Pioneers & History
He was the first to observe frog legs jerking when connected to lightning rods during a storm, leading him to suggest that tissue itself stores electricity
Galvani
This is the most widely used electrode because it consists of a thin nylon thread that subjects can barely feel, making it comfortable for prolonged testing
DTL electrode
This test measures the resting potential of the eye without any light stimulation by tracking the dipole generated by the RPE.
ElectroOculoGram (EOG)
This is the first negative trough seen after a light stimulus, originating from the photoreceptors and OFF bipolar cells.
a-wave
This technique uses a pseudorandom stimulation of hexagons to provide localized functional information across the retina.
Multifocal ERG (mf-ERG)
He corrected Galvani’s theory by demonstrating that the movement in tissue was actually caused by a flow of ions between two different metals, a principle used in modern batteries
Volta
This contact lens electrode uses a speculum to keep the eye open and provides the best Signal-to-Noise Ratio (SNR) by eliminating large eye movements
Burian Allen electrode
his ratio, which should be greater than 1.8 in a healthy eye, is calculated by dividing the Light Peak by the Dark Trough
Arden Ratio
This is the first positive peak, measured from the trough of the a-wave, originating from ON bipolar cells and other post-receptoral neurons
b-wave
To compensate for the decrease in cone density, the size of the hexagons in an mf-ERG stimulus increases as they move toward the periphery.
eccentricity
This scientist used a galvanometer to prove that a current is generated in almost all parts of a living organism and discovered the eye's standing potential
Emil du Bois-Reymond
These electrodes must record through skin, resulting in a lower recorded amplitude; however, they are a good choice for recording a "full field ERG" from millions of photoreceptors
Gold cup skin electrodes
This non-invasive test measures the flow of ions throughout the scalp to record the biopotential of the brain
ElectroEncephaloGraphy (EEG)
These high-frequency, low-amplitude wavelets are superimposed on the ascending branch of the b-wave and are likely generated by amacrine cells
Oscillatory Potentials (OPs)
In an mf-ERG, this is calculated by taking the b-wave amplitude and dividing it by the area of the stimulated hexagon
Response Density
These researchers overcame the difficulty of measuring tiny ion flows by connecting several eyes together in a series to create a larger "battery"
Holmgren, Dewar, and M’Kendrick
This component of the electrophysiology setup takes the tiny retinal signal and increases it so that computers can record the data.
Amplifier
This visual test measures biopotential changes in the primary visual cortex (V1) and is considered a sub-type of EEG.
Visual Evoked Potential (VEP)
This specific measurement describes the time it takes from the onset of a stimulus to the formation of a peak or trough.
Implicit time
This anatomical structure appears as a blue dip on a response density map because it contains no neurons.
optic nerve (or optic disc)
This term refers to the voltage change or electric current generated specifically by the flow of ions in cells, muscles, or biological tissues
biopotential
This technique is used to eliminate random noise by adding and averaging multiple traces together until the consistent features of the signal persist.
Time Averaging
This is the only visual electrophysiology test where pupil dilation is not required, as the patient needs to focus to optimally stimulate ganglion cells.
Pattern ERG
This trough occurs approximately 65-70ms after a stimulus and is used to assess the activity of ganglion cells, which are affected by glaucoma.
Photopic Negative Response (PhNR)
While cones can respond to high frequencies, the maximum temporal resolution of rods is _______, meaning they cannot contribute to a 35 Hz flicker response
10-12 Hz