Impact of a Digital Power Line Filter in the 2-Global-Flash Multifocal Electroretinogram of Glaucoma Patients Compared to Controls

Abstract

Purpose: To assess the effect of a 50 Hz power line digital filter on the response to a 2-global-flash multifocal electroretinogram (mfERG) in primary open angle glaucoma (POAG) compared to control.

Materials and methods: A 2-global-flash mfERG (VERIS™) was recorded (23 control, 34 POAG). Eight recordings were noise contaminated: 4 control, 4 POAG. Response averages from the central 10° and 7 surrounding groups were analyzed with and without a 50 Hz digital filter for the following mfERG response epochs: direct component (15–45 ms), 1st (45–75 ms) and 2nd (75–105 ms) induced components.

Results: A digital 50 Hz filter had little effect on uncontaminated with noise waveforms but, in noisy recordings, changed the waveform dramatically to resemble uncontaminated waveforms. In controls’ 50 Hz-filtered uncontaminated with noise mfERGs differed significantly from unfiltered responses in induced components. Uncontaminated with noise recordings from glaucoma patients did not differ with or without the notch filter (p > 0.1 for all three epochs of mfERG). The mfERG response in the central 10°in glaucoma patients differed significantly from controls, whether the notch filter was used or not (p < 0.001).

Conclusions: A 50 Hz notch filter allows grossly contaminated waveforms to be analyzed in a meaningful manner. With a 50 Hz filter, glaucoma patients still differed significantly from normal.

• 50 Hz
• digital power line filter
• glaucoma
• multifocal ERG
• notch filter

DECLARATION OF INTEREST

The authors have no proprietary or commercial interest in any materials discussed in the article. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This work was supported by Swiss National Science Foundation (SNSF) A.M.P.32003B-135219; A.M.P. LHW Stiftung Lichtenstein.

Notes

* The results of this manuscript have been presented as poster presentations at the ARVO Annual Meeting in 2013.