortex.
How long does an ERG test take?
The test takes about 1 hour to perform.
What is VEP in ophthalmology?
What are the uses of ERG?
The global or full-field electroretinogram (ERG) is a mass electrical response of the retina to photic stimulation. The ERG is a test used worldwide to assess the status of the retina in eye diseases in human patients and in laboratory animals used as models of retinal disease.
What is EOG signal?
Background: Electrooculogram (EOG) signal is one of the bioelectric signals acquired from the human body to study the movements of eyes and also to design and develop assistive devices. These devices can be mobility devices, video gaming devices or any other assistive device.