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Antonello Fadda, Benedetto Falsini, Brett G Jeffrey, Wadih M Zein, Paul A Sieving; A Novel Algorithm for Recording Low-Amplitude ERGs by Cycle-by-Cycle Analysis in Advanced Retinal Degeneration. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5764.
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© ARVO (1962-2015); The Authors (2016-present)
To describe and evaluate a novel algorithm for cycle-by-cycle (CxC) recording of the low-amplitude flicker electroretinogram (ERG) in patients with advanced retinal degeneration (RD)
The algorithm extends the original CxC recording method introduced by Sieving et al. [IOVS 1998 Jul;39(8):1462-9]. Novel features include: noise analysis over a large frequency band, correction of artifacts due to baseline trends and comprehensive statistical assessment using three different tests. T1: the original test, based on spread of single cycle Fourier components and confidence ellipse; T2: test against a circular confidence region based on a sample of 4 recording segments and T2circ statistic, T3: S/N ratio threshold, where noise is the average of 20 Fourier amplitudes at closely spaced frequencies and a specific S/N statistics is used [Fadda et al. IOVS 51(5), 1491. 2010]. ERGs were obtained from Burian-Allen electrodes in response to a continuous 15 s stimulus of 32 Hz, ISCEV standard flicker (3.0 cd*s/m2), recorded with a commercial system (Espion, Diagnosys LLC) and exported as a raw signal for off-line analysis. The method was applied to ERG recordings from 9 patients with RD and 4 patients with CNGB3 achromatopsia.
The off-line analysis algorithm is implemented as a Windows application running on current PCs. It processes the output of a recording protocol that was easily set-up on a commercial ERG system, maintaining the original unaltered equipment configuration. A Bland-Altman plot (Fig. 1) indicated good agreement between conventional 30Hz ERG amplitude and CxC amplitude. The algorithm provided reliable analysis of ERG recordings even for amplitudes < 10 μV, commonly found in advanced RD patients. None of the CNGB3 patients had a CxC validated response, indicating that no signal artifacts are present with our recording conditions. Within session test-retest variability of both amplitude and signal-to-noise ratio is ≤ 23% for signal amplitudes of clinical interest, a result comparable to variability for ISCEV ERG amplitudes.
This novel algorithm extracts highly reliable clinical recordings of low amplitude flicker ERGs and effectively detects artifactual responses. It is of potential value as an outcome variable in clinical trials on natural history and treatment of advanced RDs
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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