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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The electrorftinogram current flowing through pathway B can be recorded in a noninvasive manner, with extraocular electrodes, as illustrated in Fig. On the basis of the ionic mechanism. Due to the c-wave response developing over several seconds, it is susceptible to influences from electrode drift, eye movements, and blinks. Some properties of components of the cat electroretinogram revealed by local recordings under oil.

Fitting cone a-waves to the phototransduction model.

In contrast, lateral currents will cancel each other because the retinal lateral arrangement is completely symmetrical. These authors’ work was the foundation for the elrctroretinogram of analysis of the ERG used to the present day.

Electroretinography

Handbook of perception and human performance. The oscillatory potentials of the mudpuppy retina.

The multifocal ERG is used to record separate responses for different retinal locations. A small, sustained depolarizing component is seen at light onset plus a negative Electroreyinogram component.

Electroretinography – Wikipedia

Spectral sensitivity of rod vision purple circles and cone vision red squares. As stimulus intensity is increased, the b-wave increases in amplitude until a plateau is reached at intensities brighter by about 2 log units than that needed to elicit the smallest recordable b-wave. The a-wave is used as electroretinkgram independent variable and is used together with the normal b-wave: A, the ERG responses of one subject in the dark-adapted state by bright short-wavelength light stimuli.

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Analysis of the slow trans-retinal potentials in response to light.

Electroretinogram – EyeWiki

The size of the b-wave is measured from the trough of the a-wave to the peak more Initially loss of oscillatory potentials in flash ERG with subsequent reduction of b-wave amplitude. To simplify the comparison, the KRG responses are inverted; thus, basids positive deflection in this figure means a reduction in the extracellular concentration of potassium ions.

These currents will flow through different pathways, including local and remote ones. Therefore, the ERG c-wave eoectroretinogram be used to assess the functional integrity of the photoreceptors, the pigment epithelial cells, and the interactions between them.

Amplitude and Implicit Time Measurements Elcetroretinogram most common ERG response from a human, which is elicited with a full-field Ganzfeld flash of light, contains the a-wave and the b-wave as shown in Fig.

Cone electroretinography by flicker. Other traces were recorded after 30 min adaptation to white background of intensity denoted on the right more Figure 5 A, simultaneous recordings with double-barrel microelectrode of the ERG and the changes in the KRG from the distal retina of the slectroretinogram. The M-wave has also been described in the light-adapted retina of the cat 93 Clinically used mainly by ophthalmologists and optometriststhe electroretinogram ERG is used for the diagnosis of various retinal diseases.

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Biphasic form of the early receptor potential of the monkey retina. Aquantitative measure of the electrical activity of human rod photoreceptors using electroretinography.

Furthermore, electroretinogtam was shown that carriers of X-linked retinitis pigmentosa, who had no visual defects, could be identified by their reduced ERP recordings This contribution can be isolated in the laboratory by using specific drugs, but in the clinical environment, the ERG b-wave of patients reflects all contributions summed together.

Thus, the semi-saturation constant is also used as a measure of sensitivity.

The relationship between the ERG-determined CFF and stimulus intensity shows a discontinuity that marks the transition from rod vision to cone vision. The electrical response is a result of a retinal potential generated by light-induced changes in the flux of transretinal ions, primarily sodium and potassium. The spectral sensitivity curve of cone-mediated vision is the sum of all three spectral types of cone: 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.

A, the ERG responses that were elicited in the dark-adapted state using light stimuli of different intensities. In the future, more sophisticated analytical approaches may allow separation of the different contributions and allow identity of more exact sites of retinal diseases.