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 Electroretinogram: ERG – Webvision – NCBI Bookshelf

Depth recordings of extracellular concentration of potassium and of local field potentials are shown in Fig. James Dewar of Scotland subsequently performed it in humans inhowever widespread clinical application did not occur untilwhen American psychologist Lorin Riggs introduced the contact-lens electrode.

The ERG and sites and mechanisms of retinal disease, adaptation, and development. Slow P-III component of the carp electroretinogram. The intensity-response curves show excellent correlation between peak amplitude of the c-wave and peak reduction electroreetinogram potassium concentration Fig.

A light stimulus elicits an extracellular current source I that divides into two pathways; one flowing through the retina local pathway, Elevtroretinogram in Fig. In the future, more sophisticated analytical approaches may allow separation of the different contributions and allow identity of more exact sites of retinal diseases. His research interests have continued to be information processing in the vertebrate retina with a particular interest in horizontal cell physiology.

The first wave to appear immediately after turning on a light stimulus was negative on the cornea. The size of the pupil is the major determinant of light intensity to the retina. The Oscillatory Potential OP When a bright light stimulus is used to elicit the ERG in humans or in animals, low-amplitude oscillating waves can be identified on the rising phase of the b-wave.

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The oscillatory waves of the primate electroretinogram. Wachtmeister L, Dowling JE. In this figure, ERG recording was performed from one subject using 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.

Accurate measurement of the P-II amplitude can supply valuable information to the clinician on the functional integrity elevtroretinogram the retina. The a-wave of the electroretinogram is the leading edge of the fast P-III and, therefore, reflects the functional integrity of the photoreceptors. The a-wave is positive, the b-wave negative, and the d-wave negative.

Neuron-glia interaction in the brain and retina.

The concept of the paired-flash approach is that a super-bright flash delivered after a test flash will completely shut down the remaining “dark” current, and therefore, the amplitude of the a-wave, which electroretinogrram elicited by the probe flash, can be used as a measure of the prevailing rod “dark” current at that time.

The amplitude of the a-wave is measured from a baseline that is monitored before the light stimulus, to the trough of the negative wave.

These light stimuli were matched for rod-mediated vision, as can be appreciated from the comparison in more The experimental drug was injected into the right eye lower trace and saline into the left eye upper trace as more A typical early receptor potential ERP of the human eye that was elicited by a very bright light flash arrow. The most effective are potassium ions The ERG responses more Relationships between the electroretinogram a-wave, b-wave and oscillatory potentials and their application to clinical diagnosis.

It is normally masked throughout most of its period by the large, positive b-wave. However, we have to remember that the magnitude of the different resistances, and more so, the relationships between them, can also affect the ERG that is measured with extraocular electrodes.

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Electroretinography

This is the “light” current and basically reflects the reduction in the “dark” currents because of light absorption in the photoreceptor outer segments and closure of cGMP-gated cationic channels see the chapter on photoreceptors 26 Push-pull model of the primate photopic electroretinogram: The elements are stimulated in a pseudo-random sequence electroreyinogram light and dark, called a maximum length sequence or m-sequence.

Sieving PA, Nino C. Dark-adapted ERG responses of a normal subject were elicited by a standard series of light stimuli Fig. The last component, P-III, which was the most resistant to the level of anesthesia, is a cornea-negative wave that develops faster than the other two and remains as a negative potential bqsics as long as the light stimulus is on.

Specific deficit of the ON response in visual transmission by targeted disruption of the mGluR6 gene. Furthermore, exchange of information between laboratories that use different recording conditions basicw always been problematical.

If these electrodes are placed at the loci designated in Fig. Ogden TE, Ito H. Applying sink-source analysis to electrophysiological recordings of the electroretinograk ERG responses at different retinal depths further reveals the location of the b-wave P-II generators.

A reflection of ON bipolar cell activity. The spectral sensitivity curve of cone-mediated vision is the sum of all baeics spectral types of cone: Thus, the dark-adapted a-wave of this patient is characterized by smaller maximum response and reduced sensitivity. Retrieved from ” https: Third-order retinal neurons may also contribute to the ERG d-wave