PubMed · 878324
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H D Baker, F G Bargoot. 1977. Effect of stimulus presentation rate upon visual threshold.. https://doi.org/10.1016/0042-6989(77)90027-x
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In this report we present the results of a series of studies focusing on the effects of transient changes in the ocular perfusion pressure (OPP) on retinal function in normals as assessed by the flash electroretinogram (ERG). A transient increase or decrease in the OPP affected by body inversion and compression/suction ophthalmodynamometry (ODM), respectively, is shown to affect differentially the b-wave of scotopic and photopic ERG's. However, under dark-adapted conditions, the cone component of the red flash ERG b-wave exhibited a vulnerability to decreased OPP which approached that seen for the b-wave of the scotopic blue flash ERG b-wave. Similar test procedures used to investigate the functional response of the inner plexiform layer during altered OPP revealed component-specific changes in white flash scotopic oscillatory potentials (OP's). The results of these provocative tests of retinal function offer new insights into basic retinal physiology and encouraging prospects for practical clinical diagnostic procedures with enhanced sensitivity and specificity for subclinical retinal disorders.
We observed multiple maxima and minima in the electroretinogram (ERG) first harmonics which varied as a function of adaptation level, mean illuminance, and modulation depth. Based on differences in response characteristics we identified a minimum of 3 parallel mechanisms operating at 3 frequency regions within the ERG: a low frequency region (less than 10 Hz), a midfrequency region (centered near 20 Hz), and a high frequency region (centered near 40 Hz). The low frequency region was observed both in dark- and light-adapted conditions, was basically linear, and showed nonlinear behavior only at high contrasts in either light or dark adaptation. It may be modeled as a low pass filter. The midfrequency region was clearly observed only above cone threshold, was nonlinear at low contrasts, and may be modeled as a linear filter followed by an essential nonlinearity. The high frequency region was observed under high levels of light adaptation and also was nonlinear at low contrast. It may be modeled also as a linear filter followed by an essential nonlinearity.