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T.W. Kraft, H.A. Hancock; Oscillatory Potentials in Human ERGs: Timing and Amplitude Are Intensity Dependent . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5696.
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Purpose: Oscillatory potentials (OP) are a feature of the ERG that are altered in several disease states. OPs have been described as reduced in amplitude or delayed in diabetic retinopathy, glaucoma, and vascular occlusions. Although oscillatory potentials are thought to have useful diagnostic applications, some of their basic physiologic properties remain to be described. Our goal was to investigate the basic response–intensity relationship of OP in the human retina. Methods: Human subjects had one eye dilated after topical anesthetics were applied and then dark adapted for 10–15 minutes. ERGs were recorded in response to 2 ms flashes of light delivering 0.025 to 40 cd.s/m2. Stimuli were generated by a ColorBurst mini ganzfeld and recorded with a Diagnosis Espion system. Kinetics of the OPs was measured as the sum of the time to the peak (TTP) of the four most prominent peaks. The amplitude was taken as the sum of the amplitudes of those same peaks measured from the baseline. Results: The oscillatory potential kinetics of human subjects, as measured by TTP, are inversely related to stimulus intensity. OP amplitudes are directly related to stimulus intensity. At bright light intensities, the TTP and amplitude changes continue, but the rate of change is reduced. Thus, OP amplitude was inversely related to OP kinetics. OP kinetics are stable over a series of flashes and between sessions in the same individual. Conclusions: As in our previous rodent study, brighter stimuli produce larger, faster oscillatory potentials in human ERGs. We have extended the range of stimuli to go 4–fold higher than the ISCEV standard for producing OPs and found that the kinetics of the responses continue to accelerate. Thus, the use oscillatory potential amplitude or timing as an indicator of retinal disease should be approached with the understanding the inherent relationship between these two parameters.
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