ISSN: 2041-6792

Clinical Investigation

Electroretinography Innovations

Electroretinography measures the electrical responses of varied cell types within the retina, including the photoreceptors (rods and cones), inner retinal cells (bipolar and amacrine cells), and therefore the ganglion cells. Electrodes are placed on the surface of the cornea (DTL silver/nylon fiber string or ERG Jet) or on the skin beneath the attention (Sensor Strips) to live retinal responses. Retinal pigment epithelium (RPE) responses are measured with an EOG test with skin-contact electrodes placed near the canthi. During a recording, the patient's eyes are exposed to standardized stimuli and therefore the resulting signal is displayed showing the time course of the signal's amplitude (voltage). Signals are very small, and typically are measured in microvolts or nanovolts. The ERG consists of electrical potentials contributed by different cell types within the retina, and therefore the stimulus conditions (flash or pattern stimulus, whether a background light is present, and therefore the colors of the stimulus and background) can elicit stronger response from certain components.If a dim flash ERG is performed on a dark-adapted eye, the response is primarily from the rod system. Flash ERGs performed on a light-weight adapted eye will reflect the activity of the cone system. Sufficiently bright flashes will elicit ERGs containing an a-wave (initial negative deflection) followed by a b-wave (positive deflection).      

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