title: Amplitude calculation in multifocal ERG: comparison of repeatability in 30 Hz flicker and first order kernel stimulation.
abstract: BACKGROUND
  In multifocal flicker stimulation, each step of the M-sequence consists of four consecutive flashes with a frequency of 30 Hz. The resulting amplitudes can be calculated by means of a discrete fourier transformation (DFT). With this method, amplitudes can be calculated without having to localise peaks and troughs and set cursors. The purpose of this study is to compare the re-test stability of this method to conventional mfERG stimulation.
  
  
  METHODS
  We examined 27 healthy subjects using a RETI-scan device (Roland Consult, Wiesbaden). We used 61 hexagons within a 30 deg. visual field. We compared the classic first order kernel (FOK) stimulation with the multifocal 30 Hz Flicker (mfFlicker-ERG) stimulation. Repeatability was calculated using coefficients of variation.
  
  
  RESULTS
  Both methods had coefficients of 15% for the sum P1-amplitude and the DFT results, respectively. The amplitudes calculated by flicker and DFT were approximately 25% smaller than the FOK amplitudes.
  
  
  CONCLUSIONS
  This study showed no difference of re-test repeatability between the mfFlicker-ERG and the conventional first order kernel method. Since the mfFlicker-ERG method does not require a definition of peaks and troughs in order to calculate the amplitudes, we believe that a common source of error is eradicated, especially when dealing with distorted or atypical curves.
authors.affiliation: Department of Ophthalmology, RWTH Aachen University, Pauwelsstrasse 30, 52057, Aachen, Germany. bmazinani@gmx.de
authors.forename: Babac A E
authors.initials: BA
authors.lastname: Mazinani
authors.forename: Thorsten
authors.initials: T
authors.lastname: Repas
authors.forename: Andreas W A
authors.initials: AW
authors.lastname: Weinberger
authors.forename: Michael A
authors.initials: MA
authors.lastname: Vobig
authors.forename: Peter
authors.initials: P
authors.lastname: Walter
mesh_terms: D000328:Adult; D004596:Electroretinography / Q000379:methods*; D005583:Fourier Analysis; D006801:Humans; D008268:Macular Degeneration / Q000503:physiopathology*; D010775:Photic Stimulation; D015203:Reproducibility of Results; D012160:Retina / Q000502:physiology*