O que é ERG full-field?
(ffERG)
Full-field ERG tests the summed response of the entire retina. To achieve stimulation of the whole retina for full-field ERG, the flash is provided by a Ganzfeld bowl designed to uniformly illuminate the retina with full-field light. Electrodes record the summed electrical response of the retinal cells[5]. The summed electrical response is a blend of the results from a range of different cells and regions in the retina, meaning that full-field ERG (ffERG) shows the status of the retina as a whole.
The components of full-field ERG
There are three major components in the flash ERG waveform:
The first response to appear after the light flash is the negative a-wave, which reflects the electrical activity of the photoreceptors. The next response to appear is the positive b-wave. The b-wave reflects the electrical activity of the bipolar cells, which transmit signals from the photoreceptors to the inner retina in light-adapted conditions and rod response in dark-adapted conditions. After the b-wave comes the photopic negative response (PhNR). The PhNR originates from the activity of the retinal ganglion cells, the innermost cells of the retina which transmit signals to the brain via the optic nerve.
Flash vs. Flicker
Full-field ERGs can be performed with either a flash or a flicker protocol. Depending on the dark adaption status and the flash brightness settings, these waves are either generated by the cone system (light-adapted tests with bright flashes) or by the rod system (dark-adapted low-intensity flashes). In a light-adapted status the full-field ERG can be conducted as flash and flicker tests. In flash tests, the retina has time to fully recover between each flash of stimulating light. Conversely, flicker ERG gives less time between each stimulating flash. This short time between flashes does not allow the retina to return to the baseline electric potential, so the ERG result is composed of b-waves without discernible a-waves or PhNR.
ffERG Testing Standards
O International Society for Clinical Electrophysiology of Vision (ISCEV) defines the standard of light intensities, colors and repetition rates for clinical use.
A full-field electroretinogram (ffERG) test as defined by ISCEV commonly consists of 5 or 6 different test settings to test both the rod and the cone system. However, for several purposes, a single test is sufficient to provide relevant information on the status or the progression of a disease.
How is ffERG Applied and Evaluated?
Since each portion of an ERG waveform originates from a different location of the retina, the abnormalities in an ERG can help to indicate the site of retinal dysfunction. The basic measurements are the amplitudes and implicit times of the response. Amplitudes are how far the baseline electric potential of the eye dips in the a-wave and climbs in the b-wave. Implicit times are how much time elapses after the light flash until the trough of the a-wave or the peak of the b-wave. To put it more simply, amplitudes show how strong the retinal response is, and implicit times indicate how fast the retina is reacting to the light stimuli. Amplitude results that are lower than reference amplitudes may indicate cell death, while implicit response times that are slower than reference responses indicate cellular stress.
Clinical Applications of ffERG
In a clinical setting, ffERG is a powerful tool to help diagnose retinal pathology, monitor the severity of retinal dysfunction, and observe the effects of medical treatment on the retina. ffERGs have proven useful in the evaluation of disorders including diabetic retinopathy, glaucoma, and retinitis pigmentosa, as well as catching toxic drug effects on the retina before severe, vision-threatening damage is done[6].
Warning: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
Substance Tables:
The table below lists substances which may be contained within LKC’s RETeval and RETevet products. Substances listed as Type 1 are within permissible levels in one or more of LKC’s products. Substances listed as Type 2 are used in the production of some components used in LKC products and may be present at trace levels, but are typically destroyed during processing.
RETeval and RETevet Devices
| Substance | CAS # | Type | Listed as causing: |
| Nickel | 7440-02-0 | 1 | Cancer |
| Acrylonitrile | 107-13-1 | 2 | |
| Ethylbenzine | 100-41-4 | 2 | |
| Crystaline Silica | 14808-60-7 | 1 | |
| Lead | 7439-92-1 | 1 | Cancer Developmental Toxicity Male Reproductive Toxicity Female Reproductive Toxicity |
| Methylene Chloride | 75-09-2 | 2 | Cancer Female Reproductive Toxicity |
| Bisphenol A | 80-05-7 | 2 | |
| N-Hexane | 110-54-3 | 2 | Male Reproductive Toxicity |