The influence of defocus on multifocal visual evoked potentials

  • Christina Pieh
  • Michael B. Hoffmann
  • Michael Bach
Clinical Investigation

Abstract

Background

In order to assess the influence of optical factors on the multifocal visual evoked potential (mfVEP), we obtained mfVEPs with optimal refraction and compared them to recordings with various degrees of dioptrical defocus.

Methods

Monocular mfVEPs were recorded from the right eye in eight normal subjects. Dartboard stimuli with 60 sectors arranged in six concentric annuli spanning 60° were generated with a VERIS system and presented on a computer monitor. Two pairs of electrodes were placed 3 cm above and below and 3 cm to the right and left of the inion. Two sets of mfVEP records per subject were obtained, one with best-corrected visual acuity and another when the stimulus was defocused by +1.0, +2.0 or +3.0 D. A signal-to-noise ratio (SNR) measure was calculated for every response from the two channels.

Results

The effect of defocus depended on eccentricity: when defocus was at +2.0 D and higher, reducing visual acuity to <0.3, the central mfVEP responses were reduced to approximately 60%, while defocus had no marked effect at eccentricities >7°.

Conclusions

The results suggest that, in contrast to the mfERG, the mfVEP requires optimal refraction to correctly assess the cortical responses.

References

  1. 1.
    Arai M, de Faria JML, Hirose T (1999) Effects of stimulus blocking, light scattering, and distortion on multifocal electroretinogram. Jpn J Ophthalmol 43:481–489CrossRefPubMedGoogle Scholar
  2. 2.
    Bach M (1996) The Freiburg visual acuity test—automatic measurement of visual acuity. Optom Vis Sci 73:49–53PubMedGoogle Scholar
  3. 3.
    Baseler HA, Sutter EE, Klein SA, Carney T (1994) The topography of visual evoked response properties across the visual field. Electroencephalo Clin Neurophysiol 90:65–81CrossRefPubMedGoogle Scholar
  4. 4.
    Berman MS, Seki S (1982) Blur-induced changes in the visual evoked potential. Am J Optom Physiol Opt 59:556–560PubMedGoogle Scholar
  5. 5.
    Brindley GS (1972) The variability of the human striate cortex. J Physiol 225:1P–3PPubMedGoogle Scholar
  6. 6.
    Chan HL, Siu AW, Yap MK, Brown B (2002) The effect of light scattering on multifocal electroretinography. Ophthalmic Physiol Opt 22:482–490CrossRefPubMedGoogle Scholar
  7. 7.
    Charman WN (1991) Wavefront aberration of the eye: a review. Optom Vis Sci 68:574–583PubMedGoogle Scholar
  8. 8.
    Hoffmann MB, Straube S, Bach B (2003) Pattern-onset stimulation boosts central multifocal VEP responses. J Vis 3:432–439PubMedGoogle Scholar
  9. 9.
    Hood DC, Greenstein VC (2003) Multifocal VEP and ganglion cell damage: applications and limitations for the study of glaucoma. Prog Retin Eye Res 22:201–251CrossRefPubMedGoogle Scholar
  10. 10.
    Hood DC, Zhang X (2000) Multifocal ERG and VEP responses and visual fields: comparing disease-related changes. Doc Ophthalmol 100:115–137CrossRefGoogle Scholar
  11. 11.
    Katsumi O, Hirose T, Sakaue H, Mehta M, Rosenstein RB (1990) Effect of optical defocus on the steady state pattern reversal visual-evoked response. Ophthalmic Res 22:383–390PubMedGoogle Scholar
  12. 12.
    Klistorner AI, Graham SL (2001) Electroencephalogram-based scaling of multifocal visual evoked potentials: effect on intersubject amplitude variability. Invest Ophthalmol Vis Sci 42:2145–2152PubMedGoogle Scholar
  13. 13.
    Marmor MF, Hood DC, Keating D, Kondo M, Seeliger MW, Miyake Y (2003) Guidelines for basic multifocal electroretinography (mfERG). Doc Ophthalmol 106:105–115CrossRefPubMedGoogle Scholar
  14. 14.
    Palmowski AM, Berningerm T, Allgayer R, Andrielis H, Heinemann-Vernaleken B, Rudolph G (1999) Effects of refractive blur on the multifocal electroretinogram. Doc Ophthalmol 99:41–54CrossRefPubMedGoogle Scholar
  15. 15.
    Steinmetz H, Furst G, Meyer BU (1989) Craniocerebral topography within the international 10–20 system. Electroencephalogr Clin Neurophysiol 72:499–506CrossRefPubMedGoogle Scholar
  16. 16.
    Stensaas SS, Eddington DK, Dobelle WH (1974) The topography and variability of the primary visual cortex in man. J Neurosurg 40:747–755Google Scholar
  17. 17.
    Sutter EE (1991) The fast m-transform: a fast computation of cross-correlations with binary m-sequences. SIAM J Comput 20:686–694Google Scholar
  18. 18.
    Walsh G, Charman WN (1989) The effect of defocus on the contrast and phase of the retinal image of a sinusoidal grating. Ophthalmic Physiol Opt 9:398–404CrossRefPubMedGoogle Scholar
  19. 19.
    Zhang X, Hood DC, Chen CS, Hong JE (2002) A signal-to-noise analysis of multifocal VEP responses: an objective definition for poor records. Doc Ophthalmol 104:287–302CrossRefPubMedGoogle Scholar

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Christina Pieh
    • 1
  • Michael B. Hoffmann
    • 2
  • Michael Bach
    • 1
  1. 1.Sektion Funktionelle SehforschungUniversitäts-AugenklinikFreiburgGermany
  2. 2.Visual Processing LaboratoryUniversitäts-AugenklinikMagdeburgGermany

Personalised recommendations