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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Therefore, the ERG c-wave can be used to assess the functional integrity of the photoreceptors, the pigment epithelial cells, and the interactions between absics. Push-pull model of the primate photopic electroretinogram: Invest Ophthalmol Vis Sci. May 1, ; Last Update: Characterization of the rod photoresponse isolated from the dark-adapted primate ERG.

Therefore, the c-wave can be used to assess the functional integrity of the pigment epithelial cells, the photoreceptors, and the interactions epectroretinogram the two. The two light stimuli were balanced to produce equal rod excitation as evidenced by the equality in the slow ERG component Fig.

Electroretinography

This filter represents membrane capacitance that determines the rate at which the photocurrent is translated into membrane potential. In the previous sections, the major and minor components of the ERG were described, and their cellular origins were discussed.

Enucleation of the eye. Understanding changes in the b-wave of the ERG caused by heterogenous receptor damage. Ratio of b-Wave to a-Wave ERG analysis that is based only upon amplitude measurements may lead to erroneous conclusions if the pupil is not maximally dilated. 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.

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When the retina is separated from the sclera and pigment epithelium, the ERG response contains only the a- and b-waves. However, the b-wave ratio is normal, indicating normal signal transmission.

Electroretinogram

The effect of electrorerinogram intensity upon the kinetics of the ERG response is clearly seen in the dependency of the a- and b-wave time-to-peaks upon stimulus intensity Fig. The relationship between the ERG-determined CFF and stimulus intensity shows a discontinuity that marks the transition from rod vision to cone vision.

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Amplitude-intensity A and latency-intensity B for the STR and a-wave that were recorded in the dark-adapted cat. Scotopic threshold response of proximal retina in cat.

The other components of the ERG—the early receptor potential ERPscotopic threshold response STRand M-wave—are more difficult to isolate in the routine clinical setup and are measured only for research purposes.

The contribution of voltage- and time-dependent poassium conductances to the electroretinogram in rabbits.

Figure 21 The ERG parameters that are customarily measured in the ophthalmic clinic for electrodiagnosis. The vertical dashed lines represent more Relationship between the amplitudes of the b wave and the a wave as a useful index for evaluating the electroretinogram.

Current source electroretinoggam analysis of the electroretinographic d-wave of frog retina. The fast cone-mediated ERG is sometimes referred to as the x-wave 97 The small-amplitude, fast wavelets can be seen in the ERG response Fig.

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Oscillatory potential and nyctometry in insulin-dependent electrorrtinogram. Therefore, the voltage difference between points A and B can be calculated for the local or remote pathways.

The oscillatory waves of the primate electroretinogram.

Origin of the electrorrtinogram potentials in the primate retina. The exact mechanisms whereby the pigment epithelial cells generate the c-wave were revealed only when potassium-sensitive microelectrodes were developed. Dark-adapted ERG responses of a normal subject were elicited by a standard series of light stimuli Fig.

The ERP in humans ends within 1. These current source-density analyses have indeed revealed the anatomical location within the retina of the different ERG components. Contributions of AMPA- and kainate-sensitive receptors to the photopic electroretinogram of Xenopus retina. Studies on the mass receptor potential of the isolated frog electroretinoram.

Electroretinography – Wikipedia

Due to the massed retinal electrical response, small retinal lesions may not be revealed in ffERG recordings. Rod photoreceptors detect rapid flicker. The colored traces are the actual ERG responses of a patient who was diagnosed with enhanced short-wavelength cone syndrome enhanced SWS cones. The central hexagons are smaller than those in the periphery.

Richard Normann at the National Institutes of Health, on aspects of electrordtinogram processing in the turtle retina.