Multifocal pattern VEP perimetry

Analysis of sectoral waveforms

Alexander I. Klistorner*, Stuart L. Graham

*Corresponding author for this work

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Purpose: The objective detection of local visual field defects using multi-focal pattern visual evoked potentials (VEP) has recently been described. The individual waveforms show variable polarity in different parts of the visual field due to underlying cortical convolutions. Normal trace arrays were examined to determine if certain areas of similar waveform could be grouped for analysis, while minimising cancellation of data. Method: The VEP was assessed using multi-focal pseudo-randomly alternated pattern stimuli which were cortically scaled in size. Bipolar occipital electrodes were used for recording. Waveforms were compared for different locations within the fieled up to 25°of eccentricity. Analysis of sectors showing similarly shaped waveforms was performed. Twelve normal subjects were studied. Result: Grouping waveforms by sectors of similar waveform increased the total calculated upper hemifield amplitude by 60%, compared with simple summations of responses for the whole hemifield. The inferior hemifield showed more consistent waveforms throughout, with the amplitude only increasing by 11% with sectoral summation. Intra-subject variability (10.6%) is less for sectors than for individual points (17.3%). Inter-subject amplitude differences are high, calculated at 56% for individual points and 45% for sectors. Conclusions: Due to differences in waveform as a result of underlying cortical anatomy, individual VEP responses from multifocal recordings should be grouped as sectors along the vertical meridian and above and below the horizontal, rather than by hemifields or quadrants. This finding is significant if one is considering within-field grouping strategies similar to the glaucoma hemifield test used in conventional perimetry, or reporting derived overall VEP amplitudes and latencies from a multifocal recording. Large amplitude variations between individuals and small signals from horizontal and upper field seen in single channel recording, still limit the application of this technique as a form of objective perimetry.

Original languageEnglish
Pages (from-to)183-196
Number of pages14
JournalDocumenta Ophthalmologica
Volume98
Issue number2
DOIs
Publication statusPublished - 1999
Externally publishedYes

Keywords

  • Multi-focal VEP
  • Pattern stimulation
  • Visual cortex
  • Visual field

Fingerprint Dive into the research topics of 'Multifocal pattern VEP perimetry: Analysis of sectoral waveforms'. Together they form a unique fingerprint.

Cite this