May 1998
Volume 39, Issue 6
Free
Articles  |   May 1998
Multifocal topographic visual evoked potential: improving objective detection of local visual field defects.
Author Affiliations
  • A I Klistorner
    Department of Ophthalmology, Save Sight Institute, Sydney University, Australia.
  • S L Graham
    Department of Ophthalmology, Save Sight Institute, Sydney University, Australia.
  • J R Grigg
    Department of Ophthalmology, Save Sight Institute, Sydney University, Australia.
  • F A Billson
    Department of Ophthalmology, Save Sight Institute, Sydney University, Australia.
Investigative Ophthalmology & Visual Science May 1998, Vol.39, 937-950. doi:
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    • Get Citation

      A I Klistorner, S L Graham, J R Grigg, F A Billson; Multifocal topographic visual evoked potential: improving objective detection of local visual field defects.. Invest. Ophthalmol. Vis. Sci. 1998;39(6):937-950.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: To investigate the relationships between the pattern stimulation of different parts of the visual field (up to 25 degrees of eccentricity), the electrode position, and the cortical response to improve objective detection of local visual field defects. METHODS: The human visual evoked potential (VEP) was assessed using multifocal pseudorandomly alternated pattern stimuli that were cortically scaled in size. Monopolar and bipolar electrode positions were used. The visual field was investigated up to 26 degrees of eccentricity. Twelve normal subjects and seven subjects with visual field defects of different nature were studied. RESULTS: Although the monopolar response is heavily biased toward the lower hemifield, bipolar leads overlying the active occipital cortex (straddling the inion) demonstrate good signals from all areas of the visual field tested. The amplitude is almost equal for the averaged upper and lower hemifields, but the polarity is opposite, causing partial cancellation of the full-field VEP. The degree of cancellation depends mainly on latency differences between the vertical hemifields. The bipolar VEP corresponded well with Humphrey visual field defects, and it showed a loss of signal in the scotoma area. CONCLUSIONS: The multifocal VEP demonstrates good correspondence with the topography of the visual field. Recording with occipital bipolar electrode placement is superior to standard monopolar recording. To avoid a full-field cancellation effect, a separate evaluation of upper and lower hemifields should be used for the best assessment of retinocortical pathways. This technique represents a significant step toward the possible application of the multifocal VEP to objective detection of local defects in the visual field.

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