title: Impact of a Digital Power Line Filter in the 2-Global-Flash Multifocal Electroretinogram of Glaucoma Patients Compared to Controls.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: a Department of Ophthalmology , University of Basel , Basel , Switzerland and.|b Department of Ophthalmology , University of Vienna , Vienna , Austria.
authors.forename: Anna A
authors.initials: AA
authors.lastname: Ledolter
authors.affiliation: a Department of Ophthalmology , University of Basel , Basel , Switzerland and.
authors.forename: Margarita G
authors.initials: MG
authors.lastname: Todorova
authors.affiliation: a Department of Ophthalmology , University of Basel , Basel , Switzerland and.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schoetzau
authors.affiliation: a Department of Ophthalmology , University of Basel , Basel , Switzerland and.
authors.forename: Anja M
authors.initials: AM
authors.lastname: Palmowski-Wolfe
mesh_terms: D000328:Adult; D000368:Aged; D004596:Electroretinography / Q000379:methods*; D005374:Filtration; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D008875:Middle Aged; D010775:Photic Stimulation; D012160:Retina / Q000502:physiology; D012164:Retinal Diseases / Q000175:diagnosis* / Q000503:physiopathology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology
keywords: 50 Hz; digital power line filter; glaucoma; multifocal ERG; notch filter