Gold foil and noncorneal skin electrodes in pattern electroretinograms

Pattern electroretinograms (PERGs) were recorded in ten subjects employing two varieties of electrodes: a gold foil electrode inserted into the lower fornix, and a gold cup skin electrode overlying the inferior orbit. Recordings were obtained as subjects viewed a checker-board pattern that reversed with a frequency of 2.1 Hz. Check size varied from 4 degrees to 0.25 degrees, at a contrast of 98%. Two additional recordings were obtained with 0.5 degree check size, lower luminance, and lower contrast. The PERG recorded with a skin electrode was similar in configuration to the PERG recorded with a gold foil electrode, but smaller in amplitude. The equation relating the amplitude of the b-wave recorded from the foil electrode (y) to the amplitude of the b-wave recorded from the skin electrode (x) was: y = 0.127 + 2.150x, with an R value of 0.82. Latencies of both the a- and b-waves were comparable under both recording conditions. We conclude PERGs may be adequately recorded with a noncorneal skin electrode. While the gold foil electrode offers larger amplitude waveforms, the skin electrode may be successfully substituted in those patients unable to tolerate corneal contact.