P L Gehlbach1, R L Purple. 1. Department of Physiology, University of Minnesota Medical School, Minneapolis 55455.
Abstract
PURPOSE: To examine a photoelectric artifact associated with the ERG-jet corneal contact lens electrode (Universe SA, La Chaux-de-Fons, Switzerland). METHODS: An artifact associated with the ERG-jet, gold foil corneal contact lens electrode was reproduced in vitro and in vivo using 50 msec light flashes. In vitro responses were examined using light flashes that varied in intensity, duration, and wavelength. Ionic strength of the bathing solution and temperature dependence were also examined. In vivo responses were compared to similarly recorded signals using the Burian-Allen bipolar electrode. RESULTS: The artifact is not apparent with microsecond light flashes, as with the Grass PS22 Photo-stimulator connected to a Ganzfeld. Longer light flashes and increasing light intensities, however, elicit graded responses that may resemble the late PIII component of the ERG in profile and in magnitude. The artifact varies with temperature, ionic concentration of the bathing medium, and wavelength of stimulating light. The artifact also varies in magnitude and polarity from one disposable electrode to the next. Light flashes of shorter wavelengths elicit greater responses than light flashes of equal radiant energy but of longer wavelengths. CONCLUSIONS: The artifact derives from electrode polarization occurring at the interface between the gold foil and its ionic medium. Caution is required when using light stimuli longer than 2-3 msec with this and similar types of intrinsically polarizable metal electrodes.
PURPOSE: To examine a photoelectric artifact associated with the ERG-jet corneal contact lens electrode (Universe SA, La Chaux-de-Fons, Switzerland). METHODS: An artifact associated with the ERG-jet, gold foil corneal contact lens electrode was reproduced in vitro and in vivo using 50 msec light flashes. In vitro responses were examined using light flashes that varied in intensity, duration, and wavelength. Ionic strength of the bathing solution and temperature dependence were also examined. In vivo responses were compared to similarly recorded signals using the Burian-Allen bipolar electrode. RESULTS: The artifact is not apparent with microsecond light flashes, as with the Grass PS22 Photo-stimulator connected to a Ganzfeld. Longer light flashes and increasing light intensities, however, elicit graded responses that may resemble the late PIII component of the ERG in profile and in magnitude. The artifact varies with temperature, ionic concentration of the bathing medium, and wavelength of stimulating light. The artifact also varies in magnitude and polarity from one disposable electrode to the next. Light flashes of shorter wavelengths elicit greater responses than light flashes of equal radiant energy but of longer wavelengths. CONCLUSIONS: The artifact derives from electrode polarization occurring at the interface between the gold foil and its ionic medium. Caution is required when using light stimuli longer than 2-3 msec with this and similar types of intrinsically polarizable metal electrodes.