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KF Jost, G Niemeyer; ERG-Threshold in Man Compared to Cat (In Vivo/In Vitro) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1816.
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Purpose: To record and compare the scotopic threshold response (STR) in humans and in cats (in vivo and in perfused eyes). Method: In humans 13 ERG series of 7 healthy volunteers were recorded using a LKC UTAS 3000. Dark adaptation was 60 min, pupils were dilated. In cats, ERGs were recorded from 4 anesthetized and artificially ventilated cats. A reference electrode was either positioned on the sclera or in the subcutaneous tissue. A Ganzfeld-Grass stimulator was used. In vitro arterially perfused, fully dark adapted eyes from 5 cats, enucleated under deep anesthesia and analgesia, were used to record the vitreo-scleral ERG (Niemeyer G.: Prog Ret Eye Res 20/3, 2001). Intensity-response series to 50 ms light pulses from a Xenon source included thresholds of STR and b-wave. Results: The STR of the two species examined in vivo and partly in vitro were both graded corneal-negative potentials with similar waveform, maximum amplitude and dynamic range. In vitro, lower intensities sufficed to elicit measurable STRs, using pulses instead of flashes and a reference electrode at the posterior pole. Threshold intensities are as follows: View OriginalDownload SlideView OriginalDownload Slide Conclusions: Threshold intensity values of the human ERG were found to be remarkably close to those of the anesthetized cat. Pentobarbital/Gallamine anesthesia with artificial ventilation obviously does not reduce retinal sensitivity. In vitro, under the particular conditions of the perfused cat eye, threshold intensities were observed to be clearly lower than those measured in anesthetized cats.
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