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Herbert Jaegle, Eberhart Zrenner, Ditta Zobor; 30 Hz Flicker And Focal Stimulation: A Comparison Of Multifocal Ergs. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4988.
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While Flicker-ERG allows to perform Fourier analysis to estimate response magnitude and signal-noise ratio (SNR), focal stimulation requires either investigator dependant analysis or AUC calculations. Thus the aim of the study was to compare the three methods for quantification of retinal function in patients with hereditary retinal diseases.
Twenty-six patients (mean age: 35 years, range 15 to 55 years) with RP or syndromal disease were included in the study. Multifocal ERGs were recorded with a RETIScan system (Roland Consult GmbH, Germany) employing a LED-stimulator (luminance: up to 700 cd/m2). Multifocal 30 Hz flicker responses were analyzed using a Fourier transform, signal-noise ratio was estimated using the method described by Meigen & Bach (1999). Multifocal responses obtained using focal stimulation were analyzed by means of AUC calculation (signal window: 0-55 ms, noise windows: 95-150 ms), the SNR was estimated according to Zhang et al. (2002) and all segments waveforms were reviewed manually.
The 30 Hz response SNR median of all segments was 1.03 (range: 0.02 - 11.24), for only 8% the SNR was higher than 2.82 and could be considered significant. Significant magnitudes varied between 2.3 and 748 nV. The flash response SNR median was 0.20 (range: -0.69 - 4.56), 22 % were considered significant (SNR > 0.5). For the centre segment 31 and 48% waveforms were significant for 30 Hz and flash stimulation respectively. We found significant correlation between 30 Hz and flash SNRs and magnitudes for those segments with significant waveforms in both methods only. There was no significant difference between eyes. However, manual review of response waveforms suggests that in AUC analysis artefacts may be falsely picked up as response waveform.
For automatic analysis of waveforms the 30 Hz flicker stimulation is more reliable. However, with careful analysis and manual review the overall performance of both methods seems similar.
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