Question
Identify the waves marked as 1, 2 in the electroretinogram shown in the picture below ?
| A. |
1- a wave. 2- b wave. |
| B. |
1- c wave. 2- b wave. |
| C. |
1- a wave. 2- c wave. |
| D. |
1- c wave. 2- a wave. |
Show Answer
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Correct Answer � A Explanation |
 |
Ans:A.)
1- a wave.
2- b wave.
Electroretinogram (ERG)
- It is a diagnostic test that measures the electrical activity generated by neural and non-neuronal cells in the retina in response to a light stimulus.
- 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.
- Most often, ERGs are obtained using electrodes embedded in a corneal contact lens, which measure a summation of retinal electrical activity at the corneal surface.
- The a-wave, sometimes called the “late receptor potential,” reflects the general physiological health of the photoreceptors(rods and cones) in the outer retina.
- In contrast, the b-wave reflects the health of the inner layers of the retina, including the ON bipolar cells and the Muller cells.
- Two other waveforms that are sometimes recorded in the clinic are the c-wave originating in the pigment epithelium and the d-wave indicating activity of the OFF bipolar cells.
- Two principal measures of the ERG waveform are taken:
- 1) The amplitude (a) from the baseline to the negative trough of the a-wave, and the amplitude of the b-wave measured from the trough of the a-wave to the following peak of the b-wave; and
- 2) the time (t) from flash onset to the trough of the a-wave and the time (t) from flash onset to the peak of the b-wave .These times are referred to as “implicit times” in electroretinography.
