AN ELECTRICAL ARTIFACT ASSOCIATED WITH THE ERG-JET(TM) GOLD FOIL ELECTRODE

Purpose. To examine a photoelectric artifact associated with the ERG-j et(TM) corneal contact lens electrode (Universe SA, La Chaux-de-Fons, Switzerland). Methods. An artifact associated with the ERG-jet(TM), go ld foil corneal contact lens electrode was reproduced in vitro and in vivo using 50 msec light flashes. In vitro responses were examined usi ng light flashes that varied in intensity, duration, and wavelength. I onic strength of the bathing solution and temperature dependence were also examined. In vivo responses were compared to similarly recorded s ignals using the Burian-Allen bipolar electrode. Results. The artifact is not apparent with microsecond light flashes, as with the Grass PS2 2 Photo-stimulator connected to a Ganzfeld. Longer light flashes and i ncreasing light intensities, however, elicit graded responses that may resemble the late PIII component of the ERG in profile and in magnitu de. The artifact varies with temperature, ionic concentration of the b athing 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 th an light flashes of equal radiant energy but of longer wavelengths. Co nclusions. The artifact derives from electrode polarization occurring at the interface between the gold foil and its ionic medium. Caution i s required when using light stimuli longer than 2-3 msec with this and similar types of intrinsically polarizable metal electrodes.