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POST DATE: 3/12/13
Purchasing Agent:
Cynthia Greene
31 Center Drive
Building 31, Room 6A52
Bethesda, MD 20892
All responses must be submitted via email to:


Electrororetinography (ERG)

The ultrasound must have access to a preprogrammed, customized set of ISCEV compliant testing capabilities currently needed for testing NEI protocol patients.
Visual Electrophysiology system must have a set of ISCEV compliant testing capabilities. All included in one integrated space efficient visual electrophysiology system.
To include the following specifications:

  1. N.B. (blink response while testing) Saccades and recording must be continuous without interruption for the duration of the test.
  2. FO (retina light delivery) consists of 4 dark/light phases each 150 sec* long (PowerPoint slide 1)
  3. Each phase consists of a dark period and a light period with each period lasting 75 sec* (PowerPoint slide 1).
  4. LED alternation rate: 1 fixation shift (i.e. a saccade) every 2.5 sec* (PowerPoint slide 2)
  • i.e. there are 15 cycles per dark or light period
  • Amplitude Measurement Per Cycle (PowerPoint slide 3)
    • Amplitude for each half of the cycle is measured from the average voltage over the range 400 - 700 ms after each saccade (PowerPoint slide 3).
    • Amplitude for a given cycle is calculated from the difference in amplitude between the 2 halves of the cycle (PowerPoint slide 3).
    • Thus there will be 15* amplitude measurements per dark or light period. Therefore, there will be a total of 120* amplitude measurements per FO recording.
  • A sine wave is fit to the variation in amplitude over time (PowerPoint slide 4)
    • N.B. the example shows 6 dark/light phases where we are only requesting 4 in the new software.
    • Request option to do spike removal from plot of amplitude measurements v time before fitting the sine wave.
  • Parameters derived from the fit of the sine wave include**:
    • Amplitude (difference between peak and trough)
    • Peak/Trough ratio
    • Phase

    **Parameters are calculated from the sine and cone components derived from the DFT of the entire FO recording.
    *ISCEV Standard Values that differ to NEI:

    1. Each dark/light phase = 120 sec
    2. Each dark period or light period = 60 sec
    3. Fixation shifts = 1 per sec
    4. Twenty amplitude measurements per light/dark period
    5. 160 amplitude measurement per FO recording.

    Other General Recording Parameters:
    Fixation Excursion = 30 deg
    Filter: 0.05 - 30 Hz

    Electroretinography (ERG) is an eye test used to detect abnormal function of the retina (the light-detecting portion of the eye). Specifically, in this test, the light-sensitive cells of the eye, the rods and cones, and their connecting ganglion cells in the retina are examined. During the test, an electrode is placed on the cornea (at the front of the eye) to measure the electrical responses to light of the cells that sense light in the retina at the back of the eye. These cells are called the rods and cones.

    During an ERG recording session, the patient watches a standardized light stimulus, and the resulting signal is interpreted in terms of its amplitude (voltage) and time course. This test can even be performed in cooperative children, as well as sedated or anesthetized infants. The visual stimuli include flashes, called a flash ERG, and reversing checkerboard patterns, known as a pattern ERG.

    The electrodes measure the electrical activity of the retina in response to light. The information that comes from each electrode is transmitted to a monitor where it is displayed as two types of waves, labeled the A waves and B wave.

    Last Updated: March 2013