title: Visual evoked potentials during suppression in exotropic and esotropic strabismics: strabismic suppression objectified.
abstract: BACKGROUND
  We performed an electrophysiological study in order to objectify suppression in strabismus. The extent of cortical involvement in the process of interocular suppression was also explored. Possible differences in the suppressive process of esotropic and exotropic strabismics were also studied.
  
  
  METHODS
  An electroencephalographic recorder with eight leads was applied to the posterior one-third of the skull; three occipital, three parietal, and two temporal leads. We measured the activity of these visual cortical areas during stimulation of each eye under monocular as well as binocular viewing conditions with hemisinusoidal light pulses in a nature-like complex visual background. Recordings were made from six primary esotropic strabismic subjects and four primary exotropic and one consecutive exotropic strabismic subject. Also, five normal controls were studied.
  
  
  RESULTS
  A characteristic, triphasic response complex was found at approximately 80 ms following the start of each light pulse under monocular viewing conditions in the dominant and the nondominant eye. However, under dichoptic viewing conditions in the nondominant eye of all esotropic cases as well as in the nondominant eye of three of five exotropic cases, this response complex was completely absent. They showed approximately 100% reduction of their cortical response activity.
  
  
  CONCLUSIONS
  These results show the vast extent of the cortex that is involved in the suppressive process, giving a good insight in the power of suppression.
authors.affiliation: Department of Ophthalmology, The Hague Medical Center, Lijnbaan 32, 2501 CK, The Hague, The Netherlands. mjoosse@mchazglanden.nl
authors.forename: Maurits V
authors.initials: MV
authors.lastname: Joosse
authors.forename: Danielle L
authors.initials: DL
authors.lastname: Esme
authors.forename: Rob J
authors.initials: RJ
authors.lastname: Schimsheimer
authors.forename: Sandra A M
authors.initials: SA
authors.lastname: Verspeek
authors.forename: Marleen H L
authors.initials: MH
authors.lastname: Vermeulen
authors.forename: Ellen M
authors.initials: EM
authors.lastname: van Minderhout
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004569:Electroencephalography; D004948:Esotropia / Q000503:physiopathology*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005099:Exotropia / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015348:Vision, Binocular / Q000502:physiology; D015349:Vision, Monocular / Q000502:physiology; D014793:Visual Cortex / Q000503:physiopathology*