Oscillatory potential changes related to stimulus intensity and light adaptation

Abstract

The oscillatory potentials (OPs) are a series of subcomponents of the flash ERG which probably originate in the inner plexiform layer of the retina. Abnormal OPs in various forms of retinopathy include central retinal vein occlusion, congenital stationary night blindness, and diabetic retinopathy. We investigated the effects of stimulus intensity and light adaptation on the OP components identified in our laboratory. OPs were recorded from 20 adult eyes to full-field ganzfeld stimulation at four stimulus intensities from 12 to 62 cd/m2. Stimulus flashes were superimposed over a steady background luminance in the ganzfeld. Four background luminances were used over a 3-log unit range from mesopic to photopic levels. Peak-to-peak amplitude and peak implicit time measures of the OPs were obtained. Latency-intensity functions were derived for each of the four OP components at each light-adaptation level. These latency-intensity functions revealed similar curve fitting slopes for all OP subcomponents at lower light-adaptation levels. At higher levels of light adaptation the later subcomponents (OP3 and OP4) showed a flattening of the slope of the latency-intensity function. The investigator concludes that this saturation effect is related to an interaction of rod and cone contribution to the OP waveform.