ELECTRORETINOGRAM BASICS PDF

Electroretinography measures the electrical responses of various cell types in the retina, including the photoreceptors (rods and cones), inner retinal cells. Basic mechanisms of electrical field generation in the tissue. Recording protocols Electroretinography (ERG) alone does not give you necessarily a diagnosis. Electroretinogram: An electrical diagnostic test of retinal function in situ. Electro – part Show you the basic clinical test; Show some research examples. The Eye .

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Electroretinogram – EyeWiki

Other traces were recorded after 30 min adaptation to white background of intensity denoted on the right basivs Oscillatory potential and nyctometry in insulin-dependent diabetics. The M-Wave The M-wave was first described in cold-blooded vertebrates as a negative-going potential change at stimulus onset and offset The relationship between amplitude and intensity of the ERG waves can be described by the following hyperbolic function Figure 4 ERGs recording from the skate.

The size of the a-wave is measured from the baseline to the trough of the wave.

Berson EL, Howard J. Two waves are identified, the positive R1 followed by the negative R2 These studies suggested the photoreceptor layer as the origin of the fast P-III wave.

Wachtmeister L, Dowling JE. In patients, these parameters provide quantitative assessment of retinal function during the progress of retinal diseases and the success of treatment A new receptor potential of basicss monkey retina with no detectable latency. The effects of changing the diameter of the stimulating light upon the M-wave left column and the extracellular potassium concentration right column.

An evaluation of retinal electrical anisotropy. Transiently decreased a- and b-wave amplitudes under both photopic and scotopic conditions with recovery after 24 hours.

The c-wave of the direct-current-recorded electroretinogram and the standing potential of the albino rabbit eye in response to repeated series of light stimuli of different intensities. A theoretical interpretation of ERG abnormalities in central retinal vein occlusion. When the rod model Eq.

Figure 11 Isolating the oscillatory potentials from the bright flash ERG response of the human e,ectroretinogram a by applying a digital filter b.

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The origin of the electroretinogram. Color of Light Stimulus Fig. Electrkretinogram an experiment is illustrated in Fig. The early receptor potential in sex-linked retinitis pigmentosa. Marked rod dysfunction and elevated threshold electroretinograk rods and cones on dark adaptation. This current is expressed as a negative wave when recorded from the vitreous or the cornea and constitutes the fast P-III the receptor potential.

The model discussed above, or an extension of it using bright light stimuli to elicit ERG responsescan be used to analyze biophysical mechanisms of the phototransduction process.

Figure 7b The pathways of the extracellular currents that have been suggested to underlie the generation of the ERG b-wave.

Electroretinography – Wikipedia

As the stimulus intensity is increased, the ERG b-wave increases in amplitude and becomes faster in kinetics. This leads to a “push-pull model” of these cell types Now, the electroretinogram response is commonly basivs to the ERG.

Initially loss of oscillatory potentials in flash ERG with subsequent reduction of b-wave amplitude. Normal or mild to moderately reduced photopic and scotopic responses variable depending on extent of fundus involvement.

Thus, the dark-adapted a-wave of this patient is characterized by smaller maximum response and reduced sensitivity.

The ERG is also used extensively in eye research, as it provides information about the function of the retina that is not otherwise available. A disease that leads to a reduction in the maximum response R mP3 will show as a smaller maximum a-wave in the ERG that can be electrorteinogram up to fit the normal one.

Electroretinography

Depth recordings reveal that the OPs attain maximum amplitude when the microelectrode is in the inner retina The pigment epithelium cells are functionally asymmetrical cells with their basal membrane toward the choroid less permeable to potassium ions than the apical membrane retinal side.

Exposing the vertebrate retina to 2-aminophosphonobutyric acid APBa specific agonist of glutamate metabotropic receptors, eliminates the ERG b-wave 50 as shown in Fig. Differing field sizes varying from 3 degrees to 18 degrees and light stimulus frequencies have been used in the various methods, however each technique deals with the challenge of limiting amount of light scattered outside the focal test area.

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These responses reflect mainly cone contribution and can be subtracted from the responses to white light stimuli and thus isolate the rod ERG responses. Dick E, Miller RF.

Intracellular responses to light from cat pigment epithelium: In addition to its clinical diagnostic purpose, the ERG can be used during the course of drug development and in clinical trails for testing bascs safety and efficacy of new or existing drugs and treatment modalities. Figure 5 A, simultaneous recordings with double-barrel microelectrode of the ERG and the changes in the KRG from the distal retina of the frog.

Light emitting diodes LEDs produce longer flashes upto 5 milisecond, and peak time in such cases should be measured from the midpoint of the flash to compensate the effect of flash duration on the p eak tim e, according to the current ISCEV guidelines update. Frequency of Photostimulation Another experimental approach to separate rod-mediated vision from cone-mediated vision is based upon the differences in temporal properties between these two visual systems.

The multifocal ERG mfERG simultaneously measures local retinal responses from up to retinal locations within the central 30 degrees mapped topographically. Normal scotopic a-wave with selectively reduced b-wave; implicit time of b-wave is approximately the same under scotopic and photopic conditions.

Elecfroretinogram 2b The ERG of a cat in response to a 2-sec light stimulus. The potential changes that were recorded from these cells in response to light stimuli were identical in shape and temporal properties to the ERG c-wave The recording was done from the whole eyecup upper tracefollowing the separation of the retina from the pigment epithelium middle trace and after exposing the retina to aspartic acid lower trace On- and off-responses in photopic electroretinogram in complete and incomplete types of congenital stationary night blindness.

The elecgroretinogram dashed lines represent more Although the resulting response has rod and cone components, the rod component is dominant and the primary contributor to the increased amplitude and increased implicit time.