VEP / pERG (Visual Evoked Potential / Pattern Electroretinogram)

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The Diopsys NOVA VEP/pERG are painless, non-invasive vision tests that objectively (do not require a verbal response from a patient) to measure either the function of the whole visual system from your eyes to the back of the brain (VEP) or of the retina, the light sensitive layer of the eye which changes light signals into electrical signals for transmission. The use of VEPs and ERGs has been demonstrated to aid in the diagnosis and treatment of a variety of visual disorders.  In glaucoma these two electrophysiological tests have been recently shown to be the earliest marker for early glaucoma, before any nerve damage; in diabetes abnormal ERGs have been associated with early ischemia before visual presentation in the retina such as bleeding (hemorrhage) or exudation.  In amblyopia VEPs allow for: early detection in non-verbal children; an objective method of monitoring treatment and/or a method to differentiate optic nerve disease from amblyopia.  If can be used to assess objectively damage from various conditions such as stroke, traumatic brain injury, medications such as Plaquinial, etc.  It is extremely sensitive in determining the presence of demyelinating disease such as multiple sclerosis.  In summary these tests give us an objective, measureable method of assessing retinal and visual functioning without asking the patient what they see.  It can be used in infants, children, and adults.

VISUAL EVOKED POTENTIAL (VEP)

The VEP measures the electrical activity of the whole visual system.  When light from an object viewed enters our eyes, it is converted into an electric signal by the retina.  That signal travels through the optic nerve (the wire that connects the eye to the brain) back to the occipital cortex (the portion of the brain in the back of the head which is directly responsible for vision).  The VEP measures the strength of the signal (amplitude) reach

ing the visual cortex and how long it takes to get there. How The Test is Performed One of our trained technicians will properly position three sensory on the head.  There is no pain associated with the test.  The patient then looks at a series of black and white patterns that appear of “flip” or al

ELECTRORETINOGRAM (pERG)

ternate rapidly on a computer screen.  While looking at the checkerboard pattern for 10-60 seconds the instrument records the signal from the back of the head.  The entire process takes between 5-30 minutes depending on the testing performed.  Usually, we will patch each eye and record visual response of each eye independently.

The pERG is a painless, non-invasive test that measures objectively the function of the retina.  Thus, it can be used by itself for known retinal disease or in conjunction with a VER to identify the independent components of visual loss from the retina vs. the entire visual system.  Early, subtle decreases in either the amplitude of the signal (strength) or latency are markers for early glaucoma, ischemic damage to the retina in vascular diseases such as diabetes, macular degeneration, etc. The pERG measures the electrical activity of the retinal cells, which send the signal through the optic nerve and eventually to the brain.  In summary, the pERG tells us how well the retina is in sending back the electrical signal created by it. Thus pERG are beneficial in making early diagnosis, objectively looking a change in functioning, and monitoring the effects of treatment. The pERG is performed similarly   to the VEP, with the following differences: the electrodes are different, they are placed in a different location, and the targets are slightly different.