title: Pattern visual evoked potential in the diagnosis of functional visual loss.
abstract: OBJECTIVE
  To study the pattern visual evoked potential (P-VEP) in the diagnosis of functional visual loss.
  
  
  METHODS
  Retrospective study of observational case series.
  
  
  METHODS
  Seventy-two subjects whose best corrected visual acuity (VA) was 20/50 or worse, with or without visual field defect, and whose visual abnormalities could not be explained by the findings of ophthalmologic and neurologic examination were included in this study.
  
  
  METHODS
  To compare the P-VEP estimated acuity to the initial subjective VA and to the best-performed VA.
  
  
  RESULTS
  Seventy-two subjects with functional visual loss had normal P-VEPs. The initial subjective VA was 20/50 in 9 subjects and < or =20/200 in 42 subjects. After clinical examination and reassurance, the best-performed VA was > or =20/50 in 53 subjects and < or =20/200 in 8 subjects. The discrepancy between the P-VEP estimated acuity and the best-performed VA was less than 3 lines of Snellen acuity in 63 of 72 (87.5%) subjects and more than 4 lines in 6 subjects. These six subjects were three women with loss of vision of unknown origin and three men with injury-related visual loss.
  
  
  CONCLUSIONS
  P-VEP has the advantage of objectively predicting VA and is a useful test in the diagnosis of functional visual loss.
authors.affiliation: Crippled Children Vitreoretinal Research Foundation and the University of Tennessee, Department of Ophthalmology, Memphis, Tennessee, USA.
authors.forename: S
authors.initials: S
authors.lastname: Xu
authors.forename: D
authors.initials: D
authors.lastname: Meyer
authors.forename: S
authors.initials: S
authors.lastname: Yoser
authors.forename: D
authors.initials: D
authors.lastname: Mathews
authors.forename: J L
authors.initials: JL
authors.lastname: Elfervig
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010364:Pattern Recognition, Visual; D012189:Retrospective Studies; D014786:Vision Disorders / Q000175:diagnosis*; D014792:Visual Acuity; D014794:Visual Fields