title: Interpreting the multifocal visual evoked potential: the effects of refractive errors, cataracts, and fixation errors.
abstract: OBJECTIVE
  To understand how refractive errors, cataracts, and fixation errors affect multifocal visual evoked potential (mfVEP) responses.
  
  
  METHODS
  Monocular mfVEP responses were obtained using a pattern reversal dartboard display. For the control condition, visual acuity was corrected to > or =20/20 and foveal fixation was maintained. The right eye was tested under the following conditions: simulated refractive error, simulated cataract, steady eccentric fixation, and unsteady fixation.
  
  
  RESULTS
  No subject demonstrated significant abnormalities under control conditions. For the simulated refractive error condition, significant centrally located abnormalities were seen for all subjects. For the simulated cataract condition, significant abnormalities were found for three subjects. The steady eccentric fixation condition yielded abnormalities in both eyes for all subjects while the unsteady fixation condition yielded significant central abnormalities in the tested eye. With eccentric and unsteady fixation conditions, all subjects had at least one sector with a waveform polarity reversal.
  
  
  CONCLUSIONS
  While the mfVEP is a useful tool for identifying local optic nerve damage or ruling out non-organic aetiology of visual field defects, factors such as uncorrected refractive errors, cataract, eccentric fixation, and unsteady fixation can produce apparent field defects on the mfVEP. With care, these problems can be correctly identified.
authors.affiliation: Department of Psychology, Columbia University, New York, NY 10027, USA.
authors.forename: B J
authors.initials: BJ
authors.lastname: Winn
authors.forename: E
authors.initials: E
authors.lastname: Shin
authors.forename: J G
authors.initials: JG
authors.lastname: Odel
authors.forename: V C
authors.initials: VC
authors.lastname: Greenstein
authors.forename: D C
authors.initials: DC
authors.lastname: Hood
mesh_terms: D000328:Adult; D002386:Cataract / Q000503:physiopathology*; D016000:Cluster Analysis; D005074:Evoked Potentials, Visual; D006801:Humans; D008875:Middle Aged; D011336:Probability; D012030:Refractive Errors / Q000503:physiopathology*; D015357:Vision Disparity; D015349:Vision, Monocular
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