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M. C. Brown, R. F. Lowson, R. P. Hagan, A. Small, A. C. Fisher; Comparison of ERG Responses From Full Size and Mini Ganzfeld Stimulators. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4520.
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© ARVO (1962-2015); The Authors (2016-present)
To test whether full field electroretinogram (ERG) results are the same when using a hand held single eye Ganzfeld stimulator as when using a large bowl ‘full face’ stimulator.
Full field ERG tests were conducted on 10 volunteers in light and dark adapted conditions, first with a large bowl Ganzfeld stimulator, and then with a single eye hand held unit. The stimulators used were proprietary (Roland Consult, Brandenberg, Germany), and the performance parameters were measured and found to be similar in terms of flash and background luminance and for duration of the flash (both used LED flash generators).
Implicit times were similar for the two stimulators. Response amplitudes were significantly smaller with the hand held unit ranging from 50 - 80% of the responses in the large bowl. The difference was greatest for the dark adapted A wave (p<0.001) and light adapted B-wave (p<0.005).
Large and small bowl Ganzfeld stimulators for full field ERG may not produce comparable results, even if their measured technical parameters are the same. In this study the small (single eye) unit produced only 50-80% of the response amplitudes of the large bowl stimulator, and this ratio was different according to the pathways being tested. The most likely explanation is in the geometry of the units and placement with respect to the eye, achieving a full field stimulus only with the large bowl where the face is placed right within the bowl.
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