title: Steady-state multifocal visual evoked potential (ssmfVEP) using dartboard stimulation as a possible tool for objective visual field assessment.
abstract: OBJECTIVE
  To investigate whether a conventional, monitor-based multifocal visual evoked potential (mfVEP) system can be used to record steady-state mfVEP (ssmfVEP) in healthy subjects and to study the effects of temporal frequency, electrode configuration and alpha waves.
  
  
  METHODS
  Multifocal pattern reversal VEP measurements were performed at 58 dartboard fields using VEP recording equipment. The responses were measured using m-sequences with four pattern reversals per m-step. Temporal frequencies were varied between 6 and 15 Hz. Recordings were obtained from nine normal subjects with a cross-shaped, four-electrode device (two additional channels were derived). Spectral analyses were performed on the responses at all locations. The signal to noise ratio (SNR) was computed for each response using the signal amplitude at the reversal frequency and the noise at the neighbouring frequencies.
  
  
  RESULTS
  Most responses in the ssmfVEP were significantly above noise. The SNR was largest for an 8.6-Hz reversal frequency. The individual alpha electroencephalogram (EEG) did not strongly influence the results. The percentage of the records in which each of the 6 channels had the largest SNR was between 10.0 and 25.2 %.
  
  
  CONCLUSIONS
  Our results in normal subjects indicate that reliable mfVEP responses can be achieved by steady-state stimulation using a conventional dartboard stimulator and multi-channel electrode device. The ssmfVEP may be useful for objective visual field assessment as spectrum analysis can be used for automated evaluation of responses. The optimal reversal frequency is 8.6 Hz. Alpha waves have only a minor influence on the analysis. Future studies must include comparisons with conventional mfVEP and psychophysical visual field tests.
authors.affiliation: Department of Ophthalmology and University Eye Hospital, Friedrich-Alexander University Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany. folkert.horn@uk-erlangen.de.
authors.forename: Folkert K
authors.initials: FK
authors.lastname: Horn
authors.affiliation: Department of Ophthalmology and University Eye Hospital, Friedrich-Alexander University Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Selle
authors.affiliation: Department of Ophthalmology and University Eye Hospital, Friedrich-Alexander University Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Hohberger
authors.affiliation: Department of Ophthalmology and University Eye Hospital, Friedrich-Alexander University Erlangen-Nürnberg, Schwabachanlage 6, 91054, Erlangen, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Kremers
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D059629:Signal-To-Noise Ratio; D014794:Visual Fields / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology; D055815:Young Adult
keywords: Multifocal VEP; Objective visual field test; Pattern reversal; Signal-to-noise ratio; Steady-state